High-resolution x-ray spectroscopy of multicharged argon and krypton ions using a laser-produced x-ray source with a gas-puff target

Abstract

A hot and dense plasma can be produced by high-power laser irradiation of a high-pressure gas puff target. The plasma emits strong x-ray radiation in low photon-energy range (soft x-rays and XUV radiation) and is considered to be used as a debrisless laser-produced x-ray source. It was shown that the laser-irradiated gas puff plasma is an ideal source for the high-resolution spectroscopic studies of complex spectra of the multicharged ions. This paper reports our investigations of x-ray spectra of heliumlike argon and neonlike krypton ions. The gas puff targets were created with the use of a specially designed high-pressure solenoid valve operating at a backing pressure up to 15 at and quipped with a sonic-type circular nozzle of 0.5 mm in diameter. Parameters of the gas puff targets were measured using x-ray shadowgraphy and laser interferometry. To irradiate the gas puff targets we have used a Nd:glass laser, which generates 10 J pulses in 1 ns FWHM. The laser beam was focused onto the gas puff target perpendicularly in respect to the flow of gas using an aspherical lens. The diameter of a laser beam in the focus were about 100 micrometers , what ensured the radiation power density to be of order of 10<SUP>14</SUP> W/cm<SUP>2</SUP>. To measure x-ray spectra emitted by a laser-irradiated gas puff target we have used a simple focusing crystal spectrographs with a mica crystal curved into a spherical surface of radius R equals 100 mm. The spectra were recorded on Kodak RAR 2495 x-ray commercial film. The high resolving power of the spectrograph of about (lambda) /(Delta) (lambda) equals 10000 permitted high-precision wavelength spectral measurements. The measured x-ray spectra have the small spectra width of the observed lines associated with the low expansion velocity of the laser- irradiated gas puff plasma. Dielectronic sodiumlike satellites to neonlike krypton resonance lines have measured for the first time. High-resolution spectra of heliumlike argon were also obtained. The measured spectra have been used for diagnosing the plasma parameters.