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Cosmic Ray Ion Chamber

NSSDCA ID: 1961-032A-06

Mission Name: Ranger 2
Principal Investigator:Dr. H. Victor Neher


The objective of the Cosmic Ray Experiment on Ranger 2 was to measure primary cosmic radiation and other ionizing radiation in the space beyond the Earth's atmosphere. The instrument was a Neher-type cosmic ray integrating ionization chamber. It could detect protons, neutrons, alpha particles, and heavier nuclei, but had no directional resolution.

The ionization chamber was a thin (0.05 cm) steel spherical shell filled with argon. Inside the chamber was a collector made of fused quartz with a conducting coating of aquadag, and a quartz fiber with a conducting coating positioned about 0.05 cm (0.020 in.) from the collector. Radiation penetrating the shell would ionize the argon gas, and the ions would be collected by the electric field between the shell and the collector. The ionization current would discharge the collector to a point when the fiber touches and recharges it, producing a voltage pulse across a load resistor. The time between pulses varies inversely with the rate of ionization of the argon.

The minimum-energy heavy particle that can be detected is determined by the thickness of the spherical shell wall. The 0.05 cm thickness was chosen to match the thickness of the unshielded, low-energy triple coincidence proportional telescope (1961-032A-09). This gives a minimum energy for protons of 10 MeV, alpha particles of 40 MeV, and electrons of 0.5 MeV. Lower energy electrons are detected through the Bremsstrahlung process with efficiency depending on their energy. The instrument used 4 - 10 mW power. The ion chamber could be calibrated within 1 percent.

The operation of the experiment during flight was normal, but the value of the data for scientific purposes was impaired by the shortened flight and the failure of the spacecraft to reach the intended orbit. The contents of the time-count register were occasionally incorrect.

Alternate Names

  • Ranger2/CosmicRayIonChamber


  • Space Physics: Heliospheric Studies

Additional Information

Questions and comments about this experiment can be directed to: Dr. David R. Williams



NameRoleOriginal AffiliationE-mail
Dr. H. Victor NeherPrincipal InvestigatorCalifornia Institute of Technology
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