Investigation of background in large-area neutron detectors due to alpha emission from impurities in aluminium

Birch, Jens; Buffet, J.C.; Clergeau, J.F.; Esch, Patrick van; Ferraton, M.; Guérard, B.; Hall-Wilton, R.; Hultman, Lars; Höglund, Carina; Jensen, Jens; Khaplanov, A.; Piscitelli, F.

doi:10.1088/1748-0221/10/10/p10019

Cited by 8 publications

(10 citation statements)

References 22 publications

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“…The grids in Detector 1 is made with radiopure aluminum from Praxair [40], with less than 1 ppb (parts per billion) radioactive impurities such as Th and U, while the grids in Detector 2 is made with commercially available Al5754. The impact of radioactive impurities in the Al5754 alloy, such as Th and U, is alpha emissions which raises the time-independent background level in the detector [10]. Furthermore, the impact of parasitic reactions due to neutron absorption in the remaining elements in the alloy, most prominently manganese, is a photon yield (cm −3 s −1 ) 1 order of magnitude below that of aluminum [24].…”

Section: The Multi-grid Detectormentioning

confidence: 99%

“…Due to the sparsity and increased cost of helium-3 gas during the past two decades [4], as well as the performance limitation due to the expected high flux from the source, alternatives to the traditional helium-3 based neutron detectors are being developed. One such alternative is the boron-10 based Multi-Grid detector [5,6,7,8,9,10,11], invented at the Institut Laue-Langevin (ILL) [12], and jointly developed with ESS thereafter. The Multi-Grid detector is a large area cold to epithermal neutron detector, designed for time-of-flight neutron spectroscopy [13] at the upcoming CSPEC [14] (cold neutron spectroscopy) and T-REX [15] (thermal neutron spectroscopy) instruments at ESS.…”

Section: Introductionmentioning

confidence: 99%

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Time- and energy-resolved effects in the boron-10 based multi-grid and helium-3 based thermal neutron detectors

Backis

Khaplanov

Jebali

et al. 2020

Meas. Sci. Technol.

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The boron-10 based Multi-Grid detector is being developed as an alternative to helium-3 based neutron detectors. At the European Spallation Source, the detector will be used for time-of-flight neutron spectroscopy at cold to thermal neutron energies. The objective of this work is to investigate fine time-and energyresolved effects of the Multi-Grid detector, down to a few µeV, while comparing it to the performance of a typical helium-3 tube. Furthermore, it is to characterize differences between the detector technologies in terms of internal scattering, as well as the time reconstruction of ∼ µs short neutron pulses. The data were taken at the Helmholtz Zentrum Berlin, where the Multi-Grid detector and a helium-3 tube were installed at the ESS test beamline, V20. Using a Fermi-chopper, the neutron beam of the reactor was chopped into a few tens of µs wide pulses before reaching the detector, located a few tens of cm downstream. The data of the measurements show an agreement between the derived and calculated neutron detection efficiency curve. The data also provide fine details on the effect of internal scattering, and how it can be reduced. For the first time, the chopper resolution was comparable to the timing resolution of the Multi-Grid detector. This allowed a detailed study of time-and energy resolved effects, as well as a comparison with a typical helium-3 tube.

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Section: The Multi-grid Detectormentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Time- and energy-resolved effects in the boron-10 based multi-grid and helium-3 based thermal neutron detectors

Backis

Khaplanov

Jebali

et al. 2020

Meas. Sci. Technol.

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“…Each source was placed close to the entrance window of the Multi-Blade, directly outside of the cassette equipped with the individual readout electronics; it results in a solid angle acceptance of approximately 0.2 sr. A PHS for the three sources was recorded, and in absence of any source to estimate the background. The latter is the sum of the environmental background and the false counts that arises from the natural decay of radioactive contaminants typically present in standard Aluminium alloys [73]. In order to the get the PHS we sum all the counts recorded with the wires from 10 to 30 of the cassette in order to increase the statistics and to take into account only wires with approximately the same gas gain.…”

Section: Gamma Sensitivitymentioning

confidence: 99%

The Multi-Blade Boron-10-based neutron detector for high intensity neutron reflectometry at ESS

et al. 2017

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The Multi-Blade is a Boron-10-based gaseous detector introduced to face the challenge arising in neutron reflectometry at pulsed neutron sources. Neutron reflectometers are the most challenging instruments in terms of instantaneous counting rate and spatial resolution. This detector has been designed to cope with the requirements set for the reflectometers at the upcoming European Spallation Source (ESS) in Sweden. Based on previous results obtained at the Institut Laue-Langevin (ILL) in France, an improved demonstrator has been built at ESS and tested at the Budapest Neutron Centre (BNC) in Hungary and at the Source Testing Facility (STF) at the Lund University in Sweden. A detailed description of the detector and the results of the tests are discussed in this manuscript.

