Large area balloon-borne payload for the study of temporal vartability in hard x-rays

The fundamental parameters of accretion powered X-ray sources are the continuous and homogenous accretion. A breakdown of the homogenous scenario can lead to intensity fluctuations in the entire Fourier space. This paper describes a balloon-borne Large Area Scintillation counter Experiment (LASE) designed to detect microsecond variations in the flux of X-ray sources in hard X-rays upto 200 keV. In final configuration, the payload will have an area of 2400 cm(2). Presently, the proto-type instrument consists of two modules, consisting of a 3 mm and a 30 mm NaI(Tl) crystals, arranged in a back-to-back geometry and having an effective area of 400 cm(2) each. The data is spectrum analyzed in 127 channels between 20 and 200 keV and each event is time-tagged to an accuracy of 25 microseconds. The detection sensitivity of the telescope is similar to 2 x 10(-6)cm(-2)s(-1)keV(-1) for 3 hr. of source observation. The background rejection, on-board trigger system and other control parameters are described briefly. (C) 1998 COSPAR. Published by Elsevier Science Ltd.