SINAP, Shanghai
The echo-enabled harmonic generation (EEHG) scheme has remarkable efficiency for generating high harmonic microbunching with a relatively small energy modulation. A proof of principle experiment of EEHG scheme is under commissioning at Shanghai deep ultraviolet (SDUV) free electron laser (FEL) facility, where the third harmonic of the 1047nm seed laser is expected to be amplified in the 9m long radiator. Recently, to explore the advantage of EEHG scheme, higher order harmonics are under consideration seriously in SDUV-FEL. In this paper, several methods for measuring 9~15th order harmonic microbunching are comparatively analyzed. Study shows that, in comparison with the coherent transition radiation (CTR) and coherent synchrotron radiation (CSR) based diagnostics, the coherent harmonic radiation (CHR) of the radiator undulator would be a more feasible way to characterize the high order harmonic microbunching in EEHG operation of SDUV-FEL.
SINAP, Shanghai
A SASE experiment has been done at SDUV-FEL(SINAP), the spontaneous radiation and exponential growth regime are observated. The results are compared with the SASE theory.
SINAP, Shanghai
A compact hard X-ray FEL facility is proposed based on self-amplified spontaneous emission (SASE) scheme, which is aiming at generating 0.1nm coherent intense hard X-ray laser with the total facility length less than 600m. To reach this goal, low emittance S-band photo cathode injector, high gradient C-band linear accelerator and short period cryogenic undulator are used. Simulation results show that 0.1nm coherent hard X-ray FEL with peak power up to 10GW can be generated from a 50-m-long undulator when the slice emittance of the electron beam is about 0.4mm-mrad. The energy of the electron beam is only 6.4GeV which is available in accelerator length of 230m with the help of 40MV/m C-band rf system. This paper describes the physic design of this ultra-compact hard X-ray FEL facility.
SINAP, Shanghai
The high-gain seeded free-electron laser (FEL) schemes are capable of producing fully coherent radiation in the short wavelength regions. In this paper, we introduce the pre-density modulation (PDM) scheme to enhance the performance of the echo-enabled harmonic generation (EEHG) scheme and to significantly extend the short-wavelength range. The PDM is used to enhance the microbunching and reduce the electron energy spread of seeded FEL schemes by gathering most of the electron into the phase range which makes a contribution to the microbunching.