Characteristics of Laser Ablation Plasma in the Diverging Magnetic Field of a Solenoid

Abstract

Laser ablation plasma(LAP) can be used as an ion source for particle accelerators and for ion implantation. Although the too intensive current intensity of laser ion sources give them advantages over other ion sources, yet the minute duration of laser produced ion pulses limits their applications in accelerators. By introducing a solenoid into the plasma expansion region, the modulation of the plasma temporal structure had been achieved[ 1 - 3 ]. In order to study the effect of solenoid magnetic field on LAP, we used different laser energies (1~8 J) to produce LAP at different initial conditions and applied various magnetic field strengths to confine the plasma. The transverse distribution of the laser produced ions were measured with a movable faraday cup (FC) at the edge of the fringe field of the solenoid. The main parameters of the ion pulses, the total charge, the peak current, and the pulse duration, enhanced at first and then got saturated with the increasing magnetic field, no matter what the initial plasma conditions were. Unlike the nearly uniform transverse distribution of the plasma without magnetic confinement, the plasma got concentrated when the magnetic field was applied. The experimental results presented and discussed in the present work are of great significance for further understanding the characteristics of magnetically confined LAP.