A. Empl - Academia.edu (original) (raw)

Papers by A. Empl

Journal of Geophysical Research: Space Physics, 2019

This article has been accepted for publication and undergone full peer review but has not been th... more This article has been accepted for publication and undergone full peer review but has not been through the copyediting, typesetting, pagination and proofreading process, which may lead to differences between this version and the Version of Record. Please cite this article as

Journal of Instrumentation, 2016

Review of Scientific Instruments, 2017

We demonstrate techniques to improve the accuracy of the energy calibration of Timepix pixel dete... more We demonstrate techniques to improve the accuracy of the energy calibration of Timepix pixel detectors, used for the measurement of energetic particles. The typical signal from such particles spreads among many pixels due to charge sharing effects. As a consequence, the deposited energy in each pixel cannot be reconstructed unless the detector is calibrated, limiting the usability of such signals for calibration. To avoid this shortcoming, we calibrate using low energy X-rays. However, charge sharing effects still occur, resulting in part of the energy being deposited in adjacent pixels and possibly lost. This systematic error in the calibration process results in an error of about 5% in the energy measurements of calibrated devices. We use FLUKA simulations to assess the magnitude of charge sharing effects, allowing a corrected energy calibration to be performed on several Timepix pixel detectors and resulting in substantial improvement in energy deposition measurements. Next, we address shortcomings in calibration associated with the huge range (from kiloelectron-volts to megaelectron-volts) of energy deposited per pixel which result in a nonlinear energy response over the full range. We introduce a new method to characterize the non-linear response of the Timepix detectors at high input energies. We demonstrate improvement using a broad range of particle types and energies, showing that the new method reduces the energy measurement errors, in some cases by more than 90%.

Astroparticle Physics, 2018

Neutron production in lead by cosmic muons has been studied with a Gadolinium doped liquid scinti... more Neutron production in lead by cosmic muons has been studied with a Gadolinium doped liquid scintillator detector. The detector was installed next to the Muon-Induced Neutron Indirect Detection EXperiment (MINIDEX), permanently located in the Tübingen shallow underground laboratory where the mean muon energy is approximately 7 GeV. The MINIDEX plastic scintillators were used to tag muons; the neutrons were detected through neutron capture and neutron-induced nuclear recoil signals in the liquid scintillator detector. Results on the rates of observed neutron captures and nuclear recoils are presented and compared to predictions from GEANT4-9.6 and GEANT4-10.3. The predicted rates are significantly too low for both versions of GEANT4. For neutron capture events, the observation exceeds the predictions by factors of 1.65 ± 0.02 (stat.) ± 0.07 (syst.) and 2.58 ± 0.03 (stat.) ± 0.11 (syst.) for GEANT4-9.6 and GEANT4-10.3, respectively. For neutron nuclear recoil events, which require neutron energies above approximately 5 MeV, the factors are even larger, 2.22 ± 0.05 (stat.) ± 0.25 (syst.) and 3.76 ± 0.09 (stat.) ± 0.41 (syst.), respectively. Also presented is the first statistically significant measurement of the spectrum of neutrons induced by cosmic muons in lead between 5 and 40 MeV. It was obtained by unfolding the nuclear recoil spectrum. The observed neutron spectrum is harder than predicted by GEANT4. An investigation of the distribution of the time difference between muon tags and nuclear recoil signals confirms the validity of the unfolding procedure and shows that GEANT4 cannot properly describe the time distribution of nuclear recoil events. In general, the description of the data is worse for GEANT4-10.3 than for GEANT4-9.6.

on behalf of the Borexino/SOX Collaboration: M. Agostini, K. Altenmuller, S. Appel, G. Bellini, J... more on behalf of the Borexino/SOX Collaboration: M. Agostini, K. Altenmuller, S. Appel, G. Bellini, J. Benziger, N. Berton, D. Bick, G. Bonfini, D. Bravo, B. Caccianiga, L. Cadonati, F. Calaprice, A. Caminata, P. Cavalcante, A. Chavarria, A. Chepurnov, M. Cribier, D. D’Angelo, S. Davini, A. Derbin, L. di Noto, M. Durero, A. Empl, A. Etenko, S. Farinon, V. Fischer, K. Fomenko, D. Franco, F. Gabriele, J. Gaffiot, C. Galbiati, S. Gazzana, C. Ghiano, M. Giammarchi, M. Goger-Neff, A. Goretti, L. Grandi, M. Gromov, C. Hagner, Th. Houdy, E. Hungerford, Aldo Ianni, Andrea Ianni, N. Jonqueres, M. Kaiser, V. Kobychev, D. Korablev, G. Korga, D. Kryn, T. Lachenmaier, T. Lasserre, M. Laubenstein, B. Lehnert, T. Lewke, J. Link, E. Litvinovich, F. Lombardi, P. Lombardi, L. Ludhova, G. Lukyanchenko, I. Machulin, S. Manecki, W. Maneschg, S. Marcocci, J. Maricic, Q. Meindl, G. Mention, E. Meroni, M. Meyer, L. Miramonti, M. Misiaszek, M. Montuschi, P. Mosteiro, V. Muratova, R. Musenich, B. Neumair, L. Obe...

