| 1. |
- Piscitelli, Francesco, et al.
(författare)
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Neutron reflectometry on highly absorbing films and its application to (B4C)-B-10-based neutron detectors
- 2016
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Ingår i: Royal Society of London. Proceedings A. Mathematical, Physical and Engineering Sciences. - : The Royal Society. - 1364-5021 .- 1471-2946. ; 472:2185
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Tidskriftsartikel (refereegranskat)abstract
- Neutron reflectometry is a powerful tool used for studies of surfaces and interfaces. The absorption in the typical studied materials is neglected and this technique is limited only to the reflectivity measurement. For strongly absorbing nuclei, the absorption can be directly measured by using the neutron-induced fluorescence technique which exploits the prompt particle emission of absorbing isotopes. This technique is emerging from soft matter and biology where highly absorbing nuclei, in very small quantities, are used as a label for buried layers. Nowadays, the importance of absorbing layers is rapidly increasing, partially because of their application in neutron detection; a field that has become more active also due to the He-3-shortage. We extend the neutron-induced fluorescence technique to the study of layers of highly absorbing materials, in particular (B4C)-B-10. The theory of neutron reflectometry is a commonly studied topic; however, when a strong absorption is present the subtle relationship between the reflection and the absorption of neutrons is not widely known. The theory for a general stack of absorbing layers has been developed and compared to measurements. We also report on the requirements that a (B4C)-B-10 layer must fulfil in order to be employed as a converter in neutron detection.
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| 2. |
- Wiedorn, Max O., et al.
(författare)
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Megahertz serial crystallography
- 2018
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Ingår i: Nature Communications. - : Nature Publishing Group. - 2041-1723. ; 9
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Tidskriftsartikel (refereegranskat)abstract
- The new European X-ray Free-Electron Laser is the first X-ray free-electron laser capable of delivering X-ray pulses with a megahertz inter-pulse spacing, more than four orders of magnitude higher than previously possible. However, to date, it has been unclear whether it would indeed be possible to measure high-quality diffraction data at megahertz pulse repetition rates. Here, we show that high-quality structures can indeed be obtained using currently available operating conditions at the European XFEL. We present two complete data sets, one from the well-known model system lysozyme and the other from a so far unknown complex of a beta-lactamase from K. pneumoniae involved in antibiotic resistance. This result opens up megahertz serial femtosecond crystallography (SFX) as a tool for reliable structure determination, substrate screening and the efficient measurement of the evolution and dynamics of molecular structures using megahertz repetition rate pulses available at this new class of X-ray laser source.
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| 3. |
- 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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| 4. |
- Mauri, G., et al.
(författare)
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Fast neutron sensitivity of neutron detectors based on Boron-10 converter layers
- 2018
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Ingår i: Journal of Instrumentation. - 1748-0221. ; 13:3
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Tidskriftsartikel (refereegranskat)abstract
- In the last few years many detector technologies for thermal neutron detection have been developed in order to face the shortage of He-3, which is now much less available and more expensive. Moreover the He-3-based detectors can not fulfil the requirements in performance, e.g. the spatial resolution and the counting rate capability needed for the new instruments. The Boron-10-based gaseous detectors have been proposed as a suitable choice. This and other alternative technologies are being developed at ESS. Higher intensities mean higher signals but higher background as well. The signal-to-background ratio is an important feature to study, in particular the gamma-ray and the fast neutron contributions. This paper investigates, for the first time, the fast neutrons sensitivity of B-10-based thermal neutron detector. It presents the study of the detector response as a function of energy threshold and the underlying physical mechanisms. The latter are explained with the help of theoretical considerations and simulations.
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| 5. |
- Mauri, G., et al.
(författare)
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Neutron reflectometry with the Multi-Blade B-10-based detector
- 2018
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Ingår i: Proceedings of the Royal Society. Mathematical, Physical and Engineering Sciences. - : The Royal Society. - 1364-5021 .- 1471-2946. ; 474:2216
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Tidskriftsartikel (refereegranskat)abstract
- The Multi-Blade is a boron-10-based gaseous detector developed for neutron reflectometry instruments at the European Spallation Source in Sweden. The main challenges for neutron reflectometry detectors are the instantaneous counting rate and spatial resolution. The Multi-Blade has been tested on the CRISP reflectometer at the ISIS Neutron and Muon Source in the UK. A campaign of scientific measurements has been performed to study the Multi-Blade response in real instrumental conditions. The results of these tests are discussed in this paper.
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| 6. |
- Messi, F., et al.
(författare)
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Gamma- and Fast Neutron- Sensitivity of 10B- Based Neutron Detectors at ESS
- 2017
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Ingår i: 2017 IEEE Nuclear Science Symposium and Medical Imaging Conference, NSS/MIC 2017 - Conference Proceedings. - 9781538622827
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Konferensbidrag (refereegranskat)abstract
- The European Spallation Source (ESS), presently under construction in Lund, Sweden, is designed to be the world's brightest neutron source. When it will be in operation, ESS will deliver an instantaneous neutron flux on detectors that will be without precedent. A down side of the high brightness will be the increase of background, especially from gamma-rays and fast-neutrons.Considering that scattering cross-sections of many samples tend to be relatively low and that the gamma- and fast-neutronbackgrounds tend to be considerable high at spallation facilities [Che +14], the signal-to-noise ratio of a measurement needs to be maximised. The sensitivity of a thermal-neutron detector to gamma-rays and to fast-neutrons is a very important characteristic, as it defines the best achievable signal-to-noise ratio for the measurement. It is therefore crucial to measure the gamma- and fast-neutron- sensitivities of all detectors that will be installed on the instruments at ESS.
