Excited Krypton And Mercury Density Measurements In An Rf Capacitive Discharge

• Main Author: Michael, J.D.
• Format: Conference Proceeding
• Language: English
• Subjects: Density measurement; Electric discharges; Electrodes; Fluorescence; Krypton; Laser beams; Laser excitation; Length measurement; Mercury (metal); Mercury (metals); Pressure control; Pump lasers; Radio frequency; Raman scattering; Resonance; Roentgenium; Thermal effects; Vapor pressure
• ISSN: 0730-9244; 2576-7208
• DOI: 10.1109/PLASMA.1994.589100

A capacitive discharge is created in a cylindrical quartz container (80mm OD and 100mm in length) placed between a pair of circular planar electrodes. The buffer gas is Krypton (0.5 Torr), whilst the Hg vapor pressure can be controlled by changing the temperature of the 'cold finger'. At low power ( less than or equal to 10W), the axial and radial profiles of the excited Kr (5s super(3)P sub(1)) and Hg (6 super(3)P sub(1)) states are obtained by standard Laser Induced Fluorescence (LIF) techniques. Off-Resonance Raman Scattering (ORRS) [1] [2] is used at higher powers ( greater than or equal to 20W) and Hg vapor pressure ( greater than or equal to 6mTorr) to obtain the Hg (6 super(3)P sub(1)) state. This Raman method, which uses a detuned pump laser beam (10-20 cm super(-1) from resonance), was chosen rather than LIF under these conditions to avoid any self absorption of the induced fluorescence signal. Axial and radial density profiles of the Kr and Hg resonance states are obtained at various power levels and varying Hg vapor pressures. For the particular case of signals obtained using ORRS, a calibration H sub(2) cell is used to obtain absolute number densities of the Hg resonance state.