Detector
The 54-m3 detector tank was filled with 101 tons of gallium trichloride-hydrochloric acid solution, which contained 30.3 tons of gallium. The gallium in this solution acted as the target for a neutrino-induced nuclear reaction, which transmuted it into germanium through the following reaction:
- νe + 71Ga → 71Ge + e-.
The threshold for neutrino detection by this reaction is 233.2 keV, and this is also the reason why gallium was chosen: other reactions (as with chlorine-37) have higher thresholds and are thus unable to detect low-energy neutrinos. This reaction was also able to detect neutrinos from the initial proton fusion reaction of the proton-proton chain reaction, with an upper energy limit of 420 keV.
The produced germanium-71 was chemically extracted from the detector, converted to germane (71GeH4). Its decay, with a half life of 11.43 days, was detected by counters. Each detected decay corresponded to one detected neutrino.
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