Comparison of dc and superconducting rf photoemission guns for high brightness high average current beam production

A comparison of the two most prominent electron sources of high average current high brightness electron beams, dc and superconducting rf photoemission guns, is carried out using a large-scale multivariate genetic optimizer interfaced with space charge simulation codes. The gun geometry for each case is varied concurrently with laser pulse shape and parameters of the downstream beam line elements of the photoinjector to obtain minimum emittance as a function of bunch charge. Realistic constraints are imposed on maximum field values for the two gun types. The superconducting rf and dc gun emittances and beam envelopes are compared for various values of photocathode thermal emittance. The performance of the two systems is found to be largely comparable for up to 154 pC per bunch at 1.3 GHz or 200 mA provided low intrinsic emittance photocathodes can be employed.