Ion probe for beam position and profile measurement

We describe a non-perturbing diagnostic to measure the position and profile of tightly bunched (μm-sized) beams. The probe consists of a finely-focused low-energy (approx-lt 30 keV) ion beam that is injected across the path of the beam to be measured. The deflections of the ions are measured with a gated microchannel plate (MCP) detector and recorded with a video camera and frame grabber. By appropriately selecting the ion species and energy, the probe can be used with beams having a wide range of charge density. We will describe two operating regimes. The first holds for very short duration bunches, with the deflection scaling simply as the bunch charge divided by the bunch radius. More generally, the deflection depends on bunch length and must be solved numerically. We are now building a probe, using a specially-designed ion gun, that will be tested at SLAC. We will present the theory of operation of the device, discuss various possible configurations, and describe the components we are incorporating in the initial version of the probe. copyright 1995 American Institute of Physics