Method of Canceling Energy Fluctuations of a Van de Graaff Ion Beam

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Abstract
A varying correction voltage is applied to the target which cancels beam energy fluctuations. This correction voltage is a known, constant multiple of a small, variable voltage which must be applied to the outer plate of an electrostatic analyzer to keep the beam centered at the analyzer image slits. The beam current at the analyzer image slits provides the signal which, when amplified by an electronic device called the Homogenizer, drives both the outer analyzer plate and the target. The energy spread is reduced to 250±120 ev and is probably due only to the ion source. If the HH+ beam is put through the analyzer, the unlimited H+ beam also has an energy spread of 250 ev. The 1.76-Mev C13(p,γ) and 0.992-Mev Al27(p,γ) resonances were used to test performance. Our data are consistent with Γ(C13) = 75 ev and Γ(Al27) = 100 ev. The upper limit for the C13 width is 150 ev.