Background radiation measurements at high power research reactors Ashenfelter, J.; Balantekin, B.; Baldenegro, C.X. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
01/2016, Letnik:
806
Journal Article
Recenzirano
Odprti dostop
Research reactors host a wide range of activities that make use of the intense neutron fluxes generated at these facilities. Recent interest in performing measurements with relatively low event ...rates, e.g. reactor antineutrino detection, at these facilities necessitates a detailed understanding of background radiation fields. Both reactor-correlated and naturally occurring background sources are potentially important, even at levels well below those of importance for typical activities. Here we describe a comprehensive series of background assessments at three high-power research reactors, including γ-ray, neutron, and muon measurements. For each facility we describe the characteristics and identify the sources of the background fields encountered. The general understanding gained of background production mechanisms and their relationship to facility features will prove valuable for the planning of any sensitive measurement conducted therein.
The collective structure of 106Cd is elucidated by multi-step Coulomb excitation of a 3.849 MeV/A beam of 106Cd on a 1.1 mg/cm2208Pb target using GRETINA-CHICO2 at ATLAS. Fourteen E2 matrix elements ...were obtained. The nucleus 106Cd is a prime example of emergent collectivity that possesses a simple structure: it is free of complexity caused by shape coexistence and has a small, but collectively active number of valence nucleons. This work follows in a long and currently active quest to answer the fundamental question of the origin of nuclear collectivity and deformation, notably in the cadmium isotopes. The results are discussed in terms of phenomenological models, the shell model, and Kumar-Cline sums of E2 matrix elements. The 〈02+||E2||21+〉 matrix element is determined for the first time, providing a total, converged measure of the electric quadrupole strength, 〈Q2〉, of the first-excited 21+ level relative to the 01+ ground state, which does not show an increase as expected of harmonic and anharmonic vibrations. Strong evidence for triaxial shapes in weakly collective nuclei is indicated; collective vibrations are excluded. This is contrary to the only other cadmium result of this kind in 114Cd by C. Fahlander et al. (1988) 38, which is complicated by low-lying shape coexistence near midshell.
Reactor neutrino experiments have seen major improvements in precision in recent years. With the experimental uncertainties becoming lower than those from theory, carefully considering all sources of
...is important when making theoretical predictions. One source of
that is often neglected arises from the irradiation of the nonfuel materials in reactors. The
rates and energies from these sources vary widely based on the reactor type, configuration, and sampling stage during the reactor cycle and have to be carefully considered for each experiment independently. In this article, we present a formalism for selecting the possible
sources arising from the neutron captures on reactor and target materials. We apply this formalism to the High Flux Isotope Reactor (HFIR) at Oak Ridge National Laboratory, the
source for the the Precision Reactor Oscillation and Spectrum Measurement (PROSPECT) experiment. Overall, we observe that the nonfuel
contributions from HFIR to PROSPECT amount to 1% above the inverse beta decay threshold with a maximum contribution of 9% in the 1.8-2.0 MeV range. Nonfuel contributions can be particularly high for research reactors like HFIR because of the choice of structural and reflector material in addition to the intentional irradiation of target material for isotope production. We show that typical commercial pressurized water reactors fueled with low-enriched uranium will have significantly smaller nonfuel
contribution.
Efficient ion sources are needed for detecting ultratrace U and Th impurities in a copper matrix by mass spectrometry techniques such as accelerator mass spectrometry (AMS). Two positive ion sources, ...a hot-cavity surface ionization source and a resonant ionization laser ion source, are evaluated in terms of ionization efficiencies for generating ion beams of U and Th. The performances of the ion sources are characterized using uranyl nitrate and thorium nitrate sample materials with sample sizes between 20 and 40μg of U or Th. For the surface ion source, the dominant ion beams observed are UO+ or ThO+ and ionization efficiencies of 2–4% have been obtained with W and Re cavities. With the laser ion source, three-step resonant photoionization of U atoms has been studied and only atomic U ions are observed. An ionization efficiency of about 9% has been demonstrated. The performances of both ion sources are expected to be further improved.
New search for mirror neutron regeneration Broussard, L.J.; Bailey, K.M.; Bailey, W.B. ...
EPJ Web of Conferences,
01/2019, Letnik:
219
Journal Article, Conference Proceeding
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The possibility of relatively fast neutron oscillations into a mirror neutron state is not excluded experimentally when a mirror magnetic field is considered. Direct searches for the disappearance of ...neutrons into mirror neutrons in a controlled magnetic field have previously been performed using ultracold neutrons, with some anomalous results reported. We describe a technique using cold neutrons to perform a disappearance and regeneration search, which would allow us to unambiguously identify a possible oscillation signal. An experiment using the existing General Purpose-Small Angle Neutron Scattering instrument at the High Flux Isotope Reactor at Oak Ridge National Laboratory will have the sensitivity to fully explore the parameter space of prior ultracold neutron searches and confirm or refute previous claims of observation. This instrument can also conclusively test the validity of recently suggested oscillation-based explanations for the neutron lifetime anomaly.
Oral cancer is the sixteenth most common malignant neoplasm worldwide, with a high mortality rate, greater than 50% at five years, and high morbidity. The effect of oncological treatment in the oral ...cavity is broad and has multiple levels, therefore knowing these effects and preventing them is essential for avoiding an increase in the oral pathology related with oncological therapy, maintaining the quality of life of the patient, and improving the efficacy of the treatment itself.
A group of experts belonging to the fields of Dentistry, Maxillofacial Surgery and Oncology of the University of Seville and the Virgen del Rocío University Hospital of Seville in collaboration with the University of Valencia, University of Barcelona, and University of the Basque Country, developed this Clinical Practice Guideline for the proper clinical management of patients diagnosed with oral cancer. The clinical questions were formulated in PICO format. The databases consulted were Medline/PubMed and Embase/Elsevier. The systematic reviews published on the topic were identified on Tripdatabase, Cochrane Library and CRD (Centre for Reviews and Dissemination). The recommendations were prepared based on the GRADE methodology.
Various recommendations were defined, derived from the 21 PICO questions, referring to prevention, treatment and care for alterations arising from the pathology of oral cancer itself and its treatment.
The preparation of this clinical practice guideline allows recommendations to be generated based on the scientific evidence available, on dentistry actions in patients with oral cancer and undergoing oncological treatment, which may be of use to the multidisciplinary team treating this type of patient.
Neutron-rich radioactive ion beams available from the HRIBF allow a variety of measurements around the
132Sn region, including Coulomb excitation, fusion-evaporation, and neutron transfer. The
B
(
E
...2
;
0
+
→
2
+
)
value for first 2
+ excited states of even-even neutron-rich
132–136Te and
126–134Sn have been measured by Coulomb excitation in inverse kinematics. The results are discussed in terms of the shell model and the quasiparticle random phase approximation. Neutron transfer onto a
134Te beam, from
9Be and
13C targets to populate single-particle states in
135Te, has also been studied. Gamma rays from the
13C(
134Te,
12C) reaction were used to identify the
ν
i
13
/
2
state in
135Te, at an energy of 2109 keV. These and other results, and plans for future experiments with these neutron-rich beams, are presented.
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