Recoil-energy measurements of slow highly-charged ions produced by synchrotron radiation and by swift-ion impact

A novel time-of-flight technique was used to measure average energies of ions produced by inner-shell photoionization of inert-gas atoms with synchrotron radiation in order to investigate the feasibility of developing a Very Cold ion Source (VCIS). Multiply-charged Ne, Ar, Kr, and Xe ions were produced in vacancy cascades following inner-shell photoionization by x rays from a wiggler line at Stanford Synchrotron Raaiation Laboratory, and the resulting charge-state distributions and average kinetic energies were measured using a time-of-flight spectrometer. Ion energies were found to correspond essentially to room temperature, and observed ion intensities show promise for future use in very-low-energy atomic collisions and precision spectroscopy studies.

Recoil energies were similarly measured for Ne and Ar ions produced by swift-ion impact using the EN Tandem accelerator at Oak Ridge National Laboratory. Average energies for the higher charge states were found to be up to 2 orders of magnitude larger than for those produced by photoionization. Impact parameters important in the collision processes were inferred from measured recoil energies using a screened-Coulomb scattering model. Knowledge of recoil-ion energies may be useful for the future development of parasitic low-energy ion sources on heavy-ion accelerators.