Characteristics of Low-pressure Xenon ICP discharge

Emission characteristics of low-pressure, i.e. less than 6.65 kPa, xenon inductively coupled plasma (ICP) was investigated. The discharge tube was made of Pyrex glass with outer diameter of 30 mm. A 4-turns coil was wound on the tube and RF power up to 100 W with frequency of 13.56 MHz was input to initiate a discharge. The luminance of the xenon discharge drastically changed depending on the pressure. When decreasing the pressure from 6.65 kPa to 26.6 Pa, the luminance basically had a tendency to decrease except of the case when the pressure was around 39.9 Pa; the luminance was suddenly increased up to 28,000 cd/m² at 39.9 Pa, whereas it was about 2500 cd/m² at 133 Pa. The emission spectrum at 39.9 Pa showed a continuum ranged over the visible region, on the other hand, atomic and ionic line spectra were dominant at 133 Pa. At 39.9 Pa, the discharge color was white and general color rendering index was 90, which is enough for the general lighting. It is thought that the wide range visible continuum is attributed to the ion-electron recombination radiation and results in the increase in the luminance. The detailed investigation of the mode change mentioned above through the measurements of the plasma parameters such as electron density etc. is now under progress