SLAC -PUB-223 October 1966 MEASUREMENTS OF THE SLAC INJECTOR EMITTANCE*

The six-dimensional volume in phase space enclosing the beam from the SLAC injector has been measured. The design of the injector and preliminary measurements on the prototype injector were reported at the National Particle Accelerator Conference, March 10-12, 1~65.~ This paper reports on similar measurements on the completed injector as installed on the SLAC two-mile accelerator. The measurement methods reported here for both transverse and longitudinal phase volumes differ significantly from those used on the prototype injector. The transverse phase space measurement on the prototype used tk2E two,slit method described by van Steenbergen. The method reported here used a variable aperture plus a glass plate (equivalent to a photographic film). The aperture was large, i.e., it measured the current within a given radius, rather than being a differential element. The two methods and the experimental results are compared. The bunching measurement used on the prototype utilized an rf sweeper operating at the accelerator frequency, while the measurement reported on here was done by adjusting an accelerator section to 90" out of phase and thus introducing an energy spread proportional to the bunch length. The pansverse phase volume was found to be 5 x lo(mot-cm)*, the bunch length 5”, and the longitudinal momentum spread 1 mot so that the beam is contained in a six-dimensional volume in phase space