Measurement of the background spectrum of a CdTe detector at balloon altitudes

The CdTe and the CdZnTe detectors are considered to be promising detectors for the future of astronomical hard X-ray observations due to their high stopping power and high energy resolution. For the preparation of future experiments, we have performed a simple balloon experiment using a small CdTe detector (2 mm cubic) as a piggy-back mission in 2000. Its energy range was 20–140 keV band with an energy resolution of 3.0 keV at 60 keV. The balloon reached an altitude of 36.9 km, and then gradually descended. During the 10-h flight, we successfully observed the background spectrum. The flux of the background was ∼1.5 × 10-2 s-1 cm-2 keV-1 at 50 keV, being comparable to those of the past observations measured by CdZnTe detectors. We also found that the count-rate increases as the atmospheric pressure increases. No apparent line emission was observed. [Copyright &y& Elsevier]