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Search Results: 1 - 10 of 352785 matches for " D. P. Snowden-Ifft "
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High Precision Measurements of Carbon Disulfide Negative Ion Mobility and Diffusion
D. P. Snowden-Ifft,J. -L. Gauvreau
Physics , 2013, DOI: 10.1063/1.4803004
Abstract: High precision measurements were made of reduced mobility, lateral and longitudinal diffusion of CS2- negative ions in 40 Torr CS2 and a 30 - 10 Torr CS2 - CF4 gas mixture. The reduced mobility was found to be 353.0 +/- 0.5 cm^2 Torr / s V in CS2 and 397.4 +/- 0.7 cm^2 Torr / s V in the CS2 - CF4 gas mixture at STP. The lateral diffusion temperatures for these two gases (295 +/- 15 K and 297 +/- 6 K) were found to be in good agreement with room temperature. By contrast longitudinal diffusion temperature was found to be slightly elevated (319 +/- 10 (stat) +/- 8 (sys) K and 310 +/- 20 (stat) +/- 6 (sys) K) though given the errors, room temperature diffusion can not be ruled out. For lateral diffusion significant capture distances (0.21 +/- 0.07 mm and 0.15 +/- 0.03 mm) were measured while for longitudinal diffusion the results were not conclusive.
Simulations of the Nuclear Recoil Head-Tail Signature in Gases Relevant to Directional Dark Matter Searches
P. Majewski,D. Muna,D. P. Snowden-Ifft,N. J. C. Spooner
Physics , 2009, DOI: 10.1016/j.astropartphys.2010.08.007
Abstract: We present the first detailed simulations of the head-tail effect relevant to directional Dark Matter searches. Investigations of the location of the majority of the ionization charge as being either at the beginning half (tail) or at the end half (head) of the nuclear recoil track were performed for carbon and sulphur recoils in 40 Torr negative ion carbon disulfide and for fluorine recoils in 100 Torr carbon tetrafluoride. The SRIM simulation program was used, together with a purpose-written Monte Carlo generator, to model production of ionizing pairs, diffusion and basic readout geometries relevant to potential real detector scenarios, such as under development for the DRIFT experiment. The results clearly indicate the existence of a head-tail track asymmetry but with a magnitude critically influenced by two competing factors: the nature of the stopping power and details of the range straggling. The former tends to result in the tail being greater than the head and the latter the reverse.
Low Pressure Negative Ion Drift Chamber for Dark Matter Search
D. P. Snowden-Ifft,C. J. Martoff,J. M. Burwell
Physics , 1999, DOI: 10.1103/PhysRevD.61.101301
Abstract: Weakly Interacting Massive Particles (WIMPs) are an attractive candidate for the dark matter thought to make up the bulk of the mass of our universe. We explore here the possibility of using a low pressure negative ion drift chamber to search for WIMPs. The innovation of drifting ions, instead of electrons, allows the design of a detector with exceptional sensitivity to, background rejection from, and signature of WIMPs.
Discovery of Multiple, Ionization-Created Anions in Gas Mixtures Containing CS2 and O2
Daniel P. Snowden-Ifft
Physics , 2013,
Abstract: The use of negative ions in TPCs has several advantages for high-resolution rare- event detection experiments. The DRIFT experiment, for example, has taken full advantage of this technique over the past decade in a directional search for dark matter. This paper focuses on the surprising discovery of multiple species of ionization-created CS2 anions, called minority carriers, in gas mixtures containing electronegative CS2 and O2, identified by their slightly different drift velocities. Measurements of minority carriers in gas mixtures of CS2, CF4 and O2 are reported in an effort to understand the nature of these charge carriers. Regardless of the micro-physics however, this discovery offers significant practical advantages for experiments such as DRIFT, where the difference in arrival time may be used to fiducialize the original ionization event without an external start pulse.
Unique Signature of Dark Matter in Ancient Mica
Daniel P. Snowden-Ifft,Andrew J. Westphal
Physics , 1997, DOI: 10.1103/PhysRevLett.78.1628
Abstract: Mica can store (for >1 Gy) etchable tracks caused by atoms recoiling from WIMPs. Because a background from fission neutrons will eventually limit this technique, a unique signature for WIMPs in ancient mica is needed. Our motion around the center of the Galaxy causes WIMPs, unlike neutrons, to enter the mica from a preferred direction on the sky. Mica is a directional detector and despite the complex rotations that natural mica crystals make with respect to this WIMP ``wind,'' there is a substantial dependence of etch pit density on present day mica orientation.
Measurement of Carbon Disulfide Anion Diffusion in a TPC
Tohru Ohnuki,Daniel P. Snowden-Ifft,C. J. Martoff
Physics , 2000, DOI: 10.1016/S0168-9002(01)00222-4
Abstract: A Negative Ion Time Projection Chamber was used to measure the field dependence of lateral and longitudinal diffusion for CS$_2$ anions drifting in mixtures of CS$_2$ and Ar at 40 Torr. Ion drift velocities and limits on the capture distance for electrons as a function of field and gas mixture are also reported.
