Design and applications of an X-band hybrid photoinjector

J. B. Rosenzweig, A. Valloni, D. Alesini, G. Andonian, N. Bernard, L. Faillace, L. Ficcadenti, A. Fukusawa, B. Hidding, M. Migliorati, A. Mostacci, P. Musumeci, B. Oshea, L. Palumbo, B. Spataro, A. Yakub

Research output: Contribution to journalArticlepeer-review

23 Citations (Scopus)


An INFN-LNF/UCLA/URLS collaboration is developing a hybrid photoinjector in X-band. This device is an integrated structure consisting of initial standing wave gun cells connected at the input coupler to a traveling wave section. This design nearly eliminates RF reflections from the SW section; further, a 90° phase shift in the accelerating field at the coupling cell gives strong velocity bunching. The current initiative in X-band follows an S-band hybrid, now proceeding to construction at LNF and high power testing/beam production measurements at UCLA. This S-band hybrid has 1.5 cell SW and 9 cell TW sections, and produces strongly compressed 3.5 MeV beam. It can be used for novel applications; here we discuss the production of an exponential energy spectrum extending from 1 to 12 MeV to simulate the effects of radiation belt environments on space-craft. It can be optionally used with a 3 m TW linac fed from RF output of the hybrid, to boost the energy to 22 MeV. While scaling the design from S-band to X-band is conceptually simple, practical limits require changes in both RF and magnetostatic designs. As the field is limited by RF breakdown to 200 MV/m peak field, the SW section must be expanded to 2.5 cells to reach 3.5 MeV; this permits flexibility in the solenoid design. We present beam dynamics simulations that show 6D phase space compensation at 7 pC: sub-0.1 mm mrad at the emittance minimum that occurs simultaneously with a longitudinal focus of <20 fs rms. We discuss applications ranging from multi-THz coherent radiation production to ultra-fast electron diffraction.

Original languageEnglish
Pages (from-to)107-113
Number of pages7
JournalNuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment
Issue number1
Publication statusPublished - 21 Nov 2011


  • coherent radiation
  • diffraction
  • femtosecond
  • photoinjector
  • wakefield

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