Christoph Krieger Bonn

Search for solar chameleons with an InGrid based X-ray detector at the CAST experiment

The CERN Axion Solar Telescope (CAST) searches for Axions produced in the Sun. To allow CAST to also look for Chameleon particles which are in fact one of the few particle explanations for Dark Energy, new low energy X-ray detectors were required as solar Chameleons are being produced not in the Sun's core, but in the tachocline region resulting in lower energies. In October 2014 a low energy X-ray detector developed at Bonn was installed behind one of the X-ray telescopes of CAST. This detector utilizes an 'InGrid' device, a Micromegas stage created on top of a pixelized readout ASIC by means of photolithographic postprocessing. Due to the readout's high granularity, this technology allows for an energy threshold of a few hundred eV and in addition for a topological background suppression. After successful operation until December 2015 analysis of the recorded data has started. Preliminary results including the expected limit on the chameleon photon coupling will be presented.