41 research outputs found

    Developments Towards a Scaled-Up One-Dimensional Directional Dark Matter Detector

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    There are many forms of evidence that point towards an unknown form of matter, known as dark matter, making up ∼85% of the mass in the universe. Many dark matter candidates have been proposed with the Weakly Interacting Massive Particle (WIMP) being among the most favoured. There are many groups around the world actively looking for WIMPs with direct, indirect and collider searches with specific interest here in annual modulation and directional searches. The DRIFT-IId detector is the world’s largest directional dark matter detector and is operational in Boulby Mine in the UK. Members of the directional community have come together to form the CYGNUS collaboration, looking towards larger detectors with better directional sensitivity. This thesis looks towards the future scale up to larger directional detectors, specifically low-pressure gas detectors. Improvements have been made to a system used to measure the radon emanation of materials, with emanation tests taken of potential components for CYGNUS detectors. Measurements have also been taken with a small scale THGEM TPC in both CF4 and SF6 gas. The results from CF4 showed the high gas gains achievable from the THGEM detector and allowed a direct measurement of the Townsend coefficients of the gas. Gains of up to 8600 ± 150 have been achieved in low pressure SF6 with a resolution of 19%, both of these figures are the highest achieved to date. The directional sensitivity of 1D readouts has been tested with initial signals of head-tail shown in a THGEM TPC in SF6. A head-tail signature is also seen in a simplified 1D DRIFT-IId readout mode. Exclusion limits from both the full and simplified DRIFT readouts have been produced from over 100 days of background data. The result of 0.16 pb from the full analysis is the lowest limit produced by any directional detector. These results show that a one-dimensional readout may be feasible for directional WIMP detection removing the need for many hundreds or thousands of read out channels required for 3D reconstruction

    Characterisation of the Temperature-dependent Dark Rate of Hamamatsu R7081-100 10" Photomultiplier Tubes

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    Dark noise is a dominant background in photomultiplier tubes (PMTs), which are commonly used in liquid-filled particle detectors for single-photon detection to see the results of particle interactions. A major contribution to dark noise is thermionic emission from the photocathode. The dark noise of Hamamatsu R7081-100 PMTs is characterised in a temperature and purity controlled water tank, with the thermionic emission contribution isolated. The results suggest that the intrinsic dark rate of PMTs does not depend on the medium, but does follow Richardson's law of thermionic emission. There are external contributions to the overall observed PMT count rate identified, but the intrinsic PMT dark rate in water matches that measured in air.Comment: 11 pages, 7 figures, 2 tables, prepared for submission to J. Instru

    US Cosmic Visions: New Ideas in Dark Matter 2017: Community Report

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    This white paper summarizes the workshop "U.S. Cosmic Visions: New Ideas in Dark Matter" held at University of Maryland on March 23-25, 2017.Comment: 102 pages + reference

    Competence in the use of supraglottic airways by Australian surf lifesavers for cardiac arrest ventilation in a manikin

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    OBJECTIVES: Lifesavers in Australia are taught to use pocket mask (PM) rescue breathing and bag valve mask (BVM) ventilation, despite evidence that first responders might struggle with these devices. Novices have successfully used the Laryngeal Mask Airway (LMA) Supreme and iGel devices previously, but there has been no previous comparison of the ability to train lifesavers to use the supraglottic airways compared to standard techniques for cardiac arrest ventilation. METHODS: The study is a prospective educational intervention whereby 113 lifesavers were trained to use the LMA and iGel supraglottic airways. Comparisons were made to standard devices on plastic manikins. Successful ventilation was defined as achieving visible chest rise. RESULTS: The median time to first effective ventilation was similar between the PM (16 s, 95% confidence interval 16-17 s), BVM (17 s, 16-17 s) and iGel devices (18 s, 16-20 s), but longer for the LMA (36 s, 33-38 s). The iGel frequently failed to achieve ventilation (10%) compared with the PM (1%, P < 0.01) and LMA (3%, P < 0.01) but was not worse than the BVM (3%, P < 0.57). Hands-off time was similar between the BVM, LMA and iGel (10 s for each device), but worse for the PM (13 s, P = 0.001). CONCLUSION: Lifesavers using the PM and BVM perform ventilation for cardiopulmonary resuscitation well. There appears to be a limited role for supraglottic airway devices because of limitations in terms of time to first effective ventilation and reliability. Clinical validation of manikin data with live resuscitation performance is required

    Dietary composition and prey preference of a new carnivorous marsupial species, the buff-footed antechinus (Antechinus mysticus), at the northern and southern limits of its range

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    The buff-footed antechinus (Antechinus mysticus) is a newly described carnivorous marsupial from eastern Australia. We examined the diet composition and prey preference of this little known dasyurid in the southernmost (Brisbane) and northernmost (Eungella) populations. Animals were captured over three months (July–September) during 2014 encompassing the breeding period (late July and August) of the species. Seasonal sampling carried over into a second year which followed the succeeding cohort of juveniles as they dispersed from their maternal nest (summer), through their maturation (autumn), to the beginning of breeding (winter), sampling across one complete generation. The diet of A. mysticus consisted predominantly of invertebrates, with 16 prey orders identified (11 Insecta, two Arachnida, two Myriapoda, one Crustacea). Vertebrate (Family Scincidae) consumption was recorded in low abundance at both sites. The diet of A. mysticus was dominated by Araneae (spiders), Blattodea (cockroaches) and Coleoptera (beetles). Comparison of identified prey consumption in scats with prey availability in pitfall traps showed A. mysticus to be a dietary generalist, opportunistically consuming mostly invertebrate prey with supplementary predation on small vertebrates. Juvenile A. mysticus preyed predominantly on Blattodea (33.4% mean percentage volume) and Coleoptera (31.6% mean percentage volume), potentially suggesting a preference for larger, easier to catch, prey items. Further exploration into the relationship between prey and body size is required to determine this
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