| 1. |
- Abelev, Betty, et al.
(författare)
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Measurement of prompt J/psi and beauty hadron production cross sections at mid-rapidity in pp collisions at root s=7 TeV
- 2012
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Ingår i: Journal of High Energy Physics. - 1029-8479. ; :11
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Tidskriftsartikel (refereegranskat)abstract
- The ALICE experiment at the LHC has studied J/psi production at mid-rapidity in pp collisions at root s = 7 TeV through its electron pair decay on a data sample corresponding to an integrated luminosity L-int = 5.6 nb(-1). The fraction of J/psi from the decay of long-lived beauty hadrons was determined for J/psi candidates with transverse momentum p(t) > 1,3 GeV/c and rapidity vertical bar y vertical bar < 0.9. The cross section for prompt J/psi mesons, i.e. directly produced J/psi and prompt decays of heavier charmonium states such as the psi(2S) and chi(c) resonances, is sigma(prompt J/psi) (p(t) > 1.3 GeV/c, vertical bar y vertical bar < 0.9) = 8.3 +/- 0.8(stat.) +/- 1.1 (syst.)(-1.4)(+1.5) (syst. pol.) mu b. The cross section for the production of b-hadrons decaying to J/psi with p(t) > 1.3 GeV/c and vertical bar y vertical bar < 0.9 is a sigma(J/psi <- hB) (p(t) > 1.3 GeV/c, vertical bar y vertical bar < 0.9) = 1.46 +/- 0.38 (stat.)(-0.32)(+0.26) (syst.) mu b. The results are compared to QCD model predictions. The shape of the p(t) and y distributions of b-quarks predicted by perturbative QCD model calculations are used to extrapolate the measured cross section to derive the b (b) over bar pair total cross section and d sigma/dy at mid-rapidity.
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| 2. |
- Abelev, Betty, et al.
(författare)
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Underlying Event measurements in pp collisions at root s=0.9 and 7 TeV with the ALICE experiment at the LHC
- 2012
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Ingår i: Journal of High Energy Physics. - 1029-8479. ; :7
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Tidskriftsartikel (refereegranskat)abstract
- We present measurements of Underlying Event observables in pp collisions at root s = 0 : 9 and 7 TeV. The analysis is performed as a function of the highest charged-particle transverse momentum p(T),L-T in the event. Different regions are defined with respect to the azimuthal direction of the leading (highest transverse momentum) track: Toward, Transverse and Away. The Toward and Away regions collect the fragmentation products of the hardest partonic interaction. The Transverse region is expected to be most sensitive to the Underlying Event activity. The study is performed with charged particles above three different p(T) thresholds: 0.15, 0.5 and 1.0 GeV/c. In the Transverse region we observe an increase in the multiplicity of a factor 2-3 between the lower and higher collision energies, depending on the track p(T) threshold considered. Data are compared to PYTHIA 6.4, PYTHIA 8.1 and PHOJET. On average, all models considered underestimate the multiplicity and summed p(T) in the Transverse region by about 10-30%.
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| 3. |
- Al Jebali, Ramsey, et al.
(författare)
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Recent Developments SoNDe High-Flux Detector Project
- 2018
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Ingår i: Recent Developments SoNDe High-Flux Detector Project.
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Konferensbidrag (refereegranskat)abstract
- New high-flux and high-brilliance neutron sources demand a higher count-rate capability in neutron detectors. In order to achieve that goal, the Solid-State Neutron Detector (SoNDe) project is developing a scintillation-based neutron detector. It will be capable of fully exploiting the available flux at small-angle neutron scattering (SANS) instruments at high brilliance sources, such as SKADI at the European Spallation Source (ESS). The read-out of the scintillator is based on a pixelized multi-anode PMT (MaPMT), where each pixel is treated separately. In addition to enabling higher achievable count-rates, one of the design goals was to develop a modular and scalable solution that can also be used in other instruments or even contexts, such as for laboratory setups. This has been achieved by combining the complete read-out electronics along with the MaPMT into modules that can be controlled and read-out individually via a network without additional any infrastructure. An overview of the present state of development and current test results is presented, highlighting the results of previously published project reports.
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| 4. |
- 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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| 5. |
- Anevski, Dragi, et al.
