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Search Results: 1 - 10 of 449914 matches for " J. C. Lanfranchi "
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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.
Sensitivity of alkali halide scintillating calorimeters with particle identification to investigate the DAMA dark matter detection claim
Patrick Nadeau,Michael Clark,P. C. F. Di Stefano,J. -C. Lanfranchi,S. Roth,M. von Sivers,Itay Yavin
Physics , 2014, DOI: 10.1016/j.astropartphys.2015.02.001
Abstract: Scintillating calorimeters are cryogenic detectors combining a measurement of scintillation with one of phonons to provide particle identification. In view of developing alkali halide devices of this type able to check the DAMA/LIBRA claim for the observation of dark matter, we have simulated detector performances to determine their sensitivity by two methods with little model-dependence. We conclude that if performance of the phonon channel can be brought in line with those of other materials, an exposure of 10 kg-days would suffice to check the DAMA/LIBRA claim in standard astrophysical scenarios. Additionally, a fairly modest array of 5 kg with background rejection would be able to directly check the DAMA/LIBRA modulation result in 2 years.
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.
Study on Neutron-induced Background in the CRESST Experiment
H. Wulandari,F. von Feilitzsch,M. Huber,Th. Jagemann,J. Jochum,T. Lachenmaier,J. -C. Lanfranchi,W. Potzel,W. Rau,M. Stark,S. Waller
Physics , 2003,
Abstract: CRESST II is an experiment for direct WIMP search, using cryogenic detectors. The ratio of the two signals (temperature rise and scintillation light) measured for each interaction is an excellent parameter for discrimination of radioactive background. The main remaining background is the neutron flux present at the experimental site, since neutrons produce the same signals as WIMPs do. Based on Monte Carlo simulations the present work shows how neutrons from different origins affect CRESST and which measures have to be taken into account to reach the goal sensitivity.
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.
The DLAs contribution to the metal content of the high z Universe
Gustavo A. Lanfranchi,Amancio C. S. Friaca
Physics , 2001,
Abstract: We investigate the evolutionary history of the Universe's metal content focusing on the chemical abundance of several elements (N, O, S, Si, Fe, Cr, Zn) taken from observational data and predictions from chemical evolution models. The estimated abundances were observed in Damped Lyman alpha Systems (DLAs) over a wide range of redshift (z ~ 0.5-4.5). These data are compared to predictions of chemical evolution models. Since the nature of the DLAs is uncertain, they are represented by two class of models: models with galactic winds describing dwarf galaxies and with infall representing disk galaxies. In order to settle constraints for star formation timescales in DLAs, we use the ratios [alpha/Fe] and [N/alpha] in the comparison to the predictions of the models. These ratios in DLAs are only partially reproduced by the disk and dwarf galaxy models suggesting that the DLAs come from a variety of morphological types of galaxies and not only one. They also imply a typically long timescale for the star formation in these systems.
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.
Solar and Atmospheric Neutrinos: Limitations for Direct Dark Matter Searches
A. Gütlein,W. Potzel,C. Ciemniak,F. von Feilitzsch,N. Haag,M. Hofmann,C. Isaila,T. Lachenmaier,J. -C. Lanfranchi,L. Oberauer,S. Pfister,S. Roth,M. von Sivers,R. Strau?,A. Z?ller
Physics , 2010,
Abstract: In experiments for direct dark matter searches, neutrinos coherently scattering off nuclei can produce similar events as Weakly Interacting Massive Particles (WIMPs). To reach sensitivities better than about 10^-10 pb for the elastic WIMP nucleon spin-independent cross section in the zero-background limit, energy thresholds for nuclear recoils should be >2.05 keV for CaWO_4, >4.91 keV for Ge, >2.89 keV for Xe, >8.62 keV for Ar and >15.93 keV for Ne as target material. Atmospheric neutrinos limit the achievable sensitivity for the background-free direct dark matter search to >10^-12 pb.
Cryogenic silicon detectors with implanted contacts for the detection of visible photons using the Neganov-Luke Effect
X. Defay,E. Mondragon,M. Willers,A. Langenkamper,J. -C. Lanfranchi,A. Munstera,A. Zoller,S. Wawoczny,H. Steiger,F. Hitzler,C. Bruhn,S. Schonert,W. Potzel,M. Chapellier
Physics , 2015,
Abstract: There is a common need in astroparticle experiments such as direct dark matter detection, 0{\nu}\b{eta}\b{eta} (double beta decay without emission of neutrinos) and Coherent Neutrino Nucleus Scattering experiments for light detectors with a very low energy threshold. By employing the Neganov-Luke Effect, the thermal signal of particle interactions in a semiconductor absorber operated at cryogenic temperatures, can be amplified by drifting the photogenerated electrons and holes in an electric field. This technology is not used in current experiments, in particular because of a reduction of the signal amplitude with time which is due to trapping of the charges within the absorber. We present here the first results of a novel type of Neganov-Luke Effect detector with an electric field configuration designed to improve the charge collection within the semiconductor.
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