Abstract
The Spallation Neutron Source (SNS) linac beam shall be chopped in the manner which supports accumulation of protons in the accumulating ring and assures low loss and activation free extraction of charged particles from the ring to the SNS target. The Low Energy Beam Transport (LEBT) Chopper System uses four identical pulsed power supplies (pulsers) to create the required series of bipolar HV pulses. Each pulser supplies a +/- 3 kV pulse or ground to an electrostatic einzel lens split into four quadrants to deflect the beam for 200 ns to 1 us. The SNS linac Timing System provides a series of input trigger signals of different widths to drive the pulser’s MOSFET switches. The width of the pulser’s output pulse is variable for multiple purposes such as change of average beam energy delivered to the target or for a beam study process. Lower and upper pulse width limits for the Chopper System depend on the characteristics of the pulsers, LEBT load, beam energy, extraction kicker and timing system. This paper presents estimations of timing limits for the existing chopping system.
