The electrical and lumen output characteristics of an RF lamp

Summary form only given. In this work, the authors present measurements of the electrical characteristics and lumen output from a 2.65 MHz driven inductively coupled light source. Measurements were made on a spherical lamp of 3.125 inch diameter with a re-entrant cavity that houses a cylindrical ferrite core around which is wrapped the primary coil. The voltage, current and their relative phase angle was measured on the primary coil which drives the lamp. Along with this, the power transmitted to the lamp was also measured. From these measurements the RF power dissipated in plasma and the ferrite core losses were determined separately as a function of primary voltage and total RF lamp power. With a discharge present, resistive and reactive components of the primary coil impedance were also determined as a function of discharge power. The discharge voltage, the discharge current and the average plasma density were inferred from the primary coil impedance characteristics. Two lamps, one with 0.3 Torr and the other with 0.5 Torr krypton buffer gas were studied. The lumen per watt (LPW) and the voltage per turn versus lamp power were compared for the two buffer gas pressures. All the aforementioned measurements were made with a cold spot temperature fixed at 42/spl deg/C. Temperature dependence of RF lamp electrical characteristics has also been investigated.