Comparison of Langmuir probe and laser Thomson scattering for plasma density and electron temperature measurements in HiPIMS plasma

The temporal evolution of plasma density and electron temperature in high power impulse magnetron sputtering discharges has been measured using the Langmuir probe and laser Thomson scattering techniques. Measurements were performed (nonsimultaneously) at two positions within the plasma, in the low magnetic field strength region on the discharge axis and in the high magnetic field strength region of the magnetic trap, for peak power densities of 450 W cm^–2 and 900 W cm⁻², respectively. The maximum plasma densities and temperatures were 6.9 × 10¹⁹ m⁻³ and 3.7 eV in the pulse-on time, and values decayed to 4.5 × 10¹⁷ m⁻³ and 0.1 eV at times up to 250 μs into the afterglow. The results indicate that although intrusive, the Langmuir probe can provide a good indication of electron properties in regions of different electron magnetization in the discharge.