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.
8809403
Use of a wave reverberation technique to infer the density compression of shocked liquid deuterium to 75 GPa.
A novel approach was developed to probe density compression of liquid deuterium (L-D2) along the principal Hugoniot. Relative transit times of shock waves reverberating within the sample are shown to be sensitive to the compression due to the first shock. This technique has proven to be more sensitive than the conventional method of inferring density from the shock and mass velocity, at least in this high-pressure regime. Results in the range of 22-75 GPa indicate an approximately fourfold density compression, and provide data to differentiate between proposed theories for hydrogen and its isotopes.
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.
62801144
Study of a zirconium getter for purification of xenon gas
Abstract Oxygen, nitrogen and methane purification efficiencies for a common zirconium getter are measured in 1050 Torr of xenon gas. Starting with impurity concentrations near 10 −6  g/g, the outlet impurity level is found to be less than 120 ×10 −12  g/g for O 2 and less than 950×10 −12  g/g for N 2 . For methane we find residual contamination of the purified gas at concentrations varying over three orders of magnitude, depending on the purifier temperature and the gas flow rate. A slight reduction in the purifier's methane efficiency is observed after 13 mg of this impurity has been absorbed, which we attribute to partial exhaustion of the purifier's capacity for this species. We also find that the purifier's ability to absorb N 2 and methane can be extinguished long before any decrease in O 2 performance is observed, and slower flow rates should be employed for xenon purification due to the cooling effect that the heavy gas has on the getter.