Observation of Coherent Synchrotron Radiation from Three Types of Beam at NewSUBARU

Abstract

Coherent synchrotron radiation (CSR) in Tera‐Hz region was observed at NewSUBARU. Three types of CSR from three types of electron beam were detected in the storage ring. One was a radiation burst from a high‐density single‐bunched beam. The burst had a threshold current of 1.0 nC/bunch for the normal operation parameters. The second was a quasi‐dc radiation from a low current and short‐bunched beam. The ring was operated in a quasi‐isochronous (low momentum compaction factor) mode, which could store the short‐bunched beam stationary. The bunch charge was as low as 1 pC/bunch and the bunch length was as short as 4 ps FWHM. The third was a radiation pulse following injection. A short‐bunched linac beam, with a base width of 20 ps and a charge of 50 pC/bunch, emitted short‐pulsed CSR in the storage ring.