An individual medium energy proportional counter on EXOSAT had a front window of beryllium with aluminized kapton foil for thermal protection, a front chamber filled with an argon / CO 2 mixture, a rear chamber with xenon / CO 2, and a beryllium window separating the two chambers.
42.
The GIS is a gas-imaging scintillation proportional counter and is based on the GSPC that flew on the second Japanese X-ray astronomy mission TENMA . The two identical charge-coupled device ( CCD ) cameras were provided for the two SISs by a hardware team from MIT, Osaka University and ISAS.
43.
The experiment consisted of 2 cylindrical X-ray detectors : a Xenon filled proportional counter covering 5-14 keV, and a NaI ( Tl ) scintillator covering 12-1250 keV . The proportional counter was 1.27 cm in diameter and was filled with a mixture of 97 % Xenon and 3 % carbon dioxide.
44.
The experiment consisted of 2 cylindrical X-ray detectors : a Xenon filled proportional counter covering 5-14 keV, and a NaI ( Tl ) scintillator covering 12-1250 keV . The proportional counter was 1.27 cm in diameter and was filled with a mixture of 97 % Xenon and 3 % carbon dioxide.
45.
The Geiger M�ller tube and the proportional counter both use a phenomenon known as a Townsend avalanche to multiply the effect of the original ionizing event by means of a cascade effect whereby the free electrons are given sufficient energy by the electric field to release further electrons by ion impact.
46.
Of special significance for X-ray astronomy were two X-ray instruments : one designed to detect wavelengths 1-20 ?( 0.1-2 nm ) ( consisting of proportional counters with varying window thickness ) and one designed to detect wavelengths 44-60 ?( 4.4-6.0 nm ) ( consisting of proportional counters with thin Mylar windows ).
47.
Of special significance for X-ray astronomy were two X-ray instruments : one designed to detect wavelengths 1-20 ?( 0.1-2 nm ) ( consisting of proportional counters with varying window thickness ) and one designed to detect wavelengths 44-60 ?( 4.4-6.0 nm ) ( consisting of proportional counters with thin Mylar windows ).
48.
The purpose of this expedition was to test for NASA a meter called a Tissue Equivalent Proportional Counter ( TEPC ) : testing at different altitudes ( 17, 000 ft, 19, 000 ft and 21, 000 ft ) would reveal how people s bodies would be affected, including the way bodily tissues behaved, when struck by radiation, and this was important for the planning of long duration space missions.
