High intensity metal ion beam production with ECR ion sources Page: 4 of 15
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III. HIGH INTENSITY BISMUTH AND ION BEAM EMITTANCE
For the next generation Radioactive Isotope Accelerator (RIA) up to 10 p A of uranium 30+
will be needed for the heavy ion driver linac . To predict the expected ion beam emittance for
heavy ion beams extracted from an ECR ion source for injection into the RIA RFQ , 209Bi
emittance measurements were performed with the AECR-U. The emittance has been measured
over a range of charge states from 21' to 41'after the AECR-U was optimized on 209Bi27 to
produce about 1p A. Figure 2a shows the charge state distribution peaked at 27+ (30 epA or 1.1
ppA). Figure 2b shows the dependence of the normalized xx' emittance values on the Bi charge
state for an unchanged ion source tune. From Fig. 2 it is evident, that at these ion beam intensities
the normalized emittance is predominantly dependent on the charge state and not on the current.
For instance the ion beam emittance of 18.8 e A of Bi21+ was measured to be 0.07 n-mm-mrad,
while the emittance of 18e A of Bi32+ was 0.03 Tr-mm-mrad. This is consistent with the model that
high charge state ions are extracted closer to the axis of the ECR ion source plasma [8, 9]
IV. AXIAL OVENS
Two off-axis axial ovens have been developed at the 88-Inch Cyclotron. There are two main
motivations for this new oven developments. For the superconducting ECR ion source VENUS,
which is now under construction at LBNL , the use of radial ovens is no longer possible,
because the magnetic structure is closed radially.
Secondly, for the production of superheavy elements intense metal ion beams of rare isotopes like
4Ca, 365, or 8Rb are required. Since those isotopes are very expensive a minimal consumption is
desired. As shown by the Dubna group , a hot liner covering the plasma chamber walls can be
very effective in increasing the overall ion source efficiency. For this purpose an axial oven is
much better suited than a radial one.
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Wutte, Daniela; Abbott, S.; Leitner, Matthaeus A. & Lyneis, Claude M. High intensity metal ion beam production with ECR ion sources, article, September 3, 2001; California. (https://digital.library.unt.edu/ark:/67531/metadc740271/m1/4/: accessed April 19, 2019), University of North Texas Libraries, Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.