Search

We present limits on the spin-independent interaction cross section of dark matter particles with silicon nuclei, derived from data taken with a cryogenic calorimeter with 0.35 g target mass operated in the CRESST-III experiment. A baseline nuclear recoil energy resolution of (1.36 ± 0.05) eVnr, currently the lowest reported for macroscopic particle detectors, and a corresponding energy thresh-old of (10.0 ± 0.2) eVnr have been achieved, improving the sensitivity to light dark matter particles with masses below 160 MeV/c2 by a factor of up to 20 compared to previous results. We characterize the observed low energy excess, and we exclude noise triggers and radioactive contaminations on the crystal surfaces as dominant contributions.

A scintillating bolometer based on a large cubic Li$_{2}$$^{100}$MoO$_4$ crystal (45 mm side) and a Ge wafer (scintillation detector) has been operated in the CROSS cryogenic facility at the Canfranc underground laboratory in Spain. The dual-readout detector is a prototype of the technology that will be used in the next-generation $0\nu2\beta$ experiment CUPID. The measurements were performed at 18 and 12 mK temperature in a pulse tube dilution refrigerator. This setup utilizes the same technology as the CUORE cryostat that will host CUPID and so represents an accurate estimation of the expected performance. The Li$_{2}$$^{100}$MoO$_4$ bolometer shows a high energy resolution of 6 keV FWHM at the 2615 keV $\gamma$ line. The detection of scintillation light for each event triggered by the Li$_{2}$$^{100}$MoO$_4$ bolometer allowed for a full separation ($\sim$8$\sigma$) between $\gamma$($\beta$) and $\alpha$ events above 2 MeV. The Li$_{2}$$^{100}$MoO$_4$ crystal also shows a high internal radiopurity with $^{228}$Th and $^{226}$Ra activities of less than 3 and 8 $\mu$Bq/kg, respectively. Taking also into account the advantage of a more compact and massive detector array, which can be made of cubic-shaped crystals (compared to the cylindrical ones), this test demonstrates the great potential of cubic Li$_{2}$$^{100}$MoO$_4$ scintillating bolometers for high-sensitivity searches for the $^{100}$Mo $0\nu2\beta$ decay in CROSS and CUPID projects.

As noble liquid time projection chambers grow in size their high voltage requirements increase, and detailed, reproducible studies of dielectric breakdown and the onset of electroluminescence are needed to inform their design. The Xenon Breakdown Apparatus (XeBrA) is a 5-liter cryogenic chamber built to characterize the DC high voltage breakdown behavior of liquid xenon and liquid argon. Electrodes with areas up to 33 cm2 were tested while varying the cathode-anode separation from 1 to 6 mm with a voltage difference up to 75 kV. A power-law relationship between breakdown field and electrode area was observed. The breakdown behavior of liquid argon and liquid xenon within the same experimental apparatus was comparable.

In order to make improved spectral imaging measurements in the ultraviolet, visible and near infrared bands, we investigated the design of a 10 kilopixel Microwave Kinetic Inductance Detector (MKID) sensitive in these bands. We evaluate design parameters for MKIDs arrays with equally spaced resonant frequencies and high intrinsic and coupling quality factors. Resonance frequencies were chosen in the range of 2.8-4.8 GHz with an average of 2 MHz intervals. We describe the optimization of our design, including reduced cross-coupling. Through simulations, we find the average intrinsic and coupling quality factors to be on the order of 10(7) and 3 x 10(4) respectively, which are good enough for our purposes.

We present a measurement of the extraction efficiency of quasi-free electrons from the liquid into the gas phase in a two-phase xenon time-projection chamber. The measurements span a range of electric fields from 2.4 to 7.1 kV/cm in the liquid xenon, corresponding to 4.5 to 13.1 kV/cm in the gaseous xenon. Extraction efficiency continues to increase at the highest extraction fields, implying that additional charge signal may be attained in two-phase xenon detectors through careful high-voltage engineering of the gate-anode region.

We report the demonstration of a low-power pixelated readout system designed for three-dimensional ionization charge detection and digital readout of liquid argon time projection chambers (LArTPCs) . Unambiguous 3D charge readout was achieved using a custom-designed system-on-a-chip ASIC (LArPix) to uniquely instrument each pad in a pixelated array of charge-collection pads. The LArPix ASIC, manufactured in 180 nm bulk CMOS, provides 32 channels of charge-sensitive amplification with self-triggered digitization and multiplexed readout at temperatures from 80 K to 300 K . Using an 832-channel LArPix-based readout system with 3 mm spacing between pads, we demonstrated low-noise (0<50 e- RMS equivalent noise charge) and very low-power (<100 μW/channel) ionization signal detection and readout . The readout was used to successfully measure the three-dimensional ionization distributions of cosmic rays passing through a LArTPC, free from the ambiguities of existing projective techniques. The system design relies on standard printed circuit board manufacturing techniques, enabling scalable and low-cost production of large-area readout systems using common commercial facilities. This demonstration overcomes a critical technical obstacle for operation of LArTPCs in high-occupancy environments, such as the near detector site of the Deep Underground Neutrino Experiment (DUNE) . © 2018 IOP Publishing Ltd and Sissa Medialab.

