| 1. |
- Albani, Giorgia, et al.
(författare)
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Evolution in boron-based GEM detectors for diffraction measurements : From planar to 3D converters
- 2016
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Ingår i: Measurement science and technology. - : IOP Publishing. - 0957-0233 .- 1361-6501. ; 27:11
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Tidskriftsartikel (refereegranskat)abstract
- The so-called '3He-crisis' has motivated the neutron detector community to undertake an intense R&D programme in order to develop technologies alternative to standard 3He tubes and suitable for neutron detection systems in future spallation sources such as the European spallation source (ESS). Boron-based GEM (gas electron multiplier) detectors are a promising '3He-free' technology for thermal neutron detection in neutron scattering experiments. In this paper the evolution of boron-based GEM detectors from planar to 3D converters with an application in diffraction measurements is presented. The use of 3D converters coupled with GEMs allows for an optimization of the detector performances. Three different detectors were used for diffraction measurements on the INES instrument at the ISIS spallation source. The performances of the GEM-detectors are compared with those of conventional 3He tubes installed on the INES instrument. The conceptual detector with the 3D converter used in this paper reached a count rate per unit area of about 25% relative to the currently installed 3He tube. Its timing resolution is similar and the signal-to-background ratio (S/B) is 2 times lower.
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| 2. |
- Andersson Sundén, Erik, et al.
(författare)
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Evaluation of neutron spectrometer techniques for ITER using synthetic data
- 2013
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Ingår i: Nuclear Instruments and Methods in Physics Research Section A. - : Elsevier BV. - 0168-9002 .- 1872-9576. ; 701, s. 62-71
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Tidskriftsartikel (refereegranskat)abstract
- A neutron spectrometer at ITER is expected to provide estimates of plasma parameters such as ion temperature, Ti, fuel ion ratio, nt/nd, and Qthermal/Qtot, with 10-20% precision at a time resolution, Δt, of at least 100 ms. The present paper describes a method for evaluating different neutron spectroscopy techniques based on their instrumental response functions and synthetic measurement data. We include five different neutron spectrometric techniques with realistic response functions, based on simulations and measurements where available. The techniques are magnetic proton recoil, thin-foil proton recoil, gamma discriminating organic scintillator, diamond and time-of-flight. The reference position and line of sight of a high resolution neutron spectrometer on ITER are used in the study. ITER plasma conditions are simulated for realistic operating scenarios. The ITER conditions evaluated are beam and radio frequency heated and thermal deuterium-tritium plasmas. Results are given for each technique in terms of the estimated time resolution at which the parameter determination can be made within the required precision (here 10% for Ti and the relative intensities of NB and RF emission components). It is shown that under the assumptions made, the thin-foil techniques out-perform the other spectroscopy techniques in practically all measurement situations. For thermal conditions, the range of achieved Δt in the determination of Ti varies in time scales from ms (for the magnetic and thin-foil proton recoil) to s (for gamma discriminating organic scintillator).
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| 3. |
- Behrens, Thomas, et al.
(författare)
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Hormonal exposures and the risk of uveal melanoma
- 2010
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Ingår i: Cancer Causes and Control. - : Springer Science and Business Media LLC. - 1573-7225 .- 0957-5243. ; 21:10, s. 1625-1634
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Tidskriftsartikel (refereegranskat)abstract
- Several studies suggest that hormonal mechanisms may be associated with the development of uveal melanoma. Therefore, the association between the risk of uveal melanoma and exposure to hormonal exposures was investigated in a case-control study from nine European countries. Incident cases of uveal melanoma were frequency-matched to population and hospital controls by country, age, and sex. Female subjects were asked about their reproductive history, use of menopausal hormone replacement therapy and oral contraceptives. Among men, occupational handling of oils while working with transformers or capacitors which contain polychlorinated biphenyls (PCB) was solicited. Unconditional logistic regression analyses were calculated, adjusting for several potential confounders. Analyses were stratified by sex. Two hundred and ninety-three cases (165 men, 128 women) and 3,198 control subjects (2,121 men, 1,077 women) were interviewed. Among women, no associations were observed with hormonal status variables, intake of hormonal therapy or intake of oral contraceptives. Men showed an increased risk with occupational exposure to transformer/capacitor oils (OR = 2.74; Bonferroni-corrected 99.3% CI 1.07-7.02). However, these results were based on few exposed subjects only. The results of this study do not support the hypothesis of a hormonal influence in the carcinogenesis of uveal melanoma. Our finding of a potentially increased risk with PCB-containing oils requires further research.
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| 4. |
- Behrens, Thomas, et al.