(författare)
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A stochastic process approach to multilayer neutron detectors
- 2019
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Ingår i: Scandinavian Journal of Statistics. - : Wiley. - 0303-6898 .- 1467-9469. ; 46:2, s. 621-635
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Tidskriftsartikel (refereegranskat)abstract
- The sparsity of the isotope Helium-3, ongoing since 2009, has initiated a new generation of neutron detectors. One particularly promising development line for detectors is the multilayer gaseous detector. In this paper, a stochastic process approach is used to determine the neutron energy from the additional data afforded by the multilayer nature of these novel detectors. The data from a multilayer detector consist of counts of the number of absorbed neutrons along the sequence of the detector's layers, in which the neutron absorption probability is unknown. We study the maximum likelihood estimator for the intensity and absorption probability and show its consistency and asymptotic normality, as the number of incoming neutrons goes to infinity. We combine these results with known results on the relation between the absorption probability and the wavelength to derive an estimator of the wavelength and to show its consistency and asymptotic normality.
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| 6. |
- Cherkashyna, Nataliia, et al.
(författare)
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High energy particle background at neutron spallation sources and possible solutions
- 2014
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Ingår i: International Workshop on Neutron Optics and Detectors (NOP&D 2013) 2–5 July 2013, Munich, Germany. - : IOP Publishing. - 1742-6596 .- 1742-6588. ; 528, s. 012013-012013
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Konferensbidrag (refereegranskat)abstract
- Modern spallation neutron sources are driven by proton beams similar to GeV energies. Whereas low energy particle background shielding is well understood for reactors sources of neutrons (similar to 20 MeV), for high energies (100s MeV to multiple GeV) there is potential to improve shielding solutions and reduce instrument backgrounds significantly. We present initial measured data on high energy particle backgrounds, which illustrate the results of particle showers caused by high energy particles from spallation neutron sources. We use detailed physics models of different materials to identify new shielding solutions for such neutron sources, including laminated layers of multiple materials. In addition to the steel and concrete, which are used traditionally, we introduce some other options that are new to the neutron scattering community, among which there are copper alloys as used in hadronic calorimeters in high energy physics laboratories. These concepts have very attractive energy absorption characteristics, and simulations predict that the background suppression could be improved by one or two orders of magnitude. These solutions are expected to be great benefit to the European Spallation Source, where the majority of instruments are potentially affected by high energy backgrounds, as well as to existing spallation sources.
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| 7. |
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| 8. |
- Dian, Eszter, et al.
(författare)
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Shielding optimization study for 10b-based large area neutron detectors with detailed geant4 model
- 2017
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Ingår i: 2016 IEEE Nuclear Science Symposium, Medical Imaging Conference and Room-Temperature Semiconductor Detector Workshop, NSS/MIC/RTSD 2016. - : Institute of Electrical and Electronics Engineers (IEEE). - 9781509016426
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Konferensbidrag (refereegranskat)abstract
- The European Spallation Source (ESS) sets the scope on replacing 3He tube detectors where it is reasonably achievable, consequently advanced neutron detectors require a signal-To-noise (S/N) ratio high enough to be competitive with 3He tubes and satisfy scientific requirements. Advanced local shielding could provide the improved S/N. The objective of the current study is to create a tool that can be used during the shielding optimization process. The study is performed with Monte-Carlo simulations using a Geant4 version extended with NXSG4, that is capable to handle the crystal structure of specific materials, therefore the effects of neutron absorption, coherent and incoherent scattering were simulated. Validation of the extended Geant4 code, developed at ESS is also part of the current study by comparing the simulated results with analytical calculations. A detailed and realistic model of the state-of-The-Art Multi-Grid detector has been implemented, as it is almost the only prototype with published data on scattering effects. Simulations were performed for appropriate shielding materials with various monoenergetic neutron beams.A robust tool has been developed that could be effectively used to arise the S/N via optimizing the detector shielding for specific setups and requirements for all inelastic instruments.
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| 9. |
- Dian, Eszter, et al.
