Development of the hard X-ray imaging experiment timax: Laboratory images and first balloon flight

Abstract

We present calibration results and laboratory images produced by the balloon-borne hard X-ray imaging telescope TIMAX. The images were produced with an241Am radioactive source placed 45 m away from the detector plane, in the center of the field of view. It is shown that the mask 3-antimask imaging reconstruction process, when combined with flat-fielding techniques, is very effective at recovering signal-to-noise ratio lost due to systematic non-uniformity in the background measured by the 35 detectors. The experiment was launched in June 8th, 1993 from Birigui, SP, Brazil, onboard a 186,000 m3 stratospheric balloon, and remained at an atmospheric depth of ∼2 g cm−2su for ∼8 hours. Even though no scientific data were gathered in this first flight, we obtained valuable engineering data and could also calculate the sensitivity of the experiment based on the instrumental background spectrum at balloon altitudes. In the 60–70 keV energy band, the experiment can detect 3σ sources at a level of ∼1.2 x 10−4 photons cm−2 s−1 keV−1 for an integration of 6 hours at 2.1 g cm−2.