Experience with a radio frequency gun on the SSRL Injector Linac

A-SSRL/Varian-Associates-built, one-and-a-half cavity, microwave, thermionic-cathode gun has operated on the SSRL Injector Linac reliably without changing the cathode for over 10,000 hours, with no significant decrease in emission. Thus, for a pulsed electron beam, with a maximum of 0.5 A peak at 2 to 3 MeV from a 3.5 MW peak rf pulse of 2 μs pulse width at 10 pps, the apparent but small amount of back bombardment of the cathode has been tolerable. Use of a bunch-compression alpha magnet and a stripline chopper after the gun produces the required S-band 3 to 5 microbunches of electrons for injection into a standard 10-m-long linac and on into a booster synchrotron, which in turn is used to fill SPEAR. Component limitations and operating characteristics of the gun and the linac's rf system are discussed