Electron cloud measurements in heavy-ion driver for HEDP and inertial fusion energy

Abstract

The High Current Experiment (HCX) at LBNL is a driver scale single beam injector that provides a 1 MeV K+ ion beam current of 0.18 A for 5 µs. It transports high-current beams with large fill factor (ratio of the maximum beam envelope radius to the beam pipe radius) and low emittance growth that are required to keep the cost of the power plant competitive and to satisfy the target requirements of focusing ion beams to high-power density. Beam interaction with the background gas and walls desorbs electrons that can multiply and accumulate, creating an electron cloud. This ubiquitous effect grows at higher fill factors and degrades the quality of the beam. We review simulations and diagnostics tools used to measure electron production, accumulation and its properties.