• 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

• T. Tajima, W.B. Haynes, F.L. Krawczyk, M.A. Madrid, R.J. Roybal, E.I. Simakov
  LANL, Los Alamos, New Mexico
• W.A. Clemens, K. Macha, R. Manus, R.A. Rimmer, L. Turlington
  JLAB, Newport News, Virginia

An update on the study of 805 MHz elliptical SRF cavities that have been optimized for high gradient will be presented. An optimized cell shape, which is still appropriate for easy high pressure water rinsing, has been designed with the ratios of peak magnetic and electric fields to accelerating gradient being 3.75 mT/(MV/m) and 1.82, respectively. A total of 3 single-cell cavities have been fabricated and tested with various conditions. In addition, a 6-cell cavity design has been completed including multipacting simulations.