Specific activity of [11C]CO2 generated in a N2 gas target: effect of irradiation dose, irradiation history, oxygen content and beam energy
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K. Suzuki
Pure and O2-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 CO2 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 CO2. The ratio of [11C]CO2 to total C-11 was always low in a pure N2 gas target and increased with higher irradiation dose, addition of oxygen gas and by changing some part of the irradiation system. The ratios of [11C]CO2 were 22.4±1.5%, 77.8±7.1% and 94.0±4.0% in a pure N2 gas, 9.8 ppm O2-mixed N2 gas and 2000 ppm O2-mixed N2 gas, respectively. The specific activity of [11C]CO2 increased by the addition of O2 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 O2-mixed N2 gas. The effect of proton energy on the CO2 generation was also examined by degrading the proton energy with different thick energy absorbers. The amount of CO2 generated in the target depended on the proton energy, i.e., larger amount of CO2 generated with higher proton energy. Surprisingly, some amount of CO2 (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.
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- Preface: Alfred P. Wolf Memorial Issue
- Im Memoriam Alfred P. Wolf
- The centenary of a controversial discovery: actinium
- Proton-induced nuclear reactions in neptunium-237 targets. Production of plutonium tracers in the energy range 15-40 MeV
- Possibility of production of 81Rb via the 80Kr(d,n) reaction at a small cyclotron
- Positron emission intensity in the decay of 120gI
- Production of high specific activity 27Mg by fast neutron irradiation and recoil-aided leaching
- Production of strontium-82 for the Cardiogen® PET generator: a project of the Department of Energy Virtual Isotope Center
- Lutetium-177-EDTMP for bone pain palliation. Preparation, biodistribution and pre-clinical studies
- Thermochromatographic separation of no-carrier-added 186Re or 188Re from tungsten targets relevant to nuclear medical applications
- Low energy cyclotron production and chemical separation of "no carrier added" iodine-124 from a reusable, enriched tellurium-124 dioxide/aluminum oxide solid solution target
- Physicochemical and radiochemical aspects of separation of radioiodine from TeO2-targets
- Novel separation of thallium-201 using p-tert-butylcalix[4]arene derivative
- Recovery of 201Tl by ion exchange chromatography from proton bombarded thallium cyclotron targets
- Doppler broadening as a probe of the chemical environment following oxygen-14 decay
- In-target chemistry during the production of 15O and 11C using 3He reactions
- 11C-methane production in small volume, high pressure gas targets
- 11C-methylations using 11C-methyl iodide and tetrabutylammonium fluoride
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- Effect of dissolved gas on the specific activity of N-13 labeled ions generated in water by the 16O(p,α)13N reaction
- Direct n.c.a. radioiodination of weakly activated arenes using metal salts
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- Determination of trace impurities in iron-based alloy using neutron activation analysis
- EXAFS analyses of technetium(I) carbonyl complexes – stability studies in solutions
- Syntheses and structures of technetium(V) and rhenium(V) oxo complexes of peptide having KYC-sequence
