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Search Results: 1 - 10 of 258579 matches for " F. v. Feilitzsch "
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Microscopic Model for the Scintillation-Light Generation and Light-Quenching in CaWO$_4$ single crystals
S. Roth,F. v. Feilitzsch,J. -C. Lanfranchi,W. Potzel,S. Sch?nert,A. Ulrich
Physics , 2015,
Abstract: Scintillators are employed for particle detection and identification using light-pulse shapes and light quenching factors. We developed a comprehensive model describing the light generation and quenching in CaWO$_4$ single crystals used for direct dark matter search. All observed particle-dependent light-emission characteristics can be explained quantitatively, light-quenching factors and light-pulse shapes are calculated on a microscopic basis. This model can be extended to other scintillators such as inorganic crystal scintillators, liquid noble gases or organic liquid scintillators.
Thermal detector model for cryogenic composite detectors for the dark matter experiments CRESST and EURECA
Roth, S.;Ciemniak, C.;Coppi, C.;Feilitzsch, F. v.;Guetlein, A.;Isaila, C.;Lanfranchi, J. -C.;Pfister, S.;Potzel, W.;Westphal, W.
High Energy Physics - Phenomenology , 2008, DOI: 10.1088/1742-6596/136/4/042085
Abstract: The CRESST (Cryogenic Rare Event Search with Superconducting Thermometers) and the EURECA (European Underground Rare Event Calorimeter Array) experiments are direct dark matter search experiments where cryogenic detectors are used to detect spin-independent, coherent WIMP (Weakly Interacting Massive Particle)-nucleon scattering events by means of the recoil energy. The cryogenic detectors use a massive single crystal as absorber which is equipped with a TES (transition edge sensor) for signal read-out. They are operated at mK-temperatures. In order to enable a mass production of these detectors, as needed for the EURECA experiment, a so-called composite detector design (CDD) that allows decoupling of the TES fabrication from the optimization procedure of the absorber single-crystal was developed and studied. To further investigate, understand and optimize the performance of composite detectors a detailed thermal detector model which takes into account the CDD has been developed.
Cryogenic Composite Detectors for the Dark Matter Experiments CRESST and EURECA
S. Roth,C. Ciemniak,C. Coppi,F. v. Feilitzsch,A. Guetlein,C. Isaila,J. -C. Lanfranchi,S. Pfister,W. Potzel,W. Westphal
Physics , 2008,
Abstract: Weakly Interacting Massive Particles (WIMPs) are candidates for non-baryonic Dark Matter. WIMPs are supposed to interact with baryonic matter via scattering off nuclei producing a nuclear recoil with energies up to a few 10 keV with a very low interaction rate of ~10^(-6) events per kg of target material and day in the energy region of interest. The Dark Matter experiment CRESST (Cryogenic Rare Event Search with Superconducting Thermometers) and the EURECA project (European Underground Rare Event Calorimeter Array) are aimed at the direct detection of WIMPs with the help of very sensitive modularised cryogenic detectors that basically consist of a transition edge sensor (TES) in combination with a massive absorber crystal. In the CRESST experiment the search for coherent WIMP-nucleon scattering events is validated by the detection of two processes. In the scintillating absorber single crystal, CaWO_4, heat (phonons) and scintillation light are produced and detected with two independent cryogenic detectors: a phonon channel and a separate light channel. The development of such cryogenic detectors and the potential ton-scale production are investigated in this paper. To decouple the TES production from the choice of the target material in order to avoid heating cycles of the absorber crystal and to allow pretesting of the TESs, a composite detector design (CDD) for the detector production has been developed and studied. An existing thermal detector model has been extended to the CDD, in order to investigate, understand, and optimize the performance of composite detectors. This extended model, which has been worked out in detail, can be expected to provide a considerable help when tailoring composite detectors to the requirements of various experiments.
Low-Temperature Light Detectors: Neganov-Luke Amplification and Calibration
C. Isaila,C. Ciemniak,F. v. Feilitzsch,A. Gütlein,J. Kemmer,T. Lachenmaier,J. -C. Lanfranchi,S. Pfister,W. Potzel,S. Roth,M. v. Sivers,R. Strauss,W. Westphal,F. Wiest
Physics , 2011, DOI: 10.1016/j.physletb.2012.08.003
Abstract: The simultaneous measurement of phonons and scintillation light induced by incident particles in a scintillating crystal such as CaWO4 is a powerful technique for the active rejection of background induced by gamma's and beta's and even neutrons in direct Dark Matter searches. However, less than ~1% of the energy deposited in a CaWO4 crystal is detected as light. Thus, very sensitive light detectors are needed for an efficient event-by-event background discrimination. Due to the Neganov-Luke effect, the threshold of low-temperature light detectors based on semiconducting substrates can be improved significantly by drifting the photon-induced electron-hole pairs in an applied electric field. We present measurements with low-temperature light detectors based on this amplification mechanism. The Neganov-Luke effect makes it possible to improve the signal-to-noise ratio of our light detectors by a factor of ~9 corresponding to an energy threshold of ~21 eV. We also describe a method for an absolute energy calibration using a light-emitting diode.
