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Abstract The Hamamatsu R5912-HQE photomultiplier-tube (PMT) is a novel high-quantum efficiency PMT. It is currently used in the DEAP-3600 dark matter detector and is of significant interest for future dark matter and neutrino experiments where high signal yields are needed. We report on the methods developed for in-situ characterization and monitoring of DEAP's 255 R5912-HQE PMTs. This includes a detailed discussion of typical measured single-photoelectron charge distributions, correlated noise (afterpulsing), dark noise, double, and late pulsing characteristics. The characterization is performed during the detector commissioning phase using laser light injected through a light diffusing sphere and during normal detector operation using LED light injected through optical fibres. [ABSTRACT FROM AUTHOR]

Abstract The Dark matter Experiment using Argon Pulse-shape discrimination (DEAP) has been designed for a direct detection search for particle dark matter using a single-phase liquid argon target. The projected cross section sensitivity for DEAP-3600 to the spin-independent scattering of Weakly Interacting Massive Particles (WIMPs) on nucleons is 10 − 46 cm 2 for a 100 GeV/ c 2 WIMP mass with a fiducial exposure of 3 tonne-years. This paper describes the physical properties and construction of the DEAP-3600 detector. [ABSTRACT FROM AUTHOR]

The DEAP-1 low-background liquid argon detector was used to measure scintillation pulse shapes of electron and nuclear recoil events and to demonstrate the feasibility of pulse-shape discrimination down to an electron-equivalent energy of 20 keV ee . In the surface dataset using a triple-coincidence tag we found the fraction of β events that are misidentified as nuclear recoils to be < 1.4 × 10 − 7 (90% C.L.) for energies between 43–86 keV ee and for a nuclear recoil acceptance of at least 90%, with 4% systematic uncertainty on the absolute energy scale. The discrimination measurement on surface was limited by nuclear recoils induced by cosmic-ray generated neutrons. This was improved by moving the detector to the SNOLAB underground laboratory, where the reduced background rate allowed the same measurement to be done with only a double-coincidence tag. The combined data set contains 1.23 × 10 8 events. One of those, in the underground data set, is in the nuclear-recoil region of interest. Taking into account the expected background of 0.48 events coming from random pileup, the resulting upper limit on the level of electronic recoil contamination is < 2.7 × 10 − 8 (90% C.L.) between 44–89 keV ee and for a nuclear recoil acceptance of at least 90%, with 6% systematic uncertainty on the absolute energy scale. We developed a general mathematical framework to describe pulse-shape-discrimination parameter distributions and used it to build an analytical model of the distributions observed in DEAP-1. Using this model, we project a misidentification fraction of approximately 10 − 10 for an electron-equivalent energy threshold of 15 keV ee for a detector with 8 PE/keV ee light yield. This reduction enables a search for spin-independent scattering of WIMPs from 1000 kg of liquid argon with a WIMP-nucleon cross-section sensitivity of 10 − 46 cm 2 , assuming negligible contribution from nuclear recoil backgrounds. [ABSTRACT FROM AUTHOR]

Many current and future dark matter and neutrino detectors are designed to measure scintillation light with a large array of photomultiplier tubes (PMTs). The energy resolution and particle identification capabilities of these detectors depend in part on the ability to accurately identify individual photoelectrons in PMT waveforms despite large variability in pulse amplitudes and pulse pileup. We describe a Bayesian technique that can identify the times of individual photoelectrons in a sampled PMT waveform without deconvolution, even when pileup is present. To demonstrate the technique, we apply it to the general problem of particle identification in single-phase liquid argon dark matter detectors. Using the output of the Bayesian photoelectron counting algorithm described in this paper, we construct several test statistics for rejection of backgrounds for dark matter searches in argon. Compared to simpler methods based on either observed charge or peak finding, the photoelectron counting technique improves both energy resolution and particle identification of low energy events in calibration data from the DEAP-1 detector and simulation of the larger MiniCLEAN dark matter detector. [ABSTRACT FROM AUTHOR]

The DEAP-1 7 kg single phase liquid argon scintillation detector was operated underground at SNOLAB in order to test the techniques and measure the backgrounds inherent to single phase detection, in support of the DEAP-3600 Dark Matter detector. Backgrounds in DEAP are controlled through material selection, construction techniques, pulse shape discrimination, and event reconstruction. This report details the analysis of background events observed in three iterations of the DEAP-1 detector, and the measures taken to reduce them. The 222 Rn decay rate in the liquid argon was measured to be between 16 and 26 μBq kg −1 . We found that the background spectrum near the region of interest for Dark Matter detection in the DEAP-1 detector can be described considering events from three sources: radon daughters decaying on the surface of the active volume, the expected rate of electromagnetic events misidentified as nuclear recoils due to inefficiencies in the pulse shape discrimination, and leakage of events from outside the fiducial volume due to imperfect position reconstruction. These backgrounds statistically account for all observed events, and they will be strongly reduced in the DEAP-3600 detector due to its higher light yield and simpler geometry. [ABSTRACT FROM AUTHOR]