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| 7. |
- Scherzinger, Julius, et al.
(författare)
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A comparison of untagged gamma-ray and tagged-neutron yields from 241AmBe and 238PuBe sources
- 2017
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Ingår i: Applied Radiation and Isotopes. - : Elsevier BV. - 0969-8043 .- 1872-9800. ; 127, s. 98-102
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Tidskriftsartikel (refereegranskat)abstract
- Untagged gamma-ray and tagged-neutron yields from 241AmBe and 238PuBe mixed-field sources have been measured. Gamma-ray spectroscopy measurements from 1 to 5 MeV were performed in an open environment using a CeBr3 detector and the same experimental conditions for both sources. The shapes of the distributions are very similar and agree well with previous data. Tagged-neutron measurements from 2 to 6 MeV were performed in a shielded environment using a NE-213 liquid-scintillator detector for the neutrons and a YAP(Ce) detector to tag the 4.44 MeV gamma-rays associated with the de-excitation of the first-excited state of 12C. Again, the same experimental conditions were used for both sources. The shapes of these distributions are also very similar and agree well with previous data, each other, and the ISO recommendation. Our 238PuBe source provides approximately 2.6 times more 4.44 MeV gamma-rays and 2.4 times more neutrons over the tagged-neutron energy range, the latter in reasonable agreement with the original full-spectrum source-calibration measurements performed at the time of their acquisition.
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| 8. |
- Scherzinger, Julius, et al.
(författare)
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Tagging fast neutrons from a Cf-252 fission-fragment source
- 2017
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Ingår i: Applied Radiation and Isotopes. - : Elsevier BV. - 0969-8043 .- 1872-9800. ; 128, s. 270-274
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Tidskriftsartikel (refereegranskat)abstract
- Coincidence and time-of-flight measurement techniques are employed to tag fission neutrons emitted from a Cf-252 source sealed on one side with a very thin layer of Au. The source is positioned within a gaseous He-4 scintillator detector. Together with a particles, both light and heavy fission fragments pass through the thin layer of Au and are detected. The fragments enable the corresponding fission neutrons, which are detected in a NE-213 liquid-scintillator detector, to be tagged. The resulting continuous polychromatic beam of tagged neutrons has an energy dependence that agrees qualitatively with expectations. We anticipate that this technique will provide a cost-effective means for the characterization of neutron-detector efficiency in the energy range 1-6 MeV.
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| 9. |
- Jebali, R., et al.
(författare)
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A first comparison of the responses of a He-4-based fast-neutron detector and a NE-213 liquid-scintillator reference detector
- 2015
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Ingår i: Nuclear Instruments and Methods in Physics Research Section A. - : Elsevier BV. - 0168-9002 .- 1872-9576 .- 0167-5087. ; 794, s. 102-108
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Tidskriftsartikel (refereegranskat)abstract
- A first comparison has been made between the pulse-shape discrimination characteristics of a novel He-4-based pressurized scintillation detector and a NE-213 liquicl-scintillator reference detector using an Am/Be mixed-field neutron and gamma-ray source and a high-resolution scintillation-pulse digitizer. In particular, the capabilities of the two fast neutron detectors to discriminate between neutrons and gamma-rays were investigated. The NE-213 liquicl-scintillator reference cell produced a wide range of scintillation-light yields in response to he gamma-ray field of the source. In stark contrast, clue to the size and pressure of the He-4 gas volume, the He-4-based detector registered a maximum scintillation-light yield of 750 keV(ee) to the same gamma-ray field. Pulse-shape discrimination for particles with scintillation-light yields of more than 750 keV(ee) was excellent in the case of the He-4-based detector. Above 750 keV(ee) its signal was unambiguously neutron, enabling particle identification based entirely upon the amount of scintillation light produced. (C) 2015 The Authors. Published by Elsevier B.V.
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| 10. |
- Kittelmann, T., et al.
(författare)
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Using Backscattering to Enhance Efficiency in Neutron Detectors
- 2017
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Ingår i: IEEE Transactions on Nuclear Science. - : IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC. - 0018-9499 .- 1558-1578. ; 64:6, s. 1562-1573
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Tidskriftsartikel (refereegranskat)abstract
- The principle of using strongly scattering materials to recover efficiency in detectors for neutron instruments, via backscattering of unconverted thermal neutrons, is discussed in general. The feasibility of the method is illustrated through Geant4-based simulations involving thermal neutrons impinging on a specific setup with a layer of polyethylene placed behind a single-layered boron-10 thin-film gaseous detector. The results show that detection efficiencies can be as much as doubled in the most ideal scenario, but with associated adverse contributions to spatial and timing resolutions of, respectively, centimeters and tens of microseconds. Potential mitigation techniques to contain the impact on resolution are investigated and are found to alleviate the issues to some degree, at a cost of reduced gain in efficiency.
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