A. Khaplanov

B4C thin films for neutron detection

Due to the very limited availability of He-3, new kinds of neutron detectors, not based on 3He, are urgently needed. Here, we present a method to produce thin films of (B4C)-B-10, with maximized de ...

Investigation of gamma-ray sensitivity of neutron detectors based on thin converter films

Currently, many detector technologies for thermal neutron detection are in development in order to lower the demand for the rare 3He gas. Gas detectors with solid thin film neutron converters readout by gas proportional counter method have been proposed as an appropriate choice for applications where large area coverage is necessary. In this paper, we investigate the probability for γ-rays to generate a false count in a neutron measurement. Simulated results are compared to measurement with 10B thin film prototypes and a 3He detector. It is demonstrated that equal γ-ray rejection to that of 3He tubes is achieved with the new technology. The arguments and results presented here are also applicable to gas detectors with converters other than solid 10B layers, such as 6Li layers and 10BF3 gas.

Study of a high spatial resolution B-10-based thermal neutron detector for application in neutron reflectometry: the Multi-Blade prototype

Although for large area detectors it is crucial to find an alternative to detect thermal neutrons because of the 3He shortage, this is not the case for small area detectors. Neutron scattering science is still growing its instruments power and the neutron flux a detector must tolerate is increasing. For small area detectors the main effort is to expand the detectors performances. At Institut Laue-Langevin (ILL) we developed the Multi-Blade detector which wants to increase the spatial resolution of 3He-based detectors for high flux applications. We developed a high spatial resolution prototype suitable for neutron reflectometry instruments. It exploits solid 10B-films employed in a proportional gas chamber. Two prototypes have been constructed at ILL and the results obtained on our monochromatic test beam line are presented here.

10B multi-grid proportional gas counters for large area thermal neutron detectors

Introduction 10B fi lms have been studied as neutron convertors in semi-conductors [1], and in different types of gas proportional counters for neutron scattering applications: for example in [2] the detector is made of several layers of straw tubes coated on the inner side with B4C; in [3] several parallel GEM (Gas Electron Multipliers) operated with an amplifi cation gain of 1 are coated with B4C fi lms on both sides; and in [4], inclined substrates are proposed to reduce the self-absorption of fi ssion products in the convertor. These different solutions are well suited for small size detectors requiring high counting rate and high spatial resolution but not for large area detectors mounted in vacuum chambers. The multi-grid detector, introduced at the ILL in 2010 [5], is developed in collaboration with European Spallation Source (ESS) in the CRISP project (http://www.crisp-fp7.eu/) to replace 3He in large-Area Neutron detectors. We present its principle as well as some results obtained with a prototype of 8 cm × 200 cm. This contribution to the study of 10B-fi lms detectors has been done in the frame of the International Initiative to search for 3He alternative technologies (http://icnd. org/). Results obtained by other institutes are accessible via the web page of the last workshop dedicated to BF3 and 10B-fi lm detectors (http://www.ill.eu/10bbf3, see also NN 23.3, p. 6).

In-beam test of the Boron-10 Multi-Grid neutron detector at the IN6 time-of-flight spectrometer at the ILL

A neutron detector concept based on solid layers of boron carbide enriched in 1 B has been in development for the last few years as an alternative for He-3 by collaboration between the ILL, ESS and ...

Detectors for the European Spallation Source

The European Spallation Source (ESS) in Lund, Sweden will become the worlds 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.

(B4C)-B-10 Multi-Grid as an Alternative to He-3 for Large Area Neutron Detectors

Despite its present shortage, 3He continues to be the most common neutron converter for detectors in neutron scattering science. However, it is obvious that the development of large area neutron detectors based on alternative neutron converters is rapidly becoming a matter of urgency. In the technique presented here, grids each comprising 28 10B4C layers (each 1 μm thick) are used to convert neutrons into ionizing particles which are subsequently detected in proportional gas counters. The total active area of the prototype is 8 cm × 200 cm. To instrument this detector 4.6 m2 of 10B-enriched boron carbide were coated onto aluminium blades using a DC magnetron sputtering machine.Despite its present shortage, 3He continues to be the most common neutron converter for detectors in neutron scattering science. However, it is obvious that the development of large area neutron detectors based on alternative neutron converters is rapidly becoming a matter of urgency. In the technique presented, grids each comprising 30 10B4C layers (each 1 µm thick) are used to convert neutrons into ionising particles which are subsequently detected in proportional gas counters. Several prototypes, the largest with a total active area of 8 cm x 200 cm, were tested. Up to 4.6 m2 of 10B-enriched boron carbide were coated onto aluminium blades using a DC magnetron sputtering machine. Characterisation of the prototype showed neutron efficiency to be n = 53.04% for 2.5 A neutrons, which is in line with expectations from MC simulation. Gamma-sensitivity = 5 · 10-5 was measured for a broad range of energies. Long term stability measurements were also performed. These results demonstrate the potential of this technique as alternative to 3He-based position sensitive detectors.

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

Thermal neutron detector based on films of

An information-theoretical approach to image resolution applied to neutron imaging detectors based upon individual discriminator signals

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Characterization of the radiation background at the Spallation Neutron Source

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