GEANT4 simulation of the 10B-based Jalousie detector for the ESS powder diffractometers (#2710)
I. Stefanescu1, R. Hall-Wilton1, 4, G. Kemmerling2, M. Klein3, C. J. Schmidt3, 5, W. Schweika1, 2
1 European Spallation Source ERIC, Lund, Sweden
The new powder and single-crystal diffraction instruments at the future European Spallation Source require large area detectors that can cope with the expected high neutron flux, have a fast response time and provide spatial information that cannot be achieved with the state-of-the-art technologies. The instrument development teams consider using the Jalousie detector concept, which seems to provide solutions to several of the demands of these instruments. This detector consists of tens of large trapezoidal 2D position-sensitive Multi-Wire Proportional Counters with the inner walls coated with a thin layer of 10B4C. The counters are arranged to create a volume detector around the sample. Any incoming neutron can traverse up to eight converter layers inclined with an angle of 10°. This leads to a detection efficiency of ~55% at 1 A, and also provides enhanced counting rate capability.
In this paper we report the results of the Geant4 simulation of the Jalousie detector. As one of the most demanding requirements for the powder and single-crystal diffraction detectors at ESS is the very good accuracy for position determination, we modelled the detector as a collection of gas voxels arranged side-by-side to fill the ionization volume between the detector walls and the cathode. The size and shape of these gas voxels resemble closely those of the readout voxels in the real detector. This implementation allows us to study the spatial and time (depth) resolution of the detector in the absence of the physics that governs the creation and transport of the electrons in the counting gas, not yet included in the Geant4 physics lists. We will present the work performed to validate the model and the simulation strategy through comparisons with the experimental data obtained in test measurements with the Jalousie prototype detector. We will also discuss the predicted performance in terms of efficiency, position and time resolution of the ESS diffraction detectors.
Keywords: neutron scattering, 10B4C detectors, GEANT4 simulation
Multi-Blade 10B-based Detector for Neutron Reflectometry at ESS: results obtained on the CRISP reflectometer at ISIS (#1763)
F. Piscitelli1, M. Anastasopoulos1, F. Chicken1, G. Galgoczi2, 3, R. Hall-Wilton1, 4, C. Höglund1, 5, G. Mauri6, F. Messi1, 7, P. Pazmandi2, D. Raspino8, L. Robinson1, D. Varga2
1 European Spallation Source ERIC, Detector Group, Lund, Sweden
The Multi-Blade (MB) is a Boron-10-based detector conceived to face the challenge of the counting rate capability arising from the neutron reflectometry at the European Spallation Source (ESS). The current detector technology is reaching fundamental limits in counting rate capability and position resolution.
The problem with count rates is a general one, and the ESS solution could potentially be applied to existing instruments at other neutron sources.
It has been shown that aside from the improvement in counting rate capability, the MB design also decreases the spatial resolution by about a factor three over state-of-the-art helium-3-based reflectometer detectors.
The MB detector will be tested this year at the CRISP reflectometer at ISIS (Science & Technology Facilities Council in UK) in a real instrument environment. The reflectivity of several reference samples will be measured with the MB detector on CRISP and the results will be compared with the current detector installed at the instrument based on 3He. These tests are crucial to validate the Multi-Blade technology to be installed at the ESS reflectometers. These and other results including the path ahead for this project will be presented.
Keywords: thermal neutron detectors, boron-10, neutron reflectometry, gaseous detectors
Geant4 based simulation of the Multi-Blade detector for validation and investigation of scattering (#2759)
G. Galgóczi1, 2, K. Kanaki3, F. Piscitelli3, T. Kittelmann3, X. X. Cai3, 5, D. Varga1, R. Hall-Wilton3, 4
1 Hungarian Academy of Sciences, Wigner Research Centre for Physics, Budapest, Hungary
The Multi-Blade detector is one of the novel neutron detectors currently being developed at the European Spallation Source with focus on reflectometry applications. Instead of the long established helium-3 based neutron detectors a boron layer is used to convert the neutrons to Lithium ions and Alpha particles, which are easily detected by a Multi-Wire Proportional Chamber. The reflectometer requirements set by the European Spallation Source exceed the capabilities of any existing neutron detectors. One of the main challenges the Multi-Blade detector is facing is the desired extremely low scattering of neutrons inside the detector before detection. In order to understand and quantify how each part of the detector contributes to this effect, a Geant4 simulation model was developed. This contribution presents how the simulated detector performance in terms of pulse-height spectra, detection efficiency, spatial resolution, is validated against experimental results and how it can be used to determine the optimal geometrical parameters of the Multi-Blade detector.
