5Th International Conference on Automation Control Engineering & Computer Science (ACECS’18),19-22 Dec 2018, Hammamet-Tunisia Output waveforms of Blumlein-line Nitrogen Laser Circuit Based on the Distributed Parameter Model: Theoretical and Experimental Results Mohamed O. Twati Electrical and Electronic Engineering Department, University of Tripoli Tripoli, Libya m.twati@uot.edu.ly Abstract— Optical power calculation of the Blumlein-line nitrogen laser circuit based on the distributed parameter model and the decoupling approach of the laser rate equation from the electrical circuit equations is developed and investigated. The dependence of both the electrical and optical power waveforms on the spark gap inductance is performed and discussed. The saturated laser power approach is assumed in calculating the optical power. The measured laser output waveform obtained is fairly equivalent to the calculated laser power waveform based the distributed model. The theoretical work suggested here could be used to estimate some of the system parameters and help in optimization of the circuit for better system performance. Keywords— Blumlein-line; Fast discharge laser; Nitrogen laser; Power calculations; optical waveform. I. INTRODUCTION Nitrogen lasers are important because they can provide high-power short-duration pulses of ultraviolet radiation (λ = 337.1 nm). These lasers are widely used in spectroscopy and fluorescence studies, pumping of dye lasers and other research and industrial applications [1]–[6]. The performance of the nitrogen laser is basically determined by the type of electrical system used to create the discharge in the gas. Many excitation schemes were employed for pumping nitrogen lasers, however, the Blumlein transverse excitation method has become very popular, because of its low cost and ease of construction [2]–[8]. The Blumlein-line pulse forming network consists of two parallel plate transmission lines (or coaxial cables) acting as energy storage capacitors, located at both sides of the cavity charged to high voltage Vo. When one side is short-circuited, for instance using a spark gap, a transient voltage occurs across the laser cavity creating a gas discharge between the electrodes. The spark gap and the laser gap are usually represented by resistances and inductances. Depending on the relevant time constants of the spark gap and laser gap along with the wave propagation time on the transmission line, two concepts can be used in the analysis of the Blumlein-line circuit, the lumped parameter model (LPM) and the distributed parameter model (DPM). From a theoretical point of view, the LPM offers the advantage of a much simpler analysis over the DPM., however, it has the disadvantage of being valid only when the relevant time constants of the spark and laser gap are much larger than the wave propagation time on the transmission line [9]. In spite of extensive studies and investigations that have been made so far for understanding the performance of lasers based Blumlein-line pulse forming network, still extra research work has to be made that include the selection of more accurate circuit models for simulating the laser system and also the effects of the electrical parameters on the overall laser performance. The Laser is a highly integrated electro- optical system and the prediction of the behaviour of laser requires a complicated theory that must include the electric circuit parameters, the gas kinetic parameters and detailed mechanism of energy transfer of the three laser levels of the molecular nitrogen. A significant simplification of the calculation has been brought about by Fitzsimmons [10]. Instead of estimating the electron temperature by solving the energy balance equation as a part of the coupled system, they used, in a decoupled procedure, another alternative approach to predict the electron temperature. Within this framework of the assumptions, the