@misc{oai:repo.qst.go.jp:00069880,
 author = {Kitagawa, Atsushi and 北川 敦志},
 month = {Oct},
 note = {For almost components of the facility, it's not so different that the accelerated beam is carbon or not.  However, for ion sources, the production of carbon ions is harder effort than other ion species.  An ECR ion source has been developed and utilized to produce carbon ions for the clinical treatment, because its lifetime is longer than other types of ion sources. The performance of the ECR ion source is degraded due to carbon deposition on 1) an electric insulator, 2) the waveguide, 3) the plasma-chamber wall, and most of the other parts. The deposition on 3) is normally unavoidable.  The record intensity has reached 430 microAe for C4+ under good conditions, just after a cleaning; however, the beam intensity decreases to about 300 microAe caused by rapid carbon deposition after several days.  As a result, although the intensity was slightly decreasing, the source was able to produce about 240 microAe, even 4 years after without maintenance. The wall condition varied according to the contaminated ion species or the operation for different ion species before.  Since the variation often causes instability or poor reproducibility, it's better to keep two ion sources in order to frequently supply different ion species, especially., 第４８回Perticle Therapy Co-Operative Group},
 title = {Multiple charged carbon-ion production for the heavy ion therapy},
 year = {2009}
}