This experiment was a cosmic-ray detector aimed to determine the energy of light cosmic-ray nuclei. In those years, the novelty of the instrument was given by the use of a Ring Imaging Cherenkov (RICH) counter for the first time in a balloon-borne experiment. This system determined the Lorentz factor by directly measuring the angle of Cherenkov emission.
A schematic cross section of the instrument is shown at left. The main detector components are: (1) two scintillation counters, located at the top and bottom of the instrument, to provide a coincidence trigger and a measurement of the nuclear charge. (2) a hodoscope consisting of eight drift chambers (four Chambers above and below the Cherenkov counter, respectively) to determine the particle trajectory and to provide an additional charge measurement, and (3) a ring imaging Cerenkov counter to measure the Lorentz factor of the particle. An incident cosmic ray nuclei, passing down through the radiator volume produced a narrow cone of Cherenkov light centered around the trajectory of the particle. The light was reflected by the espherical mirror and focused in the image of a ring into one of the two photon detectors in the focal plane. The flat 45º mirrors served to move the focal plane and hence the photon detectors out of the trajectory of the incident particle. Since the range of sensitivity of the photon detectors was between 2200 and 1700 all the optics in the instrument worked in the vacuum UV region.
Balloon launched on: 9/25/1991 at 15:40 utc
Launch site: Scientific Flight Balloon Facility, Fort Sumner, (NM), US
Balloon launched by: National Scientific Balloon Facility (NSBF)
Balloon manufacturer/size/composition: Zero Pressure Balloon Winzen 29.470.000 cuft (Stratofilm)
Balloon serial number: W29.47-3-10 SF3-424.37-080-NSCHR-04
Flight identification number: 317N
End of flight (L for landing time, W for last contact, otherwise termination time): 9/26/1991 at 22:30 utc
Balloon flight duration (F: time at float only, otherwise total flight time in d:days / h:hours or m:minutes - ): 30 h
Landing site: 15 miles W of Newman, Texas, US
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