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

Pulse shape discrimination performance of inverted coaxial Ge detectors

We report on the characterization of two inverted coaxial Ge detectors in the context of being employed in future 76Ge neutrinoless double beta (0) decay experiments. It is an advantage that such detectors can be produced with bigger Ge mass as compared to the planar Broad Energy Ge (BEGe) or p-type Point Contact (PPC) detectors that are currently used in the Gerda and Majorana Demonstrator 0 decay experiments respectively. This will result in a lower background for the search of 0 decay due to a reduction of detector surface to volume ratio, cables, electronics and holders which are dominating nearby radioactive sources. The measured resolution near the 76Ge Q-value at 2039 keV is 2.3 keV FWHM and their pulse-shape discrimination of background events are similar to BEGe and PPC detectors. It is concluded that this type of Ge-detector is suitable for usage in 76Ge 0 decay experiments.JRC.G.2-Standards for Nuclear Safety, Security and Safeguard

Gamma Production Cross Section Measurements for 76Ge via (n,n'gamma) at GELINA

This report describes the inelastic scattering data delivered to the Institute for Nuclear and Particle Physics of TU-Dresden. The GAINS setup was used for measurements of gamma production cross sections associated with the 69th excited state of 76Ge, using the (n, n'gamma) technique. The experimental work was performed at the GELINA facility at a 200 m flight path with eight high purity germanium detectors, using highly enriched 76Ge samples. A brief description of the experimental details and the results are presented.JRC.D.5-Nuclear physic

New Nuclear Structure and Decay Results in the 76Ge-76As System

The process of neutrinoless double beta decay (0νββ) plays a key role in modern neutrino physics. Experiments on 76Ge 0νββ-decay using germanium semiconductors are at the forefront in this field. Due to the extremely low count rates expected for th

New nuclear structure and decay results in the 76Ge-76As system

The process of neutrinoless double beta decay plays a key role in modern neutrino physics. The experiments on the 76Ge neutrinoless double beta decay using germanium-semiconductors are at the forefront in this field. Due to the extremely low count rates expected for this rare decay, any kind of background event in the detector, especially at energies close to Q = 2039 keV has to be avoided. Therefore a careful investigation on the neutron-induced background was carried out. In this scope experiments investigating the inelastic-neutron-excitation of 76Ge and the de-exitation of its 69th level have been performed. The 70Ge(n,jn)68Ge crossection was measured with quasi-monoenergetic neutrons. In order to calculate the Matrixelement for the transition between the 76Ge-76As groundstates the Electron Capture at 76As has been measured for the first time.JRC.D.4-Standards for Nuclear Safety, Security and Safeguard

Neutron inelastic scattering measurements for Na, Mo, Zr, Ge, and U

Studies for advanced reactor systems such as sodium-cooled fast reactors designed for recycling of high level waste, accelerator driven systems for transmutation, and systems envisioning the use of the Th/U fuel cycle impose tight requirements on nuclear data for accurate predictions of their operation and safety characteristics. Among the identied needs established by sensitivity studies, neutron inelastic scattering on the main structural materials and actinides and some (n,xn) cross sections for actinides feature prominently. Prompt-gamma spectroscopy and time-of-flight techniques were used to measure (n,xn) cross-sections of interest. Experiments were performed at the GELINA neutron time-of-flight facility of IRMM. Results and progress concerning 235;238U, are presented and discussed for 23Na, 76Ge, Zr and Mo.JRC.D.4-Standards for Nuclear Safety, Security and Safeguard

Neutron inelastic scattering, recent experiments and their interpretation

Measurements of inelastic scattering and (n,xn)-cross sections with the (n,xnγ)-technique are performed at the GELINA neutron time-of-flight facility with two arrays consisting of high purity germanium detectors, GAINS and GRAPHEME. These measurements provide important nuclear data for criticality, reactivity and power distribution estimates in current and advanced power reactors, for the development of active material interrogation techniques for security and safeguards, and for background studies supporting the search for neutrinoless double-beta decay in experiments like GERDA, and MAJORANA and for weakly interacting massive particles. Despite significant advances in modeling, such cross sections still pose a major challenge to nuclear theory at the level of the required accuracy. GAINS is an array consisting of 12 large volume detectors used to study inelastic scattering from C to Bi with high incident neutron energy resolution. GRAPHEME using four planar detectors, is tailored for the actinides. Recent and ongoing experimental work for 23Na, 76Ge, W and 232Th is presented. The experimental work is supported and complemented by state-of-the-art nuclear modeling with the well-known TALYS code using both a phenomenological and a microscopic approach, and with resonance analysis for selected nuclides. Advances and open issues will be shown. For carbon interesting complementary results were obtained using single-crystal diamond detectors.JRC.D.4-Standards for Nuclear Safety, Security and Safeguard

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

Study of the GERDA Phase II background spectrum

The Gerda experiment, located at the Laboratori Nazionali del Gran Sasso (LNGS) of INFN in Italy, searches for the neutrinoless double beta (0νββ) decay of 76Ge. Gerda Phase II is aiming to reach a sensitivity for the 0νββ half life of 1026 yr in ∼ 3 years of physics data taking with 100 kg·yr of exposure and a background index of ∼ 10−3 cts/(keV·kg·yr). After 6 months of acquisition a first data release with 10.8 kg·yr of exposure is performed, showing that the design background is achieved. In this work a study of the Phase II background spectrum, the main spectral structures and the background sources will be presented and discussed.JRC.G.2-Standards for Nuclear Safety, Security and Safeguard