C. Weinheimer

Technical University Darmstadt, Darmstadt, Hesse, Germany

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Publications (184)471.75 Total impact

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    ABSTRACT: The XENON1T experiment is currently in the commissioning phase at the Laboratori Nazionali del Gran Sasso, Italy. In this article we study the experiment's expected sensitivity to the spin-independent WIMP-nucleon interaction cross section, based on Monte Carlo predictions of the electronic and nuclear recoil backgrounds. The total electronic recoil background in $1$ tonne fiducial volume and ($1$, $12$) keV electronic recoil equivalent energy region, before applying any selection to discriminate between electronic and nuclear recoils, is $(1.80 \pm 0.15) \cdot 10^{-4}$ ($\rm{kg} \cdot day \cdot keV)^{-1}$, mainly due to the decay of $^{222}\rm{Rn}$ daughters inside the xenon target. The nuclear recoil background in the corresponding nuclear recoil equivalent energy region ($4$, $50$) keV, is composed of $(0.6 \pm 0.1)$ ($\rm{t} \cdot y)^{-1}$ from radiogenic neutrons, $(1.8 \pm 0.3) \cdot 10^{-2}$ ($\rm{t} \cdot y)^{-1}$ from coherent scattering of neutrinos, and less than $0.01$ ($\rm{t} \cdot y)^{-1}$ from muon-induced neutrons. The sensitivity of XENON1T is calculated with the Profile Likelihood Ratio method, after converting the deposited energy of electronic and nuclear recoils into the scintillation and ionization signals seen in the detector. We take into account the systematic uncertainties on the photon and electron emission model, and on the estimation of the backgrounds, treated as nuisance parameters. The main contribution comes from the relative scintillation efficiency $\mathcal{L}_\mathrm{eff}$, which affects both the signal from WIMPs and the nuclear recoil backgrounds. After a $2$ y measurement in $1$ t fiducial volume, the sensitivity reaches a minimum cross section of $1.6 \cdot 10^{-47}$ cm$^2$ at m$_\chi$=$50$ GeV/$c^2$.
    Full-text · Article · Dec 2015
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    ABSTRACT: The separation of krypton and xenon is of particular importance for the field of direct dark matter search with liquid xenon detectors. The intrinsic contamination of the xenon with radioactive 85Kr makes a significant background for these kinds of low count-rate experiments and has to be removed beforehand. This can be achieved by cryogenic distillation, a technique widely used in industry, using the different vapor pressures of krypton and xenon. In this paper, we present an investigation on the separation performance of a single stage distillation system using a radioactive 83mKr-tracer method. The separation characteristics under different operation conditions are determined for very low concentrations of krypton in xenon at the level of 83mKr/Xe = 1.9 ⋅ 10−15, demonstrating, that cryogenic distillation in this regime is working. The observed separation is in agreement with the expectation from the different volatilities of krypton and xenon. This cryogenic distillation station is the first step on the way to a multi-stage cryogenic distillation column for the next generation of direct dark matter experiment XENON1T.
    No preview · Article · Nov 2015 · Review of Scientific Instruments
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    ABSTRACT: Highly charged ions offer the possibility to measure electronic fine structures and hyperfine structures with precisions of optical lasers. Microwave spectroscopy of transitions between Zeeman substates further yields magnetic moments (g-factors) of bound electrons, making tests of calculations in the framework of bound-state QED possible in the strong-field regime. We present the SPECTRAP and ARTEMIS experiments, which are currently being commissioned with highly charged ions in the framework of the HITRAP facility at GSI, Germany. We present the scientific outline, the experimental setups and first results with confined ions.
    No preview · Article · Nov 2015 · Physica Scripta
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    ABSTRACT: The hyperfine transitions in lithium-like and hydrogen-like bismuth were remeasured by direct laser spectroscopy at the experimental storage ring. For this we have now employed a voltage divider which enabled us to monitor the electron cooler voltage in situ. This will improve the experimental accuracy by about one order of magnitude with respect to our previous measurement using the same technique.
    No preview · Article · Nov 2015 · Physica Scripta
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    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.
    Full-text · Article · Jul 2015 · Physical Review Letters
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    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.
    Full-text · Article · Jul 2015
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    ABSTRACT: Heavy few-electron ions are relatively simple systems in terms of electron structure and offer unique opportunities to conduct experiments under extremely large electromagnetic fields that exist around their nuclei. However, the preparation of highly charged ions (HCI) has remained the major challenge for experiments. As an extension of the existing GSI accelerator facility, the HITRAP facility was conceived as a multi-stage decelerator for HCI produced at high velocity. It is designed to prepare bunches of around 105 HCI and to deliver them at low energies to various experiments. One of these experiments is SpecTrap, aiming for laser spectroscopy of trapped, cold HCI. We present the latest results on deceleration of ions in a radio-frequency quadrupole, synchrotron cooling of electrons in a trap as a preparation step for the prospective electron cooling of the HCI decelerated in HITRAP, as well as laser cooling of singly charged Mg ions for sympathetic cooling of HCI in SpecTrap.
    No preview · Article · Jul 2015
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    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.
    Full-text · Article · Jun 2015 · Nuclear Instruments and Methods in Physics Research Section A Accelerators Spectrometers Detectors and Associated Equipment
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    Full-text · Article · May 2015 · Physical Review Letters
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    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.
    Full-text · Article · Mar 2015 · European Physical Journal C
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    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
    Full-text · Article · Jan 2015 · Journal of Physics Conference Series
  • S Rosendahl · E Brown · I Cristescu · A Fieguth · C Huhmann · M Murra · C Weinheimer
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    ABSTRACT: The XENON collaboration aims for the direct detection of cold dark matter in form of weakly interacting massive particles (WIMPs). A dual phase time projection chamber filled with liquid xenon is used to detect the WIMP-nucleon interaction. For the next generation experiment XENON1T with an active target mass of 1 ton of xenon, a new distillation column to remove krypton out of xenon to a concentration of < 5 × 10−13 (0.5 ppt) natural krypton in xenon is designed and tested at the Institut für Kernphysik, Universitat Munster. The experimental setup together with two diagnostic tools is presented, as well as one stability test of a 11 hour distillation run at the designed flowrate of 3 kg per hour.
    No preview · Article · Nov 2014 · Journal of Physics Conference Series
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    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.
    Preview · Article · Nov 2014 · Journal of Instrumentation
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    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.
    Full-text · Article · Sep 2014 · Journal of Cosmology and Astroparticle Physics
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    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.
    Full-text · Article · Jul 2014 · Journal of Instrumentation
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    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.
    No preview · Article · Jul 2014 · Journal of Instrumentation
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    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.
    No preview · Article · Jun 2014 · Journal of Instrumentation
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    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.
    Full-text · Article · Jun 2014 · Journal of Instrumentation
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    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$^2$.
    Full-text · Article · Apr 2014 · Physical Review D
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    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.
    Preview · Article · Jan 2014

Publication Stats

5k Citations
471.75 Total Impact Points

Institutions

  • 2015
    • Technical University Darmstadt
      • Institute of Nuclear Physics
      Darmstadt, Hesse, Germany
  • 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
  • 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
    • Stockholm University
      Tukholma, Stockholm, Sweden
  • 2005
    • Justus-Liebig-Universität Gießen
      • II. Physikalisches Institut
      Gießen, Hesse, Germany
  • 2003
    • University of Delaware
      Ньюарк, Delaware, United States
  • 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