TUOCI01
ANL, Argonne, USA
The characteristics of X-ray free electron laser oscillators (XFELOs) [K.-J. Kim, et. al., Phys. Rev. Lett. 100, 244802 (2008)]–high-stability, high-spectral purity, and high-average brightness–will greatly enrich the era of x-ray FELs begun recently. If combined with a high-gain amplifier possibly with harmonic generation, an XFELO would constitute an ultimate x-ray machine. The drive accelerator can either be a straight SCRF linac or an ERL in energy gain mode. Sub-Angstrom stabilization of the output x-ray pulse spacing may be feasible by locking one of the longitudinal modes to a nuclear resonance such as 57Fe, opening up new opportunities for extreme x-ray metrology, with potential applications to technology and fundamental physics [B. Adams and K.-J. Kim, FEL2012]. A wide range of parameters is possible [R.R. Lindberg, FEL2012], optimized for particular accelerator or applications, such as ultra-low bunch charge for ERL [1], for short cavity length for nuclear resonance metrology, etc. The prospects for an XFELO are encouraging: Diamond as a Bragg reflector has been demonstrated for near 99% reflectivity [2] and high thermal diffusivity at cryogenic temperature [3].
[1] R. Hajima and N. Nishimori, Proc. of the FEL2009; R.R. Lindberg, FEL2012
[2] Y. Shvyd'ko, et al, Nat. Photonics 5, 539 (2011)
[3] S. Stoupin and Y. Shvyd'ko, Phys. Rev. Lett. 104, 085901(2010)
