Pulse length extension of highly charged ion beam generated from a laser ion source is experimentally demonstrated. The laser ion source (LIS) has been recognized as one of the most powerful heavy ion source. However, it was difficult to provide long pulse beams. By applying a solenoid field (90 mT, 1 m) at plasma drifting section, a pulse length of carbon ion beam reached 3.2 ls which was 4.4 times longer than the width from a conventional LIS. The particle number of carbon ions accelerated by a radio frequency quadrupole linear accelerator was 1.2 Â 10 11 , which was provided by a single 1 J Nd-YAG laser shot. A laser ion source with solenoid field could be used in a next generation heavy ion accelerator. V C 2014 AIP Publishing LLC. [http://dx.A performance of a particle accelerator strongly depends on its ion source. An intense particle source may encourage an accelerator concept to become a next generation accelerator project. Especially for heavy ion accelerators, it has been difficult to provide intense beams with highly charged states. Although there are many operating proton sources with more than a few tens of milliampere in the world, 1,2 there was no project assuming the same amount of current with highly charged heavy ion beam.Currently, electron cyclotron resonance ion source (ECRIS) is the most established ion source and commonly used in major accelerator laboratories. Electron beam ion source (EBIS) is also used to provide highly charged heavy ion beam. Both ion sources typically provide hundreds of microamperes to milliampere range of heavy ions with more than charge state ten. [3][4][5][6][7] On the other hand, laser ion source (LIS) can provide highly charged ion beam with a beam current of more than hundreds of milliampere. However, it has never been adopted by major stream of the accelerator's history since it was proposed in 1969 (Refs. 8 and 9) because of mainly three problems: beam transportation, stability, and short beam pulse.A LIS uses a pulsed high power laser focused onto a solid state target. The laser is absorbed in the target, and target temperature goes up above transition temperature from solid to vapor and plasma in the range of 10 12 W/cm 2 of laser power density. Electrons in the plasma are thermalized by absorbing laser photons by inverse Bremsstrahlung process, and ionization proceeds. Initial plasma density produced by laser ablation is much higher than that of ECRIS and EBIS. At the same time as plasma production, the laser-produced plasma expands to perpendicular to the target surface. 10 Also, plasma adiabatically expands to both transverse and longitudinal direction. This expansion makes ion beam pulse from nanosecond-to microsecond-range. Current density and pulse width of the plasma follow the relationships below during expansion T / L;(1) q / L À3 ;( 2) where, T, q, and L are pulse width, ion current density at an ion extraction point, and plasma drift distance which is the length between the target and the ion extraction point, respectively. In case short pulse wid...

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