Development and characterized of microcontroller based xenon flashlamp driver circuit

Abstract

Optical pumping using flashlamp is the preferred technique in solid state laser. Xenon flashlamp is a device that emits large amount of spectral energy in short duration pulses. Xenon is generally chosen because it yields a higher radiation output (40% -60%) for a given electrical energy than other noble gases. Triggering a flashlamp generally requires very high voltage pulse of a short duration. The objective of this project is to develop a programmable xenon flashlamp driver. Current set-up allows flashlamp to be triggered in a single mode. A fundamental study was carried out by varying the input energy from 4.48 J to 26.88 J across the flashlamp. The heart of the flashlamp driver is a PIC16F84A microcontroller that runs on a +5 V supply and clocked by a 4 MHz resonator. This microcontroller was connected to a personal computer, via serial port, acting as remote terminal. Initially, a TTL pulse output from PIC16F84A was sent out to drive a SCR. The SCR step-upped the TTL pulse to 332 ±5 volts pulse. Finally, a 1:2 transformer mixes the resulting 740 ±10 volt pulse with 2 ±0.01 kV DC voltage. The resulting voltage waveform is applied across a xenon flashlamp. Xenon gas ionizes for a brief period determined by the pulse width. This results in an electrical short circuit across the flashlamp’s electrodes. A large amount of current is drawn across the electrodes. This causes a rapid increase in the current flow through the flashlamp and initiates the desired arc lamp discharges. A Rogowski coil was used to detect the pulse current waveform. Xenon flashlamp output was detected using IPL10050 photodiode. An OPHIR BeamStar CCD Laser Beam Profiler was employed to record a plasma spectral gradient. The peak pulse current was obtained in the range of 776 A – 982 A. The bandwidth and the amplitude of the xenon flashlamp pulse were found in good agreement with the input energy. The beam profiles and dimensions of the plasma were dependent upon input energy.