Measurements of ultralow emittance and transverse coherence at the Advanced Photon Source Upgrade storage ring

Recent electron storage ring light sources continue to push towards increasingly lower electron beam sizes. In the present work, we report on the measurements of the electron beam emittance (sub 50 pm rad) achieved at the Advanced Photon Source Upgrade (APS–U), as well as its standing among electron storage ring light sources. We include a brief status update on the beam size monitor beamline at the APS–U. We conclude with a survey of measurement techniques and recent results across multiple laboratories.