Ch. Weinheimer

University of Münster, Muenster, North Rhine-Westphalia, Germany

Are you Ch. Weinheimer?

Claim your profile

Publications (177)462.37 Total impact

  • S. Rosendahl · E. Brown · I. Cristescu · A. Fieguth · C. Huhmann · O. Lebeda · M. Murra · C. Weinheimer ·

    Review of Scientific Instruments 11/2015; 86(11):115104. DOI:10.1063/1.4934978 · 1.61 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Laboratory experiments searching for galactic dark matter particles scattering off nuclei have so far not been able to establish a discovery. We use data from the XENON100 experiment to search for dark matter interacting with electrons. With no evidence for a signal above the low background of our experiment, we exclude a variety of representative dark matter models that would induce electronic recoils. For axial-vector couplings to electrons, we exclude cross-sections above 6x10^(-35) cm^2 for particle masses of m_chi = 2 GeV/c^2. Independent of the dark matter halo, we exclude leptophilic models as explanation for the long-standing DAMA/LIBRA signal, such as couplings to electrons through axial-vector interactions at a 4.4 sigma confidence level, mirror dark matter at 3.6 sigma, and luminous dark matter at 4.6 sigma.
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: We have searched for periodic variations of the electronic recoil event rate in the (2-6) keV energy range recorded between February 2011 and March 2012 with the XENON100 detector, adding up to 224.6 live days in total. Following a detailed study to establish the stability of the detector and its background contributions during this run, we performed an un-binned profile likelihood analysis to identify any periodicity up to 500 days. We find a global significance of less than 1 sigma for all periods suggesting no statistically significant modulation in the data. While the local significance for an annual modulation is 2.8 sigma, the analysis of a multiple-scatter control sample and the phase of the modulation disfavor a dark matter interpretation. The DAMA/LIBRA annual modulation interpreted as a dark matter signature with axial-vector coupling of WIMPs to electrons is excluded at 4.8 sigma.
    Physical Review Letters 07/2015; 115(9). DOI:10.1103/PhysRevLett.115.091302 · 7.51 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: The influence of space-charge on ion cyclotron resonances and magnetron eigenfrequency in a gas-filled Penning ion trap has been investigated. Off-line measurements with using the cooling trap of the WITCH retardation spectrometer-based setup at ISOLDE/CERN were performed. Experimental ion cyclotron resonances were compared with ab initio Coulomb simulations and found to be in agreement. As an important systematic effect of the WITCH experiment, the magnetron eigenfrequency of the ion cloud was studied under increasing space-charge conditions. Finally, the helium buffer gas pressure in the Penning trap was determined by comparing experimental cooling rates with simulations.
    Nuclear Instruments and Methods in Physics Research Section A Accelerators Spectrometers Detectors and Associated Equipment 06/2015; 785. DOI:10.1016/j.nima.2015.02.057 · 1.22 Impact Factor
  • Source

