title: Drift distance survey in direct plasma injection scheme for high current beam production.
abstract: In a laser ion source, plasma drift distance is one of the most important design parameters. Ion current density and beam pulse width are defined by plasma drift distance between a laser target and beam extraction position. In direct plasma injection scheme, which uses a laser ion source and a radio frequency quadrupole linac, we can apply relatively higher electric field at beam extraction due to the unique shape of a positively biased electrode. However, when we aim at very high current acceleration such as several tens of milliamperes, we observed mismatched beam extraction conditions. We tested three different ion current at ion extraction region by changing plasma drift distance to study better extraction condition. In this experiment, C(6+) beam was accelerated. We confirmed that matching condition can be improved by controlling plasma drift distance.
authors.affiliation: Department of Applied Quantum Physics and Nuclear Engineering, Kyushu University, Fukuoka 819-0395, Japan. kanesue@kune2a.nucl.kyushu-u.ac.jp
authors.forename: T
authors.initials: T
authors.lastname: Kanesue
authors.forename: M
authors.initials: M
authors.lastname: Okamura
authors.forename: K
authors.initials: K
authors.lastname: Kondo
authors.forename: J
authors.initials: J
authors.lastname: Tamura
authors.forename: H
authors.initials: H
authors.lastname: Kashiwagi
authors.forename: Z
authors.initials: Z
authors.lastname: Zhang