International Workshop on Accelerator Alignment 2026

5 Oct 2026, 09:00 → 9 Oct 2026, 17:00 Asia/Tokyo

Middle Hall 200 (Tsukuba International Congress Center)

Yuichi OKAYASU (KEK)

The series of International Workshops on Accelerator Alignment (IWAA) are devoted to large scale and high precision positioning of particle accelerators and photon science experiments, focusing on the exchange of information between geodesists, surveyors, physicists and others specialists. The fields of geodesy, geomatics, metrology and traditional surveying overlap in this unique gathering.

Participants of IWAA generally come from laboratories, institutes, universities and companies around the world whose interests include particle physics, synchrotron light and medical or industrial applications. The workshops are usually focused on practical examples for aligning components including specialized techniques to increase positioning accuracies. Mathematical models used to refine raw observation data and the use of new equipment to generate this data is covered.

IWAA2026_poster.pdf

Logos iwaa2026_r3c.png

Monday 5 October

17:00 Ice Break Party

The Ice Break Party will be held at Ristrante TSUMU on the ground floor of Tsukuba Int'l Congress Center (EPOCAL TSUKUBA).

Tuesday 6 October

08:15 Registration / Coffee

Conference opening

Convener: Yuichi OKAYASU (KEK)

1 Introduction to KEK (tentative)

Speaker: Tadashi Koseki (KEK, Director Accel. Lab.)

2 IWAA2026 organizational announcement

Speaker: Yuichi OKAYASU (KEK)

Survey & alignment I

Convener: Yuichi OKAYASU (KEK)

3 Survey Activities in KEK -Overcoming the Great East Japan Earthquake-

Japan was struck by the Great East Japan Earthquake in March 2011.
Both the KEK Tsukuba and Tokai campuses sustained damage, and the accelerators suffered extensive destruction.
Highlights of the situation immediately following the disaster and the process of recovery will be reported.

Speaker: Yuichi OKAYASU (KEK)

09:55 Coffee brake

Survey & alignment II

Convener: Yuichi OKAYASU (KEK)

4 Evaluation and integration of ATS800 laser tracker for automated survey operations at CERN

The introduction of new portable high-precision laser scanners represents a significant advancement in metrology, enabling direct high-accuracy and non-contact measurements.
CERN surveyors are currently evaluating and developing new workflows to integrate the Leica Absolute Tracker ATS800 into measurement campaigns, particularly in highly radioactive environments, where minimising personnel exposure is a critical operational requirement.
This paper presents an assessment of the ATS800’s performance under various measurement configurations. Qualification tests were performed on different reference spheres to study the possibility of deploying large-scale survey networks with permanent targets. This work has led to the development of an innovative and automated workflow, combining AI-based automatic detection of survey network targets with measurement automation through the ATS800 software development kit. This enables autonomous data acquisition and opens new possibilities for remote survey operations using an overhead crane and automated guided vehicles.

Speaker: Jean-Frédéric Fuchs (CERN)

5 Building a European Alignment Community: key outcomes from EUWAA 2025 and 2026

Since 2022, survey and alignment experts from European laboratories have met annually at the EUropean Workshop on Accelerator Alignment (EUWAA). The workshop provides a forum for building a coordinated European approach to accelerator, detector and beamline alignment. It aims to foster exchange on common challenges, best practises, future tends and to strengthen cooperation between labs. Topics include among others measurement uncertainty, software and applications, instruments and methods, alignment issues, the use of external contract companies, recruitment strategies and approaches to adjustment and least squares calculations.
A major outcome of the 3rd workshop, held at the ESRF in June 2025, was the launch of an intercomparison measurement campaign on a dedicated girder using state of the art instruments, with the objective to establish a common definition of alignment uncertainty across our community and to improve its understanding by physicists. Ten laboratories and 2 companies took part in this intercomparison. Preliminary results were presented at the fourth EUWAA workshop hosted by CERN in April 2026.
The 2026 edition also featured a series of brainstorming sessions addressing key topics for the community, including workforce development (the use of service contracts and partnerships with universities and engineering schools to support future recruitment), instruments and methods (best practices and recommendations for instrument calibration, verification and testing) and research and development.
This presentation will summarize the main outcomes of these two workshops, highlighting progress toward greater communication between European laboratories and presenting the preliminary findings of the intercomparison campaign.

Speaker: Hélène Mainaud (CERN)

6 Survey and Alignment of the EINSTEIN telescope pilot at CERN

The Einstein Telescope (ET) is a proposed third-generation gravitational-wave observatory requiring an ultra-high vacuum infrastructure of approximately 120 km with stringent alignment tolerances. To validate key engineering and installation procedures, the Einstein Telescope pilot has been constructed at CERN as a reduced-scale demonstrator using full-size representative vacuum components arranged in a shortened configuration.

This paper presents the survey and alignment methodology developed for the pilot, including fiducialisation of beam tubes and end caps, establishment of a precision survey network, setting out of supports, pre-weld alignment, and final installation using laser tracker technology. Iterative adjustment procedures with real-time feedback were used to achieve alignment with respect to the nominal beamline.

The achieved alignment accuracy is reported, highlighting the effects of manufacturing tolerances, welding distortions, structural deformation, and support system limitations. Despite gravitational sag and fabrication-induced offsets, all components were positioned within the required tolerances of the pilot configuration.

Rather than demonstrating the feasibility of a specific measurement methodology for the full observatory, the study shows alignment achievable with the existing adjustment systems. At the same time, it highlights that construction of the full-scale Einstein Telescope will require more automated survey and alignment workflows to achieve the necessary efficiency, repeatability, and scalability for large-scale deployment.

Speaker: Solomon Kamugasa (CERN)

7 Contribution of Wire Offset Measurements to a Laser Tracker Geodetic Network in the FCC Tunnel

The FCC-ee, a future 91 km circumference lepton collider planned for operation in the coming decades, requires the relative alignment of neighbouring accelerator components to be maintained better than 0.15 mm. The installation of the components in the FCC-ee arcs therefore requires a geometrical network throughout the entire tunnel to enable both the initial positioning and the precise alignment of the components. The determination of such a network, located approximately 200 m underground, is particularly challenging due to the propagation of uncertainties over the 11.3 km distances separating adjacent shafts.
Previous studies identified a Laser Tracker network as a promising solution for transferring positional information, providing satisfactory uncertainty levels in the longitudinal and vertical directions but showing limitations in the radial direction. This paper presents the benefits of combining Laser Tracker networks with wire offset measurements.

Speaker: Vincent Gerligand (CERN)

Lunch

Survey concepts & strategy I

Convener: Georg Gassner (SLAC)

8 CHAMBERS INSPECTION AND FIDUCIALIZATION FOR CBXFEL

Multiple chambers for the cavity-based X-ray free-electron laser (CBXFEL) have been designed, assembled, measured and tested by Argonne National Laboratory (ANL). The fiducialization and the features inspection of all the critical components are performed by mean of both probe-contact articulated arm and non-contact video microscope. All metrological aspects for crystal diamonds and diagnostics, including the uncertainty analysis are described in this paper.

Speaker: Davide Bianculli (Argonne National Lab)

9 Task-Specific, Intervention-Aware Virtual Metrology for Accelerator Magnet Alignment

Reliable magnet alignment requires assessing measurement capability before field implementation and selecting effective corrective actions when a measurement plan is insufficient. This study presents a task-specific, intervention-aware virtual metrology framework for the HALF GD04 magnet alignment. Laser tracker observation uncertainty is propagated through target coordinates, rigid-body pose estimation, and magnetic-center determination to eight transverse relative-position tasks. Four independent single-station datasets show that the predicted station-dependent uncertainty is consistent with observed inter-station differences. Counterfactual assessment indicates that longitudinal tracker relocation provides only limited and task-dependent improvement, with no insufficient task restored within the required threshold. Two-face measurement is therefore investigated as a protocol intervention. Paired AT960 observations reveal clear face-sensitive effects, although these effects cannot be reliably predicted for new targets from measurement geometry alone. Empirical propagation further shows that their task-level impact depends strongly on cross-target dependence, which is not identifiable from the current acquisition sequence. The framework enables pre-measurement comparison of engineering actions while explicitly reporting task trade-offs and evidence limitations. Future tunnel experiments will validate the proposed interventions using coordinated multi-target measurement cycles.

Speaker: Yliang Lin (National Synchrotron Radiation Laboratory, University of Science and Technology of China)

10 High Precision Alignment R&D Activities in NSLS-II

NSLS-II is planning an upgrade to NSLS-II U, according to beam dynamics, the current lattice design requires that the adjacent PMQ magnets on a common girder to be aligned within 15-micron (RMS). It is a much more stringent requirement considering all the error factors involved. The approaches for magnet fiducialization and girder assembly will be investigated and tested. Recent experimental results will be reported.

Speaker: Chenghao Yu (BNL)

14:30 Coffee brake

Survey & alignment III

Convener: Helene Mainaud Durand (CERN)

11 Progress of Installation and Alignment of HALF

The on-site installation of the Alignment of Hefei Advanced Light Facility (HALF) project commenced in March 2026, with all component installations scheduled to be completed by the end of the year. At present, the preliminary installation of the injector and transport line has been finished, entering the precision alignment stage in the measurement hall. Meanwhile, the preliminary installation of girders, magnets, insertion devices and vacuum chambers for the storage ring is underway. This paper introduces the installation process and current progress of the Hefei Advanced Light Source, the problems encountered during the project construction, as well as the corresponding research and technological development carried out.

