Optimizing Beam Transport in Rapidly Compressing Beams on the Neutralized Drift Compression Experiment - II

摘要

The Neutralized Drift Compression Experiment-II (NDCX-II) is an inductionlinac that generates intense pulses of 1.2 MeV helium ions for heating matterto extreme conditions. Here, we present recent results on optimizing beamtransport. The NDCX-II beamline includes a 1-meter-long drift sectiondownstream of the last transport solenoid, which is filled withcharge-neutralizing plasma that enables rapid longitudinal compression of anintense ion beam against space-charge forces. The transport section on NDCX-IIconsists of 28 solenoids. Finding optimal field settings for a group ofsolenoids requires knowledge of the envelope parameters of the beam. Imagingthe beam on scintillator gives the radius of the beam, but the envelope angledr/dz is not measured directly. We demonstrate how the parameters of the beamenvelope (r, dr/dz, and emittance) can be reconstructed from a series of imagestaken at varying B-field strengths of a solenoid upstream of the scintillator.We use this technique to evaluate emittance at several points in the NDCX-IIbeamline and for optimizing the trajectory of the beam at the entry of theplasma-filled drift section.