The addition of O 2 to gas mixtures in time projection chambers containing CS 2 has recently been... more 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.
This document presents the concept and physics case for a magnetized gaseous argon-based detector... more This document presents the concept and physics case for a magnetized gaseous argon-based detector system (ND-GAr) for the Deep Underground Neutrino Experiment (DUNE) Near Detector. This detector system is required in order for DUNE to reach its full physics potential in the measurement of CP violation and in delivering precision measurements of oscillation parameters. In addition to its critical role in the long-baseline oscillation program, ND-GAr will extend the overall physics program of DUNE. The LBNF high-intensity proton beam will provide a large flux of neutrinos that is sampled by ND-GAr, enabling DUNE to discover new particles and search for new interactions and symmetries beyond those predicted in the Standard Model.
A dominant particle pinch is observed in discharges of the Electric Tokamak (ET). As a result, th... more A dominant particle pinch is observed in discharges of the Electric Tokamak (ET). As a result, the density increases dramatically, with the profile evolving in a self-similar manner. Due to density accumulation in the absence of significant core cooling, the Troyon limit (βN = I/aB ~ 3) is reached in Ohmic plasmas in ET. The pinching rate is controlled with soft gas puffing. Hard puffing produces inverted density profiles that do not pinch due to MHD instabilities. The density threshold for pinching is n(0) ~ 1x10 m in Ohmic discharges and 3x10 m in ICRF heated discharges. The ramp-up time of the density is typically 1 second. The ramps are terminated by internal disruptions due to beta collapse without any significant radiation loss. This collapse takes place mostly above the density limit (n = 5x10 m with B = 0.25 T and R = 5 m, a = 1 m). The loop voltage remains low (0.4 V) during the ramp. In ICRF-heated discharges the ramps terminate at lower densities due to higher plasma temp...
The ProtoDUNE-SP detector is a single-phase liquid argon time projection chamber (LArTPC) that wa... more The ProtoDUNE-SP detector is a single-phase liquid argon time projection chamber (LArTPC) that was constructed and operated in the CERN North Area at the end of the H4 beamline. This detector is a prototype for the first far detector module of the Deep Underground Neutrino Experiment (DUNE), which will be constructed at the Sandford Underground Research Facility (SURF) in Lead, South Dakota, USA. The ProtoDUNE-SP detector incorporates full-size components as designed for DUNE and has an active volume of $7\times 6\times 7.2$~m$^3$. The H4 beam delivers incident particles with well-measured momenta and high-purity particle identification. ProtoDUNE-SP's successful operation between 2018 and 2020 demonstrates the effectiveness of the single-phase far detector design. This paper describes the design, construction, assembly and operation of the detector components.
The Deep Underground Neutrino Experiment (DUNE) will produce world-leading neutrino oscillation m... more The Deep Underground Neutrino Experiment (DUNE) will produce world-leading neutrino oscillation measurements over the lifetime of the experiment. In this work, we explore DUNE's sensitivity to observe charge-parity violation (CPV) in the neutrino sector, and to resolve the mass ordering, for exposures of up to 100 kiloton-megawatt-years (kt-MW-yr). The analysis includes detailed uncertainties on the flux prediction, the neutrino interaction model, and detector effects. We demonstrate that DUNE will be able to unambiguously resolve the neutrino mass ordering at a 3$\sigma$ (5$\sigma$) level, with a 66 (100) kt-MW-yr far detector exposure, and has the ability to make strong statements at significantly shorter exposures depending on the true value of other oscillation parameters. We also show that DUNE has the potential to make a robust measurement of CPV at a 3$\sigma$ level with a 100 kt-MW-yr exposure for the maximally CP-violating values $\delta_{\rm CP}} = \pm\pi/2$. Additiona...
The current status of the DRIFT (Directional Recoil Identification From Tracks) experiment at Bou... more The current status of the DRIFT (Directional Recoil Identification From Tracks) experiment at Boulby Mine is presented, including the latest limits on the WIMP spin-dependent cross-section from 1.5 kg days of running with a mixture of CS2 and CF4. Planned upgrades to DRIFT IId are detailed, along with ongoing work towards DRIFT III, which aims to be the world's first 10 m3-scale directional Dark Matter detector.
