@article{oai:repo.qst.go.jp:00081445,
 author = {安積, 隆夫 and 西森, 信行 and 稲垣, 隆宏 and 大竹, 雄次 and 田中, 均 and Asaka, Takao and Nishimori, Nobuyuki and Tanaka, Hitoshi},
 issue = {1},
 journal = {Japanese Journal of Applied Physics},
 month = {Dec},
 note = {A transparent-grid scheme is proposed for generating cathode-emittance-dominated beams in a gridded thermionic gun. In the proposed scheme, the grid emittance arising from the potential difference between the grid and grid-mesh center is suppressed by tuning the grid voltage to the gridless gun potential. We developed a 50 kV gridded thermionic gun that is followed by a 238 MHz cavity for 500 kV acceleration. The measured projected emittance as a function of grid voltage shows a clear minimum approaching the cathode emittance and agrees well with a numerical simulation and a theoretical grid emittance taking into account the longitudinal space-charge effect. The measured minimum emittance for a core part which represents 60% of a 1-nC electron bunch is 1.5 μm centerdot rad making the transparent-gridded thermionic gun a promising electron source for high brightness beam application such as a soft X-ray free-electron laser.},
 pages = {017001--017006},
 title = {Transparent-grid scheme for generating cathode-emittance-dominated beams in a gridded thermionic gun},
 volume = {60},
 year = {2020}
}