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With the prototype ECR ion source for the next carbon therapy facility in Japan a new series of measurements has been performed in order(a)to find the highest beam currents of C~(4+) ions,and(b)to study the effect of“special”gas-mixing by using a chemical compound as a feed gas.An isotopic effect has been found in a previous experiment:with deuterated methane(CD_4 gas) the C~(5+) beam currents are about 10% higher than with regular methane(CH_4 gas).For butane gases(C_4D_(10) and C_4H_(10) respectively)the isotopic effect for C~(5+) production is even stronger(>15%).For production of C~(4+) ions the isotopic effect appears to be absent.It turns out that the relative amount of carbon is much more important:acetylene gives 15% higher C~(4+) current than butane,which in turn gives about 10% higher C~(4+) ion currents than methane.
With the prototype ECR ion source for the next carbon therapy facility in Japan a new series of measurements has been performed in order (a) to find the highest beam currents of C ~ (4+) ions, and (b) to study the effect of “special ” gas-mixing by using a chemical compound as a feed gas. An isotopic effect has been found in a previous experiment: with deuterated methane (CD_4 gas) the C ~ (5+) beam currents are about 10% For production of C ~ (5+) production is even stronger (> 15%). For the production of C ~ (4+) ions the isotopic effect appears to be absent. It turns out that the relative amount of carbon is much more important: acetylene gives 15% higher C ~ (4+) current than butane, which in turn gives about 10% higher C ~ (4 +) ion currents than methane.