In September, FRIB’s electron-beam diagnostics system measured the thickness of the liquid-lithium film in the charge stripper for the first time at MSU. An electron beam traverses the lithium film simultaneously with the heavy-ion beam. This allows a continuous and online thickness measurement.

Optimum film thickness efficiently removes electrons from the heavy-ion beams to further accelerate an FRIB beam. In addition, the system measures the stability of the film, which is important to keep the FRIB beam quality.

FRIB is the first accelerator to use liquid lithium as a charge stripper. During operation, a pump continuously circulates the liquid lithium to produce a film. The lithium charge stripper will play a critical role in the FRIB linear accelerator in order to achieve design-goal beam energies beyond 200 mega electron volt/nucleon (MeV/u) and beam power up to 400 kilowatts.