Speaker: Xiaoye He (National Synchrotron Radiation Labrotory, University of Science and Technology of China)

12 Tunnel Control Network Optimisation for the Hefei Advanced Light Facility: From Monte Carlo Simulation and Data Fusion to AI4Alignment

The Hefei Advanced Light Source (HALF) facility requires a high-precision tunnel control network to support accelerator alignment, equipment installation, and long-term geometric stability. This study focuses on the design and data processing optimization of particle accelerator tunnel control networks. An automated simulation workflow based on laser tracker measurement planning is developed to generate control network layouts, organize observation schemes, and perform batch Monte Carlo evaluation. The influence of network configuration is assessed using deviations from nominal coordinates and uncertainty indicators. To improve the reliability of tunnel control results, heterogeneous observations from laser trackers, digital levels, distance constraints, and close-range photogrammetry are further considered within a unified adjustment framework. In addition, time-series deformation prediction of control network points is explored using long-term remeasurement data and machine learning models. The proposed workflow provides a reproducible and transferable strategy for improving the precision, efficiency, and reliability of control network design and data processing for the HALF facility and similar large-scale accelerator projects.

Speaker: Enchen Wu (University of Science and Technology of China)

13 Research on HALF storage ring smoothing adjustment method

As a core component of the Hefei Advanced Light Facility (HALF), the storage ring's magnetic element arrangement accuracy and beam optical performance directly affect the device's operating efficiency and beam quality. To address potential geometric deviations during the installation of the HALF storage ring, this paper focuses on smooth adjustment, establishing an analytical framework from two aspects: geometric adjustment and verification of physical and optical indicators.
By conducting constraint analysis on the positions of key magnetic components and the connection deviations of adjacent sections, it was determined whether the adjustment scheme satisfies the physical threshold conditions required for HALF storage ring operation. Secondly, based on beam dynamics, indicators such as β function, dispersion function, and closed-orbit distortion are selected to further verify the state of the geometrically adjusted storage ring and evaluate its impact on beam stability and optical matching.
Through these two levels of verification, the rationality of the smoothing adjustment scheme for the HALF storage ring can be comprehensively assessed. This study provides a reference for HALF storage ring alignment optimization and subsequent operation and commissioning.

Speaker: Qiuyu Zhang (University of Science and Technology of China)

14 TPS Survey & Alignment: Girder Settlement, Realignment, and Network Strategies

This report details the long-term settlement monitoring and local alignment adjustments of the Taiwan Photon Source (TPS) storage ring. Following successful adjustments in 2020 and 2021, the latest data (2024–2025) indicate a continuous settlement trend in specific areas, which will serve as the basis for future alignment planning. Additionally, to overcome line-of-sight obstructions caused by the shielding hutches of newly constructed experimental stations, the team tested a new approach involving the removal of ceiling shielding blocks to establish control network connections. Measurement results reveal that certain peripheral areas (e.g., the loading dock) undergo significant displacement due to seasonal temperature variations, further confirming temperature fluctuations as the primary source of error. In the future, establishing a new observation network can mitigate thermal interference and assist beamline alignment, thereby maintaining measurement reliability.

Speaker: Wei-Yang Lai (NSRRC)

16:25 Coffee brake

Survey & alignment IV

Convener: David Martin (ESRF)

15 Two Paths to Precision: Laser Tracker and Photogrammetry for PETRA IV Magnet Fiducialization

High-precision and efficient magnet referencing is required for the series
fiducialization of the large number of multipole magnets for PETRA IV.

To meet the required precision while keeping the measurement process suitable for series production,
a high degree of automation is necessary.
Two concepts for relating external magnet fiducials to the magnetic axis
measured with a vibrating stretched wire were investigated:
a photogrammetry-based approach and a laser tracker-based approach.

This work presents experimental investigations of both concepts using
prototype measurement setups. The photogrammetry approach is evaluated using
rotary stages as V-STARS feature targets, while the laser tracker approach
is tested with different target configurations, including Super CatEye
prism. Particular attention is given to the achievable measurement
precision, repeatability, robustness, and practical implementation of the
measurement procedures. The results of both approaches are compared with
respect to their suitability for an automated series fiducialization process
for PETRA IV magnets. Based on this comparison, the selected referencing
concept and the considerations leading to this decision are presented.

Speaker: Jana Barker (DESY)

16 The fire incident in 2026 and interim solutions for the GSI facility

A major fire on 5 February 2026 in the RF Gallery at GSI almost completely destroyed the installation and equipment parts of the existing facility. This fire had such serious consequences that beam operations at GSI – and consequently the First Beam Event for the new facility FAIR – could not take place. Soon after the fire, initial ideas and discussions emerged on how to enable adequate interim beam operations that would supply beams to both existing GSI experimental areas and FAIR. An overview of these possible scenarios is provided, with the first interim solutions being presented in more detail. To this end, components from GSI’s HITRAP area will be dismantled and installed in the transfer channel area. As these components are being installed in their reversed direction, the project has been named PARTIH, which is a palindrome of HITRAP.
Keywords: GSI, FAIR, fire incident, beam line and beam source conceptualizations, HITRAP/PARTIH, fiducialization, machine installation, alignment

Speaker: Torsten Miertsch (GSI Helmholtzzentrum Darmstadt)

17 Establishing the PIP-II Preliminary Control Network

Fermilab’s PIP-II project will result in a new beamline approximately 550 meters long and will require establishing a geodetic control network to align all beamline objects in the tunnel. The first installation stage involves lower-precision alignment of objects such as stands and girders. The second installation stage involves high-precision alignment of beamline components. At Fermilab, a high-precision network is normally established at the beginning and is used for both stages for convenience. However, it was not possible to establish a high-precision network before the first stage due to construction delays. Instead, a preliminary network was established which allowed for speed and flexibility of implementation while still also delivering acceptable accuracy.

Speaker: David Krawczuk (Fermi National Accelerator Laboratory)

Instrumentation I

Convener: David Martin (ESRF)

18 A hybrid ADM–IFM system for air refractive index compensation with a target uncertainty of 5 µm (k=1) up to 100 m

In IWAA 2024, we presented an absolute distance meter (ADM) for long-range measurements, achieving uncertainties below 1 mm (k=1) over distances of up to 12 km. This instrument uses two laser wavelengths, one in the visible and the other in the infrared, to measure the difference in optical path length between them. This additional measured quantity corresponds to the accumulated effect of the atmospheric dispersion along the propagation path and eliminates the need to determine the air refractive index. The instrument inherently compensates for the contributions of temperature and pressure to the air refractive index. However, achieving an uncertainty better than 300 µm with this ADM for distances below 100 m remains a challenge, whereas some applications for accelerator alignment require an uncertainty of a few µm.

To address this limitation, we propose a new instrument inspired by the above principle. It combines an ADM operating at 1550 nm with a dual-wavelength homodyne interferometer (IFM) operating at 532 nm and 1064 nm. The first measures an absolute optical path length with an uncertainty of 2 µm, while the second determines the difference in optical path length between the two interferometric wavelengths, i.e. the dispersion effect, with an uncertainty of about 20 nm, which enables a fine compensation of the atmospheric effects. The operating principle and the first experimental results will be presented, along with the issues to be resolved. Currently, the ADM can measure absolute distances up to at least 66 m, while the IFM can track subsequent distance variations caused by changes in the air refractive index. A comparison was performed between the combined ADM-IFM system and a 3-m-long interferometric bench, which demonstrated a standard deviation of less than 3 µm between the two systems. Measurements were also carried out indoors over several days at distances of 12 m and 66 m, demonstrating resolution of 2–3 µm.

Speaker: Joffray Guillory (Laboratoire Commun de Métrologie LNE-Cnam)

Wednesday 7 October

Survey concepts & strategy II

Convener: William Jansma (ANL)

19 Alignment of 3 radiographic axes

EPURE Facility (standing for “Expériences de Physique Utilisant la Radiographie Éclair”, i.e Physics Experiment using Flash radiography), located in the CEA Valduc site, is a Franco-British joint experimentations facility. The key mission of the Facility is to x-ray dense in-motion objects
simultaneously with three radiographic axis. The radiographic images are thus captured over very short timescales (a few nanoseconds), hence the term Flash radiography.
The radiographic machines implemented in the EPURE Facility use two different technologies. Two of them are Linear Induction Accelerators (LIA) and the third one is a diode-equipped inductive voltage adder (IVA) generator. Each radiographic axis has a length of over 80 meters.
A radiographic axis is composed of a radiographic machine, an object to be imaged and radiographic detectors. The three radiographic axis of the facility are aligned to comply with tolerances, that is to say linear defects inferior to ± 300 µm and angular defects inferior to 0.1°. Moreover, ‘geometric’ constraints must also be taken into account to guarantee imaging quality. Such constraints include the distance between the object to be imaged and the radiation source; or the angle between each radiographic channel.

