New pulsed power supply for the spallation neutron source Linac LEBT chopper system

Four identical pulsed power supplies (pulsers) produce a series of ± 2.5 kV pulses to power four deflection electrodes of the Spallation Neutron Source (SNS) Linac Low Energy Beam Transport (LEBT) beam chopping system. The pulsers are required to produce a 1MHz burst of adjustable-duration pulses with a 60 Hz burst repetition frequency and rise and fall times of less than 50 ns into a 200 pF load. The pulsers have experienced many failures during the last 8 years of operation and have undergone significant upgrades. The power semiconductors, associated drive electronics and timing logic circuitry have been repaired many times, resulting in damage to the proprietary printed circuit boards. Many modifications have been implemented to make the operation more reliable [1, 2]. While these improvements have increased reliability, some the components are no longer available. A new state-of-the-art pulsed power supply has been designed at the SNS to address the issues of obsolescence, reliability, serviceability and to improve overall performance. This paper will discuss the performance enhancements, describe the new SNS LEBT pulser and present the results of measurements and testing.