学術雑誌論文 Development of a laser ion source for production of high-intensity heavy-ion beams

柏木, 啓次  ,  山田, 圭介  ,  倉島, 俊

内容記述
A laser ion source has been developed as a high-intensity source for the ion implanter and the single pulsed beam of the azimuthally varying field cyclotron at TIARA. Highly charged beams of C^5+ and C^6+ ions and low-charged beams of heavy ions such as C, Al, Ti, Cu, Au, and Pt are required for the single pulse acceleration in the cyclotron and for the ion implanter, respectively. In the vacuum chamber of the ion source, a target holder on a three-dimensional linear-motion stage provides a fresh surface for each laser shot. A large-sized target with a maximum size of 300 mm 135 mm is mounted on the holder for long-term operation. The ion current (ion charge flux) in the laser-produced plasma is measured by a Faraday cup and time-of-flight spectra of each charge state are measured using a 90° cylindrical electrostatic analyzer just behind the Faraday cup. Carbon-plasma-generation experiments indicate that the source produces intense high- and low-charged pulsed ion beams. At a laser energy of 483 mJ (2.3×10^13 W/cm2), average C^6+ current of 13 mA and average C^5+ current of 23 mA were obtained over the required time duration for single-pulse acceleration in the cyclotron (49 ns for C^6+ and 80 ns for C^5+). Furthermore, at 45 mJ (2.1×10^12 W/cm2), an average C^2+ current of 1.6 mA over 0.88 μs is obtained.

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