Debris mitigation power of various buffer gases for CO2 laser produced tin plasmas.

Debris mitigation using an ambient gas is the easiest way for laser-produced plasma extreme ultraviolet light source. The debris mitigation power of hydrogen, helium and argon buffer gases against CO2 laser produced tin plasma plumes was quantitatively estimated by means of the visualization imaging system as well as the optical emission spectroscopy technique. The debris mitigation power of hydrogen buffer gas was assessed under ambient pressure ranging from 30 to 104 Pa. The debris mitigation power of the hydrogen buffer gas was determined as 150 eV mm−1 for energetic particles of 400 eV under a pressure of 104 Pa, which remained as high as 40 eV mm−1 at a pressure of 100 Pa. The maximum stopping power and collision scattering cross section of argon were measured to be almost three times larger in comparison with hydrogen and one and a half times larger than helium atmosphere at a pressure of 2000 Pa. Time-resolved optical emission spectroscopy showed that thermalizing collisions were responsible for slowing down the fast energetic ions and atoms towards a thermal equilibrium. [ABSTRACT FROM AUTHOR]