A description is given of the spectrometer used for the detection of 71Ge in the Solar Neutrino experiment GALLEX being performed in the Gran Sasso Underground Laboratory. The spectrometer consists of miniaturized proportional counters and a shield with a large well-type NaI pair (Tl) detector (active side) and an inner pure copper shield (passive side). Very careful material selection for the proportional counter- and shield-construction and radon suppression resulted in total background rates (>0.5 keV) between 0.4 and 1 count per day for many proportional counters. With energy and rise time cuts, the average rates for the relevant L- and K-peak of the 71Ge spectrum are 0.1 cpd and 0.03 cpd, respectively and, thus, are far below the signal predicted by the Standard Solar Model. Eight counter positions within the NaI pair detector have the option to detect also 69Ge and 68Ga (positron emitters) in the coincidence mode, though with slightly higher background for the 71Ge decay mode. An analysis of the different background components cannot fully account for the measured background of the proportional counters so that presumably a part of it is due to contamination during the assembling process. Here is a potential for further background reduction. After introduction, the basic concept of the experiment and the present status as of December 1991 are briefly outlined.
Heusser, G., Anselmann, P., Hampel, W., Handt, J., Kiko, J., Kirsten, T., et al. (1994). Characteristic of the GALLEX spectrometer. In Bosetti P C (a cura di), proceedings of the second conference on TRENDS IN ASTROPARTICLE PHYSICS, Aachen, October 10-12 1991, Germany (pp. 33-47). Leipzig : Teubner-Texte zur Mathematik [10.1007/978-3-663-01466-9].
Characteristic of the GALLEX spectrometer
D'ANGELO S;BERNABEI R;PAOLUZI L;
1994-01-01
Abstract
A description is given of the spectrometer used for the detection of 71Ge in the Solar Neutrino experiment GALLEX being performed in the Gran Sasso Underground Laboratory. The spectrometer consists of miniaturized proportional counters and a shield with a large well-type NaI pair (Tl) detector (active side) and an inner pure copper shield (passive side). Very careful material selection for the proportional counter- and shield-construction and radon suppression resulted in total background rates (>0.5 keV) between 0.4 and 1 count per day for many proportional counters. With energy and rise time cuts, the average rates for the relevant L- and K-peak of the 71Ge spectrum are 0.1 cpd and 0.03 cpd, respectively and, thus, are far below the signal predicted by the Standard Solar Model. Eight counter positions within the NaI pair detector have the option to detect also 69Ge and 68Ga (positron emitters) in the coincidence mode, though with slightly higher background for the 71Ge decay mode. An analysis of the different background components cannot fully account for the measured background of the proportional counters so that presumably a part of it is due to contamination during the assembling process. Here is a potential for further background reduction. After introduction, the basic concept of the experiment and the present status as of December 1991 are briefly outlined.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
