LEDA Beam Operations Milestone and Observed Beam Transmission Characteristics

Recently, the Low-Energy Demonstration Accelerator (LEDA) portion of the Accelerator Production of Tritium (APT) project reached its 100-mA, 8-hr CW beam operation milestone. LEDA consists of a 75-keV proton injector, 6.7-MeV, 350-MHz CW radio-frequency quadrupole (RFQ) with associated high-power and low-level rf systems, a short high-energy beam transport (HEBT) and high-power (670-kW CW) beam dump. During the commissioning phase it was discovered that the RFQ field level must to be approximately 5-10% higher than design in order to accelerate the full 100-mA beam with low losses. Measurements of a low-duty-factor, 100-mA beam show the beam transmission is unexpectedly low for RFQ field levels between ~90 and 105% of design. This paper will describe some aspects of LEDA operations critical to achieving the above milestone. Measurement and simulation results for reduced RFQ beam transmission near design operating conditions are also presented.