Low emittance electron beam formation with a 17 GHz RF gun

We report on electron beam quality measurement results from the Massachusetts Institute of Technology 17 GHz RF gun experiment. The 1.5 cell RF gun uses a solenoid for emittance compensation. It has produced bunch charges up to 0.1 nC with beam energies up to 1 MeV. The normalized rms emittance of the beam after 35 cm of transport from the gun has been measured by a slit technique to be $3\pi \mathrm{mm}\mathrm{mrad}$ for a 50 pC bunch. This agrees well with PARMELA simulations at these beam energies. At the exit of the electron gun, we estimate the emittance to be about $1\pi \mathrm{mm}\mathrm{mrad}$, which corresponds to a beam brightness of about $80\mathrm{A}/(\pi \mathrm{mm}\mathrm{mrad}{)}^2$. Improved beam quality should be possible with a higher energy output electron beam from the gun.