Fracture Processes Observed with A Cryogenic Detector
J. Astrom,P. C. F. Di Stefano,F. Proebst,L. Stodolsky,J. Timonen,C. Bucci,S. Cooper,C. Cozzini,F. v. Feilitzsch,H. Kraus,J. Marchese,O. Meier,U. Nagel,Y. Ramachers,W. Seidel,M. Sisti,S. Uchaikin,L. Zerle
Physics , 2005, DOI: 10.1016/j.physleta.2006.03.059
Abstract: In the early stages of running of the CRESST dark matter search using sapphire detectors at very low temperature, an unexpectedly high rate of signal pulses appeared. Their origin was finally traced to fracture events in the sapphire due to the very tight clamping of the detectors. During extensive runs the energy and time of each event was recorded, providing large data sets for such phenomena. We believe this is the first time the energy release in fracture has been directly and accurately measured on a microscopic event-by-event basis. The energy threshold corresponds to the breaking of only a few hundred covalent bonds, a sensitivity some orders of magnitude greater than that of previous technique. We report some features of the data, including energy distributions, waiting time distributions, autocorrelations and the Hurst exponent. The energy distribution appear to follow a power law, $dN/dE\propto E^{-\beta}$, similar to the power law for earthquake magnitudes, and after appropriate translation, with a similar exponent. In the time domain,the waiting time $w$ or gap distribution between events has a power law behavior at small $w$ and an exponential fall-off at large $w,$ and can be fit $\propto w^{-\alpha}e^{-w/w_0}$. The autocorrelation function shows time correlations lasting for substantial parts of an hour. An asymmetry is found around large events, with higher count rates after, as opposed to before,the large event .
Neganov-Luke amplified cryogenic light detectors for the background discrimination in neutrinoless double beta decay search with TeO$_{2}$ bolometers
M. Willers,F. v. Feilitzsch,A. Giuliani,A. Gütlein,A. Münster,J. -C. Lanfranchi,L. Oberauer,W. Potzel,S. Roth,S. Sch?nert,M. v. Sivers,S. Wawoczny,A. Z?ller
Physics , 2014, DOI: 10.1088/1748-0221/10/03/P03003
Abstract: We demonstrate that Neganov-Luke amplified cryogenic light detectors with Transition Edge Sensor read-out can be applied for the background suppression in cryogenic experiments searching for the neutrinoless double beta decay of $^{130}\text{Te}$ with TeO$_{2}$ based bolometers. Electron and gamma induced events can be discriminated from $\alpha$ events by detecting the Cherenkov light produced by the $\beta$ particles emitted in the decay. We use the Cherenkov light produced by events in the full energy peak of $^{208}\text{Tl}$ and by events from a $^{147}\text{Sm}$ source to show that at the Q-value of the neutrinoless double beta decay of $^{130}\text{Te}$ ($Q_{\beta \beta} = 2.53 \,\text{MeV}$), a separation of $e^{-}/\gamma$ events from $\alpha$ events can be achieved on an event-by-event basis with practically no reduction in signal acceptance.
Influence of Annealing on the Optical and Scintillation Properties of CaWO$_4$ Single Crystals
M. v. Sivers,C. Ciemniak,A. Erb,F. v. Feilitzsch,A. Gütlein,J. -C. Lanfranchi,J. Lepelmeier,A. Münster,W. Potzel,S. Roth,R. Strauss,U. Thalhammer,S. Wawoczny,M. Willers,A. Z?ller
Physics , 2012, DOI: 10.1016/j.optmat.2012.05.014
Abstract: We investigate the influence of oxygen annealing on the room temperature optical and scintillation properties of CaWO$_4$ single crystals that are being produced for direct Dark Matter search experiments. The applied annealing procedure reduces the absorption coefficient at the peak position of the scintillation spectrum ($\sim430$ nm) by a factor of $\sim6$ and leads to an even larger reduction of the scattering coefficient. Furthermore, the annealing has no significant influence on the \emph{intrinsic} light yield. An additional absorption occurring at $\sim400$ nm suggests the formation of O$^-$ hole centers. Light-yield measurements at room temperature where one crystal surface was mechanically roughened showed an increase of the \emph{measured} light yield by $\sim40 %$ and an improvement of the energy resolution at 59.5 keV by $\sim12 %$ for the annealed crystal. We ascribe this result to the reduction of the absorption coefficient while the surface roughening is needed to compensate for the also observed reduction of the scattering coefficient after annealing.
Neutrino oscillometry at the next generation neutrino observatory
Yu. N. Novikov,T. Enqvist,A. N. Erykalov,F. v. Feilitzsch,J. Hissa,K. Loo,D. A. Nesterenko,L. Oberauer,F. Thorne,W. Trzaska,J. D. Vergados,M. Wurm
Physics , 2011,
Abstract: The large next generation liquid-scintillator detector LENA (Low Energy Neutrino Astronomy) offers an excellent opportunity for neutrino oscillometry. The characteristic spatial pattern of very low monoenergetic neutrino disappearance from artificial radioactive sources can be detected within the long length of detector. Sufficiently strong sources of more than 1 MCi activity can be produced at nuclear reactors. Oscillometry will provide a unique tool for precise determination of the mixing parameters for both active and sterile neutrinos within the broad mass region 0.01 - 2 (eV)^2. LENA can be considered as a versatile tool for a careful investigation of neutrino oscillations.
Recoilless resonant neutrino experiment and origin of neutrino oscillations
Bilenky, S. M.;von Feilitzsch, F.;Potzel, W.
High Energy Physics - Phenomenology , 2007, DOI: 10.1063/1.2818539
Abstract: We demonstrate that an experiment with recoilless resonant emission and absorption of tritium antineutrinos could have an important impact on our understanding of the origin of neutrino oscillations.
Neutron Flux at the Gran Sasso Underground LaboratoryRevisited
H. Wulandari,J. Jochum,W. Rau,F. von Feilitzsch
Physics , 2003, DOI: 10.1016/j.astropartphys.2004.07.005
Abstract: The neutron flux induced by radioactivity at the Gran Sasso underground laboratory is revisited. We have performed calculations and Monte Carlo simulations; the results offer an independent check to the available experimental data reported by different authors, which vary rather widely. This study gives detailed information on the expected spectrum and on the variability of the neutron flux due to possible variations of the water content of the environment.
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