DATA STRUCTURE AND BURST TRIGGERING ALGORITHM IN THE INSTRUMENTS FOR STUDY OF GAMMA-RAY BURSTS
Scintillator gamma-ray spectrometers are designed in SINP MSU for a burst study. These instruments are based on phoswich detectors using combination of NaI(Tl) and CsI(Tl) crystals of different thickness. Electronic circuits realize separate integrating of first and last parts of the PMT pulse as well as the digitizing of correspondent signals for further processing in digital form. Comparison between these two signals allows one to provide reliable separation of the events in scintillators with energy release above 10 keV. The value of energy is measured using the quadratic summing of the signal amplitudes. Information unit of the instrument produce output frames of several type including time sequence, spectra and detailed record of the detector response for a fixed number of events. Also the information unit produce the burst trigger comparing the measured number of events for some time interval with the expected one, calculated from a sequence of previous readings. The burst trigger is produced when the measured value is higher than expected one more than for some threshold number of standard deviations. The limits of energy channels for monitoring, burst trigger threshold and some other values can be changed during the space experiment by a number of digital commands. The data amount coming from the instrument is about 34 MB per day continuously and ~2MB for each detected gamma-ray burst.