• V. Volkov
  BINP SB RAS, Novosibirsk
• J. Knobloch, A.N. Matveenko
  Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, Elektronen-Speicherring BESSY II, Berlin

Beam breakup (BBU) instability analyzes in superconducting multi cell cavities [V. Volkov, Phys. Rev. ST Accel. Beams 12, 011301 (2009)] is extended to FZD like RF guns. Also, its BBU instability was studied numerically on base of dipole HOM analyzes and transverse beam dynamics. An effective way to suppress the BBU instability using TE mode RF focusing is presented and technically grounded. In that way, a widespread adoption of multi cell SC cavities in powerful RF guns with stable high currents is found to be essential able.

• V. Volkov
  BINP SB RAS, Novosibirsk
• J. Knobloch, A.N. Matveenko
  Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, Elektronen-Speicherring BESSY II, Berlin

Dipole High Order Mode (HOM) interactions with a beam in a superconducting RF gun (SC RF gun) could destroy the quality of the electron beam and incite it to breakdown. For FZD like SRF gun, the characteristics of dipole HOMs including trapped HOM are calculated up to the frequency of 7.5 GHz. The behavior of the calculated parameters versus cavity longitudinal deformations has been studied. With using of dynamics calculations, dipole coupling impedances taking into account a large scale particle velocity changing at different accelerating gradients in the RF gun has been numerically calculated.