THE THERMAL DETECTION EFFICIENCY FOR RECOILS INDUCED BY LOW-ENERGY NUCLEAR-REACTIONS, NEUTRINOS OR WEAKLY INTERACTING MASSIVE PARTICLES

We report the first direct measurements on the energy dependence of th e thermal detection efficiency for heavy recoiling nuclei. Two bolomet ers made by TeO2 crystals facing each other were operated at low tempe rature and read-out independentIy, while coincidence-anticoincidence t echniques were used for particle discrimination. The experiment was ca rried out underground after implantation of both crystals with a sourc e of Ra-228. The relative response for alpha particles and nuclear rec oils with respect to electrons of the same energy (Quenching Factor) w as found to be compatible with or slightly larger than unity. Deviatio ns from constancy with energy of the QF for nuclear recoils in alpha d ecays of Ra-224, Rn-220, Po-216, Po-212 and Bi-212 Were not observed. (C) 1997 Elsevier Science B.V.