Neutron Epithermal

Landsberger S, Swift G, and Neuhoff J (1990) Nondestructive determination of arsenic in urine by epithermal neutron activation analysis and Compton suppression. Biol Trace Elem Res 26-27 27-32. 

Wolff, S. R., Liddy, D. J., Newton, G. W. A., Robinson, Y. J., and Smith, R. J. (1986). Classical and Hellenistic black glaze ware in the Mediterranean - a study by epithermal neutron-activation analysis. Journal of Archaeological Science 13 245-259. 

Gladney and Perrin [11] used epithermal neutron activation analyses to determine down to 50ppm total bromine in soils. Excellent agreement with recommended values were obtained for a range of Canadian reference soils (Table 12.4). 

BNCT was restarted in the United States in September 1994 at Brookhaven National Laboratory and shortly thereafter at MIT using epithermal neutron beams (BNL trials ended in 1999 after the treatment of 53 patients but continued at MIT) these programs are supported by the Department of Energy. Forty patients were treated by the end of 1997. In Europe, the European Commission supports a BNCT program in Petten, The Netherlands. The three first patients were treated in 1997. The thermal neutron beam program continues in Japan. 

So far, the only available sources of epithermal neutrons, with sufficient output, are nuclear reactors. However, construction of compact proton accelerators, producing epithermal neutrons of adequate energy (e.g., 2.5-MeV protons on a lithium target), has been envisaged. 

Epithermal neutrons, or neutrons having energies just above those of thermal neutrons the epithermal neutrons energy range is between a few hundredths eV and about 100 eV. 

Intermediate neutrons, which are neutrons having energies in a range that extends roughly from 100 to 100,000 eV. This range is above that of epithermal neutrons and below that of fast neutrons. 

Gladney and Perrin [6] used epithermal neutron activation analysis to determine down to 50 ppb bromine in the US Geological Survey Reference Soils GXR-2, GXR-5 and GXR-6, and the Canadian Certified Reference Soils SO-1, SO-2, SG-3 and SO-4. The values reported in Table 6.1 indicate that good agreement was obtained between neutron activation analysis results and recommended values. The relative standard deviation was on the order of 10% over the concentration range 1-15 ppm bromine ... 

Epithermal neutrons 0.5-104 Very good discrimination of materials... 

Carboranes in Boron Neutron Capture Therapy of Cancer (B7YC2). The stable isotope of boron, B (19.8% natural abundance), is very effective as a neutron capture agent with the effective nuclear cross section of 3837 bams, while the "B nucleus is incapable of undergoing a BNC reaction. Therefore, the B-emiched carborane and borane-substituted biomolecules and dmgs are selectively dehvered to the cancer cells in the human body and then the tumor-localized B nucleii are bombarded with either thermal or epithermal neutrons that results in a fission reaction producing the high energy alpha (a) particles as shown in equation (2). 

Holzbecher J, Ryan DE. 1980. Determination of uranium by thermal- and epithermal-neutron activation in natural waters and in human urine. Anal Chim Acta 119 405-408. 

Landsberger S, Wu D. 1993. Improvement of analytical sensitivities for the determination of antimony, arsenic, cadmium, indium, iodine, molybdenum, silicon and uranium in airborne particulate matter by epithermal neutron activation analysis. J Radioanalytical Nuclear Chemistry 167(2) 291-225. 

Proportional counters filled with BFs or He are used for integral measurement of thermal and epithermal neutrons. Fluxes and spectra of neutrons of intermediate or high energy can be measured with proportional counters filled with He or Hi. Instead of Hi, solid hydrogen-containing compounds such as polyethylene can be used. 

Instead of direct counting, neutron fluxes can also be determined by activation methods. Activation by (n, y) reactions (chapter 8) and subsequent measurement of the induced activity is a widely used technique. Au, In and Co are frequently applied as flux monitors. The presence of epithermal neutrons makes corrections necessary. Epithermal neutrons may be measured independently by wrapping the flux monitors in Cd or Gd which absorb the thermal neutrons. Fluxes of high-energy (fast) neu-... 

In general, activation analysis relies on the use of standards that are irradiated under the same conditions and in the same position, and are also measured under the same conditions. Monoelement standards contain a known amount of one element. If they are applied to the evaluation of other elements the ratio of the cross sections o x/o s under the special conditions of irradiation and the ratio H /Hs of the relative abundances of the decay processes that are measured must be known (subscript x is for the sample and subscript s for the standard). Knowledge of the ratio o x/o s may cause problems, because the cross sections may vary drastically with the energy of the projectiles, for instance in the energy range of epithermal neutrons. These problems are not encountered with multielement standards that contain all the elements to be determined. However, the preparation of such multielement standards may be time-consuming. 

Gd, Gd, and Hf. The properties of B are favorable, and boron compounds have been tested clinically (for over 20 years in Japan) for the treatment of melanomas, bone marrow and malignant brain tumors (82). The isotope B undergoes fission on bombardment with thermal or epithermal neutrons, giving rise to a particles that are destructive to local tissue (within 10 p,m) ... 

At a spallation source a heavy-metal target, such as Pb, W, Ta or Hg, is bombarded with energetic particles, usually protons accelerated to energies of up to 1 GeV. Neutrons freshly released from an atomic nucleus have high energies, referred to as epithermal neutrons , and must be slowed down to be useful for powder diffraction experiments. This occurs by collisions between the neutrons and the moderator - such as liquid methane or water - placed in the path of the neutron beam, which cause the exchange of energy and a trend towards (partial) thermal equilibrium. 

A maximum specific activity of approximately 850 GBq/mg was achieved when irradiation was carried out at a thermal neutron flux of 1 x 10 n-cni -s for 21 d, which corresponds to around 21% of the maximum achievable specific activity. Tlie specific activity of the Lu obtained was significantly higher than the theoretically calculated value under the irradiation conditions employed (7.9 at.%), accounting for only thermal neutron capture. This could perhaps be attributed to the contribution from epithermal neutrons (resonance integral 1087 b), which is not accounted for in theoretical calculations. 

Thermal neutrons Epithermal neutrons Fast neutrons Photons... 

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