Particle Detectors
EPE
The Energetic Particle Experiment (EPE) aboard IMP-8 was one of the first low energy (tens of keV) magnetic/solid state detector ion-electron separation and analysis systems flown in space. The Principal Investigator is D. J. Williams. Further instrumental details are summarized by Williams [NOAA Tech. Rpt. ERL 393-SEL 40, 1977]. The EPE on IMP-8 has operated successfully for 28 years and have generated a wealth of high-quality data that have led to new discoveries and have resulted in hundreds of publications. Both the CPME and EPE instruments continued to perform without problems until IMP-8 operations were terminated by NASA at the end of October 2001. The EPE cleanly separates ions and electrons in the energy range for 30 keV through several MeV. In addition to the magnetic deflection system, complementary particle observations are obtained from a low-noise detector (~18 keV discriminator level) and a thin (~5 micron) detector. One full 15 degree viewing cone perpendicular to the spacecraft spin axis (nearly normal to the ecliptic plane) and two full 13 degree viewing cones 45 degree to the spin axis are used for the EPE particle observations. Angular distributions are measured by obtaining 8 or 16 samples (depending on particle type and energy) per satellite spin period. Orientations of the 16, 22.5-degree (full-angle) sectors of the EPE on IMP-8 are illustrated in EPE sector look directions. A complete energy-angular distribution is obtained every 20.4 seconds. The EPE particle detector assembly consists of a main magnet-detector assembly and two auxiliary detector heads. All detectors are fully depleted, surface barrier, solid state detectors, and are operated with bias voltages 1.25-1.5 times the values required for full depletion. To minimize radiation damage effects, all detectors directly exposed to ion fluxes are mounted with the aluminum contact exposed to the incoming beam. For more information, see: http://sd-www.jhuapl.edu/IMP/imp_index.html