Light dark matter (LDM) in the context of dark sector theories is an attractive candidate to make... more Light dark matter (LDM) in the context of dark sector theories is an attractive candidate to make up the bulk of the mass of our Universe. This proposal presents the LDM discovery potential of a low-pressure, negative-ion, time-projection-chamber detector placed downstream of the Hall A beam-dump at Jefferson Lab receiving 10 22 electrons on target (EOT). As with the approved Beam-Dump eXperiment (BDX) the Directional Recoil Identification From Tracks Beam-Dump eXperiment (DRIFT-BDX) would run parasitically and in parallel with BDX providing additional reach, confirmation potential and different backgrounds all providing a high degree of complementarity. DRIFT-BDX is sensitive to elastic nuclear recoil events with a threshold of ~1 keV/amu recoil energy. Multiple, powerful signatures of LDM interactions are possible with BDX-DRIFT detector. Detailed calculations present cosmic ray and beam-related background estimates. The proposed experiment will be sensitive to large regions of ...
The observation of 236 MeV muon neutrinos from kaon-decay-at-rest (KDAR) originating in the core ... more The observation of 236 MeV muon neutrinos from kaon-decay-at-rest (KDAR) originating in the core of the Sun would provide a unique signature of dark matter annihilation. Since excellent angle and energy reconstruction are necessary to detect this monoenergetic, directional neutrino flux, DUNE with its vast volume and reconstruction capabilities, is a promising candidate for a KDAR neutrino search. In this work, we evaluate the proposed KDAR neutrino search strategies by realistically modeling both neutrino-nucleus interactions and the response of DUNE. We find that, although reconstruction of the neutrino energy and direction is difficult with current techniques in the relevant energy range, the superb energy resolution, angular resolution, and particle identification offered by DUNE can still permit great signal/background discrimination. Moreover, there are non-standard scenarios in which searches at DUNE for KDAR in the Sun can probe dark matter interactions.
We present results from a 54.7 live-day shielded run of the DRIFT-IId detector, the world's most ... more We present results from a 54.7 live-day shielded run of the DRIFT-IId detector, the world's most sensitive, directional, dark matter detector. Several improvements were made relative to our previous work including a lower threshold for detection, a more robust analysis and a tenfold improvement in our gamma rejection factor. After analysis, no events remain in our fiducial region leading to an exclusion curve for spindependent WIMP-proton interactions which reaches 0.28 pb at 100 GeV/c 2 , a fourfold improvement on our previous work. We also present results from a 45.4 live-day unshielded run of the DRIFT-IId detector during which 14 nuclear recoil-like events were observed. We demonstrate that the observed nuclear recoil rate of 0.31±0.08 events per day is consistent with detection of ambient, fast neutrons emanating from the walls of the Boulby Underground Science Facility.
Recent computational results suggest that directional dark matter detectors have potential to pro... more 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.
... Ideally, CT fuelling would deliver a fully ionized plasmoid containing less than 1% of the to... more ... Ideally, CT fuelling would deliver a fully ionized plasmoid containing less than 1% of the tokamak plasma inventory (per shot) to a desired radial location within the tokamak. ... The central electron temperature signal was 750 i 200 eV for this shot. ...