Abstract: T2K is a long-baseline neutrino oscillation experiment searching for appearance in a beam. The beam is produced at the J-PARC accelerator complex in Tokai, Japan, and the neutrinos are detected by the Super-Kamiokande detector located 295km away in Kamioka. A suite of near detectors (ND280) located 280 m downstream of the production target is used to characterize the components of the beam before they have had a chance to oscillate and to better understand various neutrino interactions on several nuclei. This paper describes the design and construction of two massive fine-grained detectors (FGDs) that serve as active targets in the ND280 tracker. One FGD is composed solely of scintillator bars while the other is partly scintillator and partly water. Each element of the FGDs is described, including the wavelength shifting fiber and Multi-Pixel Photon Counter used to collect the light signals, the readout electronics, and the calibration system. Initial tests and in situ results of the FGDs'' performance are also presented. [Copyright &y& Elsevier]

Abstract: New technologies, especially photo-sensors, are enabling detectors for positron emission tomography to operate in large magnetic field, to be compact and to achieve excellent timing, energy and position resolutions including depth of interaction. However, the complexity and cost of such detectors are constantly increasing. Using wavelength shifting bars in a planar geometry promises to provide excellent three-dimensional position resolution with good energy and timing resolutions at a small fraction of the cost of comparable detector. Two detector configurations are being investigated using 3×3mm2 wavelength shifting bars to collect the light from either monolithic or pixelated LYSO crystals. Promising performances have been achieved. [Copyright &y& Elsevier]

The T2K Fine Grained Detector (FGD) is an active neutrino target that uses segmented scintillator bars to observe short-range particle tracks. 8448 multipixel photon counters (MPPCs) coupled to wavelength shifting fibres detect scintillator light. An application specific integrated circuit (ASIC) shapes the MPPC waveform and uses a switched capacitor array (SCA) to store up to 511 analog samples over 10.22 \mus. High and low attenuation channels for each MPPC improve dynamic range. 12-bit serial quad-ADCs digitize ASIC analog output and interface with a field programmable gate array (FPGA). Each FPGA simultaneously reads out four ADCs and saves the synchronized samples in an external digital memory. The system produces 13.5 MB of uncompressed data with a target trigger rate of 20 Hz, and requires zero suppression to reduce data size and readout time. Firmware based data compression uses an online pulse-finder that decides whether to output pulse height information, a section of waveform, or to suppress all data. The front end FPGA transfers formatted data to data concentrator cards (DCCs) through a 2 Gb/s optical fiber interface using an efficient custom protocol. We have evaluated the performance of the FGD electronics system and the quality of its online data compression through the course of a physics data run. The average size of a compressed data acquisition is measured as 44 ~ kB. [ABSTRACT FROM PUBLISHER]

Abstract: In order to assess the performance of liquid xenon detectors for use in positron emission tomography we studied the scintillation light and ionization charge produced by 511keV photons in a small prototype detector. Scintillation light was detected with large area avalanche photodiodes while ionization electrons were collected on an anode instrumented with low noise electronics after drifting up to 3cm. Operational conditions were studied as a function of the electric field. Energy resolutions of (FWHM) were achieved by combining the scintillation light and ionization charge signals. The relationship between scintillation light and ionization signals was investigated. An analysis of the sources of fluctuations was performed in order to optimize future detector designs. [Copyright &y& Elsevier]

Abstract: The Nuclear Astrophysics program at TRIUMF, particular the one centered around the DRAGON and TUDA facilities, as well as some additional experiments will be discussed. In particular, measurements of the 12C(α,γ)16O, the 26Al(p,γ)27Si and the 40Ca(α,γ)44Ti reactions at DRAGON will be described. For the TUDA facility a measurement of 10B(α,p)13C as a test for the 18Ne(α,p)21Na measurement is presented. The development of the new cylindrical, large solid angle gas detector TACTIC will be described. In addition, new measurements refuting a temperature dependence of radioactive decay times in metals will be presented as well as GEANT4 simulations regarding the β-delayed α-spectrum of 16N will be given. [Copyright &y& Elsevier]