    Physical Review Letters 05/2015; 114(19). DOI:10.1103/PhysRevLett.114.199903 · 7.51 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: The low-background, VUV-sensitive 3-inch diameter photomultiplier tube R11410 has been developed by Hamamatsu for dark matter direct detection experiments using liquid xenon as the target material. We present the results from the joint effort between the XENON collaboration and the Hamamatsu company to produce a highly radio-pure photosensor (version R11410-21) for the XENON1T dark matter experiment. After introducing the photosensor and its components, we show the methods and results of the radioactive contamination measurements of the individual materials employed in the photomultiplier production. We then discuss the adopted strategies to reduce the radioactivity of the various PMT versions. Finally, we detail the results from screening 216 tubes with ultra-low background germanium detectors, as well as their implications for the expected electronic and nuclear recoil background of the XENON1T experiment.
    European Physical Journal C 03/2015; 75(11). DOI:10.1140/epjc/s10052-015-3657-5 · 5.08 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: The LIBELLE experiment performed at the experimental storage ring (ESR) at the GSI Helmholtz Center in Darmstadt aims for the determination of the ground state hyperfine (HFS) transitions and lifetimes in hydrogen-like (209 Bi 82+) and lithium-like (209 Bi 80+) bismuth. The study of HFS transitions in highly charged ions enables precision tests of QED in extreme electric and magnetic fields otherwise not attainable in laboratory experiments. While the HFS transition in H-like bismuth was already observed in earlier experiments at the ESR, the LIBELLE experiment succeeded for the first time to measure the HFS transition in Li-like bismuth in a laser spectroscopy experiment. 1. Introduction Highly charged ions provide a testing ground for QED calculations in extreme electric (up to 10 16 V/cm) and magnetic (up to 10 4 T) fields that cannot be created in the laboratory with conventional methods (like lasers and superconducting magnets). This approach has been used since the 1990s with various isotopes in laser spectroscopy as well as in x-ray emission spectroscopy experiments (see references in [1]). To put the results in a theoretical context precise QED calculations have to be performed, where a major issue is the large uncertainty of nuclear structure corrections. Particularly the uncertainty of the Bohr-Weisskopf effect, which arises due to the spatially smeared out magnetic moment distribution in the nucleus, is comparable in size to the total contribution of QED corrections and hinders a direct test of QED. To tackle this problem, Shabaev et al. [2] proposed to use a new approach by introducing the so-called specific difference ∆ E between the HFS splittings in H-like (∆E (1s)) and Li-like (∆E (2s)) configurations of the same isotope
    Journal of Physics Conference Series 01/2015; 583(1). DOI:10.1088/1742-6596/583/1/012002
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: The KATRIN experiment is going to search for the average mass of the electron antineutrino with a sensitivity of 0.2 eV/c2. It uses a retardation spectrometer of MAC-E filter type to accurately measure the shape of the electron spectrum at the endpoint of tritium beta decay. In order to achieve the planned sensitivity the transmission properties of the spectrometer have to be understood with high precision for all initial conditions. For this purpose an electron source has been developed that emits single electrons at adjustable total energy and adjustable emission angle. The emission is pointlike and can be moved across the full flux tube that is imaged onto the detector. Here, we demonstrate that this novel type of electron source can be used to investigate the transmission properties of a MAC-E filter in detail.
    Journal of Instrumentation 11/2014; 9(11). DOI:10.1088/1748-0221/9/11/P11020 · 1.40 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: We investigate the sensitivity of tritium $\beta$-decay experiments for keV-scale sterile neutrinos. Relic sterile neutrinos in the keV mass range can contribute both to the cold and warm dark matter content of the universe. This work shows that a large-scale tritium beta-decay experiment, similar to the KATRIN experiment that is under construction, can reach a statistical sensitivity of the active-sterile neutrino mixing of $\sin^2\theta \sim 10^{-8}$. The effect of uncertainties in the known theoretical corrections to the tritium $\beta$-decay spectrum were investigated, and found not to affect the sensitivity significantly. It is demonstrated that controlling uncorrelated systematic effects will be one of the main challenges in such an experiment.
    Journal of Cosmology and Astroparticle Physics 09/2014; 2015(02). DOI:10.1088/1475-7516/2015/02/020 · 5.81 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: The radioactive isomer $^{83\mathrm{m}}$Kr has many properties that make it very useful for various applications. Its low energy decay products, like conversion, shake-off and Auger electrons as well as X- and $\gamma$-rays are used for calibration purposes in neutrino mass experiments and direct dark matter detection experiments. Thanks to the short half-life of 1.83 h and the decay to the ground state $^{83}$Kr, one does not risk contamination of any low-background experiment with long- lived radionuclides. In this paper, we present two new applications of $^{83\mathrm{m}}$Kr. It can be used as a radioactive tracer in noble gases to characterize the particle flow inside of gas routing systems. A method of doping $^{83\mathrm{m}}$Kr into xenon gas and its detection, using special custom-made detectors, based on a photomultiplier tube, is described. This technique has been used to determine the circulation speed of gas particles inside of a gas purification system for xenon. Furthermore, 83m Kr can be used to rapidly estimate separation performance of a distillation system.
