Experiences of operating CELSIUS with a hydrogen pellet target

The CELSIUS ring is equipped with a pellet target used as an internal target for experiments at the WASA-facility. The pellet target generates a stream of frozen hydrogen pellets, the size of which is now reduced to 25–30 μm. We discuss the interaction between the pellet target and the stored beam under the influence of RF and electron cooling in terms of measurements and computer simulations. Energy loss measurements using Schottky spectra were performed to measure the effective pellet target thickness. We present Monte Carlo tracking simulations including the beam–target interaction as well as RF and electron cooling. The general behaviour is reproduced but the simulations overestimate the beam lifetime compared to observations.