Artikel in einem Journal
C. Krieger, K. Desch, J. Kaminski, M. Lupberger, T. Vafeiadis
TIPP2014 Proceedings: An InGrid based Low Energy X-ray Detector for the CAST Experiment
The CERN Axion Solar Telescope (CAST) is searching for axions and other new particles like chameleons coupling to photons and emerging from the Sun. Those particles are converted into soft X-ray photons in a high magnetic field. To enhance sensitivity for physics beyond the Standard Model it is necessary to cope with weak couplings and low energies, thus requiring an efficient background discrimination as well as a detection threshold below 1 keV. A promising candidate for a future CAST detector is an InGrid based X-ray detector. This detector combines the high spatial resolution of a pixelized read out with a highly granular Micromegas gas amplification stage. Fabrication by photolithographic postprocessing techniques allows to match the amplification grid to the pixels. The high granularity facilitates the detection of single electrons which allows to determine the X-ray energy by electron counting. Additionally, rejection of background events mostly originating from cosmic rays is provided by an event shape analysis exploiting the high spatial resolution. In order to demonstrate its low detection threshold, an InGrid based detector was tested in the CAST Detector Lab where an X-ray generator for energies down to a few hundred eV is available. Results of these tests demonstrate the detector’s ability to detect the carbon K-alpha line at 277 eV. The detector was mounted afterwards at the CAST experiment behind an X-ray telescope in order to take data during the 2014 run of CAST.