In order to meet all these constraints, alignment of the three radiographic axis rests on a fine-tuned strategy, implemented following the two main steps listed below:

• Step 1: mechanical alignment in the Facility Experimental Hall. This step is divided into different sub-steps. The overall purpose is to be able to determine the mechanical benchmark of each machine. The point of intersection of those three benchmarks represents the centre of the trial and thereby the centre of the object to be imaged. According to the object under study, it is then possible to place the detectors in front
  of the different axis. This step rests on the use of high precision measurement devices (Laser Tracker), positioning equipment (Hexapods), a cloud of localization points (topometric network) and specific equipment developed on the site;

  • Step n°2: verification of the alignment by radiography. Through the analysis of the radiographic images and the use of informatics tools developed by the technical teams, it is possible to check the misalignment of the object, to correct its position if needed and to check if the new position is in line with the requirements.

Speaker: Bastien Champeau (CEA)

20 Overview of the Future Circular Collider at CERN from the survey and alignment perspective

The Future Circular Collider (FCC) represents CERN’s flagship future project. Following the Feasibility Study Report published in 2025 and the Reference Design Phase (RDP) concluding at the end of 2027, the project faces unprecedented engineering challenges. The proposed 91 km tunnel requires the high-precision alignment of approximately 23 000 magnets, pushing existing geodetic and metrological techniques, including those currently validated by the Large Hadron Collider, to their limits regarding tolerance and scalability. This contribution introduces the FCC-ee project with current alignment requirements and addresses three key surveying challenges: extending the surface geodetic reference network to cover the FCC site; refining fiducialisation procedures; and optimizing data analysis methodologies. We provide an overview of the critical steps in the alignment process for large-scale accelerators and discuss the associated survey aspects. Furthermore, we highlight ongoing preparatory efforts currently under investigation within the RDP framework, aimed at validating solutions to meet the FCC's positioning requirements.

Speaker: Dirk Mergelkuhl (CERN)

21 Qualification of alignment systems: from theory to practice

Increasingly stringent alignment requirements in particle accelerators have led to the development of dedicated high-accuracy alignment systems. While qualification procedures exist for standard metrology instruments, no established methodology is available for the qualification of research and development alignment systems and their associated references. This paper presents a generic qualification process developed for the Compact Linear Collider (CLIC) alignment strategy and subsequently applied to the LHC and HL-LHC project. The methodology combines theoretical modelling, individual sensor qualification, short-range validation through dedicated mock-ups, and long-range validation using large-scale test facilities. Its implementation is illustrated through the qualification of the Wire Positioning System (WPS) and the Hydrostatic Levelling System (HLS). The results demonstrate the ability to characterize sensor performance, quantify environmental influences, validate alignment references, and assess long-term stability at the micrometre level. The proposed approach provides a transferable framework for the qualification of future alignment systems.

Speaker: Hélène Mainaud Durand (CERN)

09:45 Coffee brake

Survey & alignment V

Convener: Yuichi Okayasu (KEK)

22 [Title inquiry in progress]

The European Synchrotron Radiation Facility (ESRF) Extremely Brilliant Source (EBS) was installed in 2019 and commissioned in 2020. The alignment tolerances for the most demanding magnets—including the combined-function magnets, high-gradient quadrupoles, and sextupoles—were approximately 60 µm (2.5σ).

Between 2019 and 2025, no global realignment of the Storage Ring (SR) was made. During this period, however, the overall alignment quality gradually degraded due to the well-characterised ground movements at the ESRF site. Consequently, a full realignment of the SR was undertaken in 2025. The work was completed in two stages: first, during the summer shutdown, four of the 32 SR cells were realigned to validate the procedure; then, during the winter shutdown, all 32 SR cells were realigned, with the aim of bringing the magnets as close as possible to their nominal positions.

This paper/presentation describes the ground movements that motivated the realignment, presents the results achieved, and discusses the practical limits of alignment and realignment on the EBS machine using the equipment, materials, and techniques currently available at the ESRF.

Speaker: David MARTIN (ESRF)

23 A New Annual Beamline Survey Campaign at the ESRF

The European Synchrotron Radiation Facility (ESRF) operates a well-established program of comprehensive Storage Ring (SR) and regular machine surveys to maintain the geometric integrity of the accelerator and serve as the primary reference for all beamlines. Over the past three decades, the SR survey has evolved into a highly coordinated activity comprising nearly 10,000 measurements completed within a single eight-hour shift, achieving measurement uncertainties of approximately 50 μm in the radial direction (dR) and 20 μm vertically (dZ). However, until now, beamline survey campaigns have been conducted on a more ad-hoc basis, typically comprising partial or local measurements carried out only when necessitated by specific alignment interventions. Moreover, alignment requirements on the beamlines have evolved considerably and have become increasingly stringent, demanding a more systematic and rigorous monitoring approach.
To address this, ESRF has introduced a new monitoring method that extends the comprehensive SR and regular machine surveys to the beamlines through a dedicated annual survey campaign. This approach replaces the former ad-hoc practice with a systematic, full-beamline monitoring strategy tied directly to the Storage Ring reference network. These measurements provide valuable information on the long-term geometric behavior of the beamlines, enabling identification of global displacement patterns and direct comparison with the evolution of the Storage Ring reference network.
As the campaign has only recently been established, the available dataset is not yet sufficient to identify long-term trends or draw definitive conclusions. This paper presents the methodology and implementation of the annual beamline monitoring campaign, laying the foundations for future studies of the geometric evolution of ESRF beamlines and establishing the framework for ongoing stability assessment.

Speaker: Cristina GONZALEZ TORRES (ESRF)

24 In-House softwares for ESRF Survey and Alignment : current developments and perspectives

The Survey and Alignment Group measures its primary network of reference points through a full survey managed every six months. This survey consists of nearly 9,000 measurements acquired using laser tracker-based tacheometry and direct leveling with digital levels. It is carried out during the first week of each semi-annual machine shutdown and involves between one and four teams working simultaneously.

Acquiring such a large number of measurements within a limited time schedule requires the acquisition software developed in-house to be automated and adapted as much as possible, in order to minimize both measurement acquisition and geodetic computation times.

This presentation will provide an overview of the software developments implemented by the group, as well as the essential maintenance activities required to support internal development policies, facilitate code sharing, and accommodate the replacement and renewal of measurement instruments.

Particular attention will be given to the identified needs for evolving the various software tools used by the group. These developments will be illustrated through the management and updating of the coordinate systems specific to each beamline.

Speaker: Guillaume Chamblas (ESRF)

25 Beyond existing specification tools

Beyond existing specification tools: how to specify / request on a drawing an alignment specification using ISO GPS situation features

Speaker: Bertrand Nicquevert

Lunch

Optional: Excursion : Geospatial Information Authority of Japan

Optional: KEK tour

Optional: Banquet

Thursday 8 October

Tools & monitoring I

Convener: Jean-Frederic Fuchs (CERN)

26 Development of a mirror device and associated measuring method

EPURE Facility (standing for “Expériences de Physique Utilisant la Radiographie Éclair”, i.e Physics Experiment using Flash radiography), located at the CEA Valduc site, is a joint French-British experimentations facility. The key purpose of the Facility is to X-ray dense in-motion objects simultaneously with three radiographic axes. The radiographic images are thus captured over very short timescales (a few nanoseconds), hence the term Flash X-ray imaging.
The radiographic machines implemented in the EPURE Facility use two different technologies. Two of them are Linear Induction Accelerators (LIA) and the third one is a diode-equipped inductive voltage adder (IVA) generator. Each radiographic axis (from the end of the machine end to a detector) is over 80 meters in length.

Due to the facility’s geometry, when an experiment is underway, the detector for the third axis is not visible from most of the Laser Tracker measuring stations. Moreover, limited access makes it
complicated for a station to be positioned behind it. In an effort to optimize technical operations, and
with the aim to obtain a remotely operated a single Laser Tracker station, a solution needed to be found to measure the detector which is out of view.
The solution opted for consists in a fiducialized mirror device fixed on a wall ensuring a line of sight from most of the possible stations to the third axis detector. This mirror device consists in a mirror mounted onto 6 degrees of freedom positioning system and at least three SMRs. The mirror is situated in terms of the three SMR positions.

The associated measuring method (for a single target in this case) is carried out using the four steps
listed below:
- Definition of the mirror plane and its associated frame within the nominal frame;
- Measurement reading for a virtual target in the symmetry of the real target in the mirror
frame;
- Transformation from the virtual target to the real target using the symmetry’s matrix;
- Frame transformation from the mirror frame to nominal.

This method is still in development and given the results and laser beam behaviour, still requires further optical corrections.

