Status of the GERDA experiment

The study of neutrinoless double beta (0nbb) decay is the only one presently known approach to the fundamental question if the neutrino is a Majorana particle, i.e. its own anti-particle. The observation of 0nbb decay would prove that lepton number is not conserved, establish that neutrino has a Majorana component and, assuming that light neutrino is the dominating process, provide a method for the determination of its effective mass. GERDA is a new 0nbb decay experiment which is currently taking data at the Laboratori Nazionali del Gran Sasso (LNGS) of INFN in Italy. It implements a new shielding concept by operating bare diodes made from Ge with enriched 76Ge in high purity liquid argon supplemented by a water shield. The aim of GERDA is to verify or refute the recent claim of discovery, and, in a second phase, to achieve a two orders of magnitude lower background index than past experiments, to increase the sensitive mass and to collect an exposure of 100 kg yr. The paper will discuss design, physics reach, and status of data taking of GERDA.JRC.D.4-Standards for Nuclear Safety, Security and Safeguard

Test of internal halo targets in the HERA proton ring

Internal wire targets in the halo of stored proton beams provide a line source of proton-nucleus interactions for highest-rate fixed target experiments. We have studied such internal halo targets at the 820 GeV proton ring of the HERA ep collider. The tests showed that most of the protons in the beam halo -which would otherwise hit the collimators - can be brought to interaction in a relatively thin target wire at distances of 7 to 8 beam widths from the center of the beam. At less than 10% of the HERA total design current, and less than 20% of the current per bunch, interaction rates up to 8 MHz were observed, corresponding to more than 2 interactions per bunch crossing. The halo targets were used in parallel to the HERA luminosity operation; no significant disturbances of the HERA ep experiments, of the machine stability or beam quality were observed. We present data on the steady-state and transient behaviour of interaction rates and discuss the interpretation in terms of a simple beam dynamics model. Issues of short-, medium- and long-term rate fluctuations and of rate stabilization by feedback are addressed. (orig.)Available from TIB Hannover: RA 2999(94-119) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman

Irradiation tests of double-sided silicon strip detectors with a special guard ring structure

The results of the first irradiation tests of newly designed silicon microstrip detectors performed with 21 MeV protons at the Max-Planck-Institut in Heidelberg are presented. The detectors were developed and produced by the semiconductor laboratory of the Max-Planck-Institut in Munich. Novel guard ring structures allow operation of the detectors at voltages exceeding 300 V. (orig.)11 refs.SIGLEAvailable from TIB Hannover: RR 2916(95-29) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekDEGerman

Germanium Detector Array, GERDA

The GERmanium Detector Array, GERDA, is designed to search for 'neutrinoless double beta decay' (0v2ß) in 76Ge. The high-purity segmented Ge detectors will be directly submerged and operated in liquid N2 or Ar. The measurement of the half-life time of 0v2ß decay will provide information about the absolute neutrino mass scale and indirectly, the hierarchy. The design goal of GERDA is to reach a sensitivity of 0.2 eV on the effective Majorana neutrino mass (mßß). The GERDA experiment is located in hall A of the Grand Sasso national lab (LNGS) and the construction will start in 2006.JRC.D.4-Isotope measurement

The GERDA Neutrinoless Double Beta-Decay Experiment

Neutrinoless double beta-decay is the key process to gain understanding of the nature of neutrinos. The GErmanium Detector Array (GERDA) is designed to search for this decay of the isotope Ge-76. Germanium crystals enriched in Ge-76, acting as source and detector simultaneously, will be submerged directly into an ultra pure cooling medium that also serves as a radiation shield. This concept will allow for a reduction of the background by up to two orders of magnitudes with respect to earlier experiments.JRC.D.4-Isotope measurement

The GERDA experiment: status and perspectives

The GERDA experiment is located in the underground Gran Sasso laboratory. The experiment aims at studying the neutrinoless ββ decay of 76Ge. The implementation of the experiment is divided in two consecutive phases. Phase I will allow within one year of data taking to reach a sensitivity limit for the half life of the process of the order of 2.5×1025 years. Phase II, with an increased amount of active material and a background index lower by one order of magnitude than in Phase I, will allow to reach a half life limit of about 1.5×1026 years. In the present paper a brief review of the status of the experiment and its perspectives is given.JRC.D.4-Standards for Nuclear Safety, Security and Safeguard

First results of GERDA Phase II and consistency with background models

The GERDA (GERmanium Detector Array) is an experiment for the search of neutrinoless double beta decay (0νββ) in 76Ge, located at Laboratori Nazionali del Gran Sasso of INFN (Italy). GERDA operates bare high purity germanium detectors submersed in liquid Argon (LAr). Phase II of data-taking started in Dec 2015 and is currently ongoing. In Phase II 35 kg of germanium detectors enriched in 76Ge including thirty newly produced Broad Energy Germanium (BEGe) detectors is operating to reach an exposure of 100 kg·yr within about 3 years data taking. The design goal of Phase II is to reduce the background by one order of magnitude to get the sensitivity for ν02/1T = O(1026) yr. To achieve the necessary background reduction, the setup was complemented with LAr veto. Analysis of the background spectrum of Phase II demonstrates consistency with the background models. Furthermore 226Ra and 232Th contamination levels consistent with screening results. In the first Phase II data release we found no hint for a 0νββ decay signal and place a limit of this process ν02/1T> 5.3·1025 yr (90% C.L., sensitivity 4.0·1025 yr). First results of GERDA Phase II will be presented.JRC.G.2-Standards for Nuclear Safety, Security and Safeguard

First results from GERDA Phase II

Gerda is designed for a background-free search of 76Ge neutrinoless double-β decay, using bare Ge detectors in liquid Ar. The experiment was upgraded after the successful completion of Phase I to double the target mass and further reduce the background. Newly-designed Ge detectors were installed along with LAr scintillation sensors. Phase II of data-taking started in Dec 2015 with approximately 36 kg of Ge detectors and is currently ongoing. The first results based on 10.8 kgcenterdot yr of exposure are presented. The background goal of 10−3 cts/(keVcenterdot kgcenterdot yr) is achieved and a search for neutrinoless double-β decay is performed by combining Phase I and II data. No signal is found and a new limit is set at $T_{1/2}^{0\nu } > 5.3 \cdot {10^{25}}$ yr (90% C.L.).JRC.G.2-Standards for Nuclear Safety, Security and Safeguard