Low emittance electron beam formation with a 17 GHz RF gun

We report on the design, construction, and initial operation of a new 1 1/2 cell 17 GHz RF gun and beamline. Emittance compensation is achieved with a 6.5 cm long, 0.5 T solenoid placed immediately after the RF Gun. The gun operates with 50 ns, up to 5 MW, pulses from a 17.13 GHz klystron amplifier built by Haimson Research Corp. Results of initial high power operation are reported. Cold test measurements of the azimuthal symmetry of the RF gun field profile along with results of 3D electromagnetic and beam dynamics simulations are also presented. For a bunch charge of 50 to 100 pC, initial bunch length of 1 ps, and beam energy of 1 MeV, a normalized rms emittance of less than 3 πmm-mrad has been measured after 35 cm of beam transport from the gun. This corresponds to a beam brightness of about 100 A/(mm-mrad)2 at the gun exit. An rms energy spread of less than 2.5% has been previously measured and agrees well with simulations. Plans for increasing the beam energy and lowering the emittance are underway. Simulations predict that with a beam energy of 2 MeV produced by the gun, a normalized rms emittance of 0.5 π-mm-mrad can be achieved for 1 ps, 0.1 nC beam.