Search

The CDMS II experiment ran between 2003 and 2009. A total of 30 germanium and silicon ZIP detectors were operated, producing a high quality set of data that has been analyzed for evidence of and placed leading constraints on standard, low-mass, electron-recoil, and annually modulating WIMP interactions. This article will describe the general operation principles behind the CDMS detectors, report on the results of major Ge and Si detector analyses, and describe the current and future activities of the SuperCDMS program. [ABSTRACT FROM AUTHOR]

After briefly summarizing the motivations for the Λ-CDM model, I will argue rather provocatively that the many candidates already reported by indirect detection experiments are a strong indication that it is nearly impossible to distinguish a WIMP annihilation signal from astrophysical background using the indirect detection method. This structural uncertainty argues strongly in favor of direct detection of WIMP interactions in the controlled environment of the laboratory and I will describe the main strategies developed to detect WIMPs using the direct detection technique in underground sites, protected from the cosmic-ray induced background. I will show that most of the present experimental efforts is now focused on three identification techniques of nuclear recoils, i.e. charge-phonon, light-phonon and charge-scintillation simultaneous detection. Finally, since direct detection has also its own candidate, I will comment on the DAMA annual modulation candidate, and on the lessons that can be learned from the long controversy over this result. [ABSTRACT FROM AUTHOR]

The CDMS collaboration utilizes Ge detectors for their Weakly Interacting Massive Particle (WIMP) search at the Soudan mine, Minnesota. The final data run of CDMS II is complete and a detector upgrade for SuperCDMS has commenced. A SuperTower of five 1-inch thick Ge crystals has been installed and undergoing commissioning. Its surface-event rejection capability should allow SuperCDMS to continue to run background free for the next proposed phases: 15 kg Ge deployment at Soudan, and up to 150 kg Ge deployment at SNOLAB. Recent detector advances to allow a 1 tonne Ge experiment are also discussed. [ABSTRACT FROM AUTHOR]

The linear dynamic range available for Frequency-Domain-Multiplexed (FDM) read-out of TES X-ray detectors is seriously limited by the SQUID current amplifiers used for the read-out of TES-detectors. Baseband feedback is one of the ways to increase the linearity and dynamic range of SQUIDs for the TES signals. Baseband feedback is realized by demodulation, and low-pass filtering of the AM-signals at the amplified summing point, thereby retrieving the signals for each detector, and subsequent remodulation and summing of the individual detector signals with phase compensation for the delay and phase rotation at each carrier frequency. This algorithm creates sufficient gain-bandwidth at and around each carrier frequency (1–10 MHz) to reduce the error signal at the input of the SQUID amplifier for both the AC-carriers and the signals modulated onto them. The paper presents the principle, modeling, and initial results. [ABSTRACT FROM AUTHOR]

A new design for the Ge bolometers of the EDELWEISS project is described here, based on innovative interleaved charge collection electrodes with high background discrimination capabilities. The measured surface event rejection is compatible with WIMP sensitivity levels down to 10-9 picobarn (pb). Use of interleaved electrodes on the overall surface of the Ge crystal, including its lateral surface, results to a high fiducial volume of the order of 80%. Electronic setup is fairly simple with a total of five JFET based read-out amplifiers, one for the NTD-Ge heat channel and four for the ionization signal. Fabrication process is quite simple and the design is easily scalable to higher mass bolometers (1 kg Ge crystal), making it very appealing for the future 1 ton scale EUREKA Dark Matter experiment. [ABSTRACT FROM AUTHOR]

For its dark matter search the SuperCDMS collaboration has developed new Ge detectors using the same athermal phonon sensors and ionization measurement technology of CDMS II but with larger mass, superior sensor performance and increased fabrication efficiency. The improvements in fabrication are described, a comparison of CDMS II and SuperCDMS detector production yield is reported, and future scalability addressed. [ABSTRACT FROM AUTHOR]