Abstract: A new detector for nuclear astrophysics studies is being designed and built by TRIUMF and the University of York. The TRIUMF Annular Chamber for Tracking and Identification of Charged particles (TACTIC) is designed to detect low-energy charged particles from inverse kinematics reaction studies performed at the relevant astrophysical energies. TACTIC is a cylindrical ionisation/time-projection chamber with segmented anode strips, which allow the dE/dx of the particle to be determined along with the total energy. Information from drift times allows the particle trajectory to be reconstructed. This in turn identifies the interaction point along the beam axis and hence the centre of mass energy of the reaction. To amplify the expected weak signals, a gas electron multiplier (GEM) will be used in place of the usual Frisch grid. Full digital readout of the charge and timing of each anode strip will be achieved with flash ADC cards allowing pulse shape analysis of the signals. [Copyright &y& Elsevier]

A 48 channel, 40-65 MS/sec., 10 bit pulse shape digitizer card has been designed in the VME-6U form factor. The design uses 6 octal Flash Analog to Digital Converter (FADC) chips (ADS5121 or ADS5122) from Texas Instruments. The FADCs are read out by 6 Altera Cyclone FPGAs. A 7th FPGA is used to collect and merge the event fragments. The present firmware includes trigger latency buffers, waveform segment buffers, real-time digital filtering, time stamp generation, amplitude evaluation, event formatting and buffering, plus a simple VME A24D32 interface. The design also includes a source synchronous bi-directional serial LVDS link for the interconnection of the modules to a large system. The first version of the module is designed for an R&D test readout system connected to a few hundred drift chamber cathode pads or TPC cathode/anode pads. The final version is intended for the readout of the KOPIO preradiator cathode drift chamber pads (∼ 75000 channels). This version will only have the LVDS interconnect. The present design using off-the- shelf commercial components is an interesting alternative to an ASIC approach for intermediate size readout system. It occupies about 3 times the area of an equivalent ASIC system, and has comparable power dissipation. In its present form, the development version of the module can be useful as a general purpose waveform digitizer and DSP with its high density (48 channels per single width VME module) at a relatively low cost per channel. [ABSTRACT FROM AUTHOR]

Abstract: Differential cross sections for and elastic scattering were measured at five energies between 19.9 and 43.3 MeV. The use of the CHAOS magnetic spectrometer at TRIUMF, supplemented by a range telescope for muon background suppression, provided simultaneous coverage of a large part of the full angular range, thus allowing very precise relative cross section measurements. The absolute normalisation was determined with a typical accuracy of 5%. This was verified in a simultaneous measurement of muon proton elastic scattering. The measured cross sections show some deviations from phase shift analysis predictions, in particular at large angles and low energies. From the new data we determine the real part of the isospin forward scattering amplitude. [Copyright &y& Elsevier]

The direct search for dark matter in the form of weakly interacting massive particles (WIMP) is performed by detecting nuclear recoils produced in a target material from the WIMP elastic scattering. The experimental identification of the direction of the WIMP-induced nuclear recoils is a crucial asset in this field, as it enables unmistakable modulation signatures for dark matter. The Recoil Directionality (ReD) experiment was designed to probe for such directional sensitivity in argon dual-phase time projection chambers (TPC), that are widely considered for current and future direct dark matter searches. The TPC of ReD was irradiated with neutrons at the INFN Laboratori Nazionali del Sud. Data were taken with nuclear recoils of known directions and kinetic energy of 72 keV, which is within the range of interest for WIMP-induced signals in argon. The direction-dependent liquid argon charge recombination model by Cataudella et al. was adopted and a likelihood statistical analysis was performed, which gave no indications of significant dependence of the detector response to the recoil direction. The aspect ratio R of the initial ionization cloud is R < 1.072 with 90 % confidence level. [ABSTRACT FROM AUTHOR]

This Letter reports the first results of a direct dark matter search with the DEAP-3600 single-phase liquid argon (LAr) detector. The experiment was performed 2 km underground at SNOLAB (Sudbury, Canada) utilizing a large target mass, with the LAr target contained in a spherical acrylic vessel of 3600 kg capacity. The LAr is viewed by an array of PMTs, which would register scintillation light produced by rare nuclear recoil signals induced by dark matter particle scattering. An analysis of 4.44 live days (fiducial exposure of 9.87 tonday) of data taken during the initial filling phase demonstrates the best electronic recoil rejection using pulse-shape discrimination in argon, with leakage <1.2×10-7 90% C.L.) between 15 and 31 keVee. No candidate signal events are observed, which results in the leading limit on weakly interacting massive particle (WIMP)-nucleon spin-independent cross section on argon, <1.2×10-44 cm² for a 100 GeV/c² WIMP mass (90% C.L.). [ABSTRACT FROM AUTHOR]

