• C. Feng, Z.T. Zhao
  SINAP, Shanghai

A novel approach to producing coherent hard x-ray based on the echo-enabled staged harmonic generation (EESHG) scheme is proposed. This scheme is not a simple cascaded EEHG, but consists of an EEHG, a beam shifter and a conventional HGHG like configuration, which also works in the EEHG principle. In the first stage, all over the whole electron beam is energy modulated by a laser beam in the first modulator and then converts into separate energy bands by a very strong dispersion section. In the second modulator, the seed laser is adjusted so that only the tail half part of the e-beam is energy modulated, then this beam is sent through the second dispersion section which converts the energy modulated part into a density modulation. The radiation from the first stage serves as the seed laser of the second stage, the beam shifter is so tuned that the head part of the electron beam can exactly interact with the radiation from the first stage in the modulator of the second stage, so the total harmonic number will be hundreds. It is possible to do the proof-of-principle experiment of EESHG on the SDUV-FEL.