MEDIPIX COSMIC RAY TRACKING DEVICE ON BEXUS-7 STRATOSPHERIC BALLOON FLIGHT

摘要

Results of the first experiment using a MEDIPIX-type detector for cosmic ray imaging in stratospheric environment are presented. The detecting device is based on hybrid pixel detector of Medipix2-type developed at CERN with USB interface developed at Institute of Experimental and Applied Physics of Czech Technical University in Prague. The detector was used in its tracking mode allowing it to operate as an active nuclear emulsion". The actual flight time of BEXUS7 on 8th October 2008 was over 4 hours, with 2 hours at stable floating altitude of 26km. The flight opportunity was provided by Education dept. of European Space Agency (ESA) and Eurolaunch (Collaboration of SSC and DLR, German Space Agency). Whole concept served as original testbed for feasibility study of extended stratospheric flight exposures of Medipix detectors to near-space environment. Control hardware was custom designed, based on PC/104 platform. The robustness of the design allowed it to operate flawlessly as was expected from the previous extensive vacuum testing. The scientific motivation was to check height-dependent profiles of ionizing radiation. BEXUS is quite ideal platform for such in-situ measurements. Not only because of the high altitudes reached, but also due to its slow ascent velocity for statistically relevant sampling of the ambient environment. Extensive dataset of different types of cosmic ray particles image tracks were acquired in the stratospheric radiation environment, sorted and analyzed. Detector performance is evaluated for further design implications of advanced concept focusing on Cosmic Ray Induced Ionization rate measurements and for ESA Space Situational Awareness application.