Medium-Energy Particle Experiments - Electron Analyzer (MEP-e)




  • Satoshi Kasahara (The University of Tokyo)


  • Shoichiro Yokota (Osaka University)


  • Kasahara, S., K. Asamura, Y. Saito, T. Takashima, M. Hirahara, and T. Mukai, Cusp type electrostatic analyzer for measurements of medium energy charged particles, Review of Scientific Instruments, 77, 123303, doi:10.1063/1.2405358, 2006.
  • Kasahara, S., K. Asamura, K. Ogasawara, Y. Kazama, T. Takashima, M. Hirahara, and Y. Saito, A noise attenuation method for the medium-energy electron measurements in the radiation belt, Advances in Space Research, 43(5), 792-801, 2009.
  • Kasahara, S., T. Takashima, and M. Hirahara, Variability of the minimum detectable energy of an APD as an electron detector, Nuclear Inst. and Methods in Physics Research, A, 664(1), 282-288, 2012.
  • Kasahara, S., S. Yokota, T. Mitani, K. Asamura, M. Hirahara, Y. Shibano, and T. Takashima, Medium-Energy Particle experiments – electron analyser (MEP-e) for the Exploration of energization and Radiation in Geospace (ERG) mission, Earth, Planets and Space, doi:10.1186/s40623-018-0847-z, 2018.

Instrument Specifications and Measured Quantities

  • Energy range: <10 to 80 keV
  • Energy resolution: 8% (FWHM)
  • Energy steps: 16 steps per scan
  • Sensor field of view: 360° (azimuth) × 3.5° (elevation)
  • Number of detectors: 16
  • Geometric factor: 6.6×10-5 cm2 sr keV/keV per detector
  • Time resolution: 4 s for full 3-D distribution function

Measurement Principle

The electrostatic analyzer measures the energy and direction of incoming electrons. Avalanche photodiodes (APDs) are used as detectors. The energy determined by the electrostatic analyzer and the pulse height measured by the APDs are compared to eliminate background noise due to radiation.

Other Information

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