• D.C. Nguyen, H.L. Andrews, F.L. Krawczyk, N.A. Moody
  LANL, Los Alamos, New Mexico
• J.W. Lewellen, S.P. Niles, B. Rusnak
  NPS, Monterey, California

Modern electron injectors consist of an RF structure with a photocathode integrated into the first full-wave half-cell or quarter-wave full-cell. While the cathode gradients in pulsed, normal-conducting RF injectors exceed 100 MV/m, which lead to substantial dark currents, those of cw normal-conducting and superconducting RF injectors are typically 10-20 MV/m. Emittance compensation has been modeled for both NCRF and SRF injectors to generate nC electron bunches with normalized rms emittance of ~2 mm-mrad. The use of solenoid and RF focusing in combination with relatively low cathode gradients can mitigate the space-charge-induced radial expansion in nC bunches, resulting in low emittance and also low dark currents.

[1] D.C. Nguyen et al. "Overview of the 100mA average-current RF photoinjector" NIMA 528, 71
[2] A. Arnold et al. "Development of a superconducting RF photoelectron injector" NIMA 577, 440