Fiber PROES: Phase-resolved optical emission spectroscopy by time-correlated photon counting through optical fibers*

Phase-resolved optical emission spectroscopy (PROES) is a non-intrusive diagnostic tool widely used in academic research for studying electron heating dynamics and determining plasma parameters such as electron densities and electron energy distribution functions with high spatial and nanosecond time resolution in low-temperature plasmas. Surface coefficients can be determined, too. However, PROES is typically not used in industrial plasma sources, since it requires large windows for optical access to plasma reactors and expensive ICCD cameras. To overcome these limitations, we do PROES through optical fibers and based on a photomultiplier tube (PMT). Large windows and expensive cameras are no longer needed. We present Fiber PROES measurements of the spatio-temporally resolved electron dynamics in a capacitively coupled plasma and compare the results to classical PROES measurements based on an ICCD camera demonstrating its performance and functionality. In fact, Fiber PROES measurements are much faster providing options for real-time process control in applications.