Experimental results of a single emittance compensation solenoidal magnet

A new iron dominated single emittance compensation solenoidal magnet was designed to be integrated with the BNL/SLAC/UCLA 1.6 cell S-Band Photocathode rf Gun. This emittance compensated photoinjector is now in operation at the Brookhaven Accelerator Test Facility. It has produced a 0.329±0.012 pC, τ_95% = 10.9 psec electron bunches with a normalized rms transverse emittance of ε_n,rms = 1.17±0.16 φ mm mrad. POISSON field maps were used with PARMELA to optimize the emittance compensation solenoidal magnet design. Magnetic field measurements show that at the cathode plane B_z ≤10 G for a peak magnetic field of B_z,max = 3 kG. Which is in agreement with POISSON simulation. A single emittance compensation solenoidal magnet will produces a initial angular momentum of the electron bunch that manifests itself in a initial magnetic emittance term that cannot be eliminated. This magnetic emittance ε_n,rms^mag scales as 0.010 ^{π mm mrad}_G at the cathode, which is in agreement with PARMELA simulations. Experimental beam dynamics results are presented that shows relative angular rotation and spot size as a function of cathode magnetic field. These results are compared to theory.