Status of the proof-of-principle demonstration of 400 MeV H^- laser stripping at J-PARC

A proof-of-principle (POP) demonstration of 400 MeV H⁻ stripping to proton by using only lasers is under preparation at J-PARC. The motivation of the present research is to replace the stripper to laser to overcome realistic issues and practical limitations associated with stripper foil used for H⁻ charge-exchange injection (CEI) in proton accelerators. The present method comprises three steps for an H⁻ stripping by using lasers. The H⁻ is first neutralized to H⁰ by using an YAG laser, the H⁰ is excited to the upper states (called H^0∗) by using a UV laser, and finally the H^0∗ is stripper to proton by the YAG laser. A prototype of the YAG laser and the laser cavity systems to reduce the seed laser pulse energy while keeping a higher stripping efficiency have been developed and will be tested for 3 MeV H⁻ neutralization at J-PARC test facility at the end of 2020. The UV laser needed for H⁰ excitation will be developed by higher harmonic generation from the YAG laser. The effective manipulation of the H⁻ beam, which also plays an important role to reduce the laser energy has also being extensively carried out. The present experimental status of the POP demonstration is presented. (author)