W7-X DEMO coil cryogenic tests in the CEA/Saclay test facility

In the frame of the W7-X stellarator project, CEA cooperates with Max-Planck-Institut fur Plasmaphysik to perform the acceptance tests of all 70 superconducting coils of the W7-X magnet system. The test facility is now complete and its performance is being checked using the W7-X prototype coil. The main objective of the tests of the series coils is to demonstrate their proper function and to determine their margin of operation. Since many coils will be tested and compared to each other, it is important to measure the margin of operation in a reproducible way with sufficient accuracy. Either increasing the current, increasing the temperature or mixed operation can induce quenches. The test results on the prototype coil are analyzed with respect to the temperature and current margin and compared to the expected values calculated from superconducting strand data. The paper summarizes the results of these tests and the methods of evaluation.