A Laser Power-Build-Up System for H Atom Ionization

Hydrogen negative ions must be ionized with high efficiency for injection into proton accelerators, such as those used at DOE facilities. To achieve this ionization, neutral atoms are first prepared by laser excitation in a relatively low-strength magnetic field, which requires megawatt peak powers. However, the carbon foil strippers that are currently-used for this purpose become radioactive and produce uncontrolled beam loss, which limits the performance of high intensity proton sources. This project will investigate a Fabry-Perot power-recycling cavity that is capable of storing energy (stacking laser pulses) when resonant with the incident laser light. With this approach, the incident laser power will be multiplied, thereby creating fields that are sufficiently intense (MW peak powers) to excite the hydrogen atoms with high probability. Commercial Applications and other Benefits as described by the awardee Proton sources are widely used in many accelerators; hence the cavity developed in this project could find use in similar facilities (Japan Atomic Energy Research Institute, European Spallation Source). Power buildup cavities for short pulse lasers also should be applicable to wideband molecular cavity ring down spectroscopy.