Evaluation of vertical emittance in KEK-ATF by utilizing lifetime measurement

It is difficult to measure the vertical emittance of the extremely low emittance rings such as third generation synchrotron light sources or damping rings of the future linear colliders due to their small vertical beam size. In such a low emittance ring, the beam lifetime is limited by the Touschek effect and ideally proportional to the bunch volume. Thus the bunch volume, or equivalently the vertical emittance when horizontal and longitudinal beam sizes are known, can be evaluated from the measurement of the Touschek lifetime. We determine the vertical emittance of the beam in KEK Accelerator Test Facility (KEK-ATF) damping ring by the lifetime model. The evaluated vertical emittance was 0.04±0.01 nm and it was consistent with the vertical emittance measured by wire-scanner beam profile monitors.