Test-accelerators as coherent terahertz source program (t-ACTS) at Tohoku University

The beam from thermionic RF gun is quite suitable for the bunch compression by means of velocity bunching. Since the thermionic gun is very stable in general, we anticipate very short electron pulses of the bunch length around 50 fs can be provided satisfactorily. The t-ACTS program has been developed toward updating terahertz science and technology in which intense coherent synchrotron radiation (CSR) from very short electron bunches will be employed. Careful numerical simulation showed possibility of the bunch length of less than 100 fs with a bunch charge of 20 pC, which will provide sufficiently large form factor for production of CSR in the THz wavelength region. The train of short bunches will be stored in an accumulator ring. The peak brilliance of THz radiation emitted from one bunch is expected to be 5×106 photons/mrad2/0.1%bandwidth for each bending magnet of the ring.