Detection efficiency, spatial and timing resolution of thermal and cold neutron counting MCP detectors

https://doi.org/10.1016/j.nima.2009.01.041Get rights and content

Abstract

Neutron counting detectors with boron or gadolinium doped microchannel plates (MCPs) have very high detection efficiency, spatial and temporal resolution, and have a very low readout noise. In this paper we present the results of both theoretical predictions and experimental evaluations of detection efficiency and spatial resolution measured at cold and thermal neutron beamlines. The quantum detection efficiency of a detector (not fully optimized) was measured to be 43% and 16% for the cold and thermal beamlines, respectively. The experiments also demonstrate that the spatial resolution can be better than 15 μm—highest achievable with the particular MCP pore dimension used in the experiment, although more electronics development is required in order to increase the counting rate capabilities of those <15 μm resolution devices. The timing accuracy of neutron detection is on the scale of few μs and is limited by the neutron absorption depth in the detector. The good agreement between the predicted and measured performance allows the optimization of the detector parameters in order to achieve the highest spatial resolution and detection efficiency in future devices.

Introduction

Recently there has been a rapid progress in neutron sources and neutron instrumentation, enabling novel high resolution non-destructive testing techniques for material sciences, investigation of hydrogen content and storage, magnetic properties, imaging of archeological objects, to name the few. The increased brightness of modern neutron sources as well as pulsed nature of some of them, allows high resolution neutron tomography, energy resolved neutron radiography, as well as texture and residual strain analysis by measuring the shifts in Bragg diffraction edges. The performance of detection devices has to meet the challenges posed by those new techniques in order to achieve the desired resolution, reduce the data acquisition times and fully utilize the capabilities of modern neutron sources [1], [2]. Detection efficiency, spatial and timing resolutions are among the key detector parameters determining the accuracy of mentioned techniques.

Neutron counting detectors with microchannel plates suggested by Fraser [3] provide some unique capabilities for high resolution applications. Our detailed theoretical study of the detection process [4], [5] indicate that the MCP detectors can reach efficiencies as high as 50% for thermal neutrons. The preliminary experiments with out optimal microchannel plates [6] agree with the results of our predictions for the particular MCP geometry used in the measurements. In addition, detectors with neutron-sensitive MCPs can count thermal and cold neutrons with spatial resolution comparable to the pore dimensions of 10 μm [7].

Section snippets

Experimental results

In this paper we present the results of detailed experimental evaluation of MCP-based neutron counting detector, which consisted of one 10B-doped microchannel plate (8 μm pores on 11 μm centers, 100:1 L/D, 33 mm diameter) followed by a stack of two standard glass MCPs (10 μm pores on 12 μm centers, 40:1 L/D, 33 mm diameter) and a Medipix2 readout [8] positioned 0.7 mm behind the MCP stack. Muros2 [9] back-end electronics allowing externally triggered acquisition frames was used for signal processing.

Conclusion

The neutron counting MCP/Medipix2 detectors proved to have high detection efficiency—43% at the cold beam and 16% at thermal neutron beam; high spatial resolution—55 μm in high counting rate mode and <15 μm at slow counting rate with event centroiding and frame-based timing resolution of a few μs. Combination of these performance parameters makes the MCP detectors very attractive for high resolution neutron radiography, transmission Bragg edge spectroscopy and energy-resolved imaging.

Acknowledgements

The authors would like to thank their colleagues at the Czech Technical University for the Pixelman data acquisition software [15]. The work was partially funded by the DOE STTR Grants DE-FG02-07ER86322 and DE-FG02-08ER86353.

References (15)

  • R.G. Cooper

    Nucl. Instr. and Meth. A

    (2004)
  • E.H. Lehmann et al.

    Nucl. Instr. and Meth. A

    (2007)
  • G.W. Fraser et al.

    Nucl. Instr. and Meth. A

    (1990)
  • A.S. Tremsin et al.

    Nucl. Instr. and Meth. A

    (2005)
  • O.H.W. Siegmund et al.

    Nucl. Instr. and Meth. A

    (2007)
  • A.S. Tremsin et al.

    Nucl. Instr. and Meth. A

    (2008)
  • X. Llopart et al.

    Nucl. Instr. and Meth. A

    (2007)
There are more references available in the full text version of this article.

Cited by (89)

  • Simulating the secondary electron avalanche of MCP by Geant4

    2024, Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment
  • Enhanced gas-liquid absorption through natural convection studied by neutron imaging

    2022, International Journal of Heat and Mass Transfer
    Citation Excerpt :

    The temporal and spatial resolution of the images are mutually limited by the neutron flux. One is optimized on the expense of the other, both have been refined by digital detection and image processing [18-23]. In this study, exposure times of 0.1 s and 1.0 s with a resolution of 44 µm are applied.

  • Overview of spatial and timing resolution of event counting detectors with Microchannel Plates

    2020, Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment
View all citing articles on Scopus
View full text