English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Plus annual

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Tools annual

Global: Zendy Free Plan

Global: Zendy Tools monthly

Global: Zendy Plus monthly

Pure and O 2 -mixed nitrogen gases were irradiated by 18 MeV protons (14.2 MeV on target) and analyzed directly by a specially designed radio-GC system with a FID coupled to a methanyzer. Non-radioactive carbon, especially CO 2  was observed to be generated in the target chamber by irradiation and to decrease gradually with repeated irradiation. The amount of carbon was increased by the use of new materials for the front foil, transport line, and so on. Higher irradiation dose also increased the carrier carbon, where beam current affected carbon generation more strongly than irradiation time. The addition of oxygen gas to nitrogen gas also increased the amount of carrier carbon, nearly all of which was observed to be generated in the chemical form of CO 2 . The ratio of [ 11 C]CO 2  to total C-11 was always low in a pure N 2  gas target and increased with higher irradiation dose, addition of oxygen gas and by changing some part of the irradiation system. The ratios of [ 11 C]CO 2  were 22.4±1.5%, 77.8±7.1% and 94.0±4.0% in a pure N 2  gas, 9.8 ppm O 2 -mixed N 2  gas and 2000 ppm O 2 -mixed N 2  gas, respectively. The specific activity of [ 11 C]CO 2  increased by the addition of O 2  gas, but the effect of irradiation dose was not clear. Maximal specific activity of 610±150 GBq/μmol was obtained at the irradiation condition of 15 μA and 20 minutes in a 2000 ppm O 2 -mixed N 2  gas. The effect of proton energy on the CO 2  generation was also examined by degrading the proton energy with different thick energy absorbers. The amount of CO 2  generated in the target depended on the proton energy, i.e., larger amount of CO 2  generated with higher proton energy. Surprisingly, some amount of CO 2  (1.5±0.3 nmol) was still observed in the target, even in the condition that all the protons stopped in the front foil and did not irradiate the target gas.

Specific activity of [ 11 C]CO 2 generated in a N 2 gas target: effect of irradiation dose, irradiation history, oxygen content and beam energy