LUX-ZEPLIN

Abstract:

An energy resolution of Delta E = 12 eV (FWHM) was measured for the Mn-55 K alpha(1) line (E = 5.90 keV) using a single superconducting Al/AlxOy/Al tunnel junction. The total detector area of 100 x 100 mu m was illuminated, while a slit mask of about 150 mu m width was used to shadow the detector leads and substrate area from the impinging x-rays. The total electronic noise contribution to the energy resolution was measured as Delta E-elec = 7 eV (FWHM). The process of tunnel junction fabrication was optimized towards a reproducible and high-quality growth of the tunnel barrier. High-quality aluminium films promote long quasi-particle lifetimes and ensure reproducible tunnel barrier growth. The residual resistance ratio of a 1 mu m thick aluminium test film was about 100, Copyright (C) 1999 John Wiley & Sons, Ltd.

Abstract:

We have shown that for quasidiffusive phonon propagation in an isotropic crystal the diffusion coefficient D = KL8/9, where K is a material constant and L is the distance between the phonon source and point of detection. We have demonstrated this is the case for BaF2 bombarded by alpha-particles. This implies that pulse shape analysis may provide a mechanism to achieve position sensitivity in phonon mediated detectors. (C) 1999 Elsevier Science B.V. All rights reserved.

Abstract:

We have measured the time dependence of the flux of non-thermal phonons generated by α particles in a BaF2 single crystal of mass 1 g using a Series Array of Superconducting Tunnel Junctions. Taking advantage of the almost perfect elastic symmetry of BaF2, we approximate the equations of quasidiffusive propagation to give a simple diffusion equation characterized by an effective diffusion coefficient D = KL8/9, where K is a material constant and L the distance between the phonon source and the point of detection. We use this model to perform pulse-shape analysis on our data and show that agreement is excellent, and highly preferred over a ballistic pulse shape. The distributions of values of K determined for different lengths L are found to overlap strongly, in support of the law D=KL8/9. We suggest that pulse-shape analysis may provide an alternative to time-difference measurements to achieve position sensitivity in a phonon-mediated detector based on a BaF2 absorber. © 1999 American Institute of Physics.

Abstract:

We discuss the short and long term perspectives of the CRESST (Cryogenic Rare Event Search using Superconducting Thermometers) project and present the current status of the experiment and new results concerning detector development. In the search for elementary particle dark matter, CRESST is presently the most advanced deep underground, low background, cryogenic facility. The basic technique involved is to search for WIMPS (Weakly Interacting Massive Particles) by the measurement of non-thermal phonons, as created by WIMP-induced nuclear recoils. Combined with our newly developed method for the simultaneous measurement of scintillation light, strong background discrimination is possible, resulting in a substantial increase in WIMP detection sensitivity. This will allow a test of the reported positive evidence for a WIMP signal by the DAMA collaboration in the near future. In the long term, the present CRESST setup permits the installation of a detector mass up to 100 kg. In contrast to other projects, CRESST technology allows the employment of a large variety of detection materials. This offers a powerful tool in establishing a WIMP signal and in investigating WIMP properties in the event of a positive signal. © 1999 Elsevier Science B.V. All rights reserved. PACS: 95.35+d; 29.40.

Abstract:

The CRESST (Cryogenic Rare Event Search with Superconducting Thermometers) experiment at the Gran Sasso Laboratory will search for dark matter WIMPs using cryogenic detectors. In the first stage we will use four 262 g sapphire crystals with thresholds of about 0.5 keV. This low threshold gives us sensitivity to WIMP masses below 10 GeV, making CRESST complementary to other dark matter searches. The main installation in Gran Sasso is now complete and we report on the first detector tests.