Hard x-ray or gamma ray laser by a dense electron beam

A coherent x-ray or gamma ray can be created from a dense electron beam propagating through an intense laser undulator. It is analyzed by using the Landau damping theory which suits better than the conventional linear analysis for the free electron laser, as the electron beam energy spread is high. The analysis suggests that the currently available physical parameters would enable the generation of the coherent gamma ray of up to 100 keV. The electron quantum diffraction suppresses the FEL action, by which the maximum radiation energy to be generated is limited

Backward Raman compression of x-rays in metals and warm dense matters

Experimentally observed decay rate of the long wavelength Langmuir wave in metals and dense plasmas is orders of magnitude larger than the prediction of the prevalent Landau damping theory. The discrepancy is explored, and the existence of a regime where the forward Raman scattering is stable and the backward Raman scattering is unstable is examined. The amplification of an x-ray pulse in this regime, via the backward Raman compression, is computationally demonstrated, and the optimal pulse duration and intensity is estimated.Comment: 4 pages, 3 figures, submitted to PR

Orbital-selective Mass Enhancements in Multi-band Ca2−x_{2-x}Srx_{x}RuO4_{4} Systems Analyzed by the Extended Drude Model

We investigated optical spectra of quasi-two-dimensional multi-band Ca$_{2-x}$Sr$_{x}$RuO$_{4}$ systems. The extended Drude model analysis on the ab-plane optical conductivity spectra indicates that the effective mass should be enhanced near $x=0.5$. Based on the sum rule argument, we showed that the orbital-selective Mott-gap opening for the $d_{yz/zx}$ bands, the widely investigated picture, could not be the origin of the mass enhancement. We exploited the multi-band effects in the extended Drude model analysis, and demonstrated that the intriguing heavy mass state near $x=0.5$ should come from the renormalization of the $d_{xy}$ band.Comment: 4 figure

Theory of plasmon decay in dense plasmas and warm dense matter

The decay of the Langmuir waves in dense plasmas is not accurately predicted by the prevalent Landau damping theory. A dielectric function theory is introduced, predicting much higher damping than the Landau damping theory. This strong damping is in better agreement with the experimentally observed data in metals. It is shown that the strong plasmon decay leads to the existence of a parameter regime where the backward Raman scattering is unstable while the forward Raman scattering is stable. This regime may be used to create intense x-ray pulses, by means of the the backward Raman compression. The optimal pulse duration and intensity is estimated

Photonic band gap and x-ray optics in warm dense matter

Photonic band gaps for the soft x-rays, formed in the periodic structures of solids or dense plasmas, are theoretically investigated. Optical manipulation mechanisms for the soft x-rays, which are based on these band gaps, are computationally demonstrated. The reflection and amplification of the soft x-rays, and the compression and stretching of chirped soft x-ray pulses are discussed. A scheme for lasing with atoms with two energy levels, utilizing the band gap, is also studied.Comment: 3 figures, will be published on Po

X-ray Raman compression via two-stream instability in dense plasmas

A Raman compression scheme suitable for x-rays, where the Langmuir wave is created by an intense beam rather than the pondermotive potential between the seed and pump pulses, is proposed. The required intensity of the seed and pump pulses enabling the compression could be mitigated by more than a factor of 100, compared to conventionally available other Raman compression schemes. The relevant wavelength of x-rays ranges from 1 to 10 nm