Speaker: Etienne Pataille (CEA)

27 One Adjustment Engine, Many Applications: LGC as a Versatile Survey Toolbox at CERN

Since the mid-1980s, LGC (Logiciel Général de Compensation) has been CERN’s primary software for the least-squares adjustment of survey networks and alignment processes. Historically operated as a self-contained executable, it has evolved into an adjustment engine embedded within a diverse range of survey workflows. The evolution was driven by both operational needs and a deliberate strategy to open LGC beyond its original context. This strategy involved exposing the computation core as a reusable library, developing machine-readable outputs, documenting stable interfaces, and encouraging external applications. Documentation improvements and active community outreach have been integral to this effort. On the technical side, two developments stand out: a JSON serialisation format and an application programming interface (API), which together expose LGC as a callable library and provide structured access to its results.
This paper presents several domains in which LGC is now used programmatically: field acquisition, graphical survey environments, live monitoring systems, post-processing scripts, and simulation. All were built outside LGC’s C++ codebase. Where a given integration required additions to LGC itself, those were made generally available to all users. The JSON serialisation format has further given rise to standalone tools such as dynamic result reports and geographic visualisation interfaces. Some were contributed by people without any surveying or software development background, illustrating that neither use nor contribution requires deep knowledge of LGC’s internals. With LGC publicly available under an open-source licence since early 2026, these examples document CERN’s current practice and invite the broader community — surveyors, scientists, and developers alike – to use, adapt, and extent the LGC toolbox.

Speaker: Francis Klumb (CERN)

28 3D CALCULATIONFORTHEALIGNMENTOFTHEHL-LHCINNER TRIPLETSTRING TEST-STAND

The High-Luminosity Large Hadron Collider (HL-LHC)
project aims to significantly increase the LHC’s integrated
luminosity, thereby increasing the number of collisions and
expanding its physics reach. To achieve this objective, 68
new accelerator components will be installed along the 220
m of Long Straight Sections (LSS) located on either side of
the ATLAS and CMS experiments.
The Inner Triplet (IT) String test-stand was assembled and
operated in the SM18 facility at CERN in 2025 to validate
the performance, interfaces, and operational procedures of
the components in the HL-LHC final focusing region prior
to their installation in the accelerator tunnel. The IT String
consists of six cryo-assemblies containing 19 magnets along
with their cryogenic, powering and protection infrastructure,
corresponding to the HL-LHC elements installed closest to
the ATLAS and CMS interaction points (from Q1 to D1).
From an alignment perspective, the objective is to position
the magnetic axes of these six cryo-assemblies within
±0.1 mm (1𝜎). To achieve this requirement, the Full
Remote Alignment System (FRAS) will be deployed. FRAS
consists of a redundant network of alignment sensors that
continuously monitors the position of the components. The
components are supported by motorised jacks, enabling the
FRAS to compute and apply remote alignment corrections
in all six degrees of freedom (three translations and three
rotations) when required.
This paper presents the implementation and validation
of the FRAS on the IT String. It describes the calibration
of the alignment sensors, the magnetic fiducialisation of
the components, and the installation and measurement of
the sensor supports. The commissioning of the alignment
system is then presented, followed by the results obtained
under the three principal operating conditions of the IT
String: ambient temperature, under vacuum, and at nominal
cryogenic conditions. These results demonstrate that the
FRAS is capable of continuously monitoring the component
positions and maintaining the required alignment accuracy
throughout the full HL-LHC operating cycle.
The operational use cases of the FRAS,including pressure
tests, quench events, and controlled motion tests, are
presented in a complementary paper by V. Barbarroux
entitled ""Operational Use Cases and Performance of the Full
Remote Alignment System in the High-Luminosity Large
Hadron Collider Inner Triplet String Mock-up"".

Speaker: Vivien RUDE (CERN)

09:45 Coffee brake

Poster

29 [Title inquiry in progress]

Prototypes of storage ring magnets for the Siam Photon Source II (SPS-II), Thailand’s next-generation 3 GeV synchrotron light source, have been successfully developed. The prototype magnets achieved a pole profile accuracy within 20 µm and an assembly accuracy better than 40 µm. The original magnet alignment was performed using mechanical adjustment. Initial magnetic field characterization using a stretched-wire measurement system demonstrated a normalized multipole measurement repeatability within 1E-4. In this work, the magnetic field measurement and fiducialization procedures have been significantly improved through the commissioning of a high-precision measurement facility, enhanced temperature control, improved magnet support design, and the introduction of high-precision alignment grooves for magnet fiducialization. Magnet dimensional inspection and magnetic field measurements have been performed under these improved conditions. The measurement setup, fiducialization methodology, and alignment strategy will be presented, together with an updated evaluation of magnetic performance, fiducialization accuracy, and overall alignment precision for the SPS-II storage ring magnets.

Speaker: Sikharin Suphakul (Synchrotron Light Research Institute)

30 AI assisted closed-range photogrammetric measurement for accelerator alignment

The High-Luminosity Large Hadron Collider (HL-LHC) project introduces increased radiation levels in the Long Straight Sections (LSS),
creating a strong demand for automated measurement and remote alignment solutions.
To address this challenge, CERN has developed the Full Remote Alignment System (FRAS) for the LSS, together with Ecartometry Measurement by Automatic Photogrammetric Survey (EMAPS).
EMAPS enables the transfer of the geometric reference frame from the FRAS to the tunnel wire-based measurement system,
ensuring sufficient overlap between the two systems and maintaining alignment continuity.
This contribution investigates the application of neural networks to enhance the existing close-range photogrammetric processing pipeline used for accelerator alignment.
The work focuses on the detection and measurement of photogrammetric targets and stretched wires.
A YOLO26s object-detection model was trained on a combined dataset of synthetic and real images for photogrammetric target detection.
Target-centre localisation was achieved using a modified ElDet model trained on real images annotated with a commercial photogrammetry software package.
For stretched-wire detection, a YOLO26n-seg segmentation model was trained on real images using annotations derived from filtered outputs of the existing processing workflow.
The proposed solution was applied to wire offset measurements acquired by EMAPS during LHC technical stop periods.
Deep learning-based models demonstrated promising performance relative to conventional analytical approaches, achieving sub-20 µm precision.
In particular, the proposed method significantly improved the reliability of detecting photogrammetric targets and thin stretched wires in high-resolution images,
reducing both missed detections and false positives by approximately 80%.
These results constitute a significant step toward real-time, fully automated photogrammetric processing for accelerator alignment applications
while maintaining the required measurement precision.

Speaker: Dirk Mergelkuhl (cern)

31 ALIGNMENT NETWORK DESIGN FOR THE SIAM PHOTON SOURCE II

The Siam Photon Source II (SPS-II) is Thailand's next-generation 3 GeV synchrotron light source currently under construction, comprising a 270 MeV linear accelerator, a 3 GeV booster synchrotron, a 3 GeV storage ring, and beamline facilities. Achieving the designed electron beam emittance below 1 nm·rad requires precise component placement and long-term positional stability, making a robust alignment network essential for establishing a reliable reference frame for installation, verification, and future realignment. This paper presents the design of the SPS-II alignment network developed to support the installation and maintenance of the accelerator complex. The proposed system comprises a three-level hierarchical reference network: the Ground Control Network, the Primary Network, and the Alignment Network, established using floor and wall monuments distributed throughout the accelerator tunnels and experimental areas to satisfy the required positioning accuracy of ± 0.1 mm. The network geometry was designed to provide sufficient redundancy, visibility, and measurement reliability. A Laser Tracker system is used as the primary metrology instrument for three-dimensional coordinate measurements, and the network is adjusted using the Unified Spatial Metrology Network (USMN) algorithm in Spatial Analyzer (SA) software to establish a consistent and reliable coordinate system. The proposed network supports the complete installation process, including pedestal placement, girder–magnet assembly installation, alignment, and periodic verification. It also serves as a reference frame for integrating survey data throughout installation, commissioning, and future maintenance, supporting the required accuracy and long-term operational stability.

Speaker: Jullada Saetiaw (Synchrotron Light Research Institute (Public Organization),Thailand)

32 Combination of Leveling, Wire Offset, and Laser Tracker Measurements in a 3 km LHC Arc: Key Findings and Future Strategies

During the Long Shutdown 3 (LS3, from July 2026 to 2030), CERN surveyors will measure and re-align a large fraction of the 60 km accelerator beamline, requiring optimized survey procedures to ensure efficiency while maintaining accuracy and quality levels.
In preparation, CERN ‘s Geodetic Metrology group surveyed a 2.8 km Large Hadron Collider (LHC) arc during the 2024–2025 Year-End Technical Stop using standard measurement techniques, including 3D laser tracking, precision direct levelling, and ecartometry, together with wire measurements using the CERN photogrammetric train under final development.
This paper presents the measurement campaign and data acquisition for the survey of the LHC arc. The precision of each technique is evaluated and compared, and the datasets are combined using a global least-square adjustment to assess the compatibility of the different measurements. The study identifies opportunities to improve workflows and update future survey strategies particularly through increased automation and emerging measurement technologies.

Speaker: Jean-Frédéric Fuchs (CERN)

33 Cryostat Motion of the SuperKEKB Final Focus Magnets During Earthquakes

The final-focus superconducting magnet system (QCS) in the SuperKEKB interaction region is housed in a large cryostat whose position is continuously monitored by gap sensors. This monitoring system has recorded the cryostat response to numerous earthquakes with a wide range of magnitudes and epicentral distances, providing a unique opportunity to study the mechanical behavior of a large superconducting magnet system under seismic excitation.
In this paper, we analyze the cryostat motion during several representative earthquakes, from small local events to stronger regional earthquakes. Transient displacements, recovery characteristics, and residual position shifts are correlated with earthquake magnitude, epicentral distance, and ground motion measured at KEK. The results show that the cryostat responds predominantly elastically, returning close to its original position after most earthquakes, while stronger events can produce measurable residual displacements and influence the long-term positional drift. These observations provide valuable insight into the mechanical stability of the interaction region and contribute to the design, alignment, and long-term operation of superconducting magnet systems for future collider facilities.

