Design and performance of the traveling-wave beam chopper for the SSRL injector

A pulsed, split-parallel plate chopper has been designed, built, and installed as part of the preinjector of the Stanford Synchrotron Radiation Laboratory (SSRL) injector. Its function is to allow into the linear accelerator (linac) three consecutive S-band bunches from the long bunch train provided by an RF gun. A permanent magnet deflector (PMD) at the chopper entrance deflects the beam into an absorber when the chopper pulse is off. The beam is swept across a pair of slits at the beam output end when a 7 kV, 10 ns rise-time pulse passes in the opposite direction through the 75 Omega stripline formed by the deflecting plates. Bunches exiting the slits have their trajectories corrected by another PMD, and enter the linac. Beam tests demonstrate that the chopper functions as expected. >