Speaker
Description
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:
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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.
