Ultrashort electron bunches with low longitudinal emittance in multi-cell superconducting RF guns

Ultra short bunches with low longitudinal emittance obtained using multi-cell superconducting RF gun having a longitudinally shorted first cell (down to 0.15 lambda) with a divergence of an accelerating RF field pattern near the photocathode are discussed. The optimised RF gun parameters and bunch characteristics computed by PARMELA are presented. Such 10 MeV ultra short electron bunches with low longitudinal emittance compatible for additional longitudinal compression scheme having RF buncher cavity and drift space or magnetic chicane downstream of them [V. Volkov, D. Janssen. Generation of Sub-picoseconds electron bunches in superconducting RF photocathode injector (these conference)]. This work was financially supported by Forschungs Zentrum of Rossendorf.