Design of a high-brightness, high-duty factor photocathode electron gun

High brightness symmetric emittance rf photoinjector preliminary design report

“…The need to induce a strong on-axis magnetic field made the use of a superconducting cavity problematic, and the need for a high accelerating gradient eliminated the choice ofa superconducting gun altogether. The Brookhaven/Grumman [Gun I] S-band photoinjector [10] was taken as a starting point for the design of the TTF injector; the resonant frequency, waveguide coupling, intercavity coupling, and longitudinal exit aperture profile were modified to yield an L-band structure with good shunt impedance and field balance characteristics.…”

Proposed UV FEL user facility at BNL

“…The remaining question is one of repetition frequency, or average power capability. Grumman Aerospace Corporation staff in collaboration with BNL have carried out thermal studies on the BNL gun design and these indicate that a 1% duty factor is feasible for this option [8]. This duty factor allows a 2/zS average gun 'on' time at 5 kHz.…”

“…At the highest charge, the normalized rms transverse emittance should be as small as possible (_n < 81-mm.mrad). A number of options are available for the design but we will consider here a normal conducting, copper rf gun operating in a pulsed mode at a frequency of 2856 MHz, based on the BNL gun [6,7,8].…”

“…The present gun performance is quite good [6,7] and it is well matched to the needs of the UV-FEL facility. A new version of this gun is being developed [8] which will have the large duty factor capability to provide the necessary pulse repetition rate.…”

Proposed UV-FEL user facility at BNL

“…Reference [8] gives detailed simulations of a 2856 MHz radiofrequency electron gun and the results of these simulations are given in Table I below. This gun will provide 10 MeV from 3% ceUs.…”