New Experiments With Spheres-Gas (NEWS-G) is a direct dark matter detection experiment using Spherical Proportional Counters (SPCs) with light noble gases to search for low-mass Weakly Interacting ...Massive Particles (WIMPs). We report the results from the first physics run taken at the Laboratoire Souterrain de Modane (LSM) with SEDINE, a 60 cm diameter prototype SPC operated with a mixture of Ne + CH4 (0.7%) at 3.1 bars for a total exposure of 9.6 kg · days. New constraints are set on the spin-independent WIMP-nucleon scattering cross-section in the sub-GeV/c2 mass region. We exclude cross-sections above 4.4×10−37cm2 at 90% confidence level (C.L.) for a 0.5 GeV/c2 WIMP. The competitive results obtained with SEDINE are promising for the next phase of the NEWS-G experiment: a 140 cm diameter SPC to be installed at SNOLAB by summer 2018.
The NEWS-G collaboration uses spherical proportional counters (SPCs) to search for weakly interacting massive particles (WIMPs). Here, in this paper, we report the first measurements of the nuclear ...quenching factor in neon gas at 2 bar using an SPC deployed in a neutron beam at the TUNL facility. The energy-dependence of the nuclear quenching factor is modeled using a simple power law: $αE^{β}_{nr}$; we determine its parameters by simultaneously fitting the data collected with the detector over a range of energies. We measured the following parameters in Ne : CH4 at 2 bar: α= 0.2801±0.0050 (fit) ±0.0045 (sys) and β=0.0867±0.020 (fit) ±0.006 (sys). Our measurements do not agree with expected values from SRIM or Lindhard theory. We demonstrated the feasibility of performing quenching factor measurements at sub-keV energies in gases using SPCs and a neutron beam.
The CaLIPSO project is an innovative high-energy photon detector concept using trimethylbismuth as sensitive medium in a liquid ionization chamber. The detector, designed for high precision brain PET ...imaging, works as a time-projection chamber and detects Cherenkov light and charge signal. We measured the free ion yield of trimethylbismuth, which represents the number of electron-ion pairs released by the incident photon. To do so, we developed a low-noise measuring system to determine the current induced by a \Co source in the liquid with an accuracy better than 5 fA for an electric field up to 7 kV/cm. We used tetramethylsilane as benchmark liquid to validate the apparatus and we measured a zero-field free ion yield of 0.53±0.03 in agreement with measurements in literature. However, we found a zero-field free ion yield of 0.083±0.003 for trimethylbismuth, which is a factor 7 lower than the typical values for similar dielectric liquids. Quantum chemistry computations on heavy atoms tend to demonstrate a high capacity of trimethylbismuth to capture electrons which could explain the weak value. The consequences of a low free ion yield in terms of high-energy photon detection and brain PET imaging are finally discussed.
The CaLIPSO project focuses on the development of an innovative energetic-photon detector. The detector uses a "heavy" organometallic liquid: the TriMethyl Bismuth (TMBi), 82% by weight of Bismuth. ...TMBi efficiently converts through the photo-electric effect photons of energies below 1 MeV. The ionisation signal and light produced in the liquid are both detected. Beyond the measurement of gamma photon energies, this detector will allow locating photon interactions in the detector in three dimensions down to 1 mm 3 and a sub nanosecond timing accuracy. All these desirable properties can be obtained simultaneously with liquid TMBi detector.
Spherical proportional counters (SPCs) are a novel gaseous detector technology employed by the NEWS-G low-mass dark matter search experiment for their high sensitivity to single electrons from ...ionization. In this paper, we report on the first characterization of the single electron response of SPCs with unprecedented precision, using a UV-laser calibration system. The experimental approach and analysis methodology are presented along with various direct applications for the upcoming next phase of the experiment at SNOLAB. These include the continuous monitoring of the detector response and electron drift properties during dark matter search runs, as well as the experimental measurement of the trigger threshold efficiency. We measure a mean ionization energy of W=27.6±0.2 eV in Ne+CH4 (2%) for 2.8 keV x-rays, and demonstrate the feasibility of performing similar precision measurements at sub-keV energies for future gas mixtures to be used for dark matter searches at SNOLAB.
Trimethyl bismuth (TMBi) is a "heavy" transparent and dielectric organometallic liquid. This paper focuses on the measurement of TMBi's optical properties relevant for particle detection. We measured ...the TMBi transmission curve and refraction index versus wavelength, as well as the light production yield and the timing performance on a small size cell.
The NEWS-G detector at SNOLAB Balogh, L.; Beaufort, C.; Brossard, A. ...
Journal of instrumentation,
02/2023, Letnik:
18, Številka:
2
Journal Article
Recenzirano
Odprti dostop
Abstract
The New Experiments With Spheres-Gas (NEWS-G) collaboration
intends to achieve sub-GeV/c
2
Weakly Interacting
Massive Particles (WIMPs) detection using Spherical Proportional
Counters ...(SPCs). SPCs are gaseous detectors relying on ionisation
with a single ionization electron energy threshold. The latest
generation of SPC for direct dark matter searches has been installed
at SNOLAB in Canada in 2021. This article details the different
processes involved in the fabrication of the NEWS-G experiment. Also
outlined in this paper are the mitigation strategies, measurements
of radioactivity of the different components, and estimations of
induced background event rates that were used to quantify and
address detector backgrounds.
The spherical proportional counter is a gaseous detector used in a variety of applications, including direct dark matter and neutrino-less double beta decay searches. The ACHINOS multi-anode ...structure is a read-out technology that overcomes the limitations of single-anode read-out structures for large-size detectors and operation under high pressure. A resistive ACHINOS is presented, where the 3D printed central component is coated in a Diamond-Like Carbon (DLC) layer. The production and testing of the structure, in terms of stability and resolution, is described.
Background
As part of a randomized phase II trial in patients with isolated resectable colorectal peritoneal metastases (CPMs), the present study compared patient-reported outcomes (PROs) of patients ...treated with perioperative systemic therapy versus cytoreductive surgery and hyperthermic intraperitoneal chemotherapy (CRS–HIPEC) alone. Also, PROs of patients receiving perioperative systemic therapy were explored.
Patients and Methods
Eligible patients were randomized to perioperative systemic therapy (experimental) or CRS–HIPEC alone (control). PROs were assessed using EORTC QLQ-C30, QLQ-CR29, and EQ-5D-5L questionnaires at baseline, after neoadjuvant treatment (experimental), and at 3 and 6 months postoperatively. Linear mixed modeling was used to compare five predefined PROs (visual analog scale, global health status, physical functioning, fatigue, C30 summary score) between arms and to longitudinally analyze PROs in the experimental arm.
Results
Of 79 analyzed patients, 37 (47%) received perioperative systemic therapy. All predefined PROs were comparable between arms at all timepoints and returned to baseline at 3 or 6 months postoperatively. The experimental arm had worsening of fatigue mean difference (MD) + 14,
p
= 0.001, loss of appetite (MD + 15,
p
= 0.003), hair loss (MD + 18,
p
< 0.001), and loss of taste (MD + 27,
p
< 0.001) after neoadjuvant treatment. Except for loss of appetite, these PROs returned to baseline at 3 or 6 months postoperatively.
Conclusions
In patients with resectable CPM randomized to perioperative systemic therapy or CRS–HIPEC alone, PROs were comparable between arms and returned to baseline postoperatively. Together with the trial’s previously reported feasibility and safety data, these findings show acceptable tolerability of perioperative systemic therapy in this setting.
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