Speaker: Mika Masuzawa (KEK)

34 EUWAA Interlaboratory Comparison: Overview, Current Status and Initial Findings

Future accelerators and fourth-generation storage-ring light sources impose increasingly stringent requirements for component positioning, stability, alignment, and uncertainty control.
Meeting these demands requires not only accurate instrumentation but also reliable and consistent measurement practices throughout the alignment chain.
To address these challenges collectively, an interlaboratory comparison (ILC) campaign was proposed at the 2025 European Workshop on Accelerator Alignment (EUWAA).
The campaign subsequently brought together eleven European laboratories to measure a common accelerator reference object.

This contribution provides an overview of the ILC, covering its objectives, organisation, measurand definition, measurement environment, and metrology systems employed by the participating laboratories.
It also presents the comparison methodology together with the reference dataset obtained from coordinate measuring machine (CMM) measurements.
As an example of the initial findings, the influence of geometric-feature construction on the realisation of the coordinate frame of the reference object is examined.
In particular, the analysis considers how point sampling, feature-fitting methods, underlying geometry quality, and measurement uncertainty affect the realised reference frame for coordinate comparison.
The study promotes knowledge sharing and greater consistency in terminology, measurement practices, and uncertainty reporting. Its findings will inform a best-practice guide for accelerator alignment, improve future interlaboratory comparisons, and strengthen confidence in high-precision alignment.

Speaker: Hélène Mainaud Durand (CERN)

35 Evaluation of GNSS Positioning Accuracy Using RTKLIB at the KEK Tsukuba Campus

At the KEK Tsukuba Campus, seven GS10 GNSS receivers have been installed at the delivery building and the auxiliary utility building, which are located along the SuperKEKB ring road, to collect positioning observation data continuously since 2012.
Previously, specialised analysis software was used to calculate receiver positions from this data; however, due to license expiration, a large volume of observation data had accumulated without being processed into positional information. To address this, the open-source GNSS analysis software RTKLIB was employed to compute positions from the unprocessed data and convert it into an analysable format.
This report presents an evaluation of the accuracy and validity of positional data obtained through data conversion and positioning analysis using RTKLIB, based on observations collected by the seven GNSS receivers installed at the facility.

Speaker: Shu NAKAMURA (KEK)

36 Evolution of the CLS storage ring: Comparing historical survey data with beam based circumference measurements

The Canadian Light Source has been operating its 2.9GeV storage ring since 2005. Beam-based metrics, primarily radio frequency tuning and orbit correction, provide a continuous, indirect measurement of the beam’s length and indicate a decrease in the storage ring beam circumference over time. The 171m storage ring is equipped with a 155-point wall and floor network to allow location of laser trackers for precision alignment and has been regularly surveyed to update the reference network. Recent and historical survey data is compared with beam metrics and we highlight key sources of discrepancy, including thermal variations, mechanical settling, and systematic survey uncertainties.

Speaker: Joshua Erikson (Canadian Light Source)

37 First Application of the LGC2 Software to SuperKEKB Main-Ring Survey Data: A Section-to-Section Consistency Check

Alignment of SuperKEKB, whose nano-beam optics demand sub-millimetre magnet positioning, relies on laser-tracker surveys that have proven highly accurate — the surveyed ring circumference was confirmed directly by the beam during commissioning. The survey is, however, performed intermittently, while the tunnel and the interaction region move on daily, seasonal and long-term scales, and the continuous monitoring (hydrostatic levelling, gap sensors and a GPS network) is handled by separate systems rather than in a single adjustment. This motivates evaluating a rigorous, unified three-dimensional framework. We report the first application of LGC2 (Logiciel Général de Compensation), the least-squares network-adjustment software developed and maintained at CERN, to SuperKEKB main-ring survey data. For the present analysis, the ring is divided into nine sections following the existing naming convention — the Tsukuba, Oho, Fuji and Nikko regions, each split into left and right halves, plus the interaction region; these boundaries are introduced solely for the analysis and do not correspond to any change in the survey. The full data set is brought into a common machine frame with LGC2. The reconstruction is validated by comparing reference monuments measured at each section boundary. The good agreement between adjacent sections confirms the consistency of the reconstructed network and demonstrates that LGC2 is a suitable platform for integrating periodic surveys with continuous HLS and future frequency-scanning interferometry (FSI) monitoring at SuperKEKB.

Speaker: Tuyet Kim Tran (KEK)

38 Large-scale Precision Engineering Measurement in Complex Environments: From Uncertainty Modeling to Deformation Compensation

This study addresses the core problem of how to achieve high-precision measurement consistency in large-scale engineering metrology under high-noise and multi-disturbance environments.

First, for multi-station laser tracking systems, a GUM-based uncertainty propagation model is established, revealing the evolution laws of measurement accuracy and enabling accuracy optimization.

Second, to address the issues of low efficiency and poor adaptability in node layout for reference measurement, a node weight evaluation and optimization method based on network analysis is proposed. This method constructs node geometric relationships using 3D Delaunay tetrahedral networks and computes the total weight of each node based on barycentric coordinate invariance to guide node selection and network simplification. It exhibits strong robustness against variations in survey stations, measurement errors, and scale factors. In the application on the Hefei Advanced Light Facility platform, the number of nodes is reduced by 31%, while the calibration accuracy remains at 9.8 micrometers.

Finally, to address the coupling between registration and deformation in structural deformation measurement, an error propagation model for point cloud registration residuals is established, revealing the mechanisms by which deformation and noise affect rotation, translation, and residual distribution. A linear deformation inversion method is then proposed. Compared with conventional methods, the deformation estimation accuracy is improved by 46% to 97%, and the method remains stable across different deformation fields. Furthermore, the coordinate transformation accuracy is enhanced through corresponding compensation methods.

Speaker: Ting Ding (University of Science and Technology of China)

39 Laser Tracker-Based Geodetic Alignment Assessment and Realignment of Operational Beamlines at RAON

The low-energy accelerator and experimental facilities at RAON are currently in operation following the completion of installation and initial alignment. Maintaining stable beam delivery requires periodic verification of beamline alignment accuracy relative to the facility's survey control network. This poster presents a geodetic alignment assessment of major RAON experimental beamlines, including the Cyclotron, ISOL, and CLaSsy sections, using laser tracker coordinate measurements. By comparing measured component positions against their nominal reference coordinates, alignment deviations were quantified and sections requiring correction were identified, followed by precision realignment of the affected components. A comparative analysis of beam transmission efficiency before and after realignment confirmed that improved geometric consistency with the survey control network substantially enhances beam transport performance.

Speaker: Jaehyun Cho (Institute for Rare Isotope Science, Institute for Basic Science)

40 Latest advances in alignment for the SOLEIL II project thanks to a metrological approach

The SOLEIL II machine upgrade requires unprecedented alignment tolerances, down to +/- 20 µm for the most critical magnets of the storage ring. This specification demands full control of measurement uncertainties throughout the various steps of the alignment process. One of these steps is the survey, which aims to determine the position of the machine's components and thereby reconstruct its entire geometry. This is a critical step, as it is the final one that determines whether the components comply with the specified tolerances. If this step introduces excessive uncertainty in the position of the components, it can lead to bad decisions, such as validating a non-conforming alignment or, conversely, rejecting an alignment that is in fact correct. A measurement campaign was therefore conducted, in which seven surveys of the storage ring were performed in succession over a period of less than three weeks. Those surveys were intended to quantify the experimental uncertainty associated with this step and to compare it against in-house simulations. The results show that the dispersion of the machine's global shape does not exceed 30 µm in any of the three directions (k = 1), while the circumference of the machine is repeatable to better than 300 µm. Locally, at the level of an individual girder, the dispersion of the magnets does not exceed 2 µm in the three directions (k = 1).

Speaker: Youen Delalande (Synchrotron SOLEIL)

41 Magnetic Center Fiducialization Method Based on Single Stretched Wire and Precision Surface Plate

To satisfy the strict alignment tolerances of accelerator magnets for the Hefei Advanced Light Facility (HALF), it is essential to accurately fiducialize their magnetic centers. This paper describes a high-precision and efficient fiducialization method developed for HALF, based on a single stretched wire bench combined with a precision surface plate. The system enables the relative coordinates between the magnetic center and the magnet fiducials to be determined with high accuracy. Experimental results demonstrate an overall fiducialization uncertainty of better than 10 µm, fulfilling the exacting requirements for magnetic center referencing in the HALF project.

Speaker: Baohou Liu (University of Science and Technology of China)

42 Mitigating Atmospheric Angular Refraction using Dual-Wavelength Pseudo-Nondiffracting Beams: Addressing the Engineering Challenges

Precise alignment of particle accelerator components requires stable, straight-line references over distances of several hundred meters. Pseudo-nondiffracting laser beams are promising candidates for optical-based, straight-line alignment reference systems because they maintain a narrow, high-intensity inner core over extended propagation distances. However, atmospheric fluctuations in the refractive index deflect the beam from its ideal straight trajectory, which limits the achievable accuracy. These errors are traditionally avoided using vacuum infrastructure, which adds substantial complexity to the alignment system. To eliminate the need for complex vacuum infrastructure, this work investigates a system based on dual-wavelength pseudo-nondiffracting laser beams to mitigate the angular errors caused by atmospheric refraction. We present initial experimental results obtained by directly comparing beam propagation inside a 140 m enclosed pipe under both vacuum and atmospheric conditions. We discuss the key experimental and practical challenges of this approach, highlight current system limitations, and provide a basis for future optimization toward robust operation in ambient air.

