Development of superradiant THz sources at NSRRC

Abstract Linac-based coherent THz radiation sources are being developed with the NSRRC high brightness photoinjector which has been installed in the Accelerator Test Area. The injector is equipped with a laser-driven photocathode rf gun and a 5.2-m long S-band traveling-wave linac for beam acceleration. A 27 MeV electron beam of bunch length as short as 240 fs has been produced from this injector by the velocity bunching technique. Intense narrow-band superradiant THz radiation with tunable central frequency from 0.6 to 1.4 THz can be generated by injecting such ultrashort beam into a U100 gap tunable planar undulator. The other broadband THz coherent transition radiation generated by passing this beam through a metallic foil is used for bunch length measurement by autocorrelation technique. Currently the electron bunch length is measured to be 240 fs with linac field of 12.5 MV/m. The detail of the photo-injector system and generation of coherent THz sources is reported.