Preliminary results indicate that the GALLEX detector picks up essentially all of the available neutrinos.
At the Gran Sasso underground laboratory in Italy, GALLEX researchers looked for low-energy neutrinos produced by the decay of chromium-51, a specially prepared, highly radioactive isotope of chromium.
Pioneering experiments used the radiochemical techniques (see Section 3.1) applied to the observation of solar neutrinos; they are Homestake [24], GALLEX [26], and SAGE [27, 28].
A deficit of the solar neutrino signal was confirmed later by GALLEX, which, with a threshold at -0.23 MeV, found 83 [+ or -] 19(stat) [+ or -] 8 (syst) SNU to be compared to the expected 127 [+ or -] 7 SNU [26].
In 14 measurements made over nearly a year, the GALLEX researchers also found fewer solar neutrinos than predicted by theory.
"This measurement constitutes the first observation of the [proton-proton] neutrinos," says GALLEX team member Richard L.
The so-called "gallium anomaly" refers to the [v.sub.e] deficit in radioactive source calibration tests, at the gallium solar neutrino experiments SAGE and GALLEX [143].
Heusser et al., "GALLEX results from the first 30 solar neutrino runs," Physics Letters B, vol.
He described the
GALLEX experiment, so called because it uses the interaction by which a neutrino converts a nucleus of gallium-71 to germanium-71.