A beamline for fundamental neutron physics at TRIUMF Ahmed, S.; Andalib, T.; Barnes, M.J. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
05/2019, Letnik:
927
Journal Article
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This article describes the new primary proton beamline 1U at TRIUMF. The purpose of this beamline is to produce ultracold neutrons (UCN) for fundamental-physics experiments. It delivers up to 40µA of ...480MeV protons from the TRIUMF cyclotron to a tungsten spallation target and uses a fast kicker to share the beam between the Center for Molecular and Materials Science and UCN. The beamline has been successfully commissioned and operated with a beam current up to 10µA, facilitating first large-scale UCN production in Canada.
A fast-switching, high-repetition-rate magnet and power supply have been developed for and operated at TRIUMF, to deliver a proton beam to the new ultracold neutron (UCN) facility. The facility ...possesses unique operational requirements: a time-averaged beam current of40μAwith the ability to switch the beam on or off for several minutes. These requirements are in conflict with the typical operation mode of the TRIUMF cyclotron which delivers nearly continuous beam to multiple users. To enable the creation of the UCN facility, a beam-sharing arrangement with another facility was made. The beam sharing is accomplished by the fast-switching (kicker) magnet which is ramped in50μsto a current of 193 A, held there for approximately 1 ms, then ramped down in the same short period of time. This achieves a 12 mrad deflection which is sufficient to switch the proton beam between the two facilities. The kicker magnet relies on a high-current, low-inductance coil connected to a fast-switching power supply that is based on insulated-gate bipolar transistors (IGBTs). The design and performance of the kicker magnet system and initial beam delivery results are reported.
In August 2011, one of the earliest cases of influenza A(H3N2) variant A(H3N2)v virus infection was hospitalized with severe illness. To investigate the potential for healthcare-associated ...transmission of influenza A(H3N2)v, we evaluated both healthcare providers and patient contacts of the case. We found that healthcare-associated transmission was unlikely.
DEAP-3600 is a single-phase liquid argon (LAr) direct-detection dark matter experiment, operating 2 km underground at SNOLAB (Sudbury, Canada). The detector consists of 3279 kg of LAr contained in a ...spherical acrylic vessel. This paper reports on the analysis of a 758 tonne·day exposure taken over a period of 231 live-days during the first year of operation. No candidate signal events are observed in the WIMP-search region of interest, which results in the leading limit on the WIMP-nucleon spin-independent cross section on a LAr target of 3.9×10−45 cm2 (1.5×10−44 cm2) for a 100 GeV/c2 (1 TeV/c2) WIMP mass at 90% C.L. In addition to a detailed background model, this analysis demonstrates the best pulse-shape discrimination in LAr at threshold, employs a Bayesian photoelectron-counting technique to improve the energy resolution and discrimination efficiency, and utilizes two position reconstruction algorithms based on the charge and photon detection time distributions observed in each photomultiplier tube.
.
Building on the successful experience in operating the DarkSide-50 detector, the DarkSide Collaboration is going to construct DarkSide-20k, a direct WIMP search detector using a two-phase Liquid ...Argon Time Projection Chamber (LAr TPC) with an active (fiducial) mass of 23 t (20 t). This paper describes a preliminary design for the experiment, in which the DarkSide-20k LAr TPC is deployed within a shield/veto with a spherical Liquid Scintillator Veto (LSV) inside a cylindrical Water Cherenkov Veto (WCV). This preliminary design provides a baseline for the experiment to achieve its physics goals, while further development work will lead to the final optimization of the detector parameters and an eventual technical design. Operation of DarkSide-50 demonstrated a major reduction in the dominant
39
Ar background when using argon extracted from an underground source, before applying pulse shape analysis. Data from DarkSide-50, in combination with MC simulation and analytical modeling, shows that a rejection factor for discrimination between electron and nuclear recoils of
>
3
×
10
9
is achievable. This, along with the use of the veto system and utilizing silicon photomultipliers in the LAr TPC, are the keys to unlocking the path to large LAr TPC detector masses, while maintaining an experiment in which less than
<
0
.
1
events (other than
ν
-induced nuclear recoils) is expected to occur within the WIMP search region during the planned exposure. DarkSide-20k will have ultra-low backgrounds than can be measured
in situ
, giving sensitivity to WIMP-nucleon cross sections of
1
.
2
×
10
-
47
cm
2
(
1
.
1
×
10
-
46
cm
2
) for WIMPs of 1 TeV/c
2
(10 TeV/c
2
) mass, to be achieved during a 5 yr run producing an exposure of 100 t yr free from any instrumental background.
