Achievement of ultralow emittance coupling in the Australian Synchrotron storage ring

Investigations into producing an electron beam with ultralow vertical emittance have been conducted using the Australian Synchrotron 3 GeV storage ring. A method of tuning the emittance coupling (${ϵ}_{y}/{ϵ}_{x}$) has been developed using a machine model calibrated through the linear optics from closed orbits method. Direct measurements of the beam emittance have not been possible due to diagnostic limitations, however two independent indirect measurements both indicate a vertical emittance of 1.2--1.3 pm rad (${ϵ}_{y}/{ϵ}_{x}=0.01%$). Other indirect measurements support the validity of these results. This result is the smallest vertical emittance currently achieved in a storage ring.