Speaker
Description
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"".