The physics reach of a low threshold (100 eV) scintillating argon bubble chamber sensitive to coherent elastic neutrino-nucleus scattering (CE ν NS) from reactor neutrinos is studied. The sensitivity ...to the weak mixing angle, neutrino magnetic moment, and a light Z′ gauge boson mediator are analyzed. A Monte Carlo simulation of the backgrounds is performed to assess their contribution to the signal. The analysis shows that world-leading sensitivities are achieved with a one-year exposure for a 10 kg chamber at 3 m from a 1 MWth research reactor or a 100 kg chamber at 30 m from a 2000 MWthpower reactor. Such a detector has the potential to become the leading technology to study CE ν NS using nuclear reactors.
The DEAP-3600 experiment is searching for weakly interacting massive particles dark matter with a 3.3 ×103kg single phase liquid argon (LAr) target, located 2.1 km underground at SNOLAB. The ...experimental signature of dark matter interactions is kilo electron volt–scale Ar40 nuclear recoils producing 128 nm LAr scintillation photons observed by photomultiplier tubes. The largest backgrounds in DEAP-3600 are electronic recoils (ERs) induced by β and γ rays originating from internal and external radioactivity in the detector material. A background model of the ER interactions in DEAP-3600 was developed and is described in this work. The model is based on several components which are expected from radioisotopes in the LAr, from ex situ material assay measurements, and from dedicated independent in situ analyses. This prior information is used in a Bayesian fit of the ER components to a 247.2 d dataset to model the radioactivity in the surrounding detector materials. Pulse-shape discrimination separates ER and NR events. However, detailed knowledge of the ER background and activity of detector components sets valuable constraints on NR backgrounds including neutrons and alphas. In addition, the activity of Ar42 in LAr in DEAP-3600 is determined by measuring the daughter decay of K42. This cosmogenically activated trace isotope is a relevant background at higher energies for other rare event searches using atmospheric argon, e.g., DarkSide-20k, GERDA, or LEGEND. The specific activity of Ar42 in the atmosphere is found to be 40.4±5.9 μBq/kg of argon.
Characterization of the Hamamatsu VUV4 MPPCs for nEXO Gallina, G.; Giampa, P.; Retière, F. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
10/2019, Letnik:
940, Številka:
C
Journal Article
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In this paper we report on the characterization of the Hamamatsu VUV4 (S/N: S13370-6152) Vacuum Ultra-Violet (VUV) sensitive Multi-Pixel Photon Counters (MPPC)s as part of the development of a ...solution for the detection of liquid xenon scintillation light for the nEXO experiment. Various MPPC features, such as: dark noise, gain, correlated avalanches, direct crosstalk and Photon Detection Efficiency (PDE) were measured in a dedicated setup at TRIUMF. MPPCs were characterized in the range 163K≤T≤233K. At an over voltage of 3.1±0.2 V and at T=163K we report a number of Correlated Avalanches (CAs) per pulse in the 1μs interval following the trigger pulse of 0.161±0.005. At the same settings the Dark-Noise (DN) rate is 0.137±0.002Hz/mm2. Both the number of CAs and the DN rate are within nEXO specifications. The PDE of the Hamamatsu VUV4 was measured for two different devices at T=233K for a mean wavelength of 189±7nm. At 3.6±0.2 V and 3.5±0.2 V of over voltage we report a PDE of 13.4±2.6% and 11±2%, corresponding to a saturation PDE of 14.8±2.8% and 12.2±2.3%, respectively. Both values are well below the 24% saturation PDE advertised by Hamamatsu. More generally, the second device tested at 3.5±0.2 V of over voltage is below the nEXO PDE requirement. The first one instead yields a PDE that is marginally close to meeting the nEXO specifications. This suggests that with modest improvements the Hamamatsu VUV4 MPPCs could be considered as an alternative to the FBK-LF Silicon Photo-Multipliers for the final design of the nEXO detector.
Looking for Cherenkov light in liquid xenon with LoLX Galli, L.; Kharusi, S. Al; Brunner, T. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
February 2023, 2023-02-00, Letnik:
1047
Journal Article
Recenzirano
The Light-only Liquid Xenon (LoLX) experiment is designed to study the properties of light emission and transport in liquid xenon (LXe) using silicon photomultipliers (SiPMs). In addition, we also ...plan to perform long-term stability studies of the SiPMs in LXe. Another important goal of the LoLX experiment is to characterize and utilize the differences in spectrum and timing of Cherenkov and scintillation light production to develop a background discriminator for low-background LXe experiments such as, neutrino-less double beta decay searches.
In this paper we present the project status and perspectives.
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.
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