Yield of the Fricke dosimeter irradiated with the recoil [alpha] and Li ions of the [.sup.10]B[(n,[alpha]).sup.7]Li nuclear reaction: effects of multiple ionization and temperature.

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From: Canadian Journal of Chemistry(Vol. 99, Issue 4)
Publisher: NRC Research Press
Document Type: Report; Author abstract
Length: 8,269 words
Lexile Measure: 1980L

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Abstract :

Monte Carlo track chemistry simulations were used to investigate the effects of multiple ionization (MI) of water on the yields (G values) of the ferrous sulfate (Fricke) dosimeter, which was irradiated with low-energy [alpha] and lithium ion recoils from the [.sup.10]B[(n,[alpha]).sup.7]Li nuclear reaction as a function of temperature from 25 to 350 [degrees]C. Calculations were performed individually for 1.47 MeV a-particles and 0.84 MeV lithium nuclei with dose-average linear energy transfer (LET) values of ~196 and 225 keV/[micro]m at 25 [degrees]C, respectively. The total yields were obtained by summing the G values for each recoil [alpha] and Li ion weighted with its fraction of the total energy absorbed. At room temperature, our G([Fe.sup.3+]) values calculated under aerated and deaerated conditions only agreed well with the experimental results, provided the MI of water was incorporated in the simulations. This strongly supports the importance of the role of MI of water in the high-LET radiolysis of water. We also simulated the effects of MI of water on G-values for the primary species of the radiolysis of deaerated 0.4 M H2SO4 aqueous solutions by [.sup.10]B[(n,[alpha]).sup.7]Li recoils. As with the Fricke dosimeter, the best agreement between experiment and simulation was found at 25 [degrees]C when the MI of water was included in the simulations. It was also shown that G([Fe.sup.3+]) decreases slightly as a function of temperature over the range of 25-350 [degrees]C. However, at elevated temperatures, no experimental data were available with which to compare our results. Key words: liquid water, aqueous ferrous sulfate (Fricke) dosimeter, [.sup.10]B[(n,[alpha]).sup.7]Li nuclear reaction, [alpha] and Li ion recoils, radiolysis, linear energy transfer (LET), multiple ionization, temperature, Monte Carlo track chemistry simulations. Nous avons utilise des simulations Monte Carlo de la trajectoire des particules pour etudier les effets de l'ionisation multiple (IM) de l'eau sur les rendements (valeurs G) du dosimetre (de Fricke) a sulfate ferreux soumis a l'irradiation par des particules a de faible energie et des ions lithium de recul issus de la reaction nucleaire du [.sup.10]B[(n,[alpha]).sup.7]Li en fonction de la temperature (25 a 350 [degrees]C). Nous avons effectue des calculs distincts pour des particules [alpha] de 1,47 MeV et des noyaux de lithium de 0,84 MeV, les valeurs de transfert d' energie lineaire (TEL), dose ponderee, etant de ~196 et de 225 keV/[micro]m a 25 [degrees]C, respectivement. Nous avons obtenu les rendements totaux en additionnant les valeurs G pour les particules [alpha] et ions Li de recul, chacune ponderee selon la fraction correspondante de l' energie totale absorbee. A temperature ambiante, nos valeurs G([Fe.sup.3+]) calculees dans des conditions aerees et degazees ne concordaient bien avec les resultats experimentaux que si l'ionisation multiple de l'eau etait integree aux simulations. Ces resultats illustrent bien l'importance du role de l ' IM de l'eau dans la radiolyse de l'eau a TEL eleve. Nous avons egalement simule les effets de l ' IM de l'eau sur les valeurs G des especes primaires dans la radiolyse de solutions aqueuses degazees de H2SO4 (0,4 M) par les particules de [.sup.10]B[(n,[alpha]).sup.7]Li de recul. Comme avec le dosimetre de Fricke, la meilleure concordance entre les resultats experimentaux et theoriques a ete observee a 25 [degrees]C lorsque l ' IM de l'eau etait integree aux simulations. Nous avons egalement montre que la valeur G([Fe.sup.3+]) diminue legerement en fonction de la temperature dans l'intervalle de 25 a 350 [degrees]C. Toutefois, a des temperatures elevees, nous ne disposions d'aucune donnee experimentale pour comparer nos resultats. [Traduit par la Redaction] Mots-cles: eau liquide, dosimetre (de Fricke) a sulfate ferreux aqueux, reaction nucleaire du [.sup.10]B[(n,[alpha]).sup.7]Li, particules [alpha] et ions Li de recul, radiolyse, transfert d' energie lineaire (TEL), ionisation multiple, temperature, simulations Monte Carlo de la trajectoire des particules.

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Gale Document Number: GALE|A659017811