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- 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
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