ELECTRODE-LESS FERRITE-FREE CLOSED-LOOP INDUCTIVELY-COUPLED FLUORESCENT LAMP

Electrode-less ferrite-free inductively-coupled low pressure discharge was excited in the mixture of mercury vapour (similar to 10(-2) Torr) and argon (0.1 Torr) at a frequency of 2.0 MHz and lamp RF powers of (150-202) W with the help of a 6-turn induction coil. The discharge lamp of rectangular shape (50 cm in length and 7 cm in height) employed a closed-loop glass tube of 30 mm in diam. Tube walls inner surface was coated with three color phosphor (T-cc = 3100 K, R-a = 80). The induction coil made from silver-coated copper wire (rho(w) = 2.2x10(-3) Ohm/cm) was disposed on the atmospheric side of tube walls, along closed-loop lamp tube perimeter. As plasma power, P-pl, grew from 127W to 180 W, coil power losses practically were unchanged, P-coil = (25-22) W. Lamp luminous flux, Phi(v), grew with plasma power from 10430 lm (P-pl = 127 W) to 13500 lm (P-pl = 180 W), while plasma efficacy, eta(pl) = Phi(v)/P-pl, decreased from 82 to 75 lm/W, and lamp efficacy eta(v) = Phi(v)/(P-pl + P-coil) decreased from 70 to 67 lm/W.