(författare)
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Validation of Detailed Geant4 Model for Thermal Neutron Scattering using the Results of Multi-Grid Detector Prototype Test at CNCS at SNS
- 2017
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Ingår i: 2017 IEEE NUCLEAR SCIENCE SYMPOSIUM AND MEDICAL IMAGING CONFERENCE (NSS/MIC). - : IEEE. - 9781538622827
-
Konferensbidrag (refereegranskat)abstract
- The European Spallation Source (ESS) aspires to be the worlds leading neutron source of the upcoming decades, and sets the scope on replacing He-3 tube detectors where it is reasonably achievable. The Multi-Grid detector, an Ar/CO2-filled proportional chamber based on solid (B4C)-B-10 converter, is the most potent replacement technology for chopper spectroscopy. This study reproduces in a detailed Geant4 geometry of a neutron scattering instrument the data from the Multi-Grid demonstrator detector, that has been tested for a 1 year period, installed side-by-side to the He-3 tubes at the CNCS instrument at SNS. For the further understanding of the background of the detector, Monte-Carlo simulations were performed, with the ESS Coding Framework, using a Geant4 version extended with NXSG4 and NCrystal. A detailed and realistic model of the prototype was built and was validated via comparison against measured data. With this model, different sources of neutron scattering were determined and studied separately, providing a better understanding of the scattered neutron background. Due to these capabilities the model will be used in the further optimization of the detector, especially for the background reduction via shielding, which will lead to instruments with better signal-to-background ratio by design.
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| 10. |
- Dijulio, Douglas D., et al.
(författare)
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Characterization of the radiation background at the Spallation Neutron Source
- 2016
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Ingår i: VI European Conference On Neutron Scattering (ECNS2015). - : IOP Publishing. ; 746:1
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Konferensbidrag (refereegranskat)abstract
- We present a survey of the radiation background at the Spallation Neutron Source (SNS) at Oak Ridge National Laboratory, TN, USA during routine daily operation. A broad range of detectors was used to characterize primarily the neutron and photon fields throughout the facility. These include a WENDI-2 extended range dosimeter, a thermoscientific NRD, an Arktis He-4 detector, and a standard Nal photon detector. The information gathered from the detectors was used to map out the neutron dose rates throughout the facility and also the neutron dose rate and flux profiles of several different beamlines. The survey provides detailed information useful for developing future shielding concepts at spallation neutron sources, such as the European Spallation Source (ESS), currently under construction in Lund, Sweden.
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| 11. |
- Hall-Wilton, Richard, et al.
(författare)
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Detectors for the European Spallation Source
- 2012
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Ingår i: 2012 IEEE Nuclear Science Symposium and Medical Imaging Conference Record (NSS/MIC). - 1082-3654. ; , s. 4283-4289
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Konferensbidrag (refereegranskat)abstract
- The European Spallation Source (ESS) in Lund, Sweden will become the world's leading neutron source for the study of materials by 2025. First neutrons will be produced in 2019. It will be a long pulse source, with an average beam power of 5 MW delivered to the target station. The pulse length will be 2.86 ms and the repetition rate 14 Hz. The ESS is presently in a design update phase, which ends in February 2013 with a Technical Design Report (TDR). Construction will subsequently start with the goal of bringing the first seven instruments into operation in 2019 at the same time as the source. The full baseline suite of 22 instruments will be brought online by 2025. These instruments present numerous challenges for detector technology in the absence of the availability of Helium-3, which is the default choice for detectors for instruments built until today. Additionally a new generation of source requires a new generation of detector technologies to fully exploit the opportunities that this source provides. This contribution presents briefly the current status of the ESS, and outlines the timeline to completion. The number of instruments and the framework for the decisions on which instruments should be built are shown. For a conjectured full instrument suite, which has been chosen for demonstration purposes for the TDR, a snapshot of the current expected detector requirements is presented. An outline as to how some of these requirements might be tackled is shown. Given that the delivery of the ESS TDR is only a few months away, this contribution reflects strongly the content of the TDR.
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| 12. |
- 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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| 13. |
- Kanaki, Kalliopi, et al.
(författare)
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A novel small-angle neutron scattering detector geometry
- 2013
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Ingår i: Journal of Applied Crystallography. - 1600-5767. ; 46, s. 1031-1037
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Tidskriftsartikel (refereegranskat)abstract
- A novel 2 pi detector geometry for small-angle neutron scattering (SANS) applications is presented and its theoretical performance evaluated. Such a novel geometry is ideally suited for a SANS instrument at the European Spallation Source (ESS). Motivated by the low availability and high price of 3 He, the new concept utilizes gaseous detectors with B-10 as the neutron converter. The shape of the detector is inspired by an optimization process based on the properties of the conversion material. Advantages over the detector geometry traditionally used on SANS instruments are discussed. The angular and time resolutions of the proposed detector concept are shown to satisfy the requirements of the particular SANS instrument.
