A¹⁰B-based neutron detector with stacked MultiWire Proportional Counters and macrostructured cathodes

Abstract

We present the results of the measurements of the detection efficiency for a 4.7Å neutron beam incident upon a detector incorporating a stack of up to five MultiWire Proportional Counters (MWPC) with Boron-coated cathodes. The cathodes were made of Aluminum and had a surface exhibiting millimeter-deep V-shaped grooves of 45 • , upon which the thin Boron film was deposited by DC magnetron sputtering. The incident neutrons interacting with the converter layer deposited on the sidewalls of the grooves have a higher capture probability, owing to the larger effective absorption film thickness. This leads to a higher overall detection efficiency for the grooved cathode when compared to a cathode with a flat surface. Both the experimental results and the predictions of the GEANT4 model suggests that a 5-counter detector stack with coated grooved cathodes has the same efficiency as a 7-counter stack with flat cathodes. The reduction in the number of counters in the stack without altering the detection efficiency will prove highly beneficial for large-area positionsensitive detectors for neutron scattering applications, for which the cost-effective manufacturing of the detector and associated readout electronics is an important objective. The proposed detector concept could be a technological option for one of the new chopper spectrometers and other instruments planned to be built at the future European Spallation Source in Sweden. These results with macrostructured cathodes generally apply not just to MWPCs but to other gaseous detectors as well. arXiv:1309.7789v1 [physics.ins-det]

Low-temperature growth of boron carbide coatings by direct current magnetron sputtering and high-power impulse magnetron sputtering

“…The recent intense and focused search for alternatives to 3 He-based detectors has shown that detectors based on the boron isotope 10 B are feasible alternatives [1,2] both in their performance and economically [3][4][5][6][7][8][9][10]. 10 B has a relatively high neutron absorption cross section compared to 3 He, and by optimizing the design of the detector, a detection efficiency comparable to 3 He has been presented [3,11].…”

“…Additionally, the radiation hardness has recently been shown to be appropriate for these neutron detector applications [18]. Reference [12] addresses adhesion issues that often arise for micrometer-range-thick B 4 C films due to high residual film stresses in combination with low adhesive forces between the B 4 C film and the substrate. Here, the film adhesion on Al substrates was reported to improve significantly as elevated substrate temperatures between 300 and 400°C are used.…”

A novel small-angle neutron scattering detector geometry

“…Since the traditional approach with 3 He detectors is no longer a viable option for ESS instruments, owing to the unavailability of 3 He, particularly for the ESS, and its high cost (Persons & Aloise, 2011;Shea & Morgan, 2010;Cho, 2009; International Collaboration on the Development of Neutron Detectors, http://www.icnd.org), an alternative neutron technology solution based on 10 B is introduced for this application. Boron carbide ( 10 B 4 C) thin-film detectors are currently being developed by several groups worldwide and are proven to be a reliable and promising replacement for 3 He detectors (Andersen et al, 2012;Zeitelhack, 2012;Bigault et al, 2012;Correa, 2012;Stefanescu et al, 2013;Hö glund et al, 2012). The 10 B isotope has a neutron absorption cross section of about 3840 barn (1 barn = 10 À28 m 2 ) for thermal neutrons ( = 1.8 Å ) (Safford et al, 1960), which is approximately 70% of the 3 He cross section.…”

“…The largest part of the difference between the detection of an Li ion and an particle is accounted for in the algebraic efficiency calculations, as the two particles have different ranges in the coating layer. For the purposes of this study, the intrinsic detection efficiency of the gaseous detector is reasonably assumed to be very high (Sauli, 1977;Klein, 2000;Stefanescu et al, 2013), with every ion escape leading to a detection event. The conversion layer thickness can be optimized to increase the back-scattering detection efficiency further, as shown in Fig.…”

Growth and oxidization stability of cubic Zr1−xGdxN solid solution thin films

“…This has forced the community to search for alternative solutions 7,8 and the boron isotope 10 B is seen as one of the most promising replacements. [9][10][11][12][13][14][15] The main options are technologies based on 10 B 4 C thin films and this is a field in which the authors' [16][17][18] and Nowak and co-workers' 19 research and development work have enabled rapid progress. These types of detectors are mainly intended for use in large area gaseous neutron detectors and a significant fraction of the detectors at the ESS will be based on this technology.…”