Authors: Schulz, Oliver
Title: Exploration of new data acquisition and background reduction techniques for the COBRA experiment
Language (ISO): en
Abstract: This work has contributed improvements to several key aspects of the COBRA double-beta decay experiment. A new data acquisition chain was developed for pulse-shape based readout of the COBRA coplanar grid (CPG) detectors. Prototype electronics for detector signal transmission and amplification were developed, as well as a software package with algorithms for pulse shape analysis of CPG detector signals. The pulse shape data readout has already resulted in significant improvements of the detector energy resolution. Pulse shape analysis has added interaction depth information to data output of the experiment, which has already shown itself to be an effective tool to suppress part of the background. A wavelet-based data compression technique has been developed to cope with the significant increase of data volume inherent to the recording of the full detector pulse shapes. A flexible data acquisition software framework was developed along with the new DAQ hardware chain. It is designed for both research and development applications and long-term physics data collection and is now in production use at several sites in the COBRA collaboration. The framework was also designed to scale up to the requirements of a large-scale experiment and its modular nature ensures that future components can be integrated easily. This work has contributed to the reduction of the radiation background level by over an order of magnitude, achieved by the combination of new CPG detector coatings and contacting methods with nitrogen flushing of the COBRA setup to create a radon-free environment. For the first time, low-background physics data was taken with a CdZnTe pixel detector. The results show that pixel detectors present an exciting option for the future of the experiment. Work is currently under way to scale up the new CPG electronics to a high channel count. The COBRA CPG setup at LNGS is scheduled to be upgraded to a higher number of detectors in 2011, which will all be run using the new DAQ system. A detailed study of the detector pulse shapes using simulations and collimated scans, currently in progress, will yield the necessary basis for advanced CPG pulse shape analysis. This will, in the future, enable new form of background suppression like separation between single-site and multi-site events.
Subject Headings: Background reduction
Cadmium zinc telluride
COBRA experiment
CPG detector
Data aquisition
Fast ADC
Majorana neutrino
Neutrinoless double-beta decay
Pixel detector
Pulse shape analysis
Issue Date: 2011-09-20
Appears in Collections:Experimentelle Physik IV

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