In this work we optimized a clean, versatile, compact source of soft X-ray radiation (E x - ray ~ 3 keV) with an yield per shot up to 7 × 10^11 photon/shot in a plasma generated by interaction of high-contrast femtosecond laser pulses of relativistic intensity (Ilas ~ 10^18 - 10^19 W/cm^2) with supersonic argon gas jets. Using high-resolution X-ray spectroscopy approaches, the dependence of main characteristics (temperature, density, ionization composition) and the emission efficiency of the X-ray source on laser pulse parameters and properties of the gas medium were studied. The optimal conditions, when an x-ray photon yield reached maximum, have been found when the argon plasma has an electron temperature of Te ~ 220 eV, an electron density of Ne ~ 6 × 10^19 cm-3 and an average charge of Z ~ 14. In such a plasma, a coefficient of conversion to X-ray radiation with energies Ex - ray ~ 3.1 (±0.2) keV reached 8.57 × 10^-5, no processes leading to the acceleration of electrons to MeV energies occurred. It was found that the efficiency of X-ray emission of this plasma source is mainly determined by the focusing geometry, but angular distribution of X-ray radiation is isotropic.
Alkhimova Maria , Ryazantsev Sergey, Skobelev Igor, Boldarev Alexey, Feng Jie, Lu Xin, Chen Liming, Pikuz SA. The clean source of soft X-ray radiation formed in supersonic Ar gas jets by high-contrast femtosecond laser pulses of relativistic intensity[J]. High Power Laser Science and Engineering, , (): .
