In the low-energy region of a high-intensity ion linac, a strong space-charge field causes a rapid beam emittance growth over a short distance of only a few meters. The beam emittance growth leads to beam loss and machine activation, raising a serious issue for regular maintenance of the accelerator component and beam power ramp-up. We studied the mechanism of beam emittance growth due to the space-charge field based on three-dimensional particle-tracking simulation and theoretical considerations. Numerical simulations of the high-intensity H− (negative hydrogen) linac at the Japan Proton Accelerator Research Complex shows that the nonlinear terms in the space-charge field directly cause beam emittance growth and beam halo formation. We also propose a method to mitigate the beam emittance growth by using an octupole magnetic field, which arises as one of the nonlinear terms in the space-charge field. By applying this method in the simulation we have succeeded in mitigating the beam emittance growth.
No takes yet. Share an insight, caveat, or question.
Chimura et al. (2022) studied this question.