Production of Transverse Controllable Laser Density Distribution in Fermilab/Nicadd Photoinjector

The Fermilab/NICADD photoinjector laboratory consists of a photoemission electron source based on an L band rf-gun. The CsTe photocathode is illuminated by an ultra-short UV laser. The transport line from the laser to the photocathode was recently upgraded to allow imaging of an object plane located ∼ 20 m from the photocathode. This upgrade allows the generation of transverse laser distributions with controllable non-uniformity, yielding the production of an electron beam with various transverse densities patterns. Measuring the evolution of the artificial pattern on the electron bunch provides information that can be used to benchmark numerical simulations and investigate the impact of space charge. Preliminary data on these investigations are presented in the present paper.