Keywords: neutron reflectometry, GEANT4, ESS, neutron scattering, neutron detector, Multi-Blade
Gamma- and Fast Neutron- Sensitivity of 10B-based Neutron Detectors at ESS (#3259)
F. Messi1, 2
1 European Spallation Source ERIC, Lund, Sweden
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. Is therefore crucial to measure the gamma- and fast-neutron- sensitivity of detectors that will be installed on the instruments at Neutron Scattering Science Facilities.
An extension of the measurements performed on the MultiGrid detector has been performed on the MultiBlade detector beginning of this year. The MultiBlade is a 10B-based detector developed for Reflectometry applications. It consists of a stack of Multi Wire Proportional Chambers operated at atmospheric pressure with continuous gas flow.
The results from the test performed at the Source Testing Facility (STF) of Lund University, Sweden, will be presented. It has been shown that the gamma-sensitivity for this kind of detector is below 10−7 (for 100 keV threshold).
Measurements on the fast-neutron-sensitivity of the MultiBlade detector are presently undergoing at STF, including tagged and non-tagged fast neutron techniques. All tests will be presented in the talk and the results discussed in details.
These measurements are crucial to validate the detector technology to be installed at the ESS as well as at other Neutron Scattering Science Facilities and are of general interest for all kind of 10B-based neutron detectors.
Keywords: 10-Boron detector, gamma-sensitivity, fast-neutron-sensitivity, tagged neutron
Low gas pressure operation to improve performances of Multi-Grid detectors (#3449)
F. Lafont1, M. Anastasopoulos2, J. Birch3, J. - C. Buffet1, V. Buridon1, J. - F. Clergeau1, S. Cuccaro1, B. Guerard1, R. Hall-Wilton2, C. Höglund2, 3, I. Lopez Higuera2, F. Issa2, A. Khaplanov2, J. Marchal1, J. Pentenero1, M. Platz1, L. Robinson2, P. Van Esch1
1 ILL, Grenoble, France
The quest for alternatives to Helium-3 filled detectors has been going on for some years. Within the framework of the BrightnESS project, several prototypes of Multi-Grid detectors are being developed and studied in collaboration between ILL, ESS and LU. Based on neutron capture by enriched Boron-10-boron carbide layers, this detector filled with Ar-CO2 mixture is composed of hundreds of coated aluminum cells with very small dead space in between which ensures a rather good detection efficiency – about 50 % at 2.5 Å and 65 % (estimated) for the next generation. We have already demonstrated the proper operation of a 2-meter long detector during the CRISP project (2011-2014) at atmospheric pressure. In order to reduce the weight of detectors and improve their uniformity of response, we are now studying the operation of two Multi-Grid prototype detectors at low pressures (50-100 mbar) and we are demonstrating that it presents many advantages besides lowering the sensitivity to gamma rays. Among the main results, it was shown that the detectors could withstand very high counting rates (>500 kHz) with no evidence of ageing and that the average dead time at these pressures was about 320 ns. The susceptibility to pressure changes is also very low in terms of detection efficiency when it is operated between 50 to 200 mbar which guarantees a good stability of the detector. The next generation prototype will be tested in experimental conditions with a measurement in IN4 ILL instrument.
Keywords: Neutron detectors, Multi-grid technology, ESS, Boron-10 layer, BrightnESS, He-3 detectors
Development of the trench - Multi Wire Proportional Chambers for improved counting rate capability; application to neutron scattering science (#2386)
J. - C. Buffet1, J. - F. Clergeau1, S. Cuccaro1, B. Guerard1, N. Mandaroux1, J. Marchal1, J. Pentenero1, M. Platz1, P. Van Esch1
1 Insitut Laue Langevin, Grenoble, France
The future XtremeD instrument, due to start its operation in 2019, will be equipped with a large-area 2D detector for the study of powder and crystal samples under extreme conditions of pressure and magnetic field. A new concept of 3He detector, called the Trench Multi Wire Proportional Chamber (Trench-MWPC) was developed for XtremeD. Other existing diffractometer instruments at ILL could also benefit from the increased counting rate obtained with this detector configuration.
Keywords: MWPC, Neutron detection, Neutron diffraction