ABSTRACT
The energy input into the lamp between the ignition and the current peak in one cycle, we call this energy as initial energy E, versus pulse width under the condition in which the enrgy E, is at the upper limit for maintain diffused positive column is shown in Fig.4. As shown in this figure, the energy E, is almost constant against pulse width. We observed the results that as the pulse width becomes shorter, both lamp voltage and current increase with same E, . As the voltage, that is electric field, increases, direct ionisation becomes dominant and metastables are not populated due to decrease in stepwise ionisation populating metastables, and also electron temperature becomes too high to occur volume recombination due to high field. The numerical simulation done by authors tells positive column constriction is caused by increasing in volume recombination rate[2]. Short pulse causing higher electron temperature prevents volume recombination and this is the one of the ways to avoid positive column constriction and to achieve higher luminance.
