Towards Coherent Neutrino Detection Using Low-Background Micropattern Gas Detectors

The detection of low energy neutrinos ($<$ few tens of MeV) via coherent nuclear scattering remains a holy grail of sorts in neutrino physics. This uncontroversial mode of interaction is expected to profit from a sizeable increase in cross section proportional to neutron number squared in the target nucleus, an advantageous feature in view of the small probability of interaction via all other channels in this energy region. A coherent neutrino detector would open the door to many new applications, ranging from the study of fundamental neutrino properties to true "neutrino technology". Unfortunately, present-day radiation detectors of sufficiently large mass ($>$ 1 kg) are not sensitive to sub-keV nuclear recoils like those expected from this channel. The advent of Micropattern Gas Detectors (MPGDs), new technologies originally intended for use in High Energy Physics, may soon put an end to this impasse. We present first tests of MPGDs fabricated with radioclean materials and discuss the approach to assessing their sensitivity to these faint signals. Applications are reviewed, in particular their use as a safeguard against illegitimate operation of nuclear reactors. A first industrial mass production of Gas Electron Multipliers (GEMs) is succinctly described.Comment: Presented at the 2002 IEEE Nuclear Science Symposium and Medical Imaging Conference, Norfolk VA, November 10-16. Submitted to IEEE Tran. Nucl. Sci. Five pages, eight figure

New Long-term Historical Data Recording and Failure Analysis System for the CERN Cryoplants

CERN uses several liquid helium cryoplants (total of 21) for cooling large variety of superconducting devices namely: accelerating cavities, magnets for accelerators and particle detectors. The cryoplants are remotely operated from several control rooms using industrial standard supervision systems, which allows the instant display of all plant data and the trends, over several days, for the most important signals. The monitoring of the cryoplant performance during transient conditions and normal operation over several months asks for a long-term recording of all plant parameters. An historical data recording system has been developed, which collects data from all cryoplants, stores them in a centralized database over a period of one year and allows an user-friendly graphical visualization. In particular, a novel tool was developed for debugging causes of plant failures by comparing selected reference data with the simultaneous evolution of all plant data. The paper describes the new system, already in operation with 11 cryoplants

Large-Mass Ultra-Low Noise Germanium Detectors: Performance and Applications in Neutrino and Astroparticle Physics

A new type of radiation detector, a p-type modified electrode germanium diode, is presented. The prototype displays, for the first time, a combination of features (mass, energy threshold and background expectation) required for a measurement of coherent neutrino-nucleus scattering in a nuclear reactor experiment. The device hybridizes the mass and energy resolution of a conventional HPGe coaxial gamma spectrometer with the low electronic noise and threshold of a small x-ray semiconductor detector, also displaying an intrinsic ability to distinguish multiple from single-site particle interactions. The present performance of the prototype and possible further improvements are discussed, as well as other applications for this new type of device in neutrino and astroparticle physics (double-beta decay, neutrino magnetic moment and WIMP searches).Comment: submitted to Phys. Rev.

Prospects For Identifying Dark Matter With CoGeNT

It has previously been shown that the excess of events reported by the CoGeNT collaboration could be generated by elastically scattering dark matter particles with a mass of approximately 5-15 GeV. This mass range is very similar to that required to generate the annual modulation observed by DAMA/LIBRA and the gamma rays from the region surrounding the Galactic Center identified within the data of the Fermi Gamma Ray Space Telescope. To confidently conclude that CoGeNT's excess is the result of dark matter, however, further data will likely be needed. In this paper, we make projections for the first full year of CoGeNT data, and for its planned upgrade. Not only will this body of data more accurately constrain the spectrum of nuclear recoil events, and corresponding dark matter parameter space, but will also make it possible to identify seasonal variations in the rate. In particular, if the CoGeNT excess is the product of dark matter, then one year of CoGeNT data will likely reveal an annual modulation with a significance of 2-3$\sigma$. The planned CoGeNT upgrade will not only detect such an annual modulation with high significance, but will be capable of measuring the energy spectrum of the modulation amplitude. These measurements will be essential to irrefutably confirming a dark matter origin of these events.Comment: 6 pages, 6 figure

Visualization of a DNA-PK/PARP1 complex

The DNA-dependent protein kinase (DNA-PK) and Poly(ADP-ribose) polymerase-1 (PARP1) are critical enzymes that reduce genomic damage caused by DNA lesions. They are both activated by DNA strand breaks generated by physiological and environmental factors, and they have been shown to interact. Here, we report in vivo evidence that DNA-PK and PARP1 are equally necessary for rapid repair. We purified a DNA-PK/PARP1 complex loaded on DNA and performed electron microscopy and single particle analysis on its tetrameric and dimer-of-tetramers forms. By comparison with the DNA-PK holoenzyme and fitting crystallographic structures, we see that the PARP1 density is in close contact with the Ku subunit. Crucially, PARP1 binding elicits substantial conformational changes in the DNA-PK synaptic dimer assembly. Taken together, our data support a functional, in-pathway role for DNA-PK and PARP1 in double-strand break (DSB) repair. We also propose a NHEJ model where protein–protein interactions alter substantially the architecture of DNA-PK dimers at DSBs, to trigger subsequent interactions or enzymatic reactions