Digital Pulseshape Analysis by Neural Networks for the Heidelberg-Moscow-Double-Beta-Decay-Experiment

The Heidelberg-Moscow Experiment is presently the most sensitive experiment looking for neutrinoless double-beta decay. Recently the already very low background has been lowered by means of a Digital Pulseshape Analysis using a one parameter cut to distinguish between pointlike events and multiple scattered events. To use all the information contained in a recorded digital pulse, we developed a new technique for event recognition based on neural networks.Comment: 12 pages, 5 figures, accepted for publication in E. Phys. J.

GENIUS and the Genius TF: A New Observatory for WIMP Dark Matter and Neutrinoless Double Beta Decay

The GENIUS proposal is described and some of it's physics potential is outlined. Also in the light of the contradictive results from the DAMA and CDMS experiments the Genius TF, a new experimental setup is proposed. The Genius TF could probe the DAMA evidence region using the WIMP nucleus recoil signal and WIMP annual modulation signature simultaneously. Besides that it can prove the long term feasibility of the detector technique to be implemented into the GENIUS setup and will in this sense be a first step towards the realization of the GENIUS experiment.Comment: 10 pages, revtex, 4 figures, Talk was presented at 3rd International Workshop on the Identification of Dark Matter, IDM2000, York, England, September 18-22, 2000, to be publ. in proc. World Scoentific (2001). Home Page of Heidelberg Non-Accelerator Particle Physics Group (GENIUS Experiment): http://www.mpi-hd.mpg.de/non_acc/genius.htm

Phase II Upgrade of the GERDA Experiment for the Search of Neutrinoless Double Beta Decay

AbstractObservation of neutrinoless double beta decay could answer the question regarding the Majorana or Dirac nature of neutrinos. The GERDA experiment utilizes HPGe detectors enriched with the isotope 76Ge to search for this process. Recently the GERDA collaboration has unblinded data of Phase I of the experiment. In order to further improve the sensitivity of the experiment, additionally to the coaxial detectors used, 30 BEGe detectors made from germanium enriched in 76Ge will be deployed in GERDA Phase II.BEGe detectors have superior PSD capability, thus the background can be further reduced. The liquid argon surrounding the detector array will be instrumented in order to reject background by detecting scintillation light induced in the liquid argon by radiation. After a short introduction the hardware preparations for GERDA Phase II as well as the processing and characterization of the 30 BEGe detectors are discussed

A first proof of principle booster setup for the MADMAX dielectric haloscope

Axions and axion-like particles are excellent low-mass dark matter candidates. The MADMAX experiment aims to directly detect galactic axions with masses between $40\,\mu{\rm eV}$ and $400\,\mu{\rm eV}$ by using the axion-induced emission of electromagnetic waves from boundaries between materials of different dielectric constants under a strong magnetic field. Combining many such surfaces, this emission can be significantly enhanced (boosted) using constructive interference and resonances. We present a first proof of principle realization of such a booster system consisting of a copper mirror and up to five sapphire disks. The electromagnetic response of the system is investigated by reflectivity measurements. The mechanical accuracy, calibration process of unwanted reflections and the repeatability of a basic tuning algorithm to place the disks are investigated. We find that for the presented cases the electromagnetic response in terms of the group delay predicted by one-dimensional calculations is sufficiently realized in our setup. The repeatability of the tuning is at the percent level, and would have small impact on the sensitivity of such a booster.Comment: 10 pages, 12 figures; minor changes, introduction and references expanded, matches published versio

Identification of photons in double beta-decay experiments using segmented germanium detectors - studies with a GERDA Phase II prototype detector

The sensitivity of experiments searching for neutrinoless double beta-decay of germanium was so far limited by the background induced by external gamma-radiation. Segmented germanium detectors can be used to identify photons and thus reduce this background component. The GERmanium Detector Array, GERDA, will use highly segmented germanium detectors in its second phase. The identification of photonic events is investigated using a prototype detector. The results are compared with Monte Carlo data.Comment: 20 pages, 7 figures, to be submitted to NIM-

Pulse shape simulation for segmented true-coaxial HPGe detectors

A new package to simulate the formation of electrical pulses in segmented true-coaxial high purity germanium detectors is presented. The computation of the electric field and weighting potentials inside the detector as well as of the trajectories of the charge carriers is described. In addition, the treatment of bandwidth limitations and noise are discussed. Comparison of simulated to measured pulses, obtained from an 18-fold segmented detector operated inside a cryogenic test facility, are presented.Comment: 20 pages, 16 figure

Deep learning based pulse shape discrimination for germanium detectors

Experiments searching for rare processes like neutrinoless double beta decay heavily rely on the identification of background events to reduce their background level and increase their sensitivity. We present a novel machine learning based method to recognize one of the most abundant classes of background events in these experiments. By combining a neural network for feature extraction with a smaller classification network, our method can be trained with only a small number of labeled events. To validate our method, we use signals from a broad-energy germanium detector irradiated with a $^{228}$Th gamma source. We find that it matches the performance of state-of-the-art algorithms commonly used for this detector type. However, it requires less tuning and calibration and shows potential to identify certain types of background events missed by other methods.Comment: Published in Eur. Phys. J. C. 9 pages, 10 figures, 3 table

Development of an anti-Compton veto for HPGe detectors operated in liquid argon using Silicon Photo-Multipliers

A proof of concept detector is presented for scintillation light detection in liquid argon using Silicon Photo-Multipliers. The aim of the work is to build an anti-Compton veto for germanium detectors operated directly in liquid argon like in the GERDA experiment. Properties of the Multi-Pixel Photon Counter (MPPC) are studied at cryogenic temperatures. To increase the light collection efficiency of the MPPCs wavelength shifting fibers were used. A veto efficiency comparable to a similar setup with a Photo-Multiplier Tube was achieved.Comment: 18 pages, 13 figure