EXPERIMENTAL BEAM DYNAMICS IN THE SLC LINAC.

1. Abstract The component installation for the upgrade of the threekilometer linac’ for the SLAC Linear Collider (SLC) was completed in late summer 1986. The system status and measurements of beam properties made during commissioning are described in this paper. Further linac measurements are reviewed in companion papers.213’4 In simmar;, a low-emittance electron beam from a damping rinrr has been accelerated through the linac and iniected into the-north SLC Arc with negligible loss. The maximum bunch intensity is 2.9 X 10 lo electrons/pulse. A peak particle energy of 53 GeV has been reached. Operation at 47 GeV is now routine. The energy and energy spectrum of the electron beam can be rapidly measured nondestructively at high energy . These signals will be used in a fast feedback system nearing completion. The electron beam can be centered in the accelerator to about 200 pm rms. Slow feedback of the injection position and angle into the linac and injection into the north Arc are operational.5 Longitudinal and transverse wakefields have been measured and appear to be near expectations. Transverse position measurements at the end of the linac show a 120 pm horizontal and a 30 pm vertical (rms) jitter from pulse to pulse. The spot shape, including the transverse tails, also shows some jitter. The transverse position and shape fluctuations have several sources involving launch instabilities, chromatic effects, RF deflections and lattice mismatches. Continued improvements are expected. These parameter jitters would not preclude collisions. The measured invariant transverse emittances of the beam at 47 GeV are 2 x lop5 rm vertically and 12 - 25 x low5 rm horizontally at 1 x 10” e-. The horizontal emittance increases with beam intensity. Damped positrons have been injected into the linac, and trajectory correction is underway.