Search

Low background experiments need active muon veto detectors to shield them from cosmic muons. Plastic scintillator panels with WLS fiber and multi-pixel Geiger-mode avalanche photodiodes readout are widely used in such experiments due to their compactness and robustness. In this paper, results from the study of the basic MRS APD parameters, such as breakdown voltages, quenching resistors, internal gain and dark count rates are presented, as well as temperature dependencies of some of these parameters. In a small fraction of the MRS APDs, some strange dips in the I–V curves just preceding the breakdown voltage point have been observed.

The 10 Mton scale Neutrino telescope NT 200 + is operating in Lake Baikal since April, 2005. It's main physics goal is the detection of high energy neutrino cascades in the 10 2 – 10 5 TeV energy range. The NT 200 + sensitivity to astrophysical diffuse neutrinos is four times that of it's predecessor NT200 the telescope that has been operating since 1998, yielding a variety of physics results. A km-scale (Gigaton Volume) Neutrino telescope in Lake Baikal is planned, the R&D phase has started in 2006. We give the basic layout of this Baikal km3-detector, which will be made of building blocks similar to NT 200 + .

The Baikal neutrino telescope NT200 takes data since 1998. In 2005, the deployment of three additional strings for common operation with NT200 was finished. We describe the physics program and the design of the new telescope named NT200+ and present selected physical results obtained with NT200. First results from NT200+ will be presented at the conference., Comment: 4 pages, 5 figures, Proceedings of 29th International Cosmic Ray Conference (ICRC) 2005, Pune, India

The Baikal Neutrino Telescope NT200 takes data since April 1998. On April 9th, 2005, the 10 Mton scale detector NT200$+$ was put into operation in Lake Baikal. Selected results obtained during 1998-2002 with the neutrino telescope NT200 are presented., 6 pages, 7 figures, presented at 2nd VLVNT Workshop on Very Large Volume Neutrino Telescope (VLVNT2), Catania, Italy, 8-11 Nov. 2005

We review the present status of the Baikal Neutrino Project and present selected results obtained from data taken in 1998 - 2000 (780 live days). We describe the moderate upgrade of NT-200 planned for the next years and discuss a possible detector on the Gigaton scale.

The GERmanium Detector Array, G erda , is a new experiment designed to examine the neutrinoless double beta decay 0 ν β β of 76 Ge which has a lifetime of at least 10 26 years and a single energy deposition of 2039 keV. To reach the goal of 10 - 3 background events/( keV kg y ), several background reduction techniques like anti-coincidence and pulse shape analysis will be used. Cosmic muons can produce background in form of particles and radioactivity. To reject them, two independent detector systems will be integrated in G erda . One of these is a Cherenkov muon veto detector, that uses the water tank around the cryostat in which the crystals will be operated. It is equipped with 66 photomultipliers (PMTs) with 8 in. diameter. The PMT distribution was found via extensive Monte Carlo studies to reach the highest efficiencies for dangerous muons (these are muons that cause an energy deposition of around 2 MeV in the germanium detectors), even though the PMTs cover less than 0.1% of the water tank surface. High efficiencies depend strongly on the amount of detected photons. For this, as many surfaces as possible will be covered with ‘VM2000’, a highly reflective foil from 3 M. This foil has a high reflectivity in a wide range of wavelength and it also shifts photons from the UV into the optical range. It, more or less, doubles the amount of detectable photons, because the photomultipliers used, have an detection maximum between 370 and 400 nm. Thus, a detection efficiency of 98% should be easily achieved.

The GERDA experiment searches for neutrinoless double beta decay ( 0 ν β β ). To achieve a sensitivity of 10 - 3 counts / ( keV kg y ) or better within a specific region of interest (ROI), a good background identification is needed. Therefore GERDA is located in the LNGS (Laboratori Nationali del Gran Sasso) underground facility. In addition to the good rejection of cosmic muons due to the surrounding bedrocks, a dual muon veto system has to be used. For calibration and monitoring of the muon veto, two separate systems have been developed.