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| 14. |
- Kanaki, Kalliopi, et al.
(författare)
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Simulation tools for detector and instrument design
- 2018
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Ingår i: Physica. B, Condensed matter. - : Elsevier BV. - 0921-4526 .- 1873-2135. ; 551, s. 386-389
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Tidskriftsartikel (refereegranskat)abstract
- The high performance requirements at the European Spallation Source have been driving the technological advances on the neutron detector front. Now more than ever is it important to optimize the design of detectors and instruments, to fully exploit the ESS source brilliance. Most of the simulation tools the neutron scattering community has at their disposal target the instrument optimization until the sample position, with little focus on detectors. The ESS Detector Group has extended the capabilities of existing detector simulation tools to bridge this gap. An extensive software framework has been developed, enabling efficient and collaborative developments of required simulations and analyses – based on the use of the Geant4 Monte Carlo toolkit, but with extended physics capabilities where relevant (like for Bragg diffraction of thermal neutrons in crystals). Furthermore, the MCPL (Monte Carlo Particle Lists) particle data exchange file format, currently supported for the primary Monte Carlo tools of the community (McStas, Geant4 and MCNP), facilitates the integration of detector simulations with existing simulations of instruments using these software packages. These means offer a powerful set of tools to tailor the detector and instrument design to the instrument application.
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| 15. |
- Kanaki, Kalliopi, et al.
(författare)
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Statistical Energy Determination in Neutron Detector Systems for Neutron Scattering Science
- 2012
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Ingår i: 2012 IEEE Nuclear Science Symposium and Medical Imaging Conference Record (NSS/MIC). - 1082-3654. ; , s. 162-166
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Konferensbidrag (refereegranskat)abstract
- This contribution evaluates the feasibility and potential of a statistical determination of the neutron energy for thermal and cold neutrons in the new generation of neutron detectors. For the European Spallation Source (ESS), sited in Lund, Sweden, which is planned to be operational in 2019, and the world's leading source for the study of materials with neutrons by 2025, novel neutron detectors represent a critical technology that needs to be developed. The discussion here is based upon B-10 based thin-film detectors for neutron scattering science; however such a development is generalisable to other converter materials and potentially relevant to applications outside of neutron scattering science.
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| 16. |
- Kirstein, Oliver, et al.
(författare)
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Neutron position sensitive detectors for the ESS
- 2014
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Ingår i: Proceedings of Science. - : Proceedings of Science (PoS). ; Vertex2014, s. 029-029
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Konferensbidrag (refereegranskat)abstract
- The European Spallation Source (ESS) in Lund, Sweden will become the world's leading neutron source for the study of materials. It will be a long pulse source, with an average beam power of 5 MW delivered to the target station. The ESS is in the construction phase, which started in 2013 with the completion of the Technical Design Report (TDR). The instruments are being selected from conceptual proposals submitted by groups from around Europe. These instruments present numerous challenges for detector technology in the absence of the availability of Helium-3, which is the default choice for detectors for instruments built until today and due to the extreme rates expected across the ESS instrument suite. Additionally a new generation of source requires a new generation of detector technologies to fully exploit the opportunities that this source provides. To meet this challenge at a green-field site, the detectors will be sourced from partners across Europe through numerous in-kind arrangements; a process that is somewhat novel for the neutron scattering community. This contribution presents briefly the current status of detectors for the ESS, and outlines the timeline to completion. For a conjectured instrument suite based upon instruments recommended for construction, a recently updated snapshot of the current expected detector requirements is presented. A strategy outline as to how these requirements might be tackled by novel detector developments is shown. In terms of future developments for the neutron community, synergies should be sought with other disciples, as recognized by various recent initiatives in Europe, in the context of the fundamentally multi-disciplinary nature of detectors. This strategy has at its basis the in-kind and collaborative partnerships necessary to be able to produce optimally performant detectors that allow the ESS instruments to be world-leading. This foresees and encourages a high level of collaboration and interdependence at its core, and rather than each group being all-rounders in every technology, the further development of centres of excellence across Europe for particular technologies and niches.
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| 17. |
- Kittelmann, Irena, et al.
