Liquid 3He Detectors for Neutrons Villano, A. N.
Journal of low temperature physics,
2024/7, Letnik:
216, Številka:
1-2
Journal Article
Recenzirano
The
3
He(n, p) process is excellent for neutron detection between thermal and
∼
4 MeV because of the high cross section and near-complete energy transfer from the neutron to the proton. Traditional ...gaseous
3
He detectors using this process typically have high levels of radiogenic backgrounds so that they cannot measure the small neutron fluxes present in underground laboratories for dark matter experiments. I propose a cryogenic liquid
3
He detector that can be designed with tiny radiogenic backgrounds and efficiently measure neutron fluxes in low-flux environments.
Low-energy nuclear recoils (NRs) are hard to measure, because they produce few e-/h+ pairs in solids—i.e., they have low “ionization yield.” A silicon detector was exposed to thermal neutrons over ...2.5 live days, probing NRs down to 450 eV. The observation of a neutron capture-induced component of NRs at low energies is supported by the much-improved fit upon inclusion of a capture NR model. This result shows that thermal neutron calibration of very low recoil energy NRs is promising for dark matter searches, coherent neutrino experiments, and improving understanding of ionization dynamics in solids.
SuperCDMS is an experiment designed to directly detect weakly interacting massive particles (WIMPs), a favored candidate for dark matter ubiquitous in the Universe. In this Letter, we present ...WIMP-search results using a calorimetric technique we call CDMSlite, which relies on voltage-assisted Luke-Neganov amplification of the ionization energy deposited by particle interactions. The data were collected with a single 0.6 kg germanium detector running for ten live days at the Soudan Underground Laboratory. A low energy threshold of 170 eVee (electron equivalent) was obtained, which allows us to constrain new WIMP-nucleon spin-independent parameter space for WIMP masses below 6 GeV/c2.
With the aim of improving rural living standards and strengthening the security of crop production, China has adopted “family farms plus cooperatives” as the preferred mode of organization in ...agriculture. We investigate technical efficiency in crop production comparing family farms that are members of cooperatives, either as core members who have taken investment stakes or common members who have not, with their nonmember counterparts. To allow for heterogeneity in production technology among nonmembers, core members, and common members, we adopt a metafrontier estimation technique. Our data sample consists of 384 family farms in Anhui province for the year 2015. Heterogeneity among family farms, whether members of cooperatives or not, is found to be highly significant. Nonmember farms show the lowest technical efficiency and the widest gap between observed and potential production. By contrast, core members of cooperatives show the highest technical efficiency and the narrowest gap between observed and potential production. We infer that cooperative membership may allow farmers to learn more advanced technology and take advantage of productivity-enhancing practices. We further find that age and education of farm heads contribute to greater technical efficiency.
The present study examined smallholder farmer profiles based on key psychological variables associated with farm business performance in the South African context. A sample of 471 beef farmers (mean ...age = 54.15 years; SD = 14.46; men = 76%) and 426 poultry farmers (mean age = 47.28 years; SD = 13.53; women = 54.5%) provided data on a range of measures assessing attitudes, subjective norms, perceived behavioral control, personality characteristics, present and future time orientation, expected benefits of, and efficacy to perform the farm business tasks, and farm-related concerns. Latent profile analysis identified three distinct profile segments of smallholder beef and poultry farmers, respectively: Fatalists, Traditionalists, and Entrepreneurs. Our results suggested unique combinations of psychological characteristics in a sample of South African smallholder beef and poultry farmers and show a novel way of understanding enablers of, and barriers to, engaging in the farm business.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
SuperCDMS SNOLAB will be a next-generation experiment aimed at directly detecting low-mass particles (with masses ≤10 GeV/c2) that may constitute dark matter by using cryogenic detectors of two types ...(HV and iZIP) and two target materials (germanium and silicon). The experiment is being designed with an initial sensitivity to nuclear recoil cross sections ∼1×10−43 cm2 for a dark matter particle mass of 1 GeV/c2, and with capacity to continue exploration to both smaller masses and better sensitivities. The phonon sensitivity of the HV detectors will be sufficient to detect nuclear recoils from sub-GeV dark matter. A detailed calibration of the detector response to low-energy recoils will be needed to optimize running conditions of the HV detectors and to interpret their data for dark matter searches. Low-activity shielding, and the depth of SNOLAB, will reduce most backgrounds, but cosmogenically produced H3 and naturally occurring Si32 will be present in the detectors at some level. Even if these backgrounds are 10 times higher than expected, the science reach of the HV detectors would be over 3 orders of magnitude beyond current results for a dark matter mass of 1 GeV/c2. The iZIP detectors are relatively insensitive to variations in detector response and backgrounds, and will provide better sensitivity for dark matter particles with masses ≳5 GeV/c2. The mix of detector types (HV and iZIP), and targets (germanium and silicon), planned for the experiment, as well as flexibility in how the detectors are operated, will allow us to maximize the low-mass reach, and understand the backgrounds that the experiment will encounter. Upgrades to the experiment, perhaps with a variety of ultra-low-background cryogenic detectors, will extend dark matter sensitivity down to the “neutrino floor,” where coherent scatters of solar neutrinos become a limiting background.
The SuperCDMS experiment is designed to directly detect weakly interacting massive particles (WIMPs) that may constitute the dark matter in our Galaxy. During its operation at the Soudan Underground ...Laboratory, germanium detectors were run in the CDMSlite mode to gather data sets with sensitivity specifically for WIMPs with masses <10 GeV/c2. In this mode, a higher detector-bias voltage is applied to amplify the phonon signals produced by drifting charges. This paper presents studies of the experimental noise and its effect on the achievable energy threshold, which is demonstrated to be as low as 56 eVee (electron equivalent energy). The detector-biasing configuration is described in detail, with analysis corrections for voltage variations to the level of a few percent. Detailed studies of the electric-field geometry, and the resulting successful development of a fiducial parameter, eliminate poorly measured events, yielding an energy resolution ranging from ∼9 eVee at 0 keV to 101 eVee at ∼10 keVee. New results are derived for astrophysical uncertainties relevant to the WIMP-search limits, specifically examining how they are affected by variations in the most probable WIMP velocity and the Galactic escape velocity. These variations become more important for WIMP masses below 10 GeV/c2. Finally, new limits on spin-dependent low-mass WIMP-nucleon interactions are derived, with new parameter space excluded for WIMP masses ≲3 GeV/c2.
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