Track Reconstruction and Performance of DRIFT Directional Dark Matter Detectors using Alpha Particles
S. Burgos,J. Forbes,C. Ghag,M. Gold,V. A. Kudryavtsev,T. B. Lawson,D. Loomba,P. Majewski,J. E. McMillan,D. Muna,A. StJ. Murphy,G. G. Nicklin,S. M. Paling,A. Petkov,S. J. S. Plank,M. Robinson,N. Sanghi,N. J. T. Smith,D. P. Snowden-Ifft,N. J. C. Spooner,T. J. Sumner,J. Turk,T. Tziaferi
Physics , 2007, DOI: 10.1016/j.nima.2007.10.013
Abstract: First results are presented from an analysis of data from the DRIFT-IIa and DRIFT-IIb directional dark matter detectors at Boulby Mine in which alpha particle tracks were reconstructed and used to characterise detector performance--an important step towards optimising directional technology. The drift velocity in DRIFT-IIa was [59.3 +/- 0.2 (stat) +/- 7.5 (sys)] m/s based on an analysis of naturally-occurring alpha-emitting background. The drift velocity in DRIFT-IIb was [57 +/- 1 (stat) +/- 3 (sys)] m/s determined by the analysis of alpha particle tracks from a Po-210 source. 3D range reconstruction and energy spectra were used to identify alpha particles from the decay of Rn-222, Po-218, Rn-220 and Po-216. This study found that (22 +/- 2)% of Po-218 progeny (from Rn-222 decay) are produced with no net charge in 40 Torr CS2. For Po-216 progeny (from Rn-220 decay) the uncharged fraction is (100 +0 -35)%.
Measurement of the Range Component Directional Signature in a DRIFT-II Detector using 252Cf Neutrons
S. Burgos,E. Daw,J. Forbes,C. Ghag,M. Gold,C. Hagemann,V. A. Kudryavtsev,T. B. Lawson,D. Loomba,P. Majewski,D. Muna,A. St. J. Murphy,G. G. Nicklin,S. M. Paling,A. Petkov,S. J. S. Plank,M. Robinson,N. Sanghi,D. P. Snowden-Ifft,N. J. C. Spooner,J. Turk,E. Tziaferi
Physics , 2008, DOI: 10.1016/j.nima.2008.11.147
Abstract: The DRIFT collaboration utilizes low pressure gaseous detectors to search for WIMP dark matter with directional signatures. A 252Cf neutron source was placed on each of the principal axes of a DRIFT detector in order to test its ability to measure directional signatures from the three components of very low energy (~keV/amu) recoil ranges. A high trigger threshold and the event selection procedure ensured that only sulfur recoils were analyzed. Sulfur recoils produced in the CS2 target gas by the 252Cf source closely match those expected from massive WIMP induced sulfur recoils. For each orientation of the source a directional signal from the range components was observed, indicating that the detector is directional along all 3 axes. An analysis of these results yields an optimal orientation for DRIFT detectors when searching for a directional signature from WIMPs. Additional energy dependent information is provided to aid in understanding this effect.
Low Energy Electron and Nuclear Recoil Thresholds in the DRIFT-II Negative Ion TPC for Dark Matter Searches
S. Burgos,E. Daw,J. Forbes,C. Ghag,M. Gold,C. Hagemann,V. A. Kudryavtsev,T. B. Lawson,D. Loomba,P. Majewski,D. Muna,A. St. J. Murphy,S. M. Paling,A. Petkov,S. J. S. Plank,M. Robinson,N. Sanghi,D. P. Snowden-Ifft,N. J. C. Spooner,J. Turk,E. Tziaferi
Physics , 2009, DOI: 10.1088/1748-0221/4/04/P04014
Abstract: Understanding the ability to measure and discriminate particle events at the lowest possible energy is an essential requirement in developing new experiments to search for weakly interacting massive particle (WIMP) dark matter. In this paper we detail an assessment of the potential sensitivity below 10 keV in the 1 m^3 DRIFT-II directionally sensitive, low pressure, negative ion time projection chamber (NITPC), based on event-by-event track reconstruction and calorimetry in the multiwire proportional chamber (MWPC) readout. By application of a digital smoothing polynomial it is shown that the detector is sensitive to sulfur and carbon recoils down to 2.9 and 1.9 keV respectively, and 1.2 keV for electron induced events. The energy sensitivity is demonstrated through the 5.9 keV gamma spectrum of 55Fe, where the energy resolution is sufficient to identify the escape peak. The effect a lower energy sensitivity on the WIMP exclusion limit is demonstrated. In addition to recoil direction reconstruction for WIMP searches this sensitivity suggests new prospects for applications also in KK axion searches.
First Results from the DRIFT-IIa Dark Matter Detector
S. Burgos,J. Forbes,C. Ghag,M. Gold,V. A. Kudryavtsev,T. B. Lawson,D. Loomba,P. Majewski,D. Muna,A. StJ. Murphy,G. G. Nicklin,S. M. Paling,A. Petkov,S. J. S. Plank,M. Robinson,N. Sanghi,N. J. T. Smith,D. P. Snowden-Ifft,N. J. C. Spooner,T. J. Sumner,J. Turk,E. Tziaferi
Statistics , 2007, DOI: 10.1016/j.astropartphys.2007.08.007
Abstract: Data from the DRIFT-IIa directional dark matter experiment are presented, collected during a near continuous 6 month running period. A detailed calibration analysis comparing data from gamma-ray, x-ray and neutron sources to a GEANT4 Monte Carlo simulations reveals an efficiency for detection of neutron induced recoils of 94+/-2(stat.)+/-5(sys.)%. Software-based cuts, designed to remove non-nuclear recoil events, are shown to reject 60Co gamma-rays with a rejection factor of better than 8x10-6 for all energies above threshold. An unexpected event population has been discovered and is shown here to be due to the alpha-decay of 222Rn daughter nuclei that have attached to the central cathode. A limit on the flux of neutrons in the Boulby Underground Laboratory is derived from analysis of unshielded and shielded data.
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