arXiv subjects

D. N. McKinsey

Publications and source records attributed to D. N. McKinsey.

At least 91 records · Page 5Linked to original sources

arXiv2011

Scintillation and charge extraction from the tracks of energetic electrons in superfluid helium-4

An energetic electron passing through liquid helium causes ionization along its track. The ionized electrons quickly recombine with the resulting positive ions, which leads to the production of prompt scintillation light. By applying appropriate electric fields, some of the ionized electrons can be separated from their parent ions. The fraction of the ionized electrons extracted in a given applied field depends on the separation distance between the electrons and the ions. We report the determination of the mean electron-ion separation distance for charge pairs produced along the tracks of beta particles in superfluid helium at 1.5 K by studying the quenching of the scintillation light under applied electric fields. Knowledge of this mean separation parameter will aid in the design of particle detectors that use superfluid helium as a target material.

physics.ins-det↗

arXiv2011

Data Acquisition and Readout System for the LUX Dark Matter Experiment

LUX is a two-phase (liquid/gas) xenon time projection chamber designed to detect nuclear recoils from interactions with dark matter particles. Signals from the LUX detector are processed by custom-built analog electronics which provide properly shaped signals for the trigger and data acquisition (DAQ) systems. The DAQ is comprised of commercial digitizers with firmware customized for the LUX experiment. Data acquisition systems in rare-event searches must accommodate high rate and large dynamic range during precision calibrations involving radioactive sources, while also delivering low threshold for maximum sensitivity. The LUX DAQ meets these challenges using real-time baseline sup- pression that allows for a maximum event acquisition rate in excess of 1.5 kHz with virtually no deadtime. This paper describes the LUX DAQ and the novel acquisition techniques employed in the LUX experiment.

astro-ph.IM↗

arXiv2010

Lowering the low-energy threshold of xenon detectors

We show that the energy threshold for nuclear recoils in the XENON10 dark matter search data can be lowered to ~1 keV, by using only the ionization signal. In other words, we make no requirement that a valid event contain a primary scintillation signal. We therefore relinquish incident particle type discrimination, which is based on the ratio of ionization to scintillation in liquid xenon. This method compromises the detector's ability to precisely determine the z coordinate of a particle interaction. However, we show for the first time that it is possible to discriminate bulk events from surface events based solely on the ionization signal.

astro-ph.IM↗

arXiv2010

Constraints on inelastic dark matter from XENON10

It has been suggested that dark matter particles which scatter inelastically from detector target nuclei could explain the apparent incompatibility of the DAMA modulation signal (interpreted as evidence for particle dark matter) with the null results from CDMS-II and XENON10. Among the predictions of inelastically interacting dark matter are a suppression of low-energy events, and a population of nuclear recoil events at higher nuclear recoil equivalent energies. This is in stark contrast to the well-known expectation of a falling exponential spectrum for the case of elastic interactions. We present a new analysis of XENON10 dark matter search data extending to E$_{nr}=75$ keV nuclear recoil equivalent energy. Our results exclude a significant region of previously allowed parameter space in the model of inelastically interacting dark matter. In particular, it is found that dark matter particle masses $m_χ\gtrsim150$ GeV are disfavored.

astro-ph.CO↗

arXiv2010

Response to arXiv:1005.2615

Brief response to a Reply [arXiv:1005.2615] on our Comments [arXiv:1005.0838] on XENON100 recent results [arXiv:1005.0380].

astro-ph.CO↗

arXiv2010

Comments on "First Dark Matter Results from the XENON100 Experiment"

The XENON100 collaboration has recently released new dark matter limits, placing particular emphasis on their impact on searches known to be sensitive to light-mass (below 10 GeV/c^2) Weakly Interacting Massive Particles (WIMPs), such as DAMA and CoGeNT. We describe here several sources of uncertainty and bias in their analysis that make their new claimed sensitivity presently untenable. In particular, we point out additional work in this field and simple kinematic arguments that indicate that liquid xenon (LXe) may be a relatively insensitive detection medium for the recoil energies (few keV_r) expected from such low mass WIMPs.

astro-ph.CO↗

arXiv2010

A 83Krm Source for Use in Low-background Liquid Xenon Time Projection Chambers

We report the testing of a charcoal-based Kr-83m source for use in calibrating a low background two-phase liquid xenon detector. Kr-83m atoms produced through the decay of Rb-83 are introduced into a xenon detector by flowing xenon gas past the Rb-83 source. 9.4 keV and 32.1 keV transitions from decaying 83Krm nuclei are detected through liquid xenon scintillation and ionization. The characteristics of the Kr-83m source are analyzed and shown to be appropriate for a low background liquid xenon detector. Introduction of Kr-83m allows for quick, periodic calibration of low background noble liquid detectors at low energy.

physics.ins-det↗

arXiv2010

Scintillation efficiency and ionization yield of liquid xenon for mono-energetic nuclear recoils down to 4 keV