    Journal of Instrumentation 07/2014; 9(10). DOI:10.1088/1748-0221/9/10/P10010 · 1.40 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: The KArlsruhe TRItium Neutrino (KATRIN) experiment is a next-generation, large-scale tritium β-decay experiment to determine the neutrino mass by investigating the kinematics of tritium β-decay with a sensitivity of 200 meV/c2 using the MAC-E filter technique. In order to reach this sensitivity a low background level of 10−2 counts per second (cps) is required. A major background concern in MAC-E filters is the presence of Penning traps. A Penning trap is a special configuration of electromagnetic fields that allows the storage of electrically charged particles. This paper describes the mechanism of Penning discharges and the corresponding measurements performed at the test setup of the KATRIN pre-spectrometer. These investigations led to the conclusion that the observed electric breakdown, strong discharges and extremely large background rates were due to discharges caused by Penning traps located at both ends of the pre-spectrometer. Furthermore, the paper describes the design of a new set of electrodes (modified ground electrodes and new ``anti-Penning'' electrodes) to successfully remove these traps. After the installation of these electrodes in the pre-spectrometer, the measurements confirmed that the strong Penning discharges disappeared. The experience gained from the pre-spectrometer was used to design the electrode system of the main spectrometer. Recent measurements with the main spectrometer showed no indications of Penning trap related backgrounds.
    Journal of Instrumentation 07/2014; 9(07):P07028-P07028. DOI:10.1088/1748-0221/9/07/P07028 · 1.40 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: The KATRIN experiment will measure the absolute mass scale of neutrinos with a sensitivity of mν = 200meV/c2 by means of an electrostatic spectrometer set close to the tritium β-decay endpoint at 18.6keV. Fluctuations of the energy scale must be under control within ±60mV (±3ppm). Since a precise voltage measurement in the range of tens of kV is on the edge of current technology, a nuclear standard will be deployed additionally. Parallel to the main spectrometer the same retarding potential will be applied to the monitor spectrometer to measure 17.8-keV K-conversion electrons of 83mKr. This article describes the setup of the monitor spectrometer and presents its first measurement results.
    Journal of Instrumentation 06/2014; 9(06):P06022. DOI:10.1088/1748-0221/9/06/P06022 · 1.40 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: XENON is a direct detection dark matter project, consisting of a time projection chamber (TPC) that uses xenon in double phase as a sensitive detection medium. XENON100, located at the Laboratori Nazionali del Gran Sasso (LNGS) in Italy, is one of the most sensitive experiments of its field. During the operation of XENON100, the design and construction of the next generation detector (of ton-scale mass) of the XENON project, XENON1T, is taking place. XENON1T is being installed at LNGS as well. It has the goal to reduce the background by two orders of magnitude compared to XENON100, aiming at a sensitivity of $2 \cdot 10^{-47} \mathrm{cm}^{\mathrm{2}}$ for a WIMP mass of 50 GeV/c$^{2}$. With this goal, an active system that is able to tag muons and their induced backgrounds is crucial. This active system will consist of a water Cherenkov detector realized with a water volume $\sim$10 m high and $\sim$10 m in diameter, equipped with photomultipliers of 8 inches diameter and a reflective foil. In this paper we present the design and optimization study for this muon veto water Cherenkov detector, which has been carried out with a series of Monte Carlo simulations, based on the GEANT4 toolkit. This study showed the possibility to reach very high detection efficiencies in tagging the passage of both the muon and the shower of secondary particles coming from the interaction of the muon in the rock: >99.5% for the former type of events (which represent $\sim$ 1/3 of all the cases) and >70% for the latter type of events (which represent $\sim$ 2/3 of all the cases). In view of the upgrade of XENON1T, that will aim to an improvement in sensitivity of one order of magnitude with a rather easy doubling of the xenon mass, the results of this study have been verified in the upgraded geometry, obtaining the same conclusions.
    Journal of Instrumentation 06/2014; 9(11). DOI:10.1088/1748-0221/9/11/P11006 · 1.40 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: We present the first results of searches for axions and axion-like-particles with the XENON100 experiment. The axion-electron coupling constant, $g_{Ae}$, has been tested by exploiting the axio-electric effect in liquid xenon. A profile likelihood analysis of 224.6 live days $\times$ 34 kg exposure has shown no evidence for a signal. By rejecting $g_{Ae}$, larger than $7.7 \times 10^{-12}$ (90% CL) in the solar axion search, we set the best limit to date on this coupling. In the frame of the DFSZ and KSVZ models, we exclude QCD axions heavier than 0.3 eV/c$^2$ and 80 eV/c$^2$, respectively. For axion-like-particles, under the assumption that they constitute the whole abundance of dark matter in our galaxy, we constrain $g_{Ae}$, to be lower than $1 \times 10^{-12}$ (90% CL) for masses between 5 and 10 keV/c$^2$.
    Physical Review D 04/2014; 90(6). DOI:10.1103/PhysRevD.90.062009 · 4.86 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: The XENON100 experiment, situated in the Laboratori Nazionali del Gran Sasso, aims at the direct detection of dark matter in the form of weakly interacting massive particles (WIMPs), based on their interactions with xenon nuclei in an ultra low background dual-phase time projection chamber. This paper describes the general methods developed for the analysis of the XENON100 data, focusing on the 100.9 live days science run from which results on spin-independent elastic and inelastic WIMP-nucleon cross-sections have already been reported.
