In this paper, several schemes of soft X-ray and hard X-ray free electron lasers\n(XFEL) and their progress are reviewed. Self-amplified spontaneous emission (SASE)\nschemes, the high gain harmonic generation (HGHG) scheme and various enhancement\nschemes through seeding and beam manipulations are discussed, especially in view of the\ngeneration of attosecond X-ray pulses. Our recent work on the generation of attosecond\nhard X-ray pulses is also discussed. In our study, the enhanced SASE scheme is utilized,\nusing electron beam parameters of an XFEL under construction at Pohang Accelerator\nLaboratory (PAL). Laser, chicane and electron beam parameters are optimized to generate\nan isolated attosecond hard X-ray pulse at 0.1 nm (12.4 keV). The simulations show that\nthe manipulation of electron energy beam profile may lead to the generation of an isolated\nattosecond hard X-ray of 150 attosecond pulse at 0.1 nm.
Loading....