Using pulse shape discrimination to sort individual energy deposition events in a germanium crystal

A fast digital oscilloscope based pulse shape discrimination (PSD) system has been tested with intrinsic germanium detectors large enough to allow ionizing events which generate localized electron-hole pairs at a single site to be segregated from those depositing energy at several different sites in the crystal. Drift velocities of the electrons and holes result in pulses several hundred nanoseconds long. Since the electric field varies by almost a factor of 10 between the outer and inner surfaces, collection of electrons and holes can frequently be dinstinguished, and pulses due to multi-site events can be distinguished from single site events.     

A cryogenic underground observatory for rare events: CUORE, an update

CUORE is a proposed tightly packed array of 1000 TeO₂ bolometers, each being a cube 5 cm on a side with a mass of 750 g. The array consists of 25 vertical towers, arranged in a square of 5 towers by 5 towers, each containing ten layers of four crystals. The design of the detector is optimized for ultralow-background searches for neutrinoless double beta decay of ¹³⁰Te (33.8% abundance), cold dark matter, solar axions, and rare nuclear decays. A preliminary experiment involving 20 crystals of various sizes (MIBETA) has been completed, and a single CUORE tower is being constructed as a smaller scale experiment called CUORICINO. The expected performance and sensitivity, based on Monte Carlo simulations and extrapolations of present results, are reported.     

Experimental search for solar axions

A new technique has been used to search for solar axions using a single crystal germanium detector. It exploits the coherent conversion of axions into photons when their angle of incidence satisfies a Bragg condition with a crystalline plane. The analysis of approximately 1.94 kg.yr of data from the 1 kg DEMOS detector in Sierra Grande, Argentina, yields a new laboratory bound on axion-photon coupling of g_αγγ < 2.7 × 10⁻⁹GeV⁻¹, independent of axion mass up to 1 keV.     

Absolute pair production cross section measurements in Z = 82 with 1.077 MeV photons

The absolute cross section for the production of electron-positron pairs by 1.077 MeV photons on lead was measured as 2.04 ± 0.10 mb. The ratio σ(exp)/σ(theor) = 1.5. This represents the closest to threshold measurement for Z = 82.     

First results from the CERN axion solar telescope

Hypothetical axionlike particles with a two-photon interaction would be produced in the sun by the Primakoff process. In a laboratory magnetic field ("axion helioscope"), they would be transformed into x-rays with energies of a few keV. Using a decommissioned Large Hadron Collider test magnet, the CERN Axion Solar Telescope ran for about 6 months during 2003. The first results from the analysis of these data are presented here. No signal above background was observed, implying an upper limit to the axion-photon coupling g(agamma)<1.16x10(-10) GeV-1 at 95% C.L. for m(a) less, similar 0.02 eV. This limit, assumption-free, is comparable to the limit from stellar energy-loss arguments and considerably more restrictive than any previous experiment over a broad range of axion masses.     

New isomers of 185,187Tl and the departure of the h92 intruder state

Isomeric decays were observed in on-line mass-separated products following the bombardment of ¹⁸⁰W and ¹⁸²W with ¹⁴N. The isomers are placed in ^185,187Tl with half lives of 1.8 ± 0.3 and 16 ± 1 s, respectively. The systematics of the low-lying levels of ^185–201Tl strongly suggest that the h${}_{\mathrm{<mtext>9</mtext><mtext>2</mtext>}}$ level intrudes into the next lowest shell and drops below the d${}_{\mathrm{<mtext>3</mtext><mtext>2</mtext>}}$ level at ¹⁹¹Tl, crosses again at ¹⁸⁷Tl and commences to depart the shell with further decrease in N.