25 research outputs found
Mössbauer antineutrinos: Recoilless resonant emission and absorption of electron antineutrinos
No full textEntwicklung eines neuartigen zusammengesetzten Tieftemperaturdetektors für den Einsatz in einem radiochemischen solaren Neutrino Experiment
No full textTo detect the decay via electron capture of 71Ge, which is produced by the interaction of solar neutrinos on 71Ga, a cryogenic detector, exhibiting both good energy resolution and high detection efficiency (4pi) was developed. The overall efficiency of Gallium based radiochemical solar neutrino experiments can be increased drastically, if this type of detector is introduced in such an experiment. The low-temperature detectors in question are based on superconducting phase transition thermometers (TESs). A specially developed glueing technique allows thermal deposition of 71Ge onto the low-temperature detector, which is completely decoupled from the production process of the TES. Furthermore the TESs can be connected via the glueing technique to various absorber materials. Longterm measurements with reactor-activated 71Ge were successfully performed in an especially set up cryostat in the underground laboratory in Garching. In addition to that, Ir/Au-microcalorimeters using Sn-absorbers achieved a worldwide best energy resolution (for Ir/Au TESs)) of 5.9eV at 5.9keV.Zum Nachweis des Germanium-Zerfalls durch Elektroneinfang an 71Ge, das aus 71Ga durch solare Neutrinos gebildet wird, wurden Tieftemperaturdetektoren mit guter Energieauflösung und voller (4pi) Nachweiseffizienz entwickelt. Dadurch kann die Gesamteffizienz der Experimente zum Nachweis solarer Neutrinos mit Gallium wesentlich verbessert werden. Diese Detektoren verwenden supraleitende Phasenübergangsthermometer (PT). Durch eine speziell entwickelte Klebung wird ermöglicht, die thermische Abscheidung von 71Ge von der Herstellung der PT vollständig zu entkoppeln. Weiterhin können die PT mit unterschiedlichen Absorbermaterialien verbunden werden. Langzeitstabile Messungen mit reaktoraktiviertem 71Ge wurden in einem eigens dafür aufgebauten Kryostaten im Untergrundlabor Garching erfolgreich durchgeführt. Auf der Klebetechnik aufbauende Ir/Au-Mikrokalorimeter mit supraleitendem Sn-Absorber erzielten ferner eine weltweit beste Energieauflösung von 5.9eV bei 5.9keV
Displacement sensor for a gravitational redshift experiment with <sup>67</sup>Zn Mössbauer resonance
No full textA displacement sensor was constructed to monitor the motion of a piezoelectric Doppler velocity transducer in a gravitational redshift experiment with 67Zn Mössbauer resonance. The sensor uses a dc superconducting quantum interference device (SQUID) to detect small displacements of a permanent magnet. To meet the stringent requirements of the redshift experiment, the magnetic flux gradient and the pickup coil of the sensor are designed in such a way that the SQUID flux noise of 7 × 10−6 Φ0/√Hz corresponds to a displacement resolution of 6 × 10−14 m/√Hz. However, resolution up to 3 × 10−15 m/√Hz in the frequency band of 20–20 000 Hz is demonstrated. The linearity of the displacement sensor and the piezoelectric transducer are considered in detail and the resulting uncertainties associated with the Doppler modulation in the Mössbauer experiment are evaluated
Search for modulations of the solar 7Be flux in the next-generation neutrino observatory LENA
No full textA next-generation liquid-scintillator detector will be able to perform high-statistics measurements of the solar neutrino flux. In LENA, solar 7Be neutrinos are expected to cause 1.7×104 electron recoil events per day in a fiducial volume of 35 kilotons. Based on this signal, a search for periodic modulations on a subpercent level can be conducted, surpassing the sensitivity of current detectors by at least a factor of 20. The range of accessible periods reaches from several minutes, corresponding to modulations induced by helioseismic g-modes, to tens of years, allowing to study long-term changes in solar fusion rates
Neutrinoless double-beta decay and seesaw mechanism
No full textFrom the standard seesaw mechanism of neutrino-mass generation, which is based on the assumption that the lepton number is violated at a large (∼1015 GeV) scale, it follows that the neutrinoless double-beta decay (0νββ-decay) is ruled by the Majorana neutrino-mass mechanism. With this notion, we derive for the inverted neutrino-mass hierarchy the allowed ranges of the half-lives of the 0νββ-decay for nuclei of experimental interest with different sets of nuclear matrix elements. The present-day results of the calculation of the 0νββ-decay nuclear matrix elements are briefly discussed. We argue that if 0νββ-decay will be observed in future experiments sensitive to the effective Majorana mass in the inverted mass hierarchy region, then a comparison of the derived ranges with measured half-lives will allow us to probe the standard seesaw mechanism assuming that future cosmological data will establish the sum of the neutrino masses to be about 0.2 eV
Probing the Earth's interior with the LENA detector
No full textA future large-volume liquid scintillator detector such as the proposed 50 kton LENA (Low Energy Neutrino Astronomy) detector would provide a high-statistics measurement of terrestrial antineutrinos originating from -decays of the uranium and thorium chains. Additionally, the neutron is scattered in the forward direction in the detection reaction . Henceforth, we investigate to what extent LENA can distinguish between certain geophysical models on the basis of the angular dependence of the geoneutrino flux. Our analysis is based on a Monte-Carlo simulation with different levels of light yield, considering an unloaded PXE scintillator. We find that LENA is able to detect deviations from isotropy of the geoneutrino flux with high significance. However, if only the directional information is used, the time required to distinguish between different geophysical models is of the order of severals decades. Nonetheless, a high-statistics measurement of the total geoneutrino flux and its spectrum still provides an extremely useful glance at the Earth's interior
