Reduction in time jitter for free-running, nanosecond-pulsed, Xe lamp by supplementary illumination with blue light-emitting diode

We have found out a phenomenon that the large fluctuation in the repetitive frequency of emission from a free-running, nanosecond-pulsed, Xe lamp can be reduced markedly by illuminating the lamp electrodes with a light flux f rom a blue light-emitting diode. There was a wavelength dependency in the s tabilization effect. The upper limit of the effective wavelength of the ill umination light was around 750 nm, but no power dependency was observed bet ween 0.5 and 3.0 mW. The reduction in the fluctuation was observed only for a Xe lamp manufactured by a specific maker, where materials with low work function elements were mixed in its cathode electrode for the purpose of im proving standard direct current arc operation. In order to evaluate the flu ctuation quantitatively, we have constructed a system for measuring time in tervals between every pulsed emissions. Our conclusion is that the reductio n in the fluctuation is due to photoelectrons emitted from the surface of t he cathode electrode and thereby the breakdown voltage for discharge in the lamp was maintained at a fixed value. (C) 2000 American Institute of Physi cs. [S0034-6748(00)01104-7].