A new approach to ionizing radiation detection is proposed. The amount of ionization produced in a detector medium is measured by the heat generated as the charged carriers are drifted across the device under an applied voltage. The amount of energy generated can be orders of magnitude larger than that deposited by the radiation itself. A dramatic increase in detector mass can be achieved compared to simple calorimetric particle detectors for equivalent energy thresholds. It is possible to obtain a sensitivity level sufficient for single-carrier detection. The principle of operation has been demonstrated with an experimental device operated at a temperature of 1.8 K, and improved performance is expected at lower temperatures.

The Majorana Collaboration is operating an array of high purity Ge detectors to search for neutrinoless double-β decay in ^{76}Ge. The Majorana Demonstrator comprises 44.1 kg of Ge detectors (29.7 kg enriched in ^{76}Ge) split between two modules contained in a low background shield at the Sanford Underground Research Facility in Lead, South Dakota. Here we present results from data taken during construction, commissioning, and the start of full operations. We achieve unprecedented energy resolution of 2.5 keV FWHM at Q_{ββ} and a very low background with no observed candidate events in 9.95 kg yr of enriched Ge exposure, resulting in a lower limit on the half-life of 1.9×10^{25}  yr (90% C.L.). This result constrains the effective Majorana neutrino mass to below 240-520 meV, depending on the matrix elements used. In our experimental configuration with the lowest background, the background is 4.0_{-2.5}^{+3.1}  counts/(FWHM t yr).

No abstract

A new method to preferentially sense the collection of single-polarity charge carriers in ionization detectors is presented. It uses coplanar electrodes to closely emulate the function of Frisch grids commonly employed in gas and liquid ionization detectors. The coplanar electrode structure allows for easy implementation on semiconductor detectors. This method can be used to obtain good energy resolution from detectors in which only one polarity type of carriers is efficiently collected. Experimental results using a CdZnTe detector demonstrate the effectiveness of this method.

The MajoranaDemonstratorwill search for the neutrinoless double-beta(ββ0ν)decay of the isotopeGe with a mixed array of enriched and natural germanium detectors. The observation of this rare decay would indicate that the neutrino is its own antiparticle, demonstrate that lepton number is not conserved, and provide information on the absolute mass scale of the neutrino. The Demonstratoris being assembled at the 4850-foot level of the Sanford Underground Research Facility in Lead, South Dakota. The array will be situated in a low-background environment and surrounded by passive and active shielding. Here we describe the science goals of the Demonstratorand the details of its design.

No abstract

The focus of this paper is to evaluate thick, 20ϫ 20ϫ 10 and 10ϫ 10ϫ 10 mm 3 , cadmium zinc telluride ͑CZT͒, Cd 0.9 Zn 0.1 Te, crystals grown using the traveling heater method ͑THM͒. The phenomenal spectral performance and small size and low concentration of Te inclusions/precipitates of these crystals indicate that the THM is suitable for the mass production of CZT radiation detectors that can be used in a variety of applications. Our result also proves that with careful material selection using IR and high-quality fabrication processes, the theoretical energy resolution limit can be achieved.

No abstract