Speaker: Dirk Mergelkuhl (CERN)

43 Modernizing the laser tracker network adjustment workflow - an integrated software suite for accelerator alignment

This paper presents an integrated three-component software suite developed at SLAC National Accelerator Laboratory for high-precision network measurement and adjustment in accelerator alignment. The system consists of AlignTrackPro for automated laser tracker data acquisition, a modernized version of the legacy LEGO adjustment engine, and LEGO Pipeline, which provides visualization through interactive 2D network maps and error ellipses. The suite addresses a critical limitation of commercial laser tracker software: the inability to perform gravity-compensated network adjustments. In large networks, neglecting gravity-field effects on measured height differences can introduce errors of approximately 0.2 mm over 50 m baselines, which is significant relative to the sub-millimeter tolerances required in accelerator facilities. The integrated system is now in production use for SLAC facility networks.

Speaker: Witold Niewiem (SLAC, Stanford)

44 OPERATIONALUSECASESANDPERFORMANCEOFTHEFULL REMOTEALIGNMENTSYSTEM INHL-LHCINNERTRIPLETSTRING TEST-STAND

The High Luminosity upgrade of the Large Hadron Col
lider (HL-LHC) project aims to increase the integrated lu
minosity by an order of magnitude over the LHC’s original
design specifications. To achieve this objective, strict control
of the alignment of the new Inner Triplet superconducting
magnets installed around the ATLAS and CMS interaction
points is essential. This is provided by the Full Remote
Alignment System (FRAS), a three-dimensional alignment
system providing micrometric measurements at one second
acquisition rate, designed specifically for the HL-LHC pro
ject.
In preparation for the required performance of the HL
LHC, the Inner Triplet String (IT String) Test test-stand has
been implemented. This test facility replicates the new in
ner triplet region of the HL-LHC, offering the opportunity
to test the combined performance of its critical compon
ents and to gain first operational experience. As part of
this, FRAS has been deployed and commissioned on the
IT String to position the six main cryoassemblies within a
±0.1 mm (1σ) cylindrical tolerance zone relative to their
nominal positions. This paper presents the operational ex
perience and performance of FRAS on the IT String, not
only in alignment mode but across different use cases such
as vacuum pumping, cooldown and powering tests during
the main hardware commissioning phase.

Speaker: Vivien RUDE (CERN)

45 Optimal Re-alignment Strategy for MAX IV Upgrade

In preparation for the upcoming upgrade of the MAX IV Laboratory 3 GeV storage ring, tighter alignment tolerances are required for the magnet-cells to achieve the lower target beam emittance. We evaluate alignment strategies that ensure both local cell-to-cell smoothness and global alignment relative to the control network. Three candidate strategies are designed and evaluated using tailored survey measurements conducted on a single achromat. In addition to the survey results for each strategy, practical considerations such as achromat symmetry and alignment time efficiency are taken into account to determine the optimal strategy to meet the upgrade specifications.

Speaker: Behrouz Afzali Far (MAX IV Laboratory)

46 Optimal Sensor and Target Placement via Experimental Design

In high-precision metrology and geodetic network design, the achievable accuracy depends not only on the instruments
but also on the measurement geometry — in particular, on where component fiducials and instrument stations are placed.
These positions are traditionally chosen from experience and have to be fixed before any measurement is taken;
selecting them systematically therefore offers a valuable lever for reducing the measurement uncertainty.
This contribution presents a framework, built on CERN's open-source geodetic least-squares adjustment platform LGC2 (Logiciel Général de Compensation),
that applies Optimum Experimental Design (OED) to this problem.
The estimation variables are split into optimisation variables,
which define the objective function — D-optimality (error-ellipsoid volume) or A-optimality (average parameter variance) —
and bounded design variables that the optimiser searches over.
The framework draws on LGC2's modelling capabilities, particularly its local coordinate systems, called frames, parametrized by estimable parameters.
We illustrate it on a girder fiducialisation scenario, optimising the placement of fiducials on the magnet components and the positioning of the stations
to determine the components' relative position and orientation with minimised uncertainty.
The result is a systematic way to reduce the expected alignment uncertainty at the design stage, before any hardware is installed.

Speaker: Dirk Mergelkuhl (CERN)

47 Photogrammetric Auxiliary Measurement for Evaluating Accelerator Magnet Opening and Reassembly

Opening and reassembly are required in some accelerator magnet units during vacuum chamber installation, maintenance, or internal component adjustment. The reassembly state is commonly evaluated using high-precision top targets measured by laser tracker systems. This procedure provides a reliable engineering criterion for the recovery of the top-target region, but the targets are mainly distributed on the upper part of the magnet. Therefore, the relative geometric state between the upper and lower magnet halves, especially in side regions away from the top targets, cannot be directly described by the top-target residuals alone.
This study investigates a photogrammetric auxiliary measurement method for evaluating accelerator magnet opening and reassembly. Side supplemental targets are introduced around the magnet unit to provide additional geometric information beyond the top-target region, while the top targets are still used as common points for coordinate transformation and existing acceptance evaluation. A preliminary simulation is first conducted to analyze the limitation of using only top-target constraints. The results indicate that samples satisfying the top-target RMSE criterion may still show measurable geometric changes in side regions.
A photogrammetric error propagation model is then developed based on the collinearity equations, self-calibrating bundle adjustment, full point-coordinate covariance, and coordinate transformation through common top targets. Monte Carlo simulations are performed with fixed magnet geometry, simulated camera stations, image measurement noise, and interior-orientation/distortion parameter perturbations. The internal precision predicted by the full-covariance model is compared with external error statistics obtained from known simulation truth. The results are analyzed with respect to side-point height, extrapolation degree, magnet position, and coordinate constraint mode.
The proposed method provides a low-intrusion auxiliary measurement strategy for magnet opening and reassembly evaluation. It extends the available geometric information to side regions and supports a more comprehensive assessment of the reassembly state of accelerator magnet units.

Speaker: Xiaolong Wang (University of Science and Technology of China)

48 Progress on the construction of FAIR – network densification, blue-lining and installation work

Following previous IWAA presentations regarding progress on FAIR, this report outlines the status for 2025 and 2026. The campaigns over the last two years have included network measurements and their analysis, blue-lining in various machine areas, selective alignments to more complex structures in extremely hard-to-reach areas such as the Super-FRS, and the survey of parts of the machine that have already been erected. The complex structure and layout of the FAIR buildings, as well as the ongoing construction work during the installation of the machine, are reflected in the repeated network measurements and complex network analyses, which reveal ongoing settlement and other movements. This led to adjustments to the IOL (ion-optical layout) and had a direct impact on individual machine sections. Major challenges for the future include the transfer of various machine strings integrated into a large frame, the installation of the magnets on the 15° and 7.5° high energy beam transport ramps, and the installation of various sections of the Super-FRS, particularly using the FiBS system developed by the Survey & Alignment team.

Keywords: GSI, FAIR, network measurement und evaluation, blue-lining, settlements, IOL adaptations, installation tasks, magnet alignments, FiBS

Speaker: Torsten Miertsch (GSI Helmholtzzentrum Darmstadt)

49 SLAC Status Report 2026

This poster presents the survey and alignment activities at the SLAC National Accelerator Laboratory since 2024. The major projects during the last two years have been the LCLSII-HE (Linac Coherent Light Source) project.
The LCLSII-HE project includes an additional 20 Cryomodule and an upgraded Soft X-Ray Undulator line. We re-mapped the existing monument network and monitored the effect of new tunnel drilling at the LCLSII Gun area.
Smaller projects include alignment support for the SPEAR3 synchrotron ring, setup of experimental hutches for both LCLS and SSRL and our GIS services.

Speaker: Georg Gassner (SLAC National Accelerator Laboratory)

50 Spatial Integration of 3D Scan Data for a New Beamline at MAX IV

This project presents the integration of high-precision 3D scanning data
into the MAX IV spatial metrological network during the construction
of the new TomoWISE beamline.
By registering point cloud data within the facility global coordinate system,
the scanned data can be accurately overlaid with the beamline CAD model,
providing a reliable digital representation of the installation area.
This procedure supports design verification, enabling the early detection
of potential collisions, geometric discrepancies, and installation conflicts
before the installation phase. Identifying these issues in advance allows
for corrective action, reducing risks, minimizing costly rework,
and improving installation planning and execution.

