Experimental investigation of X-ray lasing in a capillary argon discharge

Results are presented from experiments on the laser generation of X-ray radiation at the wavelength λ=469 Å (ε=26.4 eV) on the 3p(J=0)?3s(J=1) transition of Ne-like Ar ions. Experiments were carried out on the SIGNAL electrophysical facility with a 3.1-mm-diameter 157-mm-long Al₂O₃ ceramic capillary filled with argon at a pressure of 0.2–1.0 Torr. The discharge current amplitude was I ～ 25–40 kA, the current rise rate being dI/dt ～ 10¹² A/s. By a vacuum X-ray diode tuned to detect X-ray photons with energies in the range 10–40 eV, laser pulses with a duration of t ₁ ～ 1 ns and maximum energy of E _1,max ～ 1 µJ were recorded. The pulses were generated 35 ns after the discharge current was switched on. The line spectra in the wavelength range of 150–500 Å showed the bright λ=469 Å line. The angular divergence of the generated X-ray laser beam was estimated to be Δ? ～ 2 mrad.