Propagation of intense laser pulses in capillary and its application to X-ray laser

We investigated the guiding of femtosecond laser pulses with an intensity of > 1016 W/cm2 in a hollow and gas-filled capillary. We measured the laser transmission versus length of two capillaries with different inner cores in a vacuum, and also the laser propagation modes in these two capillaries. We succeeded in generating an extended plasma column that was ten times longer than the Rayleigh range by propagating high intensity femtosecond laser pulses in a gas-filled capillary. We obtained a spectral blue shift in the transmitted femtosecond laser pulses with a 5 torr nitrogen-filled capillary and used this shift to demonstrate extended plasma column formation in a gas-filled capillary. We conducted a preliminary soft X-ray laser experiment as an application of this laser-pumped gas-filled capillary