Generation of X-ray radiation from a plasma in a microchannel of a copper target located in the air under the action of soft-focused femtosecond laser pulses with an intensity of 100 TW cm-2

We have studied the dependence of X-ray radiation yield in the range of more than 3 keV from a microchannel in a copper target on the laser pulse number at a (0.7–4.0) × 10¹⁴ W cm^-2 intensities of femtosecond laser radiation. A technique for estimating the intensity of laser radiation acting on the target using the slope of the X-ray bremsstrahlung spectrum is proposed. A possibility of using this technique for estimating the intensity in a femtosecond laser filament is considered.