The magnetic properties of the spheromak configuration produced by a combination of slow theta an... more The magnetic properties of the spheromak configuration produced by a combination of slow theta and Z discharges in the University of Maryland Spheromak experiment (MS) are reported. The magnetic structure of the plasma in MS has been mapped out by arrays of passive magnetic pickup coils. The Taylor relaxation process is observed during the formation phase. The magnetic profile evolves in such a way that the ratio of poloidal current Ip to poloidal flux &psgr; in the plasma approaches a constant value, where μ0Ip=kel&psgr;. When the spheromak is formed, the magnetic field configuration is close to Taylor’s minimum energy state, μ0j=kB. This constant k is related to the size of the spheromak produced. A spheromak with 1.0 T maximum field, corresponding to 650 kA poloidal current, has been produced in MS. However, due to the high plasma density (6–8×1020 m−3) and the presence of low-Z impurities (mainly carbon and oxygen), the plasma is radiation dominated with electron temperature ≤15 eV. The magnetic field decays exponentially during the decay phase. Axisymmetric equilibrium states that could exist in the configuration are calculated with a Grad–Shafranov equilibrium code. Comparison of the numerical calculation with the experimental measurements indicates that the magnetic-field structure stays close to the equilibrium state as the plasma decays.
The current status of the DRIFT (Directional Recoil Identification From Tracks) experiment at Bou... more The current status of the DRIFT (Directional Recoil Identification From Tracks) experiment at Boulby Mine is presented, including the latest limits on the WIMP spin-dependent cross-section from 1.5 kg days of running with a mixture of CS2 and CF4. Planned upgrades to DRIFT IId are detailed, along with ongoing work towards DRIFT III, which aims to be the world's first 10 m 3-scale directional Dark Matter detector.
We report the first results of nondisruptive, central fueling of a tokamak by the injection of an... more We report the first results of nondisruptive, central fueling of a tokamak by the injection of an accelerated spheromak compact toroid (CT). Interferometry measurements indicate central fueling of the tokamak plasma on a fast time scale (<0.5 ms), with more than 50% of the CT mass used ...
The current status of the DRIFT (Directional Recoil Identification From Tracks) experiment at Bou... more The current status of the DRIFT (Directional Recoil Identification From Tracks) experiment at Boulby Mine is presented, including the latest limits on the WIMP spin-dependent cross-section from 1.5 kg days of running with a mixture of CS2 and CF4. Planned upgrades to DRIFT IId are detailed, along with ongoing work towards DRIFT III, which aims to be the world's first 10 m 3-scale directional Dark Matter detector.
The addition of O 2 to gas mixtures in time projection chambers containing CS 2 has recently been... more 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.
This document presents the concept and physics case for a magnetized gaseous argon-based detector... more This document presents the concept and physics case for a magnetized gaseous argon-based detector system (ND-GAr) for the Deep Underground Neutrino Experiment (DUNE) Near Detector. This detector system is required in order for DUNE to reach its full physics potential in the measurement of CP violation and in delivering precision measurements of oscillation parameters. In addition to its critical role in the long-baseline oscillation program, ND-GAr will extend the overall physics program of DUNE. The LBNF high-intensity proton beam will provide a large flux of neutrinos that is sampled by ND-GAr, enabling DUNE to discover new particles and search for new interactions and symmetries beyond those predicted in the Standard Model.
A dominant particle pinch is observed in discharges of the Electric Tokamak (ET). As a result, th... more A dominant particle pinch is observed in discharges of the Electric Tokamak (ET). As a result, the density increases dramatically, with the profile evolving in a self-similar manner. Due to density accumulation in the absence of significant core cooling, the Troyon limit (βN = I/aB ~ 3) is reached in Ohmic plasmas in ET. The pinching rate is controlled with soft gas puffing. Hard puffing produces inverted density profiles that do not pinch due to MHD instabilities. The density threshold for pinching is n(0) ~ 1x10 m in Ohmic discharges and 3x10 m in ICRF heated discharges. The ramp-up time of the density is typically 1 second. The ramps are terminated by internal disruptions due to beta collapse without any significant radiation loss. This collapse takes place mostly above the density limit (n = 5x10 m with B = 0.25 T and R = 5 m, a = 1 m). The loop voltage remains low (0.4 V) during the ramp. In ICRF-heated discharges the ramps terminate at lower densities due to higher plasma temp...