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: In this paper we describe a new variant of null ellipsometry to determine thicknesses and optical properties of thin films on a substrate at cryogenic temperatures. In the PCSA arrangement of ellipsometry the polarizer and the compensator are placed before the substrate and the analyzer after it. Usually, in the null ellipsometry the polarizer and the analyzer are rotated to find the searched minimum in intensity. In our variant we rotate the polarizer and the compensator instead, both being placed in the incoming beam before the substrate. Therefore the polarisation analysis of the reflected beam can be realized by an analyzer at fixed orientation. We developed this method for investigations of thin cryogenic films inside a vacuum chamber where the analyzer and detector had to be placed inside the cold shield at a temperature of T ≈ 90 K close to the substrate. All other optical components were installed at the incoming beam line outside the vacuum chamber, including all components which need to be rotated during the measurements. Our null ellipsometry variant has been tested with condensed krypton films on a highly oriented pyrolytic graphite substrate (HOPG) at a temperature of T ≈ 25 K. We show that it is possible to determine the indices of refraction of condensed krypton and of the HOPG substrate as well as thickness of krypton films with reasonable accuracy.
    The Review of scientific instruments 12/2013; 84(12):123103. DOI:10.1063/1.4838555 · 1.61 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: The XENON100 dark matter experiment uses liquid xenon in a time projection chamber (TPC) to measure xenon nuclear recoils resulting from the scattering of dark matter Weakly Interacting Massive Particles (WIMPs). In this paper, we report the observation of single-electron charge signals which are not related to WIMP interactions. These signals, which show the excellent sensitivity of the detector to small charge signals, are explained as being due to the photoionization of impurities in the liquid xenon and of the metal components inside the TPC. They are used as a unique calibration source to characterize the detector. We explain how we can infer crucial parameters for the XENON100 experiment: the secondary-scintillation gain, the extraction yield from the liquid to the gas phase and the electron drift velocity.
    Journal of Physics G Nuclear and Particle Physics 11/2013; G41(3). DOI:10.1088/0954-3899/41/3/035201 · 2.78 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: The KATRIN (KArlsruhe TRItium Neutrino) experiment aims to determine the mass of the electron antineutrino with a sensitivity of 200meV by precisely measuring the electron spectrum of the tritium beta decay. This will be done by the use of a retarding spectrometer of the MAC-E-Filter type. To achieve the desired sensitivity the stability of the retarding potential of -18.6kV has to be monitored with a precision of 3ppm over at least two months. Since this is not feasible with commercial devices, two ppm-class high voltage dividers were developed, following the concept of the standard divider for DC voltages of up to 100kV of the Physikalisch-Technische Bundesanstalt (PTB). In order to reach such high accuracies different effects have to be considered. The two most important ones are the temperature dependence of resistance and leakage currents, caused by insulators or corona discharges. For the second divider improvements were made concerning the high-precision resistors and the thermal design of the divider. The improved resistors are the result of a cooperation with the manufacturer. The design improvements, the investigation and the selection of the resistors, the built-in ripple probe and the calibrations at PTB will be reported here. The latter demonstrated a stability of about 0.1ppm/month over a period of two years.
    Journal of Instrumentation 09/2013; 8(10). DOI:10.1088/1748-0221/8/10/P10026 · 1.40 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: The XENON100 experiment, installed underground at the Laboratori Nazionali del Gran Sasso (LNGS), aims to directly detect dark matter in the form of Weakly Interacting Massive Particles (WIMPs) via their elastic scattering off xenon nuclei. This paper presents a study on the nuclear recoil background of the experiment, taking into account neutron backgrounds from ($\alpha$,n) and spontaneous fission reactions due to natural radioactivity in the detector and shield materials, as well as muon-induced neutrons. Based on Monte Carlo simulations and using measured radioactive contaminations of all detector components, we predict the nuclear recoil backgrounds for the WIMP search results published by the XENON100 experiment in 2011 and 2012, 0.11$^{+0.08}_{-0.04}$ events and 0.17$^{+0.12}_{-0.07}$ events, respectively, and conclude that they do not limit the sensitivity of the experiment.
    Journal of Physics G Nuclear and Particle Physics 06/2013; 40(11). DOI:10.1088/0954-3899/40/11/115201 · 2.78 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: A single photon counting system has been developed for efficient detection of forward emitted fluorescence photons at the Experimental Storage Ring (ESR) at GSI. The system employs a movable parabolic mirror with a central slit that can be positioned around the ion beam and a selected low noise photomultiplier for detection of the collected photons. Compared to the previously used system of mirror segments installed inside the ESR the collection efficiency for forward-emitted photons is improved by more than a factor of 5. No adverse effects on the stored ion beam have been observed during operation besides a small drop in the ion current of about 5% during movement of the mirror into the beam position. The new detection system has been used in the LIBELLE experiment at ESR and enabled for the first time the detection of the ground-state hyperfine M1 transition in lithium-like bismuth (209Bi80+) in a laser-spectroscopy measurement.
    Journal of Instrumentation 05/2013; 8(09). DOI:10.1088/1748-0221/8/09/P09018 · 1.40 Impact Factor

