The neutralization efficiency of negative ion neutral beam injectors is a major issue for future fusion reactors. Photon neutralization might be a valid alternative to present gas neutralizers, but still with several challenges for a valid implementation. Some concepts have been presented so far but none has been validated yet. A novel photoneutralization concept is discussed here, based on an annular cavity and a duplicated frequency laser beam (recirculation injection by nonlinear gating). The choice of lithium triborate as the material for the second harmonic extractor is discussed and a possible cooling method via crystal slicing is presented; laser intensity enhancement within the cavity is evaluated in order to quantify the achievable neutralization rate. Mockups of the critical components are proposed as intermediate steps toward system realization.
All Science Journal Classification (ASJC) codes
Fassina, A., Pretato, F., Barbisan, M., Giudicotti, L., & Pasqualotto, R. (2016). A feasibility study of a NBI photoneutralizer based on nonlinear gating laser recirculation. Review of Scientific Instruments, 87(2), -. [02B318]. https://doi.org/10.1063/1.4935897