| 1. |
- Arnadottir, Anna, et al.
(author)
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Promenad med Partiklar
- 2021
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Artistic work (other academic/artistic)abstract
- Thanks to binoculars, telescopes and spectroscopes, we have been able to look further out into the Universe than would ever have been possible with the naked eye. In the same way, there is a whole Universe in the other direction. Among cells, molecules, and down to atoms. But down in the nuclear world, telescopes are not needed. No, there we take the help of the small neutrons themselves.
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| 2. |
- Al Jebali, Ramsey, et al.
(author)
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Recent Developments SoNDe High-Flux Detector Project
- 2018
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In: Recent Developments SoNDe High-Flux Detector Project.
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Conference paper (peer-reviewed)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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| 3. |
- Greiff, Marcus, et al.
(author)
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Gamma-Ray Imaging with Spatially Continuous Intensity Statistics
- 2021
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In: Proc. 2021 IEEE/RSJ Int. Conf.Intelligent Robots and Systems (IROS2021), Sep 27 - Oct 1, 2021, Prague, Czech Republic. ; , s. 5234-5239
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Conference paper (peer-reviewed)abstract
- Novel methods for the inference of radiation intensityfunctions defined over known surfaces are proposed, intendedfor use in surveying applications with mobile spectrometers.Previous approaches, based on the maximum likelihoodexpectation maximization (ML-EM) framework with Poissonlikelihoods, are extended to better handle spatially continuousintensity statistics using ideas from Gaussian filtering. Theresulting algorithm is evaluated against a classical ML-EMmethod, and a recently proposed sparse additive point sourcelocalization (APSL) algorithm in a Monte-Carlo simulationstudy. The new generalized ASPL (GASPL) is shown tocompare favorably in terms of estimation accuracy when thetrue intensity is not well described by a set of point sources.Finally, the GASPL is used in an experiment where a detector ismounted to an unmanned aerial vehicle to estimate the intensityand location of radioactive sources placed in a meadow.
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| 4. |
- Mauritzson, Nicholai, et al.
(author)
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GEANT4-based calibration of an organic liquid scintillator
- 2022
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In: Nuclear Instruments & Methods in Physics Research. Section A: Accelerators, Spectrometers, Detectors, and Associated Equipment. - : Elsevier BV. - 0168-9002. ; 1023
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Journal article (peer-reviewed)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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| 5. |
- Rofors, Emil
(author)
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A Fast Pixelated Thermal-Neutron Detector
- 2020
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Doctoral thesis (other academic/artistic)abstract
- This thesis presents the study of a position-sensitive scintillation-based detector called the Solid-State Neutron Detector (SoNDe). SoNDe is being developed for cold- and thermal-neutron detection at the small-angle neutron scattering (SANS) instrument SKADI at the European Spallation Source (ESS), currently under construction in Lund, Sweden. The response of the detector scintillator, multi-anode photomultiplier (MAPMT), and readout electronics has been investigated using particles relevant in the 6Li(n,3H)α reaction that is at the heart of the detection principle of SoNDe. Scintillation light was read out by the 8×8 pixel H12700A MAPMT. The pixel signal is strongly dependent on position and in general several pixels will register a signal (a hit) above a given threshold. To optimize planned detector operation at ESS, the number of pixels above set thresholds was investigated, with the maximization of the single-hit efficiency over the largest possible area as the primary goal. Paper I describes introductory tests validating the detector concept using signal generators and neutrons read out using the SoNDe electronics. Paper II is the first of three systematic irradiation studies and is performed with a broad α-particle beam from a radioactive source using a VME-based data-acquisition system. Scans of highly focused beams of protons and deuterons from a Pelletron across the detector are presented in Paper III. Scans of a collimated thermal-neutron beam from a reactor read out using the SoNDe readout electronics is presented in Paper IV. A simulation model developed using Geant4 and tuned with the measurements reported in Papers I-IV is described in detail in Paper V. For all of the beams employed in this thesis, the optimal threshold for single-hit efficiency was found at a value of ~50% of the mean of the full-deposition peak. Of the detected particles, ~80% were registered in a single pixel. Lower thresholds resulted in higher pixel multiplicities. These events could be localized with better than 5 mm position resolution and could potentially facilitate operation of the detector in a higher multiplicity mode while still fulfilling the 6 mm neutron position-reconstruction accuracy requirement set by the SANS program to be performed at the SKADI instrument.
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| 6. |
- Scherzinger, Julius, et al.
(author)
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A comparison of untagged gamma-ray and tagged-neutron yields from 241AmBe and 238PuBe sources
- 2017
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In: Applied Radiation and Isotopes. - : Elsevier BV. - 0969-8043 .- 1872-9800. ; 127, s. 98-102
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Journal article (peer-reviewed)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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| 7. |
- Scherzinger, Julius, et al.
(author)
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Tagging fast neutrons from a Cf-252 fission-fragment source
- 2017
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In: Applied Radiation and Isotopes. - : Elsevier BV. - 0969-8043 .- 1872-9800. ; 128, s. 270-274
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Journal article (peer-reviewed)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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