Soft X-rays in the 00 : 18 UT solar flare on April 22, 1994

The IRIS spectrometer employs scintillation and proportional counters with large-sized windows. It offers possibility for measuring X-ray flux of flar e precursors and micro- and nanoflares as well as studying fine time struct ures in hard X-rays during the impulsive phase of strong solar flares. Char acteristics of the spectrometer (time resolution, number of energy channels , sensitivity to soft X-rays) are automatically changeable depending on mea sured X-ray flux. The essential properties of the IRIS spectrometer are lis ted in Table 1 (for detailed description see Kocharov et al, 1989, and Char ikov et al, 1997). (C) 2000 Published by Elsevier Science Ltd. All rights r eserved.