Electrode-less ferrite-free inductivelycoupled low pressure discharge was excited in the mixture of mercury vapour (~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 6turn 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 (Тcc = 3100 K, Ra = 80). The induction coil made from silver-coated copper wire (ρw = 2.2x10–3 Ohm/cm) was disposed on the atmospheric side of tube walls, along closed-loop lamp tube perimeter. As plasma power, Ppl, grew from 127W to 180 W, coil power losses practically were unchanged, Pcoil = (25–22) W. Lamp luminous flux, Фv, grew with plasma power from 10430 lm (Ppl =127 W) to 13500 lm (Ppl =180 W), while plasma efficacy, ηpl = Фv/Ppl, decreased from 82 to 75 lm/W, and lamp efficacy ηV = Фv/(Ppl + Pcoil) decreased from 70 to 67 lm/W. 1. Shaffer J.W. and Godyak V.A. The Development f low frequency high output electrode­less fluorescent lamp // J. Illum. Eng. Soc., 1999, № 28, p.142.
2. Popov O.A., Chandler R.T. Inductively-coupled transformer­type light source operated at frequencies of 150–400 kHz and RF power of (200–500) W // High Temp. Phys. 2007, № 4, p. 795.
3. Popov O.A., Chandler R. Ferrite-free high power electrodeless fluorescent lamp operated at a frequency of 160–1000 kHz // Plasma Sources Sci. Technol. 2002, Vol. 11, № 2, p.218.
4. Elenbaas W. Light Sources. – New York: Crane, Russak & Co. 1972, p. 240.
5. Levchenko V.A., Popov O.A., Svitnev S.A., Starshinov P.V. Electrical and Emission Characteristics of a transformer type lamp with discharge tube of 16.6 mm in diam. // Light & Engineering, 2016, № 2, pp. 77–81.

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• ferrite­free inductive discharge
• fluorescent lamp
• low pressure mercury plasma
• coil power losses
• lamp and plasma efficacy
• radiofrequency voltage (RF)