Excitation and kinetic equilibria in an argon inductively coupled plasma torch—I: Coolant flow only

• Published in: Spectrochimica acta. Part B: Atomic spectroscopy 1989, Vol.44 (2), p.165-174
• Main Authors: Bydder, E.L., Miller, G.P.
• Format: Article
• Language: English
• Subjects: Exact sciences and technology; Physics; Physics of gases, plasmas and electric discharges; Physics of plasmas and electric discharges; Plasma devices
• ISSN: 0584-8547; 1873-3565
• DOI: 10.1016/0584-8547(89)80018-7

A relaxation method very sensitive to any deviation from excitational equilibrium and which yields accurate values of the temperature ratio T e/ T g, (where T e and T g are the electron and gas temperature respectively) is used to investigate the equilibrium state of a single flow (coolant only) argon inductively coupled plasma. The results show that for an input power of 1200 W the excited states (4p and higher) are in partial local thermal equilibrium out to a radius of 7 mm. In the central region ( r ⩽ 3 mm) the plasma is in kinetic equilibrium with the gas temperature within 3% of the electron temperature, with T e ≈ 10000K. At r = 6 mm, T e/ T g ranges from 1.3 at 15 mm below the top of the work-coil to 1.06 at 5mm above the work-coil. As the power is reduced from 1200 W to 800 W, T e/ T g changes by typically 6% illustrating that the input power level is not a critical parameter in determining the plasma equilibrium.