(författare)
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Geant4 based simulations for novel neutron detector development
- 2014
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Ingår i: 20th International Conference on Computing in High Energy and Nuclear Physics (Chep2013), Parts 1-6. - : IOP Publishing. - 1742-6596 .- 1742-6588. ; 513, s. 022017-022017
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Konferensbidrag (refereegranskat)abstract
- A Geant4-based Python/C++ simulation and coding framework, which has been developed and used in order to aid the R&D efforts for thermal neutron detectors at neutron scattering facilities, is described. Built upon configurable geometry and generator modules, it integrates a general purpose object oriented output file format with meta-data, developed to facilitate a faster turn-around time when setting up and analysing simulations. Also discussed are the extensions to Geant4 which have been implemented in order to include the effects of low-energy phenomena such as Bragg diffraction in the polycrystalline support materials of the neutron detectors. Finally, an example application of the framework is briefly shown.
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| 18. |
- 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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| 19. |
- Mauritzson, Nicholai, et al.
(författare)
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GEANT4-based calibration of an organic liquid scintillator
- 2022
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Ingår i: Nuclear Instruments & Methods in Physics Research. Section A: Accelerators, Spectrometers, Detectors, and Associated Equipment. - : Elsevier BV. - 0168-9002. ; 1023
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Tidskriftsartikel (refereegranskat)abstract
- A light-yield calibration of an NE 213A organic liquid scintillator detector has been performed using bothmonoenergetic and polyenergetic gamma-ray sources. Scintillation light was detected in a photomultipliertube, and the corresponding pulses were subjected to waveform digitization on an event-by-event basis. Theresulting Compton edges have been analyzed using a GEANT4 simulation of the detector which models boththe interactions of the ionizing radiation as well as the transport of scintillation photons. The simulation is calibrated and also compared to well-established prescriptions used to determine the Compton edges,resulting ultimately in light-yield calibration functions. In the process, the simulation-based method produced information on the gain and intrinsic pulse-height resolution of the detector. It also facilitated a previously inaccessible understanding of the systematic uncertainties associated with the calibration of the scintillation-light yield. The simulation-based method was also compared to well-established numerical prescriptions for locating the Compton edges. Ultimately, the simulation predicted as much as 17% lower light-yield calibrations than the prescriptions. These calibrations indicate that approximately 35% of the scintillation light associated with a given gamma-ray reaches the photocathode. It is remarkable how well two 50 year old prescriptions for calibrating scintillation-light yield in organic scintillators have stood the test of time.
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| 20. |
- Muraro, Andrea, et al.
(författare)
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Performance of the high-efficiency thermal neutron BAND-GEM detector
- 2018
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Ingår i: Progress of Theoretical and Experimental Physics. - : Oxford University Press (OUP). - 2050-3911. ; :2
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Tidskriftsartikel (refereegranskat)abstract
- Newhigh-count-rate detectors are required for future spallation neutron sources where large-area and high-efficiency (>50%) detectors are envisaged. In this framework, Gas Electron Multiplier (GEM) is one of the detector technologies being explored, since it features good spatial resolution (<0.5 cm) and timing properties, has excellent rate capability (MHz/mm(2)) and can cover large areas (some m(2)) at low cost. In the BAND-GEM (boron array neutron detector GEM) approach a 3D geometry for the neutron converter cathode was developed that is expected to provide an efficiency >30% in thewavelength range of interest for small angle neutron scattering instruments. A system of aluminum grids with thin walls coated with a 0.59 mu m layer of (B4C)-B-10 has been built and positioned in the first detector gap, orthogonally to the cathode. By tilting the grid system with respect to the beam, there is a significant increase of effective thickness of the borated material crossed by the neutrons. As a consequence, both interaction probability and detection efficiency are increased. This paper presents the results of the performance of the BAND-GEM detector in terms of efficiency and spatial resolution.
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| 21. |
- Scherzinger, Julius, et al.
(författare)
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Tagging fast neutrons from an (241)Am/(9)Be source.
- 2015
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Ingår i: Applied Radiation and Isotopes. - : Elsevier BV. - 0969-8043. ; 98, s. 74-79
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Tidskriftsartikel (refereegranskat)abstract
- Shielding, coincidence, and time-of-flight measurement techniques are employed to tag fast neutrons emitted from an (241)Am/(9)Be source resulting in a continuous polychromatic energy-tagged beam of neutrons with energies up to 7MeV. The measured energy structure of the beam agrees qualitatively with both previous measurements and theoretical calculations.
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