Liquid Xenon (LXe) is an excellent material for experiments designed to detect dark matter in the form of Weakly Interacting Massive Particles (WIMPs). A low energy detection threshold is essential for a sensitive WIMP search. The understanding of the relative scintillation efficiency (Leff) and ionization yield of low energy nuclear recoils in LXe is limited for energies below 10 keV. In this paper, we present new measurements that extend the energy down to 4 keV, finding that Leff decreases with decreasing energy. We also measure the quenching of scintillation efficiency due to the electric field in LXe, finding no significant field dependence.

physics.ins-det↗

arXiv2010

Design and Performance of the XENON10 Dark Matter Experiment

XENON10 is the first two-phase xenon time projection chamber (TPC) developed within the XENON dark matter search program. The TPC, with an active liquid xenon (LXe) mass of about 14 kg, was installed at the Gran Sasso underground laboratory (LNGS) in Italy, and operated for more than one year, with excellent stability and performance. Results from a dark matter search with XENON10 have been published elsewhere. In this paper, we summarize the design and performance of the detector and its subsystems, based on calibration data using sources of gamma-rays and neutrons as well as background and Monte Carlo simulations data. The results on the detector's energy threshold, energy and position resolution, and overall efficiency show a performance that exceeds design specifications, in view of the very low energy threshold achieved (<10 keVr) and the excellent energy resolution achieved by combining the ionization and scintillation signals, detected simultaneously.

astro-ph.IM↗

arXiv2009

Calibration of a Liquid Xenon Detector with Kr-83m

We report the preparation of a Kr-83m source and its subsequent use in calibrating a liquid xenon detector. Kr-83m atoms were produced through the decay of Rb-83 atoms trapped in zeolite molecular sieve and were then introduced into liquid xenon. Decaying Kr-83m nuclei were detected through liquid xenon scintillation. Conversion electrons with energies of 9.4 keV and 32.1 keV from the decay of Kr-83m were both observed. This calibration source will allow the characterization of the scintillation and ionization response of noble liquid detectors at low energies, highly valuable for the search for WIMP dark matter. Kr-83m may also be useful for measuring fluid flow dynamics, both to understand purification in noble liquid-based particle detectors, as well as for studies of classical and quantum turbulence in superfluid helium.

physics.ins-det↗

arXiv2009

Calibration of liquid argon and neon detectors with $^{83}Kr^m$

We report results from tests of $^{83}$Kr$^{\mathrm{m}}$, as a calibration source in liquid argon and liquid neon. $^{83}$Kr$^{\mathrm{m}}$ atoms are produced in the decay of $^{83}$Rb, and a clear $^{83}$Kr$^{\mathrm{m}}$ scintillation peak at 41.5 keV appears in both liquids when filling our detector through a piece of zeolite coated with $^{83}$Rb. Based on this scintillation peak, we observe 6.0 photoelectrons/keV in liquid argon with a resolution of 6% ($σ$/E) and 3.0 photoelectrons/keV in liquid neon with a resolution of 19% ($σ$/E). The observed peak intensity subsequently decays with the $^{83}$Kr$^{\mathrm{m}}$ half-life after stopping the fill, and we find evidence that the spatial location of $^{83}$Kr$^{\mathrm{m}}$ atoms in the chamber can be resolved. $^{83}$Kr$^{\mathrm{m}}$ will be a useful calibration source for liquid argon and neon dark matter and solar neutrino detectors.

astro-ph.IM↗

arXiv2009

Studying the normal-fluid flow in Helium-II using metastable helium molecules

We demonstrate that metastable helium molecules can be used as tracers to visualize the flow of the normal fluid in superfluid $^{4}$He using a laser-induced-fluorescence technique. The flow pattern of a normal-fluid jet impinging on the center of a copper disc is imaged. A ring-shaped circulation structure of the normal fluid is observed as the jet passes across the disc surface. The fluorescence signal for the molecules trapped in the circulation structure is measured as a function of time after we turn off the molecule source. The radiative lifetime and density of the molecules can be determined by fitting the measured data using a simple analytic model. We also discuss a proposed experiment on using a previously developed molecule tagging-imaging technique to visualize the normal-fluid velocity profile during the transition of quantum turbulence in a thermal counterflow channel.

physics.atom-ph↗

arXiv2009

Metastable helium molecules as tracers in superfluid liquid $^{4}$He

Metastable helium molecules generated in a discharge near a sharp tungsten tip operated in either pulsed mode or continuous field-emission mode in superfluid liquid $^{4}$He are imaged using a laser-induced-fluorescence technique. By pulsing the tip, a small cloud of He$_{2}^{*}$ molecules is produced. At 2.0 K, the molecules in the liquid follow the motion of the normal fluid. We can determine the normal-fluid velocity in a heat-induced counterflow by tracing the position of a single molecule cloud. As we run the tip in continuous field-emission mode, a normal-fluid jet from the tip is generated and molecules are entrained in the jet. A focused 910 nm pump laser pulse is used to drive a small group of molecules to the vibrational $a(1)$ state. Subsequent imaging of the tagged $a(1)$ molecules with an expanded 925 nm probe laser pulse allows us to measure the velocity of the normal fluid. The techniques we developed demonstrate for the first time the ability to trace the normal-fluid component in superfluid helium using angstrom-sized particles.