Work financed by the Spanish Ministerio de Economía y Competitividad (MINECO, projects ESP2014-59306-JIN, ESP2014-53672-C3-2-P, ESP2016-76683-C3-2-R), the European Space Agency (ESA, CTP Contract “Optimization of a European TES array”) and the European Commission (H2020 project AHEAD: Integrated Activities for the high energy astrophysics domain”). Personnel from ICMAB acknowledge financial support from MINECO, through the Severo Ochoa Programme for Centres of Excellence in R&D (SEV-2015-04969). RMJ wishes to thank MINECO for her FPI contract. We also thank PTB for providing the SQUIDs.

Accepted: 2015-11-30

Temperature sensors fabricated from ultra-low radioactivity materials have been developed for low-background experiments searching for neutrinoless double-beta decay and the interactions of WIMP dark matter. The sensors consist of electrical traces photolithographically-patterned onto substrates of vapor-deposited parylene. They are demonstrated to function as expected, to do so reliably and robustly, and to be highly radio-pure. This work is a proof-of-concept study of a technology that can be applied to broad class of electronic circuits used in low-background experiments.

In this paper properties of various undoped CeF3 scintillators were investigated at room and liquid nitrogen (LN2) temperatures. The study was focused on measurements of radioluminescence spectra, decay time, non-proportional response to X-and gamma-rays, energy and intrinsic resolution at different temperature environment. Surprisingly, all the tested pure CeF3 crystals show non-proportional response up to 5.1 MeV gamma ray energy, which is contrary to the typical nonproportionality observed below 100 keV for most of the inorganic scintillators. The investigation of the phenomenon occurring in CeF3 scintillators would be another step to get a better knowledge of the scintillators nature, which still has not been entirely understood., QC 20130816

Two samples of 10 mm diameter and 10 mm height CdWO4 and ZnWO4 scintillators were studied at room and liquid nitrogen temperatures. At room temperature the crystals were coupled to a Photonis XP3212 photomultiplier. During experiments at low temperatures a Large Area Avalanche Photodiode was used as a photodetector. Measurements of light output, c of the light yield and intrinsic resolution as a function of gamma-ray energies were performed at both temperatures. The non-proportionality for the two crystals reveals temperature dependence, showing a more proportional behavior at liquid nitrogen temperature. Intrinsic energy resolution values for both crystals also show temperature dependence., QC 20120611

The South Pole Telescope (SPT) is a dedicated 10-meter diameter telescope optimized for mm-wavelength surveys of the Cosmic Microwave Background (CMB) with arcminute resolution. The first instrument deployed at SPT features a 960 element array of horn-coupled bolometers. These devices consist of fully lithographed spider-web absorbers and aluminum-titanium bilayer transition edge sensors fabricated on adhesive-bonded silicon wafers with embedded metal backplanes. The focal plane is cooled using a closed cycle pulse-tube refrigerator, and read-out using Frequency Domain Multiplexed Superconducting Quantum Interference Devices (SQUIDs.) Design features were chosen to optimize sensitivy in the atmospheric observing bands available from the ground, and for stability with the frequency domain multiplexed readout system employed at SPT, and performance was verified with a combination of laboratory tests and field observations. In 2008 the SPT surveyed 200 square-degrees at 150 and 220 GHz. These data have been analyzed using a cross-spectrum analysis and multi-band Markov Chain Monte Carlo parameter fitting using a model that includes lensed primary CMB anisotropy, secondary thermal (tSZ) and kinetic (kSZ) Sunyaev-Zel'dovich anisotropies, unclustered synchrotron point sources, and clustered dusty point sources. In addition to measuring the power spectrum of dusty galaxies at high signal-to-noise, the data primarily constrain a linear combination of the kSZ and tSZ anisotropy contributions (at 150 GHz and ell=3000): DtSZ3000 + 0.5 DkSZ3000 = 4.5 ± 1.0 &mu K2, and place the lowest limits yet measured on secondary anisotropy power.

We report the present results of the CUORICINO experiment, a cryogenic experiment on neutrinoless Double Beta Decay (DBD) of 130Te consisting of an array of 62 TeO2 crystals with a total active mass of 40:7 kg. The array is framed inside a dilution refrigerator, heavily shielded against environmental radioactivity and high-energy neutrons, and it is operated at a temperature of 8mK in the Gran Sasso Underground Laboratory. After several improvements the live time of the experiment is near 75%.

During a Double Beta Decay experiment performed at Laboratori Nazionali del Gran Sasso, a 274 hours low-threshold background spectra was collected with a 340 g TeO2 detector. The MIBETA experiment consists of 20 Tellurium oxide crystals working as bolometers at T = 10 mK in a dilution refrigerator. We present here the analysis carried out on a single detector to search for possible WIMP signal. The values of parameters which are essential in the search for WIMP's, like energy resolution (similar to 2 keV), energy threshold (10 keV) and nuclear quenching factor (similar or equal to 1) have been experimentally determined and are discussed in detail. The exclusion plot of the spin-independent cross section of WIMP's on the nuclei is reported.