High Brightness Superconducting RF Photo Injector Gun Cavity

Next generation electron accelerators for research, medical, defense or industrial use are in need of electron sources operating at high repetition rates of 1 MHz and beyond, with normalized emittance of 1 mm-mrad or less and bunch charge as much as one nC or more. In Phase I we will numerically optimize a superconducting (niobium) RF photo injector gun cavity (SRF gun), which can provide unprecedented flexibility to vary beam pulse patterns in the MHz regime and beyond. We will develop an engineering design, built and tested the cavity at Jefferson Laboratory in Phase II. Based on the success, the SRF gun could be tested and operated with beam in collaborating facilities in Phase III to pave the way for next generation light sources. We will design and numerically optimize the conceptual layout of a novel high beam brightness SRF gun that does not require an opening in the center of the back wall and avoids the complex cathode exchange system, but still allows an exchange or refurbishment of the cathode, which will be a deposited superconducting lead spot. The demountable back plate has the major benefit to clean the cavity cells independently from the back wall carrying the photo cathode. This mitigates risks of cavity contamination and eases fabrication and chemical post-processing to achieve high accelerating fields, a key parameter to guarantee high brightness beams. The usage of SRF guns is needed to produce high brightness electron beams, which is a fundamental requirement in large-scale machines such as linac-driven Free Electron Lasers (FEL). The work will be similarly beneficial to small scale devices such as laser-plasma accelerators or Inverse Compton Back-Scattering sources that produce high average flux x-rays for industrial and medical applications