Here, we present the calibration data and describe the analysis done on the GRAPE 2014 flight data. Incorporating Anti-coincidence shield data (which served as a surrogate for the background) was also found to improve the analysis. We found that the background depended mostly on the atmospheric depth, pointing zenith angle and instrument temperatures. We have developed a technique based on the Principle Component Analysis (PCA) to estimate the background for the Crab observation. Analysis of data from the first two balloon flights of GRAPE has been challenging due to significant changes in the background level during each flight. The main goal of these balloon flights was to measure the gamma ray polarization of the Crab Nebula. The Gamma Ray Polarimeter Experiment (GRAPE), a balloon borne polarimeter for 50~300 keV gamma rays, successfully flew in 20. Results of the extraterrestrial flux require an extensive detailed analysis of the time-varying background because of activation buildup and balloon spatial drifts.Īnalysis of Data from the Balloon Borne Gamma RAy Polarimeter Experiment (GRAPE) It is shown that the measurements of the atmospheric fluxes are consistent with earlier results after allowance is made for an additional component of the background due to beta(+) decays produced by neutron- and proton-initiated interactions with materials in and near the detector. It also allows a measurement of the background component of the 0.511-MeV flux produced by beta(+) decays in materials inside the CsI(Na) shield. This system is used primarily to allow measurements of the two escape peaks associated with high-energy gamma ray lines. The spectrometer consists of four 40-cu-cm Ge(Li) crystals operating in the energy range 0.06-10 MeV this cluster of detectors is surrounded by a CsI(Na) anticoincidence shield. S.Ī collimated high-resolution gamma ray spectrometer was flown on a balloon over Palestine, Texas, on June 10, 1974, to obtain measurements of the terrestrial and extraterrestrial 0.511-MeV gamma rays. Measurement of 0.511-MeV gamma rays with a balloon-borne Ge/Li/ spectrometer The improved understanding of these components leads to several recommended techniques for reducing the background. The principal components of the continuum background in spectrometers with GE detectors and thick active shields are: (1) elastic neutron scattering of atmospheric neutrons on the Ge nuclei (2) aperture flux of atmospheric and cosmic gamma rays (3) beta decays of unstable nuclides produced by nuclear interactions of atmospheric protons and neutrons with Ge nuclei and (4) shield leakage of atmospheric gamma rays. Results compare well with measurements made in the 20 keV to 10 MeV energy range by the Goddard Low Energy Gamma-ray Spectrometer (LEGS). The calculations are based on newly available interaction cross sections and new analytic techniques, and are the most detailed and accurate published to date. Instrumental background in balloon-borne gamma-ray spectrometers is presented. The buoyant force acting on the box can be calculated with (1)į = (0.3 m) (0.4 m) (0.1 m) ( 1000 kg/m 3) ( 9.Instrumental background in balloon-borne gamma-ray spectrometers and techniques for its reduction
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