The specific activity of the β decay of 39 Ar in atmospheric argon is measured using the DEAP-3600 detector. DEAP-3600, located 2 km underground at SNOLAB, uses a total of (3269 ± 24) kg of liquid argon distilled from the atmosphere to search for dark matter. This detector is well-suited to measure the decay of 39 Ar owing to its very low background levels. This is achieved in two ways: it uses low background construction materials; and it uses pulse-shape discrimination to differentiate between nuclear recoils and electron recoils. With 167 live-days of data, the measured specific activity at the time of atmospheric extraction is (0.964 ± 0.001 stat ± 0.024 sys ) Bq/kg atmAr , which is consistent with results from other experiments. A cross-check analysis using different event selection criteria and a different statistical method confirms the result. [ABSTRACT FROM AUTHOR]

The Aria cryogenic distillation plant, located in Sardinia, Italy, is a key component of the DarkSide-20k experimental program for WIMP dark matter searches at the INFN Laboratori Nazionali del Gran Sasso, Italy. Aria is designed to purify the argon, extracted from underground wells in Colorado, USA, and used as the DarkSide-20k target material, to detector-grade quality. In this paper, we report the first measurement of argon isotopic separation by distillation with the 26 m tall Aria prototype. We discuss the measurement of the operating parameters of the column and the observation of the simultaneous separation of the three stable argon isotopes: 36 Ar , 38 Ar , and 40 Ar . We also provide a detailed comparison of the experimental results with commercial process simulation software. This measurement of isotopic separation of argon is a significant achievement for the project, building on the success of the initial demonstration of isotopic separation of nitrogen using the same equipment in 2019. [ABSTRACT FROM AUTHOR]

TACTIC (TACTIC web site: http://tactic.triumf.ca) is a new detector for low-energy nuclear reactions currently under development at TRIUMF. The cylindrical ionization chamber allows three-dimensional reconstruction of particle tracks by means of a two-dimensional anode array combined with a TOF measurement of the drift electrons. In addition, the integrated charge for each pulse provides information about the energy loss of the particle and therefore allows a better identification of the nuclear species producing the track. The geometry of TACTIC covers a large angular range permitting the measurement of differential cross-sections over a large solid angle. It will be ideal for investigations of nuclear processes pertinent to the field of nuclear astrophysics. [ABSTRACT FROM AUTHOR]

A spectrometer for β-detected nuclear magnetic resonance (β-NMR) has been commissioned at the ISAC facility at TRIUMF. A beam of low energy highly spin polarized 8Li+ can be decelerated and implanted into ultra-thin structures 6–400 nm thick. β-NMR provides local information on the electronic and magnetic properties of materials which is similar to conventional NMR but can be used as a sensitive probe of ultra-thin films, interfaces and other nanostructures. We report here on the status of the spectrometer and preliminary results on a simple metal film. [Copyright &y& Elsevier]

Aria is a plant hosting a 350 m cryogenic isotopic distillation column, the tallest ever built, which is being installed in a mine shaft at Carbosulcis S.p.A., Nuraxi-Figus (SU), Italy. Aria is one of the pillars of the argon dark-matter search experimental program, lead by the Global Argon Dark Matter Collaboration. It was designed to reduce the isotopic abundance of 39 Ar in argon extracted from underground sources, called Underground Argon (UAr), which is used for dark-matter searches. Indeed, 39 Ar is a β -emitter of cosmogenic origin, whose activity poses background and pile-up concerns in the detectors. In this paper, we discuss the requirements, design, construction, tests, and projected performance of the plant for the isotopic cryogenic distillation of argon. We also present the successful results of the isotopic cryogenic distillation of nitrogen with a prototype plant. [ABSTRACT FROM AUTHOR]

This paper presents the Mechanical Ventilator Milano (MVM), a novel intensive therapy mechanical ventilator designed for rapid, large-scale, low-cost production for the COVID-19 pandemic. Free of moving mechanical parts and requiring only a source of compressed oxygen and medical air to operate, the MVM is designed to support the long-term invasive ventilation often required for COVID-19 patients and operates in pressure-regulated ventilation modes, which minimize the risk of furthering lung trauma. The MVM was extensively tested against ISO standards in the laboratory using a breathing simulator, with good agreement between input and measured breathing parameters and performing correctly in response to fault conditions and stability tests. The MVM has obtained Emergency Use Authorization by U.S. Food and Drug Administration (FDA) for use in healthcare settings during the COVID-19 pandemic and Health Canada Medical Device Authorization for Importation or Sale, under Interim Order for Use in Relation to COVID-19. Following these certifications, mass production is ongoing and distribution is under way in several countries. The MVM was designed, tested, prepared for certification, and mass produced in the space of a few months by a unique collaboration of respiratory healthcare professionals and experimental physicists, working with industrial partners, and is an excellent ventilator candidate for this pandemic anywhere in the world. [ABSTRACT FROM AUTHOR]

