Radiation and electrical characteristics of ferrite-free closed-loop inductively-coupled low mercury pressure UV lamps of 375 mm in length and 120 mm in width were experimentally studied. Discharges were excited at a frequency of 1.7 MHz and lamp RF power, Рlamp = (95–170) W. It was in quartz closed-loop tubes of 16.6 mm in inner diam. and of 815 mm in length, in the mixture of mercury vapour (7 х 10–3 mm Hg) with Ar (0.7 and 1.0 mm Hg) and with the mixture of 30 % Ne + 70 % Ar (0,7 and 1,0 mm Hg). The 3-turn induction coil made from litz wire with a low specific linear resistance (ρw = 1.4 x 10–4 Ohm/cm) was disposed on the lamp surface along the closed-loop tube perimeter. In lamps with buffer gas pressure of 1,0 mm Hg, the increase of lamp power from 95 to 150 W caused the decrease of induction coil power losses, Pcoil, from (6–7) W to (3–4) W. Also in these lamps increased induction coil power efficiency, ƞcoil = 1 – Pcoil/Plamp, from 92 % to 97 % and lamp UV radiation (λ = 254 nm) generation efficiency, ƞe, 254, from 57 % to 66 %. The decrease of buffer gas pressure from 1.0 to 0.7 mm Hg caused the decrease of ƞe, 254 by (10–20)%. 1. Isupov M.V., Krotov S.V., Litvintzev A.Y., Ulanov I.M. An induction UV lamp. Light and Engineering, 2008. V16, #1, pp. 67–71. 2. Kobayashi S., Hatano A. High-intensity low-pressure electrodeless mercury-argon lamp for UV disinfection of wastewater. Journal of Water and Environment Technology, 2005. V3, #1, pp. 71–76. 3. Levchenko V.A., Popov O.A., Svitnev S.A., Starshinov P.V. Experimental research into the electrical and optical characteristics of electrodeless UV lamps of the transformer type. Light and Engineering, 2015. V23, #1, pp. 60–64. 4. Levchenko V.A., Popov O.A., Svitnev C.A., Starshinov P.V. 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Ferrite-free inductively-coupled light source of 300–400 W power at the frequency of 200–400 kHz. [Induktsionnyi besferritnyi istochnik sveta moshchnoctyu 300–400 W na chastote 200–400 kHz]. MPEI Bulletin, 2010. #2, pp. 159–164. 9. Starshinov P.V., Popov O.A., Irkhin I.V., Levchenko V.A., Vasina V.N. Electrodeless UV lamp on the basis of low pressure mercury discharge in a closed non-ferrite tube. Light and Engineering, 2019. V27, #6, pp. 133–136. 10. Starshinov P.V., Popov O.A., Irkhin I.V., Vasina V.N., Levchenko V.A. Electrical and radiation characteristics of ferrite-free closed-loop inductively-coupled mercury discharge UV lamps [Elektricheckie i izluchatelnye kharakteristiki induktivnykh besferritnykh rtutnykh UF lamp v zamknutykh trubkakh]. MPEI Bulletin, 2019. #3, pp. 87–97. 11. Popov O.A. Research of inert gas pressure influence on characteristics of inductive fluorescent lamps. [Issledovanie vliyaniya davleniya inertnogo gaza na kharakteristiki induktsionnykh lyuminescentnykh lamp]. MPEI Bulletin, 2013. #3, pp. 76–84. 12. Ekaterina V. Lovlya and Oleg A. Popov. Power losses in RF inductor of ferrite-free closed-loop inductively-coupled low pressure mercury lamps. Light and Engineering, 2020. V27. (accepted for publication) 13. Reizer Yu.P. Physics of Gaseous Discharges [Fizika gazovogo razryada]. М.: Nauka, 1987, 592 p. 14. Hyo–Chang Lee, Seung Ju Oh, Chin–Wookn Chung. Experimental observation of the skin effect on plasma uniformity in inductively coupled plasmas with a radio frequency bias // Plasma Sources Sci. Technol, 2012. V21, #3, pp. 035003. 15. Nikiforova, V.A., Popov O.A. RF frequency and discharge current effects on plasma parameters radial distributions in the ferrite-free inductively-coupled discharge in the closed-loop tube [Vliyanie chastoty VCh polya i razryadnogo toka na radialnoe raspredelenie parametrov plazmy induktsionnogo besferritnogo razryada v zamknutoy trubke]. MPEI Bulletin, 2012. #1, pp. 108–114. 16. Aleksandrov A.F., Vavilin K.V., Kralkina E.A., Neklyudova P.A. and Pavlov V.B. Plasma parameters investigation of the RF inductive plasma source with diameter 46 cm. Part I. Plasma parameters in the skin layer [Issledovanie parametrov plazmy induktivnogo VCh istochnika plazmy diametrom 46 cm. Ч.I. Parametry plazmy v oblasti skin-sloya]. Applied Physics [Prikladnaya fizika], 2013. #5, pp. 34–37. 17. Svitnev C.A., Popov O.A., Levchenko V.A., Starshinov P.V. Characteristics of low pressure ferrite-free inductive discharge. Part 1. RF inductor electrical characteristics. 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• ferrite-free inductively-coupled discharge
• closed-loop tube
• Ilikeeva
• low pressure mercury plasma
• induction coil
• UV resonant radiation