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تسجيل مستخدم جديدSearch for Cosmic-Ray Antiparticles with Balloon-borne and Space-borne Experiments
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Ph. von Doetinchem
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This thesis discusses two different approaches for the measurement of cosmic-ray antiparticles in the GeV to TeV energy range. The first part of this thesis discusses the prospects of antiparticle flux measurements with the proposed PEBS detector. The project allots long duration balloon flights at one of Earths poles at an altitude of 40 km. GEANT4 simulations were carried out which determine the atmospheric background and attenuation especially for antiparticles. The second part covers the AMS-02 experiment which will be installed in 2010 on the International Space Station at an altitude of about 400 km for about three years to measure cosmic rays without the influence of Earths atmosphere. The present work focuses on the anticoincidence counter system (ACC). The ACC is needed to reduce the trigger rate during periods of high fluxes and to reject external particles crossing the tracker from the side or particles resulting from interactions within the detector which would otherwise disturb the clean charge and momentum measurements. The last point is especially important for the measurement of antinuclei and antiparticles.
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This work discusses the prospects of antiparticle flux measurements with the proposed PEBS detector. The project foresees long duration balloon flights at one of Earths poles at an altitude of 40 km. The sky coverage of flights at the poles is presen
ted. In addition, cosmic-ray measurements at the poles (small rigidity cut-offs) give the possibility to study solar modulation effects down to energies of about 0.1 GeV. Furthermore, systematic effects due to interactions of cosmic rays in the atmosphere are important. These effects were studied with the Planetocosmics simulation software based on GEANT4 in the energy range 0.1 - 1000 GeV.
An attitude determination system for balloon-borne experiments is presented. The system provides pointing information in azimuth and elevation for instruments flying on stratospheric balloons over Antarctica. In-flight attitude is given by the real-t
ime combination of readings from star cameras, a magnetometer, sun sensors, GPS, gyroscopes, tilt sensors and an elevation encoder. Post-flight attitude reconstruction is determined from star camera solutions, interpolated by the gyroscopes using an extended Kalman Filter. The multi-sensor system was employed by the Balloon-borne Large Aperture Submillimeter Telescope for Polarimetry (BLASTPol), an experiment that measures polarized thermal emission from interstellar dust clouds. A similar system was designed for the upcoming flight of SPIDER, a Cosmic Microwave Background polarization experiment. The pointing requirements for these experiments are discussed, as well as the challenges in designing attitude reconstruction systems for high altitude balloon flights. In the 2010 and 2012 BLASTPol flights from McMurdo Station, Antarctica, the system demonstrated an accuracy of <5 rms in-flight, and <5 rms post-flight.
The physical processes postulated to explain the high-energy emission mechanisms of compact astrophysical sources often yield polarised soft gamma rays (X-rays). PoGOLite is a balloon-borne polarimeter operating in the 25-80 keV energy band. The pola
risation of incident photons is reconstructed using Compton scattering and photoelectric absorption in an array of phoswich detector cells comprising plastic and BGO scintillators, surrounded by a BGO side anticoincidence shield. The polarimeter is aligned to observation targets using a custom attitude control system. The maiden balloon flight is scheduled for summer 2011 from the Esrange Space Centre with the Crab and Cygnus X-1 as the primary observational targets.
PoGOLite is a hard X-ray polarimeter operating in the 25-100 keV energy band. The instrument design is optimised for the observation of compact astrophysical sources. Observations are conducted from a stabilised stratospheric balloon platform at an a
ltitude of approximately 40 km. The primary targets for first balloon flights of a reduced effective area instrument are the Crab and Cygnus-X1. The polarisation of incoming photons is determined using coincident Compton scattering and photo-absorption events reconstructed in an array of plastic scintillator detector cells surrounded by a bismuth germanate oxide (BGO) side anticoincidence shield and a polyethylene neutron shield. A custom attitude control system keeps the polarimeter field-of-view aligned to targets of interest, compensating for sidereal motion and perturbations such as torsional forces in the balloon rigging. An overview of the PoGOLite project is presented and the outcome of the ill-fated maiden balloon flight is discussed.
We present the second generation BLASTbus electronics. The primary purposes of this system are detector readout, attitude control, and cryogenic housekeeping, for balloon-borne telescopes. Readout of neutron transmutation doped germanium (NTD-Ge) bol
ometers requires low noise and parallel acquisition of hundreds of analog signals. Controlling a telescopes attitude requires the capability to interface to a wide variety of sensors and motors, and to use them together in a fast, closed loop. To achieve these different goals, the BLASTbus system employs a flexible motherboard-daughterboard architecture. The programmable motherboard features a digital signal processor (DSP) and field-programmable gate array (FPGA), as well as slots for three daughterboards. The daughterboards provide the interface to the outside world, wi
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