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Titolo:
Mechanism of nitrogen-13-labeled ammonia formation in a cryogenic water target
Autore:
Firouzbakht, ML; Schlyer, DJ; Wolf, AP; Fowler, JS;
Indirizzi:
Brookhaven Natl Lab, Dept Chem, Upton, NY 11973 USA Brookhaven Natl Lab Upton NY USA 11973 ab, Dept Chem, Upton, NY 11973 USA
Titolo Testata:
NUCLEAR MEDICINE AND BIOLOGY
fascicolo: 4, volume: 26, anno: 1999,
pagine: 437 - 441
SICI:
0969-8051(199905)26:4<437:MONAFI>2.0.ZU;2-4
Fonte:
ISI
Lingua:
ENG
Soggetto:
RECOIL N-13 ATOMS; PROTON IRRADIATION; F-18 FLUORIDE; ACCELERATORS;
Keywords:
N-13 ammonia; positron-emitting isotopes; cryogenic targets;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Life Sciences
Citazioni:
29
Recensione:
Indirizzi per estratti:
Indirizzo: Schlyer, DJ Brookhaven Natl Lab, Dept Chem, Upton, NY 11973 USA BrookhavenNatl Lab Upton NY USA 11973 m, Upton, NY 11973 USA
Citazione:
M.L. Firouzbakht et al., "Mechanism of nitrogen-13-labeled ammonia formation in a cryogenic water target", NUCL MED BI, 26(4), 1999, pp. 437-441

Abstract

Methods for producing N-13 ammonia via the O-16(p,alpha)N-13 nuclear reaction utilizing a cryogenic target have been investigated. These targets included frozen carbon dioxide and pure frozen water. Results from these targets were compared with the more traditional liquid water target with and without additives. A very dramatic difference was found between the pure water target in the frozen state when compared with the liquid state. When frozen, more than 95% of the nitrogen-13 activity is in the chemical form of ammonia at all radiation doses. In contrast, the liquid water target yielded predominately nitrates and nitrites at high radiation doses. When frozen carbon dioxide was irradiated under these conditions, more than 95% of the nitrogen-13 activity was in the form of nitrate and nitrite. The nitrogen oxides remained on the surface of the target and could be easily removed from the surface with pure water. The wash solution was converted to [N-13]ammoniausing the DeVarda's alloy method for reduction. It was determined that levels of [N-13]ammonia sufficient for diagnostic medical procedures could be produced directly using the frozen water targets or from frozen carbon dioxide with a wet chemical reduction. These results have significance particularly in the design of targetry for low-energy, high-beam current accelerators, because targets of this design can be used with either no vacuum isolation window or a very thin window. The substitution of carbon-13-enriched carbon dioxide for natural carbon dioxide gives access to the C-13(p,n)N-13 nuclear reaction, which allows protons energies as low as 6 MeV to be used to produce useable quantities of N-13 ammonia. The mechanism of these reactions has been explored to determine why there are such dramatic differences in the product distribution between the frozen state and the liquid or gaseous state. NUCL MED BIOL 26;4:437-441, 1999. (C) 1999 Elsevier Science Inc. All rights reserved.

ASDD Area Sistemi Dipartimentali e Documentali, Università di Bologna, Catalogo delle riviste ed altri periodici
Documento generato il 25/01/20 alle ore 18:29:54