40099983
First observation of excited states in Li-12
The neutron-unbound ground state and two excited states of {sup 12}Li were formed by the two-proton removal reaction from a 53.4-MeV/u {sup 14}B beam. The decay energy spectrum of {sup 12}Li was measured with the Modular Neutron Array (MoNA) and the Sweeper dipole superconducting magnet at the National Superconducting Cyclotron Laboratory. Two excited states at resonance energies of 250 +- 20 keV and 555 +- 20 keV were observed for the first time and the data are consistent with the previously reported s-wave ground state with a scattering length of a{sub s}=-13.7 fm.
111274459
Microgap multiwire chambers
The multiwire proportional counter (MWPC) is well established device for capturing x-ray images at synchrotron sources such as at the synchrotron radiation source (SRS) at Daresbury. The latest generation of synchrotrons can deliver much more intense x-ray fluxes than the SRS which itself produces xray fluxes well beyond the capabilities of current photon counting detectors. There is an imminent demand for 2-D photon counting detectors which can cope with rates >10 5 photons/mm 2 /sec locally and readout systems with an unbuffered throughput of >10 7 events per second. This must be achieved with a high dynamic range and a good efficiency. The detector development group at the SRS have developed the wire microgap detector to address these problems. A new readout system has been designed using a highly parallel approach. Each detector channel in the detector is separately instrumented, and the data is accumulated using fast, state-of-the-art electronics systems. A prototype of the system has been constructed and tested with the 2 dimensional wire microgap detector. We report the results of the use of a wire microgap linear detector on the SRS and the first results from the 2D wire microgap detector system.
85552363
A simple high-sensitivity technique for purity analysis of xenon gas
We report on the development and performance of a high-sensitivity purity-analysis technique for gaseous xenon. The gas is sampled at macroscopic pressure from the system of interest using a UHV leak valve. The xenon present in the sample is removed with a liquid-nitrogen cold trap, and the remaining impurities are observed with a standard vacuum massspectroscopy device. Using calibrated samples of xenon gas spiked with known levels of impurities, we find that the minimum detectable levels of N2, O2, and methane are 1·10 −9 g/g, 160·10 −12 g/g, and 60·10 −12 g/g respectively. This represents an improvement of about a factor of 10000 compared to measurements performed without a cold trap.
123009611
A search for weakly interacting dark matter with the LUX experiment
Cosmological and astrophysical measurements indicate that our galaxy is filled with a new type of matter previously unknown to physics. This "dark matter" apparently has no electromagnetic or strong interactions, but an interaction of the strength of the weak nuclear force is strongly suggested by the data. The LUX collaboration is attempting to detect the faint signature of weakly interacting dark matter as it passes through the earth. The experiment searches for recoiling atomic nuclei in a target consisting of 350 kg of liquefied xenon. LUX is the largest experiment of its type ever attempted, and it is expected to improve upon current experimental sensitivities by two orders of magnitude. The experiment is being assembled at the Sanford Underground Science and Engineering Laboratory (SUSEL) in Lead, South Dakota, USA, and first data is expected in 2011. We report on the status of LUX and the prospects for future large-scale dark matter searches with liquid xenon.