Experimental Characterization of Space Charge in IZIP Detectors

Interleaved ionization electrode geometries offer the possibility of efficient rejection of near-surface events. The CDMS collaboration has implemented this interleaved approach for the charge and phonon readout for our germanium detectors. During a recent engineering run with negligible ambient radiation, the detectors were found to lose ionization stability more quickly than expected. This paper summarizes studies done in order to determine the underlying cause of the instability, as well as possible running modes that maintain stability without unacceptable loss of livetime. Additionally, first results are shown for the new version IZIP mask which attempts to improve the overall stability of the detectors.United States. Dept. of Energy (Grant DE-AC02-76SF00515)National Science Foundation (U.S.) (Awards 0705052, 0902182, 1004714, and 0802575

Both Reintroduction and Recolonization Likely Contributed to the Re-establishment of a Fisher Population in East-central Alberta

Recently, Stewart et al. (2017) investigated the origins of contemporary fisher populations in the Cooking Lake Moraine (CLM) of east-central Alberta, Canada, where fishers (Pekania pennanti) from Ontario and Manitoba, Canada were reintroduced in the early 1990s. To address this objective, Stewart et al. (2017) compared microsatellite alleles from extant fisher populations in the CLM to those from Ontario, Manitoba, and other Alberta populations. They reported that the CLM population clustered with adjacent native Alberta populations, consistent with recolonization, but also that 2 of 109 microsatellite alleles in the CLM occurred only in the source populations from Ontario and Manitoba. Rather than allowing for the possibility that these alleles descended from reintroduced fishers, the authors speculated that they represented random mutations among fishers that recolonized the area naturally from nearby populations in Alberta, and concluded that the reintroduction had failed completely. We disagree with this conclusion for 2 reasons. We contend it is more likely that the 2 alleles represent a genetic signature from the individuals released during the reintroduction, rather than being the result of mutations. We further suggest that, irrespective of the genetic legacy of introduced fishers in the recovered population, the presence of reintroduced fishers in the CLM may have helped facilitate natural recolonization of the area by fishers from surrounding areas. In our view, Stewart et al.’s (2017) findings do not demonstrate conclusively that the reintroduction program failed; on the contrary, we argue that their findings indicate that reintroduced fishers likely contributed to the long-term persistence of fishers in the CLM. The uncertainty surrounding this case underscores the importance of genetic monitoring following reintroductions.https://digitalcommons.snc.edu/faculty_staff_works/1032/thumbnail.jp

Monte Carlo Comparisons to a Cryogenic Dark Matter Search Detector with low Transition-Edge-Sensor Transition Temperature

We present results on phonon quasidiffusion and Transition Edge Sensor (TES) studies in a large, 3 inch diameter, 1 inch thick [100] high purity germanium crystal, cooled to 50 mK in the vacuum of a dilution refrigerator, and exposed with 59.5 keV gamma-rays from an Am-241 calibration source. We compare calibration data with results from a Monte Carlo which includes phonon quasidiffusion and the generation of phonons created by charge carriers as they are drifted across the detector by ionization readout channels. The phonon energy is then parsed into TES based phonon readout channels and input into a TES simulator

Phonon Quasidiffusion in Cryogenic Dark Matter Search Large Germanium Detectors

We present results on quasidi usion studies in large, 3 inch diameter, 1 inch thick [100] high purity germanium crystals, cooled to 50 mK in the vacuum of a dilution refrigerator, and exposed with 59.5 keV gamma-rays from an Am-241 calibration source. We compare data obtained in two di erent detector types, with di erent phonon sensor area coverage, with results from a Monte Carlo. The Monte Carlo includes phonon quasidi usion and the generation of phonons created by charge carriers as they are drifted across the detector by ionization readout channels.United States. Dept. of Energy (Grant DE-FG02-04ER41295)United States. Dept. of Energy (Grant DE-FG02-07ER41480)National Science Foundation (U.S.) (Grant PHY-0542066)National Science Foundation (U.S.) (Grant PHY-0503729)National Science Foundation (U.S.) (Grant PHY-0503629)National Science Foundation (U.S.) (Grant PHY-0504224)National Science Foundation (U.S.) (Grant PHY-0705078)National Science Foundation (U.S.) (Grant PHY-0801712

Validation of Phonon Physics in the CDMS Detector Monte Carlo

The SuperCDMS collaboration is a dark matter search effort aimed at detecting the scattering of WIMP dark matter from nuclei in cryogenic germanium targets. The CDMS Detector Monte Carlo (CDMS-DMC) is a simulation tool aimed at achieving a deeper understanding of the performance of the SuperCDMS detectors and aiding the dark matter search analysis. We present results from validation of the phonon physics described in the CDMS-DMC and outline work towards utilizing it in future WIMP search analyses.Comment: 6 Pages, 5 Figures, Proceedings of Low Temperature Detectors 14 Conferenc

The level-1 trigger for the SuperCDMS experiment at SNOLAB

The SuperCDMS SNOLAB dark matter search experiment aims to be sensitive to energy depositions down to Script O(1 eV). This imposes requirements on the resolution, signal efficiency, and noise rejection of the trigger system. To accomplish this, the SuperCDMS level-1 trigger system is implemented in an FPGA on a custom PCB. A time-domain optimal filter algorithm realized as a finite impulse response filter provides a baseline resolution of 0.38 times the standard deviation of the noise, $σ_{n}$, and a 99.9% trigger efficiency for signal amplitudes of 1.1 $σ_{n}$ in typical noise conditions. Embedded in a modular architecture, flexible trigger logic enables reliable triggering and vetoing in a dead-time-free manner for a variety of purposes and run conditions. The trigger architecture and performance are detailed in this article

A Search for WIMPs with the First Five-Tower Data from CDMS

We report first results from the Cryogenic Dark Matter Search (CDMS II) experiment running with its full complement of 30 cryogenic particle detectors at the Soudan Underground Laboratory. This report is based on the analysis of data acquired between October 2006 and July 2007 from 15 Ge detectors (3.75 kg), giving an effective exposure of 121.3 kg-d (averaged over recoil energies 10--100 keV, weighted for a weakly interacting massive particle (WIMP) mass of 60 \gev). A blind analysis, incorporating improved techniques for event reconstruction and data quality monitoring, resulted in zero observed events. This analysis sets an upper limit on the WIMP-nucleon spin-independent cross section of 6.6$\times10^{-44}$ cm$^2$ (4.6$\times10^{-44}$ cm$^2$ when combined with previous CDMS Soudan data) at the 90% confidence level for a WIMP mass of 60 \gev. By providing the best sensitivity for dark matter WIMPs with masses above 42 GeV/c$^2$, this work significantly restricts the parameter space for some of the favored supersymmetric models.Comment: 5 pages, 4 figures, submitted to PRL 28 March 200