The ProtoDUNE-SP detector is a single-phase liquid argon time projection chamber (LArTPC) that wa... more The ProtoDUNE-SP detector is a single-phase liquid argon time projection chamber (LArTPC) that was constructed and operated in the CERN North Area at the end of the H4 beamline. This detector is a prototype for the first far detector module of the Deep Underground Neutrino Experiment (DUNE), which will be constructed at the Sandford Underground Research Facility (SURF) in Lead, South Dakota, USA. The ProtoDUNE-SP detector incorporates full-size components as designed for DUNE and has an active volume of $7\times 6\times 7.2$~m$^3$. The H4 beam delivers incident particles with well-measured momenta and high-purity particle identification. ProtoDUNE-SP's successful operation between 2018 and 2020 demonstrates the effectiveness of the single-phase far detector design. This paper describes the design, construction, assembly and operation of the detector components.
The Deep Underground Neutrino Experiment (DUNE) will produce world-leading neutrino oscillation m... more The Deep Underground Neutrino Experiment (DUNE) will produce world-leading neutrino oscillation measurements over the lifetime of the experiment. In this work, we explore DUNE's sensitivity to observe charge-parity violation (CPV) in the neutrino sector, and to resolve the mass ordering, for exposures of up to 100 kiloton-megawatt-years (kt-MW-yr). The analysis includes detailed uncertainties on the flux prediction, the neutrino interaction model, and detector effects. We demonstrate that DUNE will be able to unambiguously resolve the neutrino mass ordering at a 3$\sigma$ (5$\sigma$) level, with a 66 (100) kt-MW-yr far detector exposure, and has the ability to make strong statements at significantly shorter exposures depending on the true value of other oscillation parameters. We also show that DUNE has the potential to make a robust measurement of CPV at a 3$\sigma$ level with a 100 kt-MW-yr exposure for the maximally CP-violating values $\delta_{\rm CP}} = \pm\pi/2$. Additiona...
The current status of the DRIFT (Directional Recoil Identification From Tracks) experiment at Bou... more The current status of the DRIFT (Directional Recoil Identification From Tracks) experiment at Boulby Mine is presented, including the latest limits on the WIMP spin-dependent cross-section from 1.5 kg days of running with a mixture of CS2 and CF4. Planned upgrades to DRIFT IId are detailed, along with ongoing work towards DRIFT III, which aims to be the world's first 10 m3-scale directional Dark Matter detector.
Light dark matter (LDM) in the context of dark sector theories is an attractive candidate to make... more Light dark matter (LDM) in the context of dark sector theories is an attractive candidate to make up the bulk of the mass of our Universe. This proposal presents the LDM discovery potential of a low-pressure, negative-ion, time-projection-chamber detector placed downstream of the Hall A beam-dump at Jefferson Lab receiving 10 22 electrons on target (EOT). As with the approved Beam-Dump eXperiment (BDX) the Directional Recoil Identification From Tracks Beam-Dump eXperiment (DRIFT-BDX) would run parasitically and in parallel with BDX providing additional reach, confirmation potential and different backgrounds all providing a high degree of complementarity. DRIFT-BDX is sensitive to elastic nuclear recoil events with a threshold of ~1 keV/amu recoil energy. Multiple, powerful signatures of LDM interactions are possible with BDX-DRIFT detector. Detailed calculations present cosmic ray and beam-related background estimates. The proposed experiment will be sensitive to large regions of ...
The observation of 236 MeV muon neutrinos from kaon-decay-at-rest (KDAR) originating in the core ... more The observation of 236 MeV muon neutrinos from kaon-decay-at-rest (KDAR) originating in the core of the Sun would provide a unique signature of dark matter annihilation. Since excellent angle and energy reconstruction are necessary to detect this monoenergetic, directional neutrino flux, DUNE with its vast volume and reconstruction capabilities, is a promising candidate for a KDAR neutrino search. In this work, we evaluate the proposed KDAR neutrino search strategies by realistically modeling both neutrino-nucleus interactions and the response of DUNE. We find that, although reconstruction of the neutrino energy and direction is difficult with current techniques in the relevant energy range, the superb energy resolution, angular resolution, and particle identification offered by DUNE can still permit great signal/background discrimination. Moreover, there are non-standard scenarios in which searches at DUNE for KDAR in the Sun can probe dark matter interactions.
