Neutron Imaging Detectors

The spatial resolution can be measured in a number of ways, including the contrast between two absorbing bars as the bar width and separation is varied, or by measuring the width of a sharp edge.17 The effects of the PSF, including A.g, on measuring the water profile are discussed in more detail in Section 3.1.5. 

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C. Grunzweig, G. Frei, E. Lehmann, G. Kuhne, C. David, Highly absorbing gadolinium test device to characterize the performance of neutron imaging detector systems. Rev. Sci. Instrum. 78, 053708 (2007)... 

J. (2011) Large area high resolution neutron imaging detector for fuel cell research. J. Power Sources, 196, 4631-4637. 

There are two principal neutron imaging techniques in NR - direct and transfer (indirect). In the former the neutron converter and the detector are simultaneously exposed in the neutron beam while in the transfer technique only the converter screen is exposed and activated by the neutrons, and transfered out of the neutron beam to subsequently expose the detector. Various types of IP can be used in both of neutron imaging techniques. 

Fast Neutron Imaging Telescope (FNIT). The FNIT detector [Moser et al., 2004a] is sensitive to solar neutrons in the energy range 3-100 MeV, and is intended to be operated on inner heliosphere missions. 

It was clearly demonstrated that the composite BN semiconductor polycrystalline bulk detectors with BN grains embedded in a polymer matrix operate as an effective detector of thermal neutrons even if they contain natural boron only (Uher et al. 2007). A reasonable signal-to-noise ratio was achieved with detector thickness of about 1 mm. A Monte Carlo simulation of neutron thermal reactions in the BN detector was done to estimate the detection efficiency and compare with widely used He-based detectors to prove advantages of BN detectors. They are found to be promising for neutron imaging and for large area sensors. 

The nanosecond pulsed beam with time gating at the detector and the associated particle method (APM) render the three-dimensional (3D) elemental analysis of solids possible (Overley 1987 Rynes et al. 1999). The APM is based mainly on the D-D and D-T reactions by the detection of He and He particles, respectively, emitted at 180° to the neutron direction. The 4-5 cm/ns travel time of the neutrons allows the imaging of the interrogated volume along the direction of the ns pulsed neutrons with a spatial resolution of 5 cm. Some 2D-3D fast neutron imaging principles and techniques are summarized by Gozani (1994), Mikerov et al. (1998, 2001), and Chen and Lanza (2001), while typical thermal neutron radiography systems are demonstrated by Balasko et al. 1998, 2001) and Shaikh et al. (1998, 2001). 

Pekula, N., Heller, K., Chuang, PA., Turhem, A., Mench, M.M., Bienizer, J.S., and Unlu, K. (2005) Study of water distribution and transport in a polymer electrolyte fuel cell using neutron imaging, Nucl. Instrum. Methods Phys. Res. Sect. A Accelerators Spectrometers Detectors Associated... 

N. Pekula, A. Heller, P. A. Chuang, A., Turhan, M. M. Mench, J. S. Brenizer and K. Unlu, Study of Water Distribution and Transport in a Polymer Electrolyte Fuel Cell using Neutron Imaging, Nucl. Instrum. Methods Phys. Res. Sect. A Accelerators, Spectrometers, Detectors and Associated Equipment, Vol. 542, Issues 1-3, No. 21, pp. 134-144, 2005. 

Neutron or y Sensors Neutron- or y -based sensors are similar in concept to the X-ray sensors. They use different forms of excitation and different detectors, but the basic forms of transmission or backscatter follow the pattern described above. Both normally rely on extensive computation for signal processing called computed tomography, where the detector signals are combined to synthesize an image of the irradiated object. 

A second type of image-plate detector employs gadolinium oxide, which absorbs a neutron and emits a gamma ray, which in turn exposes the image plate. Image plates have higher spatial resolution but lower efficiency than multiwire detectors. 

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