Measurements on a high current conventional fluorescent lamp and comparison with the numerical model

There is increasing interest in electrodeless lamps as, amongst other reasons, the lifetime is considerably longer than the conventional discharge lamps. Furthermore, reactions between the electrodes and the plasma are avoided, which makes the choice of the filling less restricted. One special class of electrodeless lamps are the inductive fluorescent lamps. With respect to the mechanism of light generation these lamps are similar to the common mercury fluorescent lamp. Inside mainly UV radiation is created which is converted into visible light by a fluorescent powder situated at the wall of the bulb. Besides the lack of electrodes, the other main difference between electrodeless and conventional fluorescent lamps is the plasma current. A typical current in a conventional fluorescent lamp is 400 mA, much lower than that in the inductively coupled lamp: 5 to 10 A. Based on the design parameters, like the driving current and gas pressures, macroscopic quantities such as the production of light and heat are calculated. This model basically consists of two parts: one describing the gas discharge and an other describing the coupling between the coil and the plasma. The discharge physics differs from that used in models on the more conventional fluorescent lamp, since due to the much higher plasma current it is expected that the electron density is much higher. This means that step-wise excitation has to be taken into account. In this contribution measurements are presented which are used to verify the gas discharge model