Neutron transmission

Signal-to-noise considerations make most neutron-based explosive detection approaches very difficult to implement. The basis for combining multiple detection approaches (FNA, along with thermal gamma detection and neutron transmission spectroscopy) in a FNAP application that preserves the small volume advantage of a APSTNG remains to be established. There are distinct advantages associated with the API approach, but the concomitant reductions in available neutron flux, issues of tube lifetime, and the intrinsic poor spatial resolution must be taken into consideration for potential applications. 

M. S. Chmelik, R. J. Rasmussen, R. M. S. Schofield, G. E. Sieger, H. W. Lefevre, J. C. Overley, C. J. BeU, Analysis of Bhnd Tests for Explosives in Luggage Through Fast-Neutron Transmission Spectroscopy (FNTS), University of Oregon, Eugene, OR, January 1997. 

B. J. Micklich, C. L. Fink, L. Sagalovsky, F. L. Smith, T. J. Yule, Feasibihty of Explosive Detection Using Fast-Neutron Transmission Spectroscopy, Report No. DOT/FAA/CT-96/ XX, 1996. 

A sketch of a thermal neutron transmission gauge is shown in Fig 16. It contains the same basic components as a fast neutron moderation gauge... 

The variation of neutron count rate with charge weight by thermal neutron transmission is shown in Fig 17 for a brass cylinder (5cm long x 1.3cm diam x 0.8mm thick wall) with RDX as the charge (fill capacity, lOg). Each point represents a 10-sec count. Non-linearity of response at the top and bottom of the cylinder is due to... 

Fig 16 Sketch of Thermal Neutron Transmission Gauge for Measurement of Charge Weight... 

In fast neutron moderation, the count rate should increase with a hydrogenous sample between source and detector, whereas the reverse is expected for thermal neutron transmission. These measurements show that thermal neutron... 

Fast Neutron Moderation and Thermal Neutron Transmission for Charge Weight Measurement... 

Charge 3 Hydrogen Content, % Bulk Density Hydrogen Density Increase in Count Rate by Fast Neutron Moderation, % Decrease in Count Rate by Thermal Neutron Transmission, %... 

Neutron radiography measures the spatially resolved neutron transmission through a sample. The neutron transmission is derived from the Lambert-Beer Law of attenuation, which in differential form is... 

Fig. 9. Principles of pulsed fast neutron transmission analysis. No, open beam intensity with no material in...

P.K. Van Staagen, T.G. Miller, B.C. Gibson and R.A. Krauss, High speed data acquisition for contraband identification using neutron transmission, AIP Conf. Proc., 392(pt. 2) (1997) 853-856. 

T.J. Yule, B.J. Micklich, C.L. Fink and L. Sagalovsky, Fast-neutron transmission spectroscopy for illicit substance detection, Proc. SPIE, 2867 (1997) 239-242 in International Conference Neutrons in Research and Industry (ed. by George Vourvopoulos). 

The Practicality of Pulsed Fast Neutron Transmission Spectroscopy for Aviation Safety. Report by the National Materials Advisory Board of the Commission on Engineering and Technical Systems, National Research Council, National Academy Press, Washington DC (1999). 

Mel nichenko, Y. B. Klepko, V. V. Shilov, V. V., "Critical Phenomena in a Polymer-Solvent System Slow Neutron Transmission Technique," Polymer, 29, 1010 (1988). 

Recently, the ratios of the neutron total SCS of H and D, Q = au/a/, inferred from neutron transmission (NT) experiments on H20 / D20 mixtures were found to be in agreement with the tabulated value Qtab = 81.67/7.63 = 10.7 [Blostein 2003 (a)]. It was concluded that the strong Q reductions pre-... 

Additionally, a neutron transmission (NT) experiment on H20 / D20 mixtures was recently presented, reporting results in agreement with conventional theory and claiming to present a proof of the absence of the QE effect under consideration [Blostein 2003 (a)]. However, also this experiment does not provide the appropriate, and well defined, sub-femtosecond scattering time [Karlsson 2004], Moreover, it was discussed by Karlsson and Mayers that the neutron coherence length in this NT experiment is much shorter than that in NCS (being about 2.5 A, cf. [Karlsson 2003 (b)]). Thus there are no reasons whatsoever to expect deviations from the conventional, individual particle cross sections [Karlsson 2004],... 

After monodispersity tests, the most important physical assay is that of the sample and buffer transmission measurement. These are required for accurate sample-buffer subtractions (below) and for and matchpoint determinations (Section 2.5). Since the neutron transmissions of HjO and H20 range from about... 

Neutron moisture gauges Neutron transmission and scatter methods can be used to measure total hydrogen content, and assumes a constant hydrocarbon hydrogen. 

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