Timepix background studies for double beta decay experiments

Abstract

The double beta decay (β β ) is very challenging subject of today's physics. It can be used as a powerful tool to test neutrino properties (e.g. Dirac or Majorana type of neutrino) and lepton number conservation. However, these experiments demand very high sensitivity and very strong background reduction. We have been performing intensive R&D towards the use of pixel detector Timepix in the β β decay experiments. The Timepix device, operated in Time Over Threshold (TOT) mode, provides spectroscopic capabilities in each individual pixel. The main advantage of such detector is its ability to identify and reject background signals (e.g. tracks made by electrons, alpha particles, muons). It would efficiently recognize the signal of β β decay processes. Two pixel detectors, Si (pixel size 55×55 µm 2 ) and CdTe (pixel size 110×110 µm 2 ), were tested in the surface laboratory as well as in the underground laboratories, from the point of view of intrinsic background and the results are presented. Low background materials for construction of the setup were also identified. The first prototype of Silicon Pixel Telescope (SPT) has been tested and future improvements are also presented.

Characterization of a pixelated CdTe Timepix detector operated in ToT mode

“…Here, it can be used both as a source and a detector, avoiding the need for a source foil surrounded by other types of detectors. The excellent tracking capabilities of the Timepix chip combined with its energy sensitivity are powerful tools for dissociating events of interest from background [27,28]. In this case, the use of telescopes with two TPX-CdTe devices facing each other would permit an increase in statistics and tracking efficiency.…”

Improvement of the energy resolution of pixelated CdTe detectors for applications in 0νββsearches

“…Currently four 4 × 4 arrays of 1 × 1 × 1 cm 3 detectors are taking data in the underground laboratory LNGS. Another technology investigated in COBRA were fine pixelated CdTe detectors with a pixel pitch in the order of 100 µm [7,8], mainly the Timepix detector. This would offer the possibility of background rejection by identifying the particles by their track topologies.…”

Rejection of α-particle background for neutrinoless double beta decay search with pixel detectors

“…The main approach of COBRA is to use cubic CdZnTe coplanar grid detectors (CPG) with a size of 1 cm 3 of which two 4 × 4 arrays started taking data in the Italian underground laboratory LNGS in April 2012 [7], currently four 4 × 4 arrays are taking data. A different approach that was investigated in the COBRA-collaboration was the use of pixelated CdTe detectors [5,6]. These are more difficult to scale to larger masses than the CPGs, currently the sensitive volume of the pixel detectors is lower, so more detectors would be required, and the technology is more complex [8].…”