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“…A significant effort has been made to understand and reduce the background in the Multi-Grid and other solid boron converter based detectors. As a part of this, the α-, γ-and fast neutron background components have been studied and reduced, as described in [34], [37] and [38], respectively. These background components are also omitted from the simulation, as the remnant background is negligible in comparison with the implemented instrument-related background sources [25].…”

Section: Model Of Demonstrator Test On Cncs Instrument At Snsmentioning

confidence: 99%

Scattered neutron background in thermal neutron detectors

Dian

Kanaki

Ehlers

et al. 2018

Nuclear Instruments and Methods in Physics Research Section A:

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Inelastic neutron scattering instruments require very low background; therefore the proper shielding for suppressing the scattered neutron background, both from elastic and inelastic scattering is essential. The detailed understanding of the background scattering sources is required for effective suppression. The Multi-Grid thermal neutron detector is an Ar/CO 2 gas filled detector with a 10 B 4 C neutron converter coated on aluminium substrates. It is a large-area detector design that will equip inelastic neutron spectrometers at the European Spallation Source (ESS). To this end a parameterised Geant4 model is built for the Multi-Grid detector. This is the first time thermal neutron scattering background sources have been modelled in a detailed simulation of detector response. The model is validated via comparison with measured data of prototypes installed on the IN6 instrument at ILL and on the CNCS instrument at SNS. The effect of scattering originating in detector components is smaller than effects originating elsewhere. IntroductionInelastic neutron scattering is a very powerful technique for exploring atomic and molecular motion, as well as magnetic and crystal field excitations [1]. Timeof-Flight (ToF) spectrometers allow a broad phase space to be measured in a single setting; this is typically achieved with a large area detector array [2]. In typical state-of-the-art neutron instruments [2][3][4][5][6][7][8], this detector array can be 10-50 m 2 . One of the main performance criteria of these spectrometers is typically defined by the Signal-to-Background Ratio (SBR), therefore understanding and enhancing the latter is important for the instrument optimisation. In particular, scattered neutrons have a significant contribution to the SBR. The estimation of the SBR is done currently on a series of prescriptions based on observations of historical instrument installation.As a consequence of the recent restructuring of the 3 He market [9], a need for cost effective 3 He-replacing detector solutions is raised [10], especially for inelastic neutron scattering instruments, where large area detectors with high SBR are required. A potent new solution for this type of instruments is the Multi-Grid detector [11; 12], which will be used for the three Time-of-Flight chopper spectrometers at ESS [13][14][15][16]. The Multi-Grid design was invented at the Institut Laue-Langevin (ILL) [17; 18], and the detector now is jointly developed by the ILL and the ESS within the CRISP [19] and BrightnESS [20] projects.The Multi-Grid detector is an Ar/CO 2 -filled proportional chamber with a solid boron-carbide ( 10 B 4 C) neutron converter, enriched in 10 B [21][22][23]. The basic unit of the Multi-Grid detector is the grid, an aluminium frame; thin aluminium lamellas, coated on their both sides with boron-carbide, the so called blades are placed in this frame, parallel with each other and the entrance window of the grid, dividing the grid into cells. In the detector the grids are structured into columns, and this way the cells ...

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Investigation of background in large-area neutron detectors due to alpha emission from impurities in aluminium

Cited by 8 publications

References 22 publications

Time- and energy-resolved effects in the boron-10 based multi-grid and helium-3 based thermal neutron detectors

Time- and energy-resolved effects in the boron-10 based multi-grid and helium-3 based thermal neutron detectors

The Multi-Blade Boron-10-based neutron detector for high intensity neutron reflectometry at ESS

Scattered neutron background in thermal neutron detectors

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