Measuring and Improving the Momentum Acceptance and Horizontal Acceptance at MAX III

Lifetime measurements for varying horizontal scraper positions performed at different RF frequencies suggested a horizontal aperture restriction in the MAX III synchrotron light source. A combination of local orbit distortions and horizontal scraper measurements pinpointed the location of the horizontal aperture restriction to the center of the main cavity straight section. The aperture restriction was determined to be located 10.4 ± 0.3 mm from the beam center. The precise result was achieved by measurements and calculations of the Touschek lifetime as a function of the main cavity voltage. Realignment of the main cavity increased the average lattice momentum acceptance from 0.0116 ± 0.0003 to 0.0158 ± 0.0003 and the horizontal acceptance from 26 ± 2 × 10 −6 m to larger than 44 ± 2 × 10 −6 m. The increase in momentum acceptance increased the lifetime in MAX III by a factor of two.