A new low background gamma spectrometer equipped with an anti-cosmic device

A well type Ge detector and a 48 percent relative efficiency coaxial Ge detector are used with cosmic ray anticoincidence shielding (plastic scintillating plates). Although these devices have lower performance than those placed in an underground laboratory, their advantage is that they can be used in a normal laboratory environment. The background is reduced by 4 or 5 in the whole 30 keV to 2.7 MeV energy range and by 5 to 10 in the energy range below 500 keV. Under these conditions, the count rates are smaller than 10(-4) count s(-1)keV(-1).