physics.flu-dyn↗

arXiv2008

The scintillation and ionization yield of liquid xenon for nuclear recoils

XENON10 is an experiment designed to directly detect particle dark matter. It is a dual phase (liquid/gas) xenon time-projection chamber with 3D position imaging. Particle interactions generate a primary scintillation signal (S1) and ionization signal (S2), which are both functions of the deposited recoil energy and the incident particle type. We present a new precision measurement of the relative scintillation yield \leff and the absolute ionization yield Q_y, for nuclear recoils in xenon. A dark matter particle is expected to deposit energy by scattering from a xenon nucleus. Knowledge of \leff is therefore crucial for establishing the energy threshold of the experiment; this in turn determines the sensitivity to particle dark matter. Our \leff measurement is in agreement with recent theoretical predictions above 15 keV nuclear recoil energy, and the energy threshold of the measurement is 4 keV. A knowledge of the ionization yield \Qy is necessary to establish the trigger threshold of the experiment. The ionization yield \Qy is measured in two ways, both in agreement with previous measurements and with a factor of 10 lower energy threshold.

astro-ph↗

arXiv2008

Scintillation time dependence and pulse shape discrimination in liquid argon

Using a single-phase liquid argon detector with a signal yield of 4.85 photoelectrons per keV of electronic-equivalent recoil energy (keVee), we measure the scintillation time dependence of both electronic and nuclear recoils in liquid argon down to 5 keVee. We develop two methods of pulse shape discrimination to distinguish between electronic and nuclear recoils. Using one of these methods, we measure a background and statistics-limited level of electronic recoil contamination to be $7.6\times10^{-7}$ between 60 and 128 keV of nuclear recoil energy (keVr) for a nuclear recoil acceptance of 50% with no nuclear recoil-like events above 72 keVr. Finally, we develop a maximum likelihood method of pulse shape discrimination using the measured scintillation time dependence and predict the sensitivity to WIMP-nucleon scattering in three configurations of a liquid argon dark matter detector.

nucl-ex↗

arXiv2008

Limits on spin-dependent WIMP-nucleon cross-sections from the XENON10 experiment

XENON10 is an experiment to directly detect weakly interacting massive particle (WIMPs), which may comprise the bulk of the non-baryonic dark matter in our Universe. We report new results for spin-dependent WIMP-nucleon interactions with 129-Xe and 131-Xe from 58.6 live-days of operation at the Laboratori Nazionali del Gran Sasso (LNGS). Based on the non-observation of a WIMP signal in 5.4 kg of fiducial liquid xenon mass, we exclude previously unexplored regions in the theoretically allowed parameter space for neutralinos. We also exclude a heavy Majorana neutrino with a mass in the range of 10 GeV -2 TeV as a dark matter candidate under standard assumptions for its density and distribution in the galactic halo.

astro-ph↗

arXiv2007

Detection and Imaging of He_2 Molecules in Superfluid Helium

We present data that show a cycling transition can be used to detect and image metastable He$_2$ triplet molecules in superfluid helium. We demonstrate that limitations on the cycling efficiency due to the vibrational structure of the molecule can be mitigated by the use of repumping lasers. Images of the molecules obtained using the method are also shown. This technique gives rise to a new kind of ionizing radiation detector. The use of He$_2$ triplet molecules as tracer particles in the superfluid promises to be a powerful tool for visualization of both quantum and classical turbulence in liquid helium.

nucl-ex↗

arXiv2007

First Results from the XENON10 Dark Matter Experiment at the Gran Sasso National Laboratory

The XENON10 experiment at the Gran Sasso National Laboratory uses a 15 kg xenon dual phase time projection chamber (XeTPC) to search for dark matter weakly interacting massive particles (WIMPs). The detector measures simultaneously the scintillation and the ionization produced by radiation in pure liquid xenon, to discriminate signal from background down to 4.5 keV nuclear recoil energy. A blind analysis of 58.6 live days of data, acquired between October 6, 2006 and February 14, 2007, and using a fiducial mass of 5.4 kg, excludes previously unexplored parameter space, setting a new 90% C.L. upper limit for the WIMP-nucleon spin-independent cross-section of 8.8 x 10^{-44} cm^2 for a WIMP mass of 100 GeV/c^2, and 4.5 x 10^{-44} cm^2 for a WIMP mass of 30 GeV/c^2. This result further constrains predictions of supersymmetric models.

astro-ph↗