We present results from a 54.7 live-day shielded run of the DRIFT-IId detector, the world's most ... more We present results from a 54.7 live-day shielded run of the DRIFT-IId detector, the world's most sensitive, directional, dark matter detector. Several improvements were made relative to our previous work including a lower threshold for detection, a more robust analysis and a tenfold improvement in our gamma rejection factor. After analysis, no events remain in our fiducial region leading to an exclusion curve for spindependent WIMP-proton interactions which reaches 0.28 pb at 100 GeV/c 2 , a fourfold improvement on our previous work. We also present results from a 45.4 live-day unshielded run of the DRIFT-IId detector during which 14 nuclear recoil-like events were observed. We demonstrate that the observed nuclear recoil rate of 0.31±0.08 events per day is consistent with detection of ambient, fast neutrons emanating from the walls of the Boulby Underground Science Facility.
Recent computational results suggest that directional dark matter detectors have potential to pro... more 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.
... Ideally, CT fuelling would deliver a fully ionized plasmoid containing less than 1% of the to... more ... Ideally, CT fuelling would deliver a fully ionized plasmoid containing less than 1% of the tokamak plasma inventory (per shot) to a desired radial location within the tokamak. ... The central electron temperature signal was 750 i 200 eV for this shot. ...
The magnetic properties of the spheromak configuration produced by a combination of slow theta an... more The magnetic properties of the spheromak configuration produced by a combination of slow theta and Z discharges in the University of Maryland Spheromak experiment (MS) are reported. The magnetic structure of the plasma in MS has been mapped out by arrays of passive magnetic pickup coils. The Taylor relaxation process is observed during the formation phase. The magnetic profile evolves in such a way that the ratio of poloidal current Ip to poloidal flux &psgr; in the plasma approaches a constant value, where μ0Ip=kel&psgr;. When the spheromak is formed, the magnetic field configuration is close to Taylor’s minimum energy state, μ0j=kB. This constant k is related to the size of the spheromak produced. A spheromak with 1.0 T maximum field, corresponding to 650 kA poloidal current, has been produced in MS. However, due to the high plasma density (6–8×1020 m−3) and the presence of low-Z impurities (mainly carbon and oxygen), the plasma is radiation dominated with electron temperature ≤15 eV. The magnetic field decays exponentially during the decay phase. Axisymmetric equilibrium states that could exist in the configuration are calculated with a Grad–Shafranov equilibrium code. Comparison of the numerical calculation with the experimental measurements indicates that the magnetic-field structure stays close to the equilibrium state as the plasma decays.
The current status of the DRIFT (Directional Recoil Identification From Tracks) experiment at Bou... more The current status of the DRIFT (Directional Recoil Identification From Tracks) experiment at Boulby Mine is presented, including the latest limits on the WIMP spin-dependent cross-section from 1.5 kg days of running with a mixture of CS2 and CF4. Planned upgrades to DRIFT IId are detailed, along with ongoing work towards DRIFT III, which aims to be the world's first 10 m 3-scale directional Dark Matter detector.
We report the first results of nondisruptive, central fueling of a tokamak by the injection of an... more We report the first results of nondisruptive, central fueling of a tokamak by the injection of an accelerated spheromak compact toroid (CT). Interferometry measurements indicate central fueling of the tokamak plasma on a fast time scale (<0.5 ms), with more than 50% of the CT mass used ...
The current status of the DRIFT (Directional Recoil Identification From Tracks) experiment at Bou... more The current status of the DRIFT (Directional Recoil Identification From Tracks) experiment at Boulby Mine is presented, including the latest limits on the WIMP spin-dependent cross-section from 1.5 kg days of running with a mixture of CS2 and CF4. Planned upgrades to DRIFT IId are detailed, along with ongoing work towards DRIFT III, which aims to be the world's first 10 m 3-scale directional Dark Matter detector.
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Papers by J. Gauvreau