Payload 13 Information

Abstract:
Among the last astronomy frontiers, are the polarization measurements of X-ray and gamma ray emissions from as diverse phenomena as gamma ray bursts, pulsars, AGNs, etc. If so far, e.g., gamma ray circular polarimeters have not yet been developed, for linear polarization Cadmium Telluride (CdTe) spectrometers are the most promising detectors for future space missions. Stratospheric balloons provide enough time to test polarimetry measurements and calibrate background radiation. We propose flying a large ( > 3 kg ) payload for characterization of such background in the 20–1000 keV energy range, using a small 4x4 pixels CdTe prototype. This may not be the “sexiest” experiment, but is crucial for future steps, providing also hands-on experience for undergrad students, within an international collaboration. Instrumentation wise we plan upgrading the electronics and detection capacities of the Compact Array of Cadmium Telluride Micro Spectrometers (CACTuS). During its balloon flight, in 2002, it collected data just for single events background. We now propose to explore the implementation of a coincidence logic (using single multichannel Application Specific Integrated Circuits) for double & multiple events. Double events (two hits in different pixels, the first interaction being a Compton) are essential to determine Compton photons' new direction and therefore the polarization direction.