The activation of materials due to exposure to cosmic rays may become an important background source for experiments investigating rare event phenomena. DarkSide-20k, currently under construction at the Laboratori Nazionali del Gran Sasso, is a direct detection experiment for galactic dark matter particles, using a two-phase liquid-argon Time Projection Chamber (TPC) filled with 49.7 tonnes (active mass) of Underground Argon (UAr) depleted in 39Ar. Despite the outstanding capability of discriminating γ / β background in argon TPCs, this background must be considered because of induced dead time or accidental coincidences mimicking dark-matter signals and it is relevant for low-threshold electron-counting measurements. Here, the cosmogenic activity of relevant long-lived radioisotopes induced in the experiment has been estimated to set requirements and procedures during preparation of the experiment and to check that it is not dominant over primordial radioactivity; particular attention has been paid to the activation of the 120 t of UAr used in DarkSide-20k. Expected exposures above ground and production rates, either measured or calculated, have been considered in detail. From the simulated counting rates in the detector due to cosmogenic isotopes, it is concluded that activation in copper and stainless steel is not problematic. The activity of 39Ar induced during extraction, purification and transport on surface is evaluated to be 2.8% of the activity measured in UAr by DarkSide-50 experiment, which used the same underground source, and thus considered acceptable. Other isotopes in the UAr such as 37Ar and 3H are shown not to be relevant due to short half-life and assumed purification methods. [ABSTRACT FROM AUTHOR]

Laser spectroscopy experiments at radioactive ion beam facilities around the world investigate properties of exotic nuclei for scientific endeavours such as, but not limited to, the investigation of nuclear structure. Advancements in experimental sensitivity and performance are continuously needed in order to extend the reach of nuclei that can be measured. The collinear fast beam laser spectroscopy ( Cfbs ) setup at Triumf , coupled to an out-of-plane radio-frequency quadrupole Paul trap, enables measurements of some of the most fundamental nuclear properties for long-lived ground and isomeric states. The first comprehensive overview of the Cfbs experiment is provided along with descriptions of key developments that extend the reach of laser spectroscopy experiments. A novel data acquisition technique structured around three-dimensional spectra is presented, where the integration of a custom multi-channel-scalar provides photon counts correlated with arrival time and acceleration voltage for post-experiment analysis. In addition, new rapid light manipulation techniques are discussed that suppress undesirable hyperfine pumping effects and regain losses in experimental efficiency. [ABSTRACT FROM AUTHOR]

Abstract: The T2K experiment is a long baseline neutrino oscillation experiment. Its main goal is to measure the last unknown lepton sector mixing angle by observing appearance in a beam. It also aims to make a precision measurement of the known oscillation parameters, and , via disappearance studies. Other goals of the experiment include various neutrino cross-section measurements and sterile neutrino searches. The experiment uses an intense proton beam generated by the J-PARC accelerator in Tokai, Japan, and is composed of a neutrino beamline, a near detector complex (ND280), and a far detector (Super-Kamiokande) located 295km away from J-PARC. This paper provides a comprehensive review of the instrumentation aspect of the T2K experiment and a summary of the vital information for each subsystem. [Copyright &y& Elsevier]

The TIGRESS spectrometer is an array of escape suppressed, highly segmented, HPGe clover detectors, consisting of 896 channels, with around 1000 auxiliary detector channels available. The acquisition system is all digital, each detector signal is digitized and any filtering and subsequent processing is performed digitally. The system has been designed to integrate data flow, clock distribution, trigger, and acquisition control through the same serial links. A hierarchical trigger system is implemented, allowing various combinations of incoming trigger requests to be decided locally, or passed to any of the higher levels for final decision. [ABSTRACT FROM AUTHOR]

A new facililty for conducting beta-detected nuclear magnetic resonance (β-NMR) investigations of condensed matter systems has recently been constucted at TriUniversity Meson Facility in Vancouver, Canada. The unique features of this new facility are described, and some preliminary results on 8Li+ in GaAs are presented. [Copyright &y& Elsevier]