A Fast Faraday Cup for Measuring Neutralized Drift Compression*

Heavy ion drivers for high energy density physics applications and inertial fusion energy use space-charge-dominated beams which require longitudinal bunch compression in order to achieve sufficiently high beam intensity at the target. The Neutralized Drift Compression Experiment-1A (NDCX-1A) at Lawrence Berkeley National Laboratory is used to determine the physics limits for neutralized drift compression. NDCX-1A investigates the physics of longitudinal focusing of an intense ion beam, achieved by imposing an initial velocity tilt on the drifting beam and neutralizing the beam's space-charge with background plasma. Accurately measuring the longitudinal compression of the beam pulse with high resolution is critical for NDCX-1A. The design and preliminary experimental results for a fast Faraday cup which measures the total beam current at the focal plane as a function of time are summarized.