Editing Explorer 11 (section)

=== Crystal Sandwich / Cherenkov Counter ===
[[File:Explorer 11 gamma.gif|thumb|Gamma-ray detector placed onboard Explorer 11 satellite]]
[[File:Explorer 11 gamma sketch.gif|thumb|Diagram of gamma-ray detector]]
The instrumentation for the Explorer 11 crystal sandwich [[Cherenkov detector]] experiment was the same as that used for the gamma-ray telescope experiment. The gamma-ray experiment was designed by researchers at the [[Massachusetts Institute of Technology]] (MIT) primarily to detect cosmic gamma rays greater than 50 [[Electronvolt|MeV]]. Charged particle data were collected using the same instrument. This telescope was used to determine the intensity and pitch-angle distribution of geomagnetically trapped [[proton]]s. The telescope consisted of an anticoincidence plastic shield, layers of [[Sodium iodide]] (NaI) and [[Caesium iodide]] (CsI) crystals, and a cylindrical Cherenkov detector. When the anticoincidence requirement of the plastic scintillator shield was removed, charged particle information was recorded by all three counters. In addition, charged particle coincidences between the crystal sandwich and Cherenkov detectors were recorded. In this mode, directional information was obtained. The solid-angle-area factor of the telescope was about {{cvt|4.3|cm2}}. The look direction of the telescope was identical to the symmetry axis of the spacecraft. For a beam incident parallel to the look direction of the telescope, the detection efficiency fell to 0 at 15° from this direction. The energy thresholds for each detector were as follows: (1) scintillation plastic (upper portion), [[electron]]s -350 keV, protons -3.5 MeV, (2) scintillation plastic (lower portion), electrons -400 keV, protons -35 MeV, (3) crystal sandwich, electrons -400 keV, protons -75 MeV, and (4) Cherenkov, electrons -15 MeV, protons -350 MeV. The accumulation time for the charged particle data was approximately 30 seconds. A single scaling circuit in Explorer 11 permitted one channel at a time to be monitored. During the 7 months in which the instrument was turned on and working in orbit, only 141 hours (3%) were considered useful observing time. During this time, the telescope was monitored for gamma rays and charged particles.<ref name="Experiment2">{{cite web |url=https://nssdc.gsfc.nasa.gov/nmc/experiment/display.action?id=1961-013A-02|title=Experiment: Crystal Sandwich/Cherenkov Counter|publisher=NASA|date=28 October 2021|access-date=4 November 2021}} {{PD-notice}}</ref>