Metallic magnetic calorimeters allow a high energy resolution even using absorbers with large heat capacities. For this reason, they are well suited for applications such as ionizing radiation metrology requiring gamma-ray spectrometry with high detection efficiencies. We are developing detectors for gamma-ray spectrometry with gold absorbers (1.0 mm diameter, 0.33 mm thickness) that have an intrinsic detection efficiency of about 60% at 100 keV. They have a theoretical energy resolution of 23 eV at 20 mK. The paramagnetic Au:Er sensor is coupled to a two-stage SQUID setup via a meander shaped pickup coil made of a niobium thin-film. For a temperature of 13 mK, one of our detectors showed an energy resolution of 58 eV at 81 keV. The baseline energy resolutions were 46 eV and 68 eV respectively at 13 mK and 20 mK, which is more than calculated; the measured signal sizes were smaller than expected. This problem can be overcome by sputter-depositing the sensor (enriched in 166Er) on the meander pickup coil; both the niobium and the Au:Er thin films are of high quality. The thermodynamic properties of a sputter-deposited sensor were characterized below 100 mK for different bias currents up to 140 mA in the meander shaped pick-up coil. We obtained a good agreement between the measured and calculated magnetizations, heat capacities and signal sizes. Hence, using these sensors for the next gamma-ray magnetic calorimeter, we expect a significant improvement of the energy resolution in the near future. [ABSTRACT FROM AUTHOR]

The identification of Dark Matter is an outstanding question of contemporary physics. I summarize the main experimental strategies developed to answer this question, focusing on cryogenic detectors and comparing these detectors to their double-phase xenon and argon competitors. I discuss in particular the main developments in charge-phonon (CDMS, EDELWEISS) and light-phonon detectors (CRESST, ROSEBUD). Finally, I discuss the prospects of WIMP detection within the next few years by the CDMS, CRESST, EDELWEISS and XENON experiments, and their successors EURECA, GEODM and XENON-1 ton. [ABSTRACT FROM AUTHOR]

The newly commissioned SuperCDMS Soudan experiment aims to search for WIMP dark matter with a sensitivity to cross sections of 5×10-45cm2 and larger (90% CL upper limit). This goal is facilitated by a new set of germanium detectors, 2.5 times more massive than the ones used in the CDMS-II experiment, and with a different athermal phonon sensor layout that eliminates radial degeneracy in position reconstruction of high radius events. We present characterization data on these detectors, as well as improved techniques for correcting position-dependent variations in pulse shape across the detector. These improvements provide surface-event discrimination sufficient for a reach of 5×10-45cm2. [ABSTRACT FROM AUTHOR]

During the past year, the first results from a new generation of instruments based on kilopixel-scale arrays of cryogenic detectors have been released. I will review the history of low temperature detector arrays which has enabled this development, the science which has driven this rapid progress, describe the instruments now in operation and their initial scientific results, and speculate on the developments we may see in the next decade. [ABSTRACT FROM AUTHOR]

The present status of the Cryogenic Underground Observatory for Rare Events (CUORE) is presented along with the latest results from its prototype, CUORICINO. [ABSTRACT FROM AUTHOR]

The CDMS-II collaboration’s Cold Dark Matter search presently sets the most competitive exclusion limit in the world for the direct detection of the hypothesized Weakly Interacting Massive Particles (WIMPs) that constitute the cold dark matter of the Universe. Our experiment utilizes Ge (and Si) crystals as the target detectors, each with a mass of 250 g (100 g) and cooled to 30 mK. To eliminate natural radioactive sources as background the experiment is conducted in a well-shielded environment in the Soudan Mine, Minnesota, and has been operating for the last two years. To aid in the identification of a possible WIMP-candidate event, the detectors are designed to measure both the ionization and athermal phonon signals produced by each candidate event. The athermal phonon signal is measured using superconducting aluminum films on the crystal surface connected to tungsten transition edge sensors. The latest WIMP-search results from Soudan will be presented, along with projections for the future. © 2006 American Institute of Physics [ABSTRACT FROM AUTHOR]

The present status of the Cryogenic Underground Observatory for Rare Events (CUORE) is presented along with the latest results from its operating prototype, CUORICINO. © 2006 American Institute of Physics [ABSTRACT FROM AUTHOR]