Development of GEM detector for tokamak SXR tomography system: Preliminary laboratory tests

The GEM based detecting system is currently being developed for poloidal tomography to be used at WEST project tokamak. It consists of two GEM detectors of planar and of cylindrical geometry for the vertical and horizontal ports, respectively. Several laboratory tests were conducted to assess the performance of the prototype detectors and verify the proposed design. For that, the measurements of the detectors with 55Fe source and X-ray generator were performed. The detector’s behavior was tested for two gas mixtures: Ar/CO2 and Ar/CO2/CF4 and the detector amplification dependencies on high photon flux, start-up and applied high voltages are demonstrated. The cluster sizes of the generated anode charge and energy resolution are also provided.