(författare)
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Occupational exposure to electromagnetic fields and sex-differential risk of uveal melanoma
- 2010
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Ingår i: Occupational and Environmental Medicine. - : BMJ. - 1470-7926 .- 1351-0711. ; 67:11, s. 751-759
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Tidskriftsartikel (refereegranskat)abstract
- Objectives The association between occupational exposure to electromagnetic fields (EMF) and the risk of uveal melanoma was investigated in a case-control study in nine European countries. Methods Incident cases of uveal melanoma and population as well as hospital controls were included and frequency matched by country, 5-year birth cohort and sex. Subjects were asked whether they had worked close to high-voltage electrical transmission installations, computer screens and various electrical machines, or in complex electrical environments. Measurements of two Scandinavian job-exposure matrices were applied to estimate lifelong cumulative EMF exposure. Unconditional logistic regression analyses, stratified by sex and eye colour were calculated, adjusting for several potential confounders. Results 293 patients with uveal melanoma and 3198 control subjects were interviewed. Women exposed to electrical transmission installations showed elevated risks (OR 5.81, 95% CI 1.72 to 19.66). Positive associations with exposure to control rooms were seen among men and women, but most risk increases were restricted to subjects with dark iris colour. Application of published EMF measurements revealed stronger risk increases among women compared to men. Again, elevated risks were restricted to subjects with dark eye colour. Conclusion Although based on a low prevalence of exposure to potential occupational sources of EMF, our data indicate that exposed dark-eyed women may be at particular risk for uveal melanoma.
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| 5. |
- Behrens, Thomas, et al.
(författare)
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Occupational exposure to endocrine-disrupting chemicals and the risk of uveal melanoma
- 2012
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Ingår i: Scandinavian Journal of Work, Environment and Health. - : Scandinavian Journal of Work, Environment and Health. - 0355-3140 .- 1795-990X. ; 38:5, s. 476-483
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Tidskriftsartikel (refereegranskat)abstract
- Objectives We investigated the association between occupational exposure to endocrine-disrupting chemicals (EDC) and the risk of uveal melanoma using international data of a case control study from nine European countries. Methods After exclusion of proxy interviews, 280 cases and 3084 control subjects were included in the final analysis. Information on possible exposure to EDC was derived from 27 job-specific questionnaires (JSQ), which solicited detailed questions on occupational tasks. Relative risk estimates were based on the JSQ and potential exposure to a group of endocrine-disrupting agents. We constructed several exposure scores, taking into account intensity of exposure, use of personal protective equipment, and exposure duration. We calculated unconditional logistic regression analyses, adjusting for country, age, sex, eye color and a history of ocular damage due to intense ultraviolet (UV) exposure. Results The overall exposure prevalence to EDC was low reaching a maximum of 11% for heavy metals with endocrine-disrupting properties. Although working in some industries was associated with increased melanoma risk [such as dry cleaning: odds ratio (OR) 6.15, 95% confidence interval (95% CI) 2.0-18.96 and working in the glass manufacturing industry: OR 3.49, 95% CI 1.10-11.10], agent-specific risks were not elevated. The strongest possible risk increase was observed for organic solvents with endocrine-disrupting properties (OR 1.31, 95% CI 0.78-2.21). Calculation of exposure scores did not indicate consistently elevated results with higher score values. Sensitivity analyses did not alter these results. Conclusion Occupational exposure to EDC was not associated with an increased risk for uveal melanoma.
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| 6. |
- Behrens, Thomas, et al.
(författare)
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Pesticide exposure in farming and forestry and the risk of uveal melanoma
- 2012
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Ingår i: Cancer Causes and Control. - : Springer. - 0957-5243 .- 1573-7225. ; 23:1, s. 141-151
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Tidskriftsartikel (refereegranskat)abstract
- Since pesticides are disputed risk factors for uveal melanoma, we studied the association between occupational pesticide exposure and uveal melanoma risk in a case-control study from nine European countries.Incident cases of uveal melanoma and population as well as hospital controls were included and frequency-matched by country, 5-year age groups and sex. Self-reported exposure was quantified with respect to duration of exposure and pesticide application method. We calculated the exposure intensity level based on application method and use of personal protective equipment. Odds ratios (OR) and 95% confidence intervals (95% CI) were estimated by unconditional logistic regression analyses and adjusted for several potential confounders.293 case and 3,198 control subjects were interviewed. We did not identify positive associations with activities in farming or forestry, pesticide application or pesticide mixing. No consistent positive associations were seen with exposure intensity level scores either. The only statistically significantly raised association in this study was for exposure to chemical fertilizers in forestry (OR = 8.93; 95% CI 1.73-42.13), but this observation was based on only six exposed subjects. Results did not change when we restricted analyses to morphologically verified cases and excluded proxy interviews as well as cancer controls. We did not observe effect modification by sex or eye color.Risk estimates for pesticide exposures and occupational activities in agriculture and forestry were not increased and did not indicate a hormonal mechanism due to these exposures.
