After 30 years of operation, the Cockcroft-Walton based injector at the Fermi National Accelerator Laboratory has been replaced by a new beam line including a dimpled magnetron 35 keV source in combination with a 750 keV four-rod radio frequency quadrupole (RFQ). The new injector is followed by the existing drift tube linac. Prior to installation, a test beam line was built which included the magnetron source and the four-rod RFQ with a number of beam measurement instrumentation. The first beam test with the RFQ showed an output energy deviation greater than 2.5%. Other problems also showed up which led to investigations of the output energy, power consumption and transmission properties using rf simulations which were complemented with additional beam measurements. The sources of this deviation and the mechanical modifications of the RFQ to solve this matter will be presented in this paper. Meanwhile, the nominal output energy of 750 keV has been confirmed and the new injector with the four-rod RFQ is in full operation.

A new test stand at Fermi National Accelerator Laboratory (FNAL) is being constructed to carry out experiments to develop and upgrade the present magnetron-type sources of H(-) ions of up to 80 mA at 35 keV in the context of the Proton Improvement Plan. The aim of this plan is to provide high-power proton beams for the experiments at FNAL. The technical details of the construction and layout of this test stand are presented, along with a prospective set of diagnostics to monitor the sources.

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The Fermilab H-injector will be upgraded from a Cockcroft-Walton system to a 750 keV RFQ (radio frequency quadrupole) system. Part of the upgrade is the addition of a fast chopper in the LEBT (low energy beam transport) just before the RFQ. The novelty of this chopper is that it reflects rather than deflects beam. It also has low capacitance < 10 pF so that the rise and fall times of the beam pulse are dominated by cabling and the MOSFET switches. In fact, the measured rise and fall time of the chopped beam have been measured and they are better than 150 ns at 15 Hz.

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