Indian cosmic ray experiment ions (Anuradha) in space shuttle spacelab-3 using CR-39 detectors

An Indian experiment in spacelab-3 has been designed to perform the measurements of ionization states, flux and energy spectrum of elements of Z = 2-26 in the anomalous component of cosmic radiation in the energy region 5-100 MeV/amu. In this experiment, we are using thin CR-39 (DOP) sheets (thickness 250μm) specially prepared by Pershore Moulding Ltd., England, using 32 hrs. curing cycle and 1% dioctyl phythalate. Our study of track response does not show any significant depth dependence or surface to surface variation for this detector. The detector calibration to different accelerated heavy ion beams is presented in separate paper in this conference. The alignment of different sheets in detector module is done using 50 MeV α-beam from VECC, Calcutta, India. The detector module consists of two stacks. The bottom stack is rotated in discrete steps of 40 arc sec once in every 10 sec below top stack which is fixed with main instrument body. This will give time information for each event. The threshold rigidity of the particle will be calculated from arrival time information, spacelab data and trajectory calculations. The lower bound ionization state of a particle can be determined from magnetic threshold rigidity and its total energy. The energy is determined by measuring the total ranges of arriving particles in bottom stack. The 45 kg instrument was successfully flown in NASA's space shuttle spacelab-3 mission during April 29 to May 6, 1985 at an altitude of 352 km and an inclination of 57° latitude.