Ionization of Acetylene Mixtures and Other Mixtures by Pu<sup>239</sup> Alpha Particles.

Moe, H.J.; Bortner, T.E.; Hurst, G. S.

doi:10.1021/j150550a010

Cited by 28 publications

(7 citation statements)

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“…The W-value for 30:10:1 Torr of CS 2 :CF 4 :O 2 gas is under study. But the addition of about 1% of O 2 to the conventional CS 2 +CF 4 gas mixture is expected to change the W-value by only about 0.3 eV [30][31][32]. This is within the uncertainty of 25.2±0.6 eV measured by Ref.…”

Section: Discussionsupporting

confidence: 52%

First measurement of nuclear recoil head-tail sense in a fiducialised WIMP dark matter detector

et al. 2016

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Recent computational results suggest that directional dark matter detectors have potential to probe for WIMP dark matter particles below the neutrino floor. The DRIFT-IId detector used in this work is a leading directional WIMP search time projection chamber detector. We report the first measurements of the detection of the directional nuclear recoils in a fully fiducialised lowpressure time projection chamber. In this new operational mode, the distance between each event vertex and the readout plane is determined by the measurement of minority carriers produced by adding a small amount of oxygen to the nominal CS 2 +CF 4 target gas mixture. The CS 2 +CF 4 +O 2 mixture has been shown to enable background-free operation at current sensitivities. Sulfur, fluorine, and carbon recoils were generated using neutrons emitted from a 252 Cf source positioned at different locations around the detector. Measurement of the relative energy loss along the recoil tracks allowed the track vector sense, or the so-called head-tail asymmetry parameter, to be deduced. Results show that the previously reported observation of head-tail sensitivity in pure CS 2 is well retained after the addition of oxygen to the gas mixture.

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Section: Discussionsupporting

confidence: 52%

First measurement of nuclear recoil head-tail sense in a fiducialised WIMP dark matter detector

et al. 2016

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“…However, the results of Refs. [32,33,34] suggest that the addition of 1 Torr O 2 will change the W-value by ∼ 1%, which is a factor of two smaller than the uncertainty of the W-value used here [31]. Fluctuations in the 55 Fe energy measurement were observed at the ∼ 4% level over the course of the full 46.3 live-day dataset.…”

Section: Discussionmentioning

confidence: 75%

First background-free limit from a directional dark matter experiment: Results from a fully fiducialised DRIFT detector

Battat

Brack

Daw

et al. 2015

Physics of the Dark Universe

105

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The addition of O 2 to gas mixtures in time projection chambers containing CS 2 has recently been shown to produce multiple negative ions that travel at slightly different velocities. This allows a measurement of the absolute position of ionising events in the z (drift) direction. In this work, we apply the z-fiducialisation technique to a directional dark matter search. We present results from a 46.3 live-day source-free exposure of the DRIFT-IId detector run in this new mode. With full-volume fiducialisation, we have achieved the first background-free operation of a directional detector. The resulting exclusion curve for spindependent WIMP-proton interactions reaches 1.1 pb at 100 GeV/c 2 , a factor of 2 better than our previous work. We describe the automated analysis used here, and argue that detector upgrades, implemented after the acquisition of these data, will bring an additional factor of 3 improvement in the near future.arXiv:1410.7821v3 [hep-ex] 23 Jul 2015 DRIFT-IId detector and science runsThe DRIFT experiment is sited at a depth of 1.1 km in the STFC Boulby Underground Science Facility [29], which provides 2805 m.w.e. shielding against cosmic rays. The TPC is housed inside a stainless steel cubic vacuum vessel, surrounded on all sides with 44 g cm −2 of polypropylene pellets to shield against neutrons from the cavern walls. The vessel was filled with a mixture of 30:10:1 Torr CS 2 :CF 4 :O 2 gas, and sealed for the duration of each run. This departure from the normal mode of operation, in which gas is flowed at a constant rate of one complete vacuum vessel change (590 g) /d, was necessary due to safety concerns over sources of ignition in the constant flow system. These concerns have since been addressed with modifications to the gas system.The DRIFT-IId NITPC consists of a thin-film (0.9 µm aluminised Mylar), texturised central cathode [25] at a potential of -31.9 kV faced on either side by two 1 m 2 multi-wire proportional chambers (hereafter, the 'left' and 'right' MWPCs) at a distance of 50 cm. In this way, two 50-cm-long drift regions are defined. A field cage of 31 stainless steel rings on either side steps down the voltage smoothly between the central cathode and the MWPCs to ensure a uniform electric field of 580 V cm −1 throughout the drift regions. The MWPCs are made up of a central grounded anode plane of 20 µm diameter stainless steel wires with 2 mm pitch, sandwiched between two perpendicular grid planes of 100 µm wires at -2884 V, again with 2 mm pitch and separated by 1 cm from the anode plane. A full description of the detector can be found in Ref. [30].Both the inner grid and anode planes have every eighth wire joined together and read out as one, such that a single 'octave' of wires reads out 8 × 2 = 16 mm in x and y: large enough to contain the recoil events of interest. The outermost 52 (41) wires of the 512 total on the inner grid (anode) planes are grouped together into x (y) veto regions, reducing the fiducial volume of the detector to 0.80 m 3 . The anode and grid veto signal...

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“…The W value for a mixture of gases must be determined experimentally; it is not in general equal to the weighted mean of the values for the components of the mixture. Information for a number of mixtures is provided by Bortner and Hurst (1954); Moe, et al, (1957);and Valentine and Curran (1958).…”

Section: Average Energy Per Ion Pair Wmentioning

confidence: 99%

Physical aspects of irradiation: recommendations of the International Commission on Radiological Units and Measurements (ICRU) report 10B 1962

1964

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Ionization of Acetylene Mixtures and Other Mixtures by Pu²³⁹ Alpha Particles.

Cited by 28 publications

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First measurement of nuclear recoil head-tail sense in a fiducialised WIMP dark matter detector

First measurement of nuclear recoil head-tail sense in a fiducialised WIMP dark matter detector

First background-free limit from a directional dark matter experiment: Results from a fully fiducialised DRIFT detector

Physical aspects of irradiation: recommendations of the International Commission on Radiological Units and Measurements (ICRU) report 10B 1962

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Ionization of Acetylene Mixtures and Other Mixtures by Pu239 Alpha Particles.

Cited by 28 publications

References 0 publications

First measurement of nuclear recoil head-tail sense in a fiducialised WIMP dark matter detector

First measurement of nuclear recoil head-tail sense in a fiducialised WIMP dark matter detector

First background-free limit from a directional dark matter experiment: Results from a fully fiducialised DRIFT detector

Physical aspects of irradiation: recommendations of the International Commission on Radiological Units and Measurements (ICRU) report 10B 1962

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Ionization of Acetylene Mixtures and Other Mixtures by Pu²³⁹ Alpha Particles.