Abstract:
Background Space charge effects pose a significant challenge in high-current ion beam transport, particularly in low-energy beam transport (LEBT) systems where beam intensity is high and energy is relatively low. Active injection of gas has been proposed as an effective method to mitigate these effects. However, for negative hydrogen ion beams, the physical mechanisms involved are highly complex due to competing processes such as ionization, electron stripping, etc.
Purpose This study aims to investigate the interaction mechanisms between negative hydrogen ion beams and gas within an LEBT system, and to evaluate the influence of gas species and pressure on beam parameters including emittance and beam current.
Methods Numerical simulations based on the particle-in-cell (PIC) method were conducted using the Warp code, incorporating physical processes including ionization, electron stripping, and elastic scattering. A three-dimensional simulation model was established to analyze space charge compensation effects under nitrogen and argon gas environments. Experimental measurements of beam current and emittance were simultaneously carried out at the XiPAF accelerator facility to validate simulation results.
Results Both simulations and experiments revealed that the effects of gas scattering and electron stripping cannot be neglected in space charge compensation of negative hydrogen ion beams.
Conclusions This research highlights the complexity of space charge compensation in negative hydrogen ion beams and emphasizes the need to consider multiple physical interactions in the design and operation of high-current LEBT systems. The findings provide practical insights for optimizing gas compensation parameters in similar accelerator facilities.
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