Speaker: Albert Torrente (MAX IV Laboratory)

51 Survey Control Network Maintenance and Coordinate Update Strategy at RAON Heavy-Ion Accelerator

RAON requires a stable geodetic reference framework to support the precision alignment of accelerator beamlines and experimental devices. This work presents the maintenance of the RAON survey control network, including periodic measurements to evaluate floor monument stability and update alignment reference coordinates. As measurements must be completed within limited shutdown periods, recent efforts have focused on streamlining the workflow, optimizing instrument deployment, and improving coordinate update procedures without compromising network reliability, integrating digital leveling for vertical coordinates with laser tracker measurements for horizontal coordinates. Furthermore, within the Unified Spatial Metrology Network (USMN) analysis, an extended overlapping stationing strategy is proposed, broadening per-station coverage to maximize the number of monuments jointly observed by adjacent stations. This increased geometric redundancy is anticipated to strengthen the network's global rigidity during bundle adjustment and is expected to contribute to more reliable coordinate updates.

Speaker: Jongdae Joo (Institute for Rare Isotope Science, Institute for Basic Science)

IWAA2026_WEP04_Poster_Joo.pdf

IWAA2026_WEP04_Proceedings_Joo.pdf

52 Towards a quasi-Limitless beam: Using convolution integrals to evaluate response of Structured Laser Beams to quadrant detectors

Structured Laser Beams (SLBs) offer a viable alternative in generating straight reference lines for long-distance alignment systems in particle accelerators. While prior research has utilized quadrant detectors to demonstrate displacement sensitivity for various beam types, this study extends that evaluation to an optical system experimentally verified to diverge by only 0.1 mrad at a propagation distance of 900 m. We calculated the irradiance of the beam produced by the optical system from a set of transmittance functions. We then evaluated the response of the produced beam to the quadrant detector using convolution integrals. Key insights from this study are vital for possibly scaling quadrant detectors to effectively evaluate beam displacement at the extreme propagation distances required by future colliders, such as the Future Circular Collider (FCC) and the Compact Linear Collider (CLIC).

Keywords: accelerator alignment, convolution integrals, quadrant detectors, structured laser beams

Speaker: Thoreenz Soldevilla (National Institute of Physics, University of the Philippines Diliman)

11:25 Lunch, IOC committee @ 301

Tools & monitoring II

Convener: Xiaoye He (NSRL)

53 A Modular and Sustainable Software Ecosystem for High-Precision Survey and Alignment at CERN

Maintaining high-precision survey and alignment software at accelerator facilities is challenging due to small teams, regular staff turnover, and incoming engineers with limited domain or programming experience. At CERN, years of fragmented development had produced a heterogeneous survey software landscape, with several applications abandoned after their original developers left. The creation of a dedicated Survey Software section in 2019 established long-term ownership, combining experienced surveying engineers with IT graduates on two-to-three-year rotations.
The team modernised and rationalised its software ecosystem by retiring obsolete applications, consolidating functionality around shared and validated computational libraries, and replacing legacy programming languages with a reduced, maintainable technology stack centred on C++, Python, and modern frameworks. Moreover, standardised data interfaces ensure interoperability between tools, and with CERN’s survey database through a dedicated API. Quality assurance practices—including version control, continuous integration, testing, and documentation—were introduced to improve reliability, reproducibility, and user confidence. SurveyPad, a unified delivery platform, provides access to desktop applications, scripts, and web services built on this common foundation.
The benefits have been substantial. The shared architecture has lowered the barrier to contribution, enabling students and non-specialist engineers to develop and deploy more than ten production tools, including applications for publishing survey results to CERN’s Geographic Information System (GIS) and automated measurement quality control. Open workflows, comprehensive documentation, and structured onboarding have strengthened transparency, facilitated knowledge transfer, and improved long-term maintainability.
Our experience shows that sustainable survey software depends not only on technical coherence - a reduced stack, standardised interfaces, shared libraries - but also on organisational discipline: clear ownership, documentation, and knowledge.

Speaker: Francis Klumb (CERN)

54 Hydrostatic Leveling Systems at the Advanced Photon Source

Achieving and maintaining the alignment tolerances required for the upgraded Advanced Photon Source (APS) is a significant challenge, particularly in the presence of ground motion and settlement. To monitor vertical displacement and transfer elevation over long distances, two hydrostatic leveling systems (HLSs) are being deployed at APS.
The storage ring system consists of 105 HLS sensors designed to characterize both relative floor motion at each insertion device front end and global floor motion throughout the storage ring tunnel. A second system, comprising 2 HLS sensors, is being implemented to transfer X-ray source-point elevations to the Long Beamline Building (LBB), approximately 200 meters away.
This presentation will describe the design and intended application of both systems and summarize the current status of their deployment. As neither system is fully operational, we welcome discussion and feedback from attendees with experience in commissioning and using similar systems.

Speaker: Nicholas Bechtold (Argonne National Laboratory)

55 FCC-ee MDI alignment monitoring mock up update

The Future Circular Collider (FCC) is a proposed next-generation collider at CERN, intended to succeed the High-Luminosity upgrade of the LHC. A key element of this project is the Machine Detector Interface (MDI), which forms the link between the accelerator and the detector and fine-tunes the beams immediately before collision by optimizing beam parameters to maximize luminosity. To achieve the extremely small β* values required for the FCC-ee luminosity goals, the final-focus quadrupoles must be positioned only about 2.4 m from the interaction point, placing them inside the detector volume. Achieving the target luminosity therefore requires the position of these quadrupoles to be measured and continuously monitored with approximately 30 µm precision. The lack of suitable metrological solutions, due to extremely constraining conditions, has motivated the development of a novel application of Frequency Scanning Interferometry (FSI), named IMD-FSI (In-line, Multiplexed and Distributed FSI). IMD-FSI is intended to be deployed as a deformation-monitoring system capable of reconstructing the three-dimensional shape of the monitored structure. This paper reviews the development of IMD-FSI, from the underlying deformation models to the successive prototype generations developed so far, including a half-scale mock-up currently under test, and discusses the remaining validation steps required for deployment in the FCC-ee MDI.

Speaker: Léonard WATRELOT (CERN)

56 OPERATIONALUSECASESANDPERFORMANCEOFTHEFULL REMOTEALIGNMENTSYSTEM INHL-LHCINNERTRIPLETSTRING TEST-STAND

The High Luminosity upgrade of the Large Hadron Col
lider (HL-LHC) project aims to increase the integrated lu
minosity by an order of magnitude over the LHC’s original
design specifications. To achieve this objective, strict control
of the alignment of the new Inner Triplet superconducting
magnets installed around the ATLAS and CMS interaction
points is essential. This is provided by the Full Remote
Alignment System (FRAS), a three-dimensional alignment
system providing micrometric measurements at one second
acquisition rate, designed specifically for the HL-LHC pro
ject.
In preparation for the required performance of the HL
LHC, the Inner Triplet String (IT String) Test test-stand has
been implemented. This test facility replicates the new in
ner triplet region of the HL-LHC, offering the opportunity
to test the combined performance of its critical compon
ents and to gain first operational experience. As part of
this, FRAS has been deployed and commissioned on the
IT String to position the six main cryoassemblies within a
±0.1 mm (1σ) cylindrical tolerance zone relative to their
nominal positions. This paper presents the operational ex
perience and performance of FRAS on the IT String, not
only in alignment mode but across different use cases such
as vacuum pumping, cooldown and powering tests during
the main hardware commissioning phase.

Speaker: Vivien RUDE (CERN)

Poster

Instrumentation II

Convener: Francis Klumb (CERN)

57 New developments in Leica Absolute Tracker ATS800 point cloud handling

Since the launch of the Leica Absolute Tracker ATS800 mid of 2025 we have gained a lot of experience regarding customer applications through several demonstrations, benchmarks and test campaigns. These experiences have led to significant improvements in the handling of point clouds produced by the ATS800. The presentation will give an overview about the improvements prepared for an upcoming release.

Speaker: Matthias Saure (Leica Geosystems AG)

Survey & alignment VI

Convener: Francis Klumb (CERN)

58 Survey and Alignment of the Fermilab Mu2e Detector Solenoids

The Mu2e experiment at Fermilab will be 10,000 times more sensitive than previous experiments looking for muon-to-electron conversion. This precise and complex apparatus will be able to produce 200 million billion muons per year. The Mu2e experiment layout in the MC-2 Building consists of three superconducting solenoids magnets: Production Solenoid (PS), Transport Solenoid (TS), and Detector Solenoid (DS). These solenoids will produce and transport the low-energy intense muon beam and then detect the conversion to electrons from stopped muons. This paper summarizes the survey and alignment of the Mu2e experiment solenoids using the Laser Tracker.

Speaker: Babatunde O’Sheg Oshinowo (Fermi National Accelerator Laboratory)

59 Forty Years of Survey and Alignment at Duke University Free Electron Laser Laboratory

Duke University Free Electron Laser Laboratory originally started at Stanford University in the Mid 1980's. The entire facility moved to Duke University in the late 1988.

In this presentation, methodology and technic of the survey and alignment of the beamlines in every step from start to present time will be discussed in detail.

Speaker: Mark Emamian (Duke University)

60 After the Upgrade: Survey & Alignment Activities at the Advanced Photon Source

The Advanced Photon Source (APS) Upgrade project received its final approval in January 2026, having delivered on its full scope on budget and ahead of schedule. The upgraded facility is now fully operational, and user experiments are underway. During the upgrade project the APS Survey and Alignment team also underwent a major transformation. Along with bringing on new technicians and engineers, we implemented a paradigm shift in our approach to accelerator alignment. This talk will present an overview of the status of survey and alignment at the APS and our plans for future improvement.

