Concept of High-Power CW IR-THz Source for the Radiation Source ELBE Upgrade

The Radiation Source ELBE at Helmholtz-Zentrum Dresden-Rossendorf (HZDR) is a user facility based on a 1 mA - 40 MeV CW SRF LINAC. Presently HZDR is considering upgrade options for the ELBE or its replace- ment with a new CW, SRF LINAC-based user facility. A part of the user requirements is the capability to generate IR and THz pulse in the frequency range from 0.1 through 30 THz, with pulse energies in the range from 100 J through a few mJ, at the repetition rate between 100 kHz and 1 MHz. This corresponds to the pulse energy in- crease, dependent on the wavelength, by a factor from 100 through 1000. In this contribution, we outline key aspects of a concept, which would allow to achieve such parameters. These aspects are: 1 - use of a beam with longitudinal density modulation and bunching factor of about 0.5 at the fundamental frequency; 2 - achieving the density modulation through the mechanism similar to the one used in optical klystron (OK); 3 – generating the necessary for the modulation optical beam by an FEL oscillator, and 4 - using two electron injectors. First injec- tor would provide a beam for the FEL oscillator. Second high charge injector would provide the beam for the high pulse energy generation for users. All-in-all the concept of the new radiation source is very similar to an OK, but operating with two beams simultaneously.