Improved Fnal Linac Beam Choppers

The Fermilab Linac uses two electrostatic beam deflection systems as beam choppers, a 750-keV system located between the ion source and the input to the Linac and a 200-MeV system at the output of the Linac. This paper discusses the 750-keV chopper experience with both proton and negative ion beams and the ability of these systems to tailor the Linac beam to the diverse requirements of its users; normal accelerator injection, neutron therapy beam, and electron cooling experiments. This flexibility plus a cleaner beam pulse, improved thyratron operation, and mechanical modularity are the results of recent improvements. Additional benefits have been increased reliability and ease of service to the 750-keV chopper.