LUX-ZEPLIN

Abstract:

The alpha decay of 210Po is a dangerous background to rare event searches. Here, we describe observations related to this alpha decay in the Cryogenic Rare Event Search with Superconducting Thermometers (CRESST). We find that lead nuclei show a scintillation light yield in our CaWO4 crystals of 0.0142 ± 0.0013 relative to electrons of the same energy. We describe a way to discriminate this source of nuclear recoil background by means of a scintillating foil, and demonstrate its effectiveness. This leads to an observable difference in the pulse shape of the light detector, which can be used to tag these events. Differences in pulse shape of the phonon detector between lead and electron recoils are also extracted, opening the window to future additional background suppression techniques based on pulse shape discrimination in such experiments. © 2009 Elsevier B.V.

Abstract:

We have constructed an instrument, CryoEDM, to measure the neutron electric dipole moment to a precision of 10-28 e cm at the Institut Laue-Langevin. The main characteristic is that it is operating entirely in a cryogenic environment, at temperatures of 0.7 K within superfluid helium. Ultracold neutrons are produced in a superthermal source and stored within the superfluid in a storage cell which is held in a magnetic and electric field. NMR measurements are carried out to look for any shifts in the neutron Larmor precession frequency associated with the electric field and the neutrons are detected in-situ in the superfluid. Low temperature SQUID magnetometry is used to monitor the magnetic field. We report on the current status of the project that is now being commissioned and give an outlook on the future exploitation of the instrument. © 2010 IOP Publishing Ltd.

Abstract:

The CRESST experiment monitors 300 g CaWO4 crystals as targets for particle interactions in an ultra low background environment. In this paper, we analyze the background spectra that are recorded by three detectors over many weeks of data taking. Understanding these spectra is mandatory if one wants to further reduce the background level, and allows us to cross-check the calibration of the detectors. We identify a variety of sources, such as intrinsic contaminations due to primordial radioisotopes and cosmogenic activation of the target material. In particular, we detect a 3.6 keV X-ray line from the decay of 41Ca with an activity of (26 ± 4) μ Bq, corresponding to a ratio 41 Ca / 40 Ca = (2.2 ± 0.3) × 10- 16. © 2009 Elsevier B.V. All rights reserved.

Abstract:

Oxide crystal scintillators play a considerable role in fundamental and applied researches. However, working out of new generation of high-sensitivity equipment and new methods of research puts higher requirements. The ZnBO 4 (B = W, Mo) crystals were grown from charge in platinum crucibles with high frequency heating, using the Czochraiski method. The raw powder with optimum composition was prepared by solid phase high temperature synthesis using ZnO and BO3 (B = W,Mo) with 4-5N purity. Single crystals with sizes up to ∅ 50× 100 mm were grown and scintillation elements of various sizes and shapes (cylinders, rectangular and hexahedron prisms) were produced. High spectrometric characteristics were obtained for ZnWO4:R = 8-10% under excitation by 137Cs [Eγ= 662 keV), low radiation background (less than 0.2 mBq/kg) and low afterglow (0.002%, 20 ms after excitation). The obtained results demonstrate good prospects for ZnWO 4 and ZnM0O4 crystal scintillators for application in low-count rate experiments, searching for double beta decay processes, interaction with dark matter particles, and also studies of rare decay processes. The material has also a, good potential for application in modern tomography, scintillation bolometers and for other major researches using scintillators.