M. Agostini, K. Altenmüller, S. Appel, G. Bellini, J. Benziger, N. Berton, D. Bick, G. Bonfini, D... more M. Agostini, K. Altenmüller, S. Appel, G. Bellini, J. Benziger, N. Berton, D. Bick, G. Bonfini, D. Bravo, B. Caccianiga, F. Calaprice, A. Caminata, P. Cavalcante, A. Chepurnov, M. Cribier, D. D’Angelo, S. Davini, A. Derbin, L. di Noto, I. Drachnev, M. Durero, A. Empl, A. Etenko, S. Farinon, V. Fischer, K. Fomenko, D. Franco, F. Gabriele, J. Gaffiot, C. Galbiati, C. Ghiano, M. Giammarchi, M. Göger-Neff, A. Goretti, M. Gromov, C. Hagner, T. Houdy, E. Hungerford, Aldo Ianni, Andrea Ianni, N. Jonquères, M. Kaiser, V. Kobychev, D. Korablev, G. Korga, D. Kryn, T. Lachenmaier, T. Lasserre, M. Laubenstein, B. Lehnert, J. Link, E. Litvinovich, F. Lombardi, P. Lombardi, L. Ludhova, G. Lukyanchenko, I. Machulin, W. Maneschg, S. Marcocci, J. Maricic, G. Mention, E. Meroni, M. Meyer, L. Miramonti, M. Misiaszek, M. Montuschi, V. Muratova, R. Musenich, B. Neumair, L. Oberauer, M. Obolensky, F. Ortica, L. Pagani, M. Pallavicini, L. Papp, L. Perasso, A. Pocar, G. Ranucci, A. Razeto, A. Re, A. Romani...

AIP Conference Proceedings, 2001

The first experiment in Lambda-hypernuclear spectroscopy using the high-precision electron beam a... more The first experiment in Lambda-hypernuclear spectroscopy using the high-precision electron beam at Jefferson laboratory (JLab) has been carried out. The hypernuclear spectrometer system (HNSS) was used to measure spectra from the 12C(e,e&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#39;K+)12LambdaB reaction with sub-1-MeV resolution, the best energy resolution obtained thus far in hypernuclear spectroscopy with magnetic spectrometers. This paper describes the HNSS and the preliminary results for the

Proceedings of XVI International Workshop on Neutrino Telescopes — PoS(NEUTEL2015), 2016

Physical Review Letters, 2018

EPJ Web of Conferences, 2016

Journal of Physics: Conference Series, 2017

Physics of Particles and Nuclei, 2016

Neutrino produced in a chain of nuclear reactions in the Sun starting from the fusion of two prot... more Neutrino produced in a chain of nuclear reactions in the Sun starting from the fusion of two protons, for the first time has been detected in a realtime detector in spectrometric mode. The unique properties of the Borexino detector provided an oppurtunity to disentangle pp-neutrino spectrum from the background components. A comparison of the total neutrino flux from the Sun with Solar luminosity in photons provides a test of the stability of the Sun on the 10 5 years time scale, and sets a strong limit on the power production in the unknown energy sources in the Sun of no more than 4% of the total energy production at 90% C.L.

Journal of Physics: Conference Series, 2016

Content from this w ork may be used under the term s of the Creative Commons Attribution 3.0 lice... more Content from this w ork may be used under the term s of the Creative Commons Attribution 3.0 licence. Any further distribution of this work m ust m aintain attribution to the author(s) and the title of the work, journal citation and DOI.

Cosmic muon interactions are important contributors to backgrounds in underground detectors when ... more Cosmic muon interactions are important contributors to backgrounds in underground detectors when searching for rare events. Typically neutrons dominate this background as they are particularly difficult to shield and detect in a veto system. Since actual background data is sparse and not well documented, simulation studies must be used to design shields and predict background rates. This means that validation of any simulation code is necessary to assure reliable results. This work studies the validation of the FLUKA simulation code, and reports the results of a simulation of cosmogenic background for a liquid argon two-phase detector embedded within a water tank and liquid scintillator shielding.

Physics of Particles and Nuclei, 2015

Physics Procedia, 2015

We present a 1353 days measurement of the geo-neutrino flux in Borexino: the signal was found to ... more We present a 1353 days measurement of the geo-neutrino flux in Borexino: the signal was found to be 14.3 ± 4.4 events. This result translates into S geo = (38.8 ± 12.0) TNU when a Th/U fixed chondritic mass ratio of 3.9 is assumed. Furthermore Borexino data are compatible with a mantle geo-neutrino signal of (15.4 ± 12.3) TNU.

Structure and Dynamics of Elementary Matter, 2004

Comprehensive analysis of heavy ion reactions at low and intermediate energies is made using the ... more Comprehensive analysis of heavy ion reactions at low and intermediate energies is made using the Boltzmann Master Equation theory and a Relativistic Quantum Molecular Dynamics model, respectively. As an example of the large variety of applications of such a study, a result concerning space radiation protection is presented.