Publication Stats

4k Citations
462.37 Total Impact Points


  • 2006-2015
    • University of Münster
      • Institute of Nuclear Physics
      Muenster, North Rhine-Westphalia, Germany
  • 2014
    • Karlsruhe Institute of Technology
      Carlsruhe, Baden-Württemberg, Germany
  • 2012
    • Columbia University
      • Department of Physics
      New York City, NY, United States
    • Max Planck Institute for Nuclear Physics
      Heidelburg, Baden-Württemberg, Germany
    • Rice University
      • Department of Physics and Astronomy
      Houston, Texas, United States
  • 2000-2011
    • University of Bonn
      • Helmholtz-Institut für Strahlen- und Kernphysik
      Bonn, North Rhine-Westphalia, Germany
  • 1993-2010
    • Johannes Gutenberg-Universität Mainz
      • Institute of Physics
      Mayence, Rheinland-Pfalz, Germany
  • 2009
    • Physikalisch-Technische Bundesanstalt
      Brunswyck, Lower Saxony, Germany
  • 2001-2008
    • CERN
      • Physics Department (PH)
      Genève, Geneva, Switzerland
  • 2005
    • Justus-Liebig-Universität Gießen
      • II. Physikalisches Institut
      Gießen, Hesse, Germany
  • 2003
    • University of Delaware
      Ньюарк, Delaware, United States
  • 2001-2003
    • Stockholm University
      • Department of Physics
      Tukholma, Stockholm, Sweden
  • 1997-2001
    • Humboldt-Universität zu Berlin
      Berlín, Berlin, Germany
  • 1998
    • Technion - Israel Institute of Technology
      H̱efa, Haifa District, Israel
  • 1996
    • Kinki University
      Ōsaka, Ōsaka, Japan