The VHF-Gun Electron, an electron source optimized for high-brightness, high-duty-cycle applications.
(Lawrence Berkeley National Laboratory)
Aula Salvini (LNF INFN)
In the last decade, the development/proposal of MHz-class repetition rate electron applications such as free electron lasers (FELs), inverse Compton scattering sources, and ultrafast electron diffraction and microscopy (UED/UEM), called for the development of new gun schemes capable of generating high brightness beams at such high rates. The VHF-Gun, a 186 MHz room-temperature continuous wave RF photo-gun developed at the Lawrence Berkeley Laboratory (LBNL) was one of the answers to that call. The VHF-Gun was constructed and tested in the APEX facility at LBNL successfully demonstrating all design parameters and the generation of electron beams with the required brightness. A close version of the APEX VHF-Gun was fabricated at LBNL and delivered to SLAC to operate as the electron source for the LCLS-II, the new X-ray FEL in construction at Stanford, and the original VHF-Gun is presently used for generating the beams for HiRES, the UED program at LBNL.
But the game it is not over yet! For example, the recently approved upgrade of the LCLS-II towards higher energies (LCLS-II HE), and the always brightness-starving UED and UEM applications, would greatly benefit from a further increase of the electron beam brightness. In response to that, our group at LBNL started to study possible upgrades of the VHF-Gun scheme that would allow for the desired performance improvement. Several conceptual options were identified and last year, we received funds for developing such concepts up to a more mature level.
After a description of the existing VHF-Gun and of its main experimental results, the upgrade options under consideration are presented.