Measurement of Na and I recoil discrimination and detection efficiency in a cooled ‘UVIS’ NaI crystal for dark matter searches

✍ Scribed by N.J.C. Spooner; G.J. Davies; C.H. Lally; N.J.T. Smith; M. van den Putte; P.F. Smith; J.D. Lewin; G.T.A. Squier; P. Jagpal

• Publisher: Elsevier Science
• Year: 1996
• Tongue: English
• Weight: 581 KB
• Volume: 5
• Category: Article
• ISSN: 0927-6505
• DOI: 10.1016/0927-6505(96)00032-1

✦ Synopsis

The UVIS dark matter detector, proposed by Spooner and Smith (Phys. Lett. B 314 (1993) 430), consists of (<1000 \mathrm{ppm}) Tl doped NaI scintillator operated at (100-200 \mathrm{~K}), with measurement of UV and visible scintillation components used to discriminate between electrons (gammas) and Na or I recoils. Presented here are results of measurements of the gamma/nuclear recoil discrimination power of a Kyropolous NaI ( (0.5 \mathrm{ppm}) TI) UVIS test detector operated at (160 \mathrm{~K}), with monoenergetic neutrons used to induce nuclear recoils via elastic scattering. Defining the statistical gain factor for (N) events as (C_{\mathrm{m}} / N^{1 / 2}), the coefficient (C_{\mathrm{m}}) was measured as a function of photoelectron pulse height. At 40 photoelectrons (C_{\mathrm{m}}) was found to be 0.5 (corresponding to (90 %) rejection of gammas with (20 %) loss of neutron events). The scintillation efficiency for (\mathrm{Na}) and I recoils relative to electrons was also measured at (160 \mathrm{~K}) and found to be (35 \pm 5 %) for (\mathrm{Na}) recoils and (10 \pm 2 %) for iodine.