TRIAC Progress Report - KEK

ut differs from the electron-loss pattern, could be due to the direct injection of 1 + ions
for charge breeding; the injected ions may be preferentially stopped and captured on the
extraction side as a result of ion-plasma collisions
Additionally, a strong azimuthal asymmetric component localized near the central
region and a symmetric component localized on the extraction side, were observed in
the wall-loss distribution of the metallic 111 In ions. They account for 13.5 and 38.5 % of
the total side-wall loss of 111 In, respectively. They were not observed for xenon.
Therefore, the presence of such components in the wall-loss pattern of indium could be
why non-volatile metallic elements have lower charge breeding efficiency than gaseous
elements. We suggested that the charge breeding efficiencies for metallic ions at the
KEKCB could be improved by further optimization of the injection conditions for
charge breeding. However, it is not straightforward to further optimize our present
injection system than we have already performed for charge breeding non-volatile
metallic ions. Actually, the injection conditions can be varied by the parameters related
to the conditions of ECR plasma, which are not usually controllable in injection.
Therefore, more experimental works are required in order to identify the origin of the
loss patterns of metallic ions during the injection for charge breeding. Detailed
theoretical simulations are also highly desirable for gaining better understanding of the
present observations.
2-3-4. Beam impurities from KEKCB
The ECR plasma inherently produces a variety of ions from residual gases, the
plasma chamber, and other sources. Such ions are considered as impurities for the beam
of interest. To evaluate the impurity quantitatively, we accelerated background ions up
to 178 keV / nucleon by using the post-accelerator at the TRIAC [2-8]. As an example,
the background ions of A/q = 7.68 were selected by using an analyzing magnet and slits
with a full width of 10 mm along the horizontal direction (covering both sides of the
central trajectory) located at exit of the magnet. The magnet had a resolving power of
about 100 when the slits were open to 2-mm width. It is possible to identify the mass
number of impurity ions by measuring the total energy of the beams, since the
acceleration of the impurities has the same energy per nucleon. In the first trial, we
observed various heavy elements with an intensity of 10 7 ~ 10 8 pps. After this test, all
the materials exposed to the ECR plasma were converted to aluminum, since some of
them were made of stainless steal and chromium. Before installation, we ground their
surface using a sand blaster and high-pressure purified water, and cleaned them by
ultrasonic cleaning in order to remove any elements that had attached to their surfaces in
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