Proof-of-principle demonstration of high efficiency laser-assistedH−beam conversion to protons

Thin carbon foils are used as strippers for charge exchange injection into high intensity proton rings. However, the stripping foils become radioactive and produce uncontrolled beam loss, which is one of the main factors limiting beam power in high intensity proton rings. Recently, we presented a scheme for laser stripping an ${\mathrm{H}}^{\ensuremath{-}}$ beam for the Spallation Neutron Source (SNS) ring. First, ${\mathrm{H}}^{\ensuremath{-}}$ atoms are converted to ${\mathrm{H}}^{0}$ by a magnetic field, then ${\mathrm{H}}^{0}$ atoms are excited from the ground state to the upper levels by a laser, and the excited states are converted to protons by a magnetic field. In this paper we report on the proof-of-principle demonstration of this scheme to give high efficiency (around 90%) conversion of ${\mathrm{H}}^{\ensuremath{-}}$ beam into protons at SNS in Oak Ridge. The experimental setup is described, and comparison of the experimental data with simulations is presented.