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| 7. |
- Croci, Gabriele, et al.
(författare)
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A high-efficiency thermal neutron detector based on thin 3D (B4C)-B-10 converters for high-rate applications
- 2018
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Ingår i: Europhysics letters. - : IOP Publishing. - 0295-5075 .- 1286-4854. ; 123:5
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Tidskriftsartikel (refereegranskat)abstract
- new position-sensitive thermal neutron detector based on boron-coated converters has been developed as an alternative to today's standard He-3-based technology for application to thermal neutron scattering. The key element of the development is a novel 3D (B4C)-B-10 converter which has been ad hoc designed and realized with the aim of combining a high neutron conversion probability via the B-10(n, alpha)(7) Li reaction together with an efficient collection of the produced charged particles. The developed 3D converter is composed of thin aluminium grids made by a micro-waterjet technique and coated on both sides with a thin layer of( 10)B(4)C. When coupled to a GEM detector this converter allows reaching neutron detection efficiencies close to 50% at neutron wavelengths equal to 4 angstrom. In addition, the new detector features a spatial resolution of about 5 min and can sustain counting rates well in excess of 1 MHz/cm(2). The newly developed neutron detector will enable time-resolved measurements of different kind of samples in neutron scattering experiments at high flux spallation sources and can find a use in applications where large areas and custom geometries of thermal neutron detectors are foreseen.
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| 8. |
- Croci, Gabriele, et al.
(författare)
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I-BAND-GEM : a new way for improving BAND-GEM efficiency to thermal and cold neutrons
- 2019
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Ingår i: The European Physical Journal Plus. - : Springer Science and Business Media LLC. - 2190-5444. ; 134:4
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Tidskriftsartikel (refereegranskat)abstract
- .The BAND-GEM detector represents one of the novel thermal neutron detection devices that have been developed in order to fulfil the needs of high intensity neutron sources that, like ESS (the European Spallation Source), will start operation in the next few years. The first version of this detector featured a detection efficiency of about 40% for neutrons with a wavelength of 4 angstrom, a spatial resolution of about 6mm and a rate capability in the order of some MHz/cm(2). The novelty of this device is represented by an improved 3D converter cathode (10 cm thick) based on (B4C)-B-10-coated aluminum grids positioned in a controlled gas mixture volume put on top of a Triple GEM amplifying stage. The position where the neutron interacts in the converter depends on their energy and it was observed that the first version of the detector would suffer from an efficiency decrease for long (>5 angstrom) neutron wavelength. This paper describes how the new 3D cathode allowed improving the detection efficiency at long neutron wavelengths while keeping all the benefits of the first BAND-GEM version.
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| 9. |
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| 10. |
- Gatu Johnson, Maria, 1978-, et al.
(författare)
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Neutron emission from beryllium reactions in JET deuterium plasmas with 3He minority
- 2010
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Ingår i: Nuclear Fusion. - : IOP Publishing. - 0029-5515 .- 1741-4326. ; 50:4, s. 045005-
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Tidskriftsartikel (refereegranskat)abstract
- Recent fast ion studies at JET involve ion cyclotron resonance frequency (ICRF) heating tuned to minority He-3 in cold deuterium plasmas, with beryllium evaporation in the vessel prior to the session. During the experiments, the high-resolution neutron spectrometer TOFOR was used to study the energy spectrum of emitted neutrons. Neutrons of energies up to 10MeV, not consistent with the neutron energy spectrum expected from d(d,n)He-3 reactions, were observed. In this paper, we interpret these neutrons as a first-time observation of a Be-9(He-3, n)C-11 neutron spectrum in a tokamak plasma, a conclusion based on a consistent analysis of experimental data and Monte Carlo simulations. Be-9(a, n)C-12 and Be-9(p, n)B-9 reactions are also simulated for p and a fusion products from d(He-3, a) p reactions; these two-step processes are seen to contribute on a level of about 10% of the single-step process in Be-9(He-3, n) C-11. Contributions to the total neutron yield from the Be-9(3He, n)C-11 reaction are found to be in the range 13 +/- 3 to 57 +/- 5%. We demonstrate how TOFOR can be used to simultaneously (i) probe the deuterium distribution, providing reliable measurements of the bulk deuterium temperature, here in the range 3.2 +/- 0.4 to 6.3 +/- 1.0 keV and (ii) provide an estimate of the beryllium concentration (in the range 0.48 +/- 0.17 to 6.4 +/- 1.7% of n(e) assuming T-3He = 300 keV). The observation of Be-9 related neutrons is relevant in view of the upcoming installation of a beryllium-coated ITER-like wall on JET and for ITER itself. An important implication is possible neutron-induced activation of the ITER vessel during the low-activation phase with ICRF heating tuned to minority He-3 in hydrogen plasmas.
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