Speaker: William Jansma (Argonne National Laboratory)

Friday 9 October

Survey concepts & strategy III

Convener: Georg Gassner (SLAC National Accelerator Laboratory)

61 Latest advances in alignment for the SOLEIL II project thanks to a metrological approach

The SOLEIL II machine upgrade requires unprecedented alignment tolerances, down to +/- 20 µm for the most critical magnets of the storage ring. This specification demands full control of measurement uncertainties during the different steps of the alignment process. For this specific purpose, a rigorous metrological approach has been developed and applied throughout the entire alignment strategy. This approach aims to characterise, optimise and monitor the performance of each measurement step. Such characterisation consisted in a measurement campaign in which seven surveys of the storage ring were carried out in succession over a period of less than three weeks. Those surveys were intended to quantify the experimental uncertainty associated with this step and to compare it against in-house simulations. The results show that the dispersion of the machine shape does not exceed 30 µm in any of the three directions (k=1). Moreover, the circumference of the machine is repeatable to better than 200 µm.

The proposed talk will introduce the metrological approach adopted at SOLEIL and will present the main results obtained. First, excellent control of the laser tracker's measurement uncertainty was achieved, better than 4 µm on the coordinates of a point at 2 m distance (k=1), through a range of characterisations and optimisations. Second, the multi-survey campaign demonstrated that a single survey provides excellent control of both the storage ring's circumference — compared against the RF frequency reference — and its global and local shape. Finally, the way alignment tolerances are simulated by physicists has significantly evolved, bringing them closer to the reality of the alignment process.

Speaker: Youen Delalande (Synchrotron SOLEIL)

62 Scorpius Unified Spatial Metrology Network (USMN) Optimization, Predictive Network Design, and Empirical Results

In 2021, a design was proposed as the foundational
metrology network for the forthcoming Scorpius linear
particle accelerator. By contrasting simulated network conditions
with empirical findings, this paper highlights the
benefits of predictive network design for novel or unfamiliar
operational environments. Located at the Nevada National
Security Site’s (NNSS) Primary Underground Laboratory
for Subcritical Experimentation (PULSE), the
Scorpius metrology network spans a total area of approximately
838 m2 and is 140 m at its maximum length. Due to
unique environmental constraints, the design of the network
was limited to two primary planes offset by 0.61 m.
To ensure compliance with project requirements, the design
of the network was completed using an iterative process
in which a Unified Spatial Metrology Network
(USMN) was modeled in SpatialAnalyzer®. The overall
goal of the simulation, in conjunction with other design parameters,
is to determine the total estimated error for placement
of the Scorpius beamline. The chosen figure of merit
(FOM), root mean square (RMS) of point error, was minimized
across several dozen permutations and provided an
associated overall point error of 25 μm. A parametric simulation
study was conducted on the monument network design
parameters, such as spacing, grid geometry, and
tracker placement, as means to optimize the monument network.
The simulated FOM was combined with several
other design inputs to calculate the estimated total error for
final placement of the Scorpius beamline. In April of 2026,
metrologists completed network measurements and analysis
of the as-built Scorpius metrology network. Based on
data collected and lessons learned from other parts of the
Scorpius project, additional monument nests were added to
the as-built design. Original estimates, derived from the institutional
knowledge of Subject Matter Experts (SMEs)
consulting on the project, projected the as-built configuration
would provide a FOM with a magnitude double that of
the simulation. The final as-built USMN analysis provided
a FOM of 17.8 μm, much smaller than expected given the
as-built real-world conditions.
*Work supported by the U.S. Department of Energy National
Nuclear Security Administration (NNSA) Office of
Defense Programs under the Advanced Sources and Detectors
(ASD) project. Los Alamos National Laboratory is operated
by Triad National Security, LLC for the National
Nuclear Security Administration of the U.S. Department of
Energy under Contract No. 89233218CNA000001.
†dea@lanl.gov
Keywords: Unified Spatial Metrology Network (USMN),
Metrology, SpatialAnalyzer®, Root Mean Squared (RMS),
Nevada National Security Site (NNSS), Primary Underground
Laboratory for Subcritical Experimentation
(PULSE), Scorpius, Figure of Merit (FOM), Optimization,
Predictive Network Design,

Speaker: Daniel E. Archuleta (Los Alamos National Laboratory)

FRO02_Daniel_E_Archuleta.pdf

09:20 Coffee brake

Instrumentation III

Convener: Helene Mainaud Durand (CERN)

63 Installation and Alignment of the Linear Injector for Hefei Advanced Light Facility (HALF) and Deformation Monitoring

The operational stability of large-scale particle accelerators—such as synchrotron light sources, and free-electron lasers—is fundamentally dependent on the sub-micron structural integrity and thermal stability of their components. However, the sprawling physical scale and extreme environments (high radiation, cryogenic temperatures, and electromagnetic interference) pose significant challenges for traditional monitoring technologies. This paper proposes a novel, comprehensive "Global-to-Local" health monitoring architecture designed to ensure the long-term alignment and structural reliability of accelerator facilities.

Speaker: Wei Wang (University of Science and Technology of China)

64 Evaluation and Deployment of a Robotic Tracing Workflow for HL-LHC Beamline and Services at CERN

The 2028 installation phase of CERN's High-Luminosity Large Hadron Collider (HL-LHC) project will require precise positioning of hundreds of accelerator components and accompanying infrastructure within extremely tight integration tolerances. Floor tracing of reference marks is an important prerequisite for installation activities, providing the geometric references used by installation teams before final alignment operations. Traditionally, these stake-out operations are performed manually by surveyors using total station, a reliable but time-consuming and physically demanding process over long distances.
To address these challenges, CERN's Geodetic Metrology group has evaluated the HP SitePrint robotic tracing system as a potential solution for large-scale floor marking during Long Shutdown 3 (LS3). Beyond the assessment of the robot itself, the project focused on the development of a new survey workflow enabling its integration into CERN's alignment and installation processes.
A comprehensive experimental campaign was conducted in accelerator tunnel conditions to evaluate the robot's performance in terms of accuracy and repeatability but also to further study its operational robustness and compatibility with current CERN operations.
A new workflow was also developed to streamline data creation and communication between surveyors, equipment owners and databases. This involved adapting and enhancing tools to handle the rising number of tracing requests in the denser installation environment.
This paper will introduce the resulting workflow establishing a straightforward methodology for the automated tracing of accelerator components and services, as well as the strategy implemented for future tracing activities during the HL-LHC tracing campaign scheduled for 2027.

Speaker: Jean-Frédéric Fuchs (CERN)

65 Evaluation of Orientation To Gravity (OTG) procedure of AT500 Leica laser tracker and comparative assessment with AT403 Leica laser tracker

This study compares the vertical measurement accuracy of two Leica laser trackers: the AT500, which uses Orientation to Gravity (OTG), and the AT403, which provides continuous dual-axis compensation. Laboratory tests using a network of ten stations with a maximum baseline of 18 m showed that OTG correction produces vertical angle uncertainties of up to 0.4 arcsec, making single-instrument vertical positioning 25–50% less precise than continuous compensation. Long-term monitoring over 10.5 hours revealed high-frequency fluctuations of 0.8 arcsec peak-to-peak for the AT500. Network simulations based on a 560 m particle accelerator alignment showed that combining OTG measurements with traditional leveling produces vertical positioning errors about 30% larger than continuously compensated systems with leveling, while omitting gravity correction entirely increases errors by 135%. OTG procedures therefore provide acceptable vertical accuracy for large-scale applications when combined with leveling, but measurement networks must account for the resulting uneven precision distribution, especially for points far from leveling lines. The dual-OTG protocol, which brackets measurements with initial and final gravity determinations, reduces the vertical angle uncertainty from 0.4 arcsec to 0.2 arcsec (a 50% reduction) compared to single-OTG measurement.

Speaker: Witold Niewiem (SLAC, Stanford)

66 Validation of the Ecartometry Measurement by Automatic Photogrammetric Survey (EMAPS) prototype

This paper presents the validation procedure and performance assessment of a new prototype named Ecartometry Measurement by Automatic Photogrammetric Survey (EMAPS).
Developed for the High-Luminosity LHC (HL-LHC) project, the system measures the horizontal offset between a stretched wire and a target,
contributing to the development of high-accuracy, automated and remote alignment measurements.
Photogrammetric wire offset and target measurements enable the precise transfer of planimetric geometry over long distances while embracing the perspective of automation.
In this context, the development of EMAPS has enabled reliable measurements that could be integrated into automated survey workflows.
Several measurement campaigns were conducted to evaluate the system’s performance and compare it with established instruments and methods,
including manual wire-offset measurements, the Full Remote Alignment System (FRAS), and the Leica ATS800.
The results demonstrate a measurement precision of approximately 12 μm (1 𝜎), an accuracy of about 20 μm (1 𝜎) and the measurement process
is up to three times faster than conventional manual wire-offset techniques, prior to automated displacement.
These comparisons confirm the capability of EMAPS to provide accurate and repeatable measurements while significantly improving operational efficiency,
making it a promising solution for future automated measurement applications.

Speaker: Dirk Mergelkuhl (CERN)

Closing

Convener: Yuichi OKAYASU (KEK)