Optimized discharge excitation techniques for short pulse gas lasers : TEA CO2 laser

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dc.contributor.advisorVon Bergmann, Hubertus M.en_ZA
dc.contributor.advisorRohwer, Erich G.en_ZA
dc.contributor.authorKyeyune, Farooqen_ZA
dc.contributor.otherStellenbosch University. Faculty of Science. Dept. of Physics.en_ZA
dc.date.accessioned2013-12-02T07:32:06Zen_ZA
dc.date.accessioned2014-01-21T09:25:37Zen_ZA
dc.date.accessioned2014-07-10T09:35:41Z
dc.date.available2016-12-31T03:00:07Z
dc.date.issued2013-12en_ZA
dc.descriptionThesis (MSc)--Stellenbosch University, 2013.en_ZA
dc.description.abstractENGLISH ABSTRACT: Transversely excited atmospheric (TEA) CO2 lasers have found numerous established and potential applications in both industry and research. However, the development of laser systems which can meet the demands of these applications is usually hampered by two key issues: the excitation circuit and the method of preionization. For example, the conventional thyratron-based exciters can no longer meet the requirements in high repetition rate applications. Therefore, new technologies and improved excitation techniques should be developed. In this thesis the development of an efficient all solid-state switched exciter for pumping a TEA CO2 laser and the evaluation of a miniature TEA CO2 laser preionized by corona discharge are presented. The excitation circuit consists of an insulated gate bipolar transistor (IGBT) as the primary switch, two stages of magnetic pulse compression (MPC) and a fast pulse transformer. Three magnetic core candidates that can be used in the MPC network and the pulse transformer were experimentally investigated. Fe-based nanocrystalline ferromagnetic material, FINEMET was found to have the best properties for the current application and was subsequently used in the development of the exciter. A surface-wire corona preionized miniature TEA CO2 laser was evaluated and the results were compared to those of an earlier spark array preionized laser. The corona preionizer was constructed from a ceramic tube (Al2O3) and a fine wire stretched along the surface of the tube. When this extremely efficient yet comparatively inexpensive preionizer was applied to the laser, output pulse energy of 230 mJ with pulse duration of FWHM ~70 ns was obtained from a small discharge volume of 50 cm3. This energy output was found to be higher than that obtained from a spark preionized laser with the same discharge volume. Moreover the discharge stability was also found to improve drastically. These results can therefore be used as a reference when developing full scale corona preionized laser systems.en_ZA
dc.description.abstractAFRIKAANSE OPSOMMING: Transversaal opgewekte atmosferiese (TOA) CO2 lasers het breë toepassing in industrie ennavorsing en toon baie potensiaal. Die gebruik van hierdie lasers word egter ingeperk deur twee kern probleme: die opwekkingstroombaan en die metode waarmee die lasermedium vooraf geïoniseer word. Byvoorbeeld kan die algemene “thyratron” gebaseerde opwekkers nie byhou wanneer die herhalingstempo te hoog raak nie. Sodoende is daar ’n behoefte vir die ontwikkeling van nuwe tegnologie en beter opwekkingstegnieke. In hierdie tesis word die ontwikkeling van ’n effektiewe opwekker, met slegs vaste toetstand skakelaars, vir ’n TOA CO2, asook die evaluering van ’n miniatuur TOA CO2 laser wat met ‘n vooraf geïoniseer word deur ’n korona ontlading voorgelê. Die opwekkerstroombaan bestaan uit ’n geïnsuleerde hek bipolêre transistor (IHBT) as die primêre skakelaar, twee vlakke van magnetiese puls kompressie (MPK) en ’n vinnige puls transformator. Drie tipes magnetiese kerne wat gebruik kan word in die MPK netwerk en die transformator is eksperimenteel ondersoek. Die yster gebaseerde nanokristalyne ferromagnetiese materiaal, FINEMET het die beste eienskappe getoon vir hierdie toepassing en is gevolglik gebruik in die ontwikkeling van die opwekker. ’n Miniatuur TOA CO2 laser met ’n oppervlak-geleier korona vir vooraf ionisasie is ondersoek en die resultate is vergelyk met die van ’n vorige TOA CO2 sisteem wat werk met ’n reeks vonkgapings vir vooraf ionisasie. Die korona vooraf ionisasie sisteem bestaan uit ’n keramiek buis (Al2O3) en ’n fyn geleier wat gespan is oor die oppervlak van die buis. Wanneer hierdie hoogs effektiewe dog eenvoudige vroeë ioniseerder aangewend word het ons puls energieë gemeet van 230 mJ met ’n pulslengte van ~70 ns uit ’n ontladings volume van 50 cm3. Ons het bevind dat hierdie energie hoër is as die energie verkrygbaar vanaf die laser met dieselfde ontladings volume wat die vonkgapings gebruik vir vooraf ioniseering . Verder is bevind dat die ontladingstabiliteit drasties beter was. Hierdie resultate kan vervolgens gebruik word as ’n verwysing wanner volskaal laser sisteme met korona vooraf ionisasie ontwikkel word.af_ZA
dc.embargo.terms2016-12-31en_ZA
dc.format.extentxii, 74 pages ; illustrationsen_ZA
dc.identifier.urihttp://hdl.handle.net/10019.1/95486
dc.language.isoen_ZAen_ZA
dc.publisherStellenbosch : Stellenbosch Universityen_ZA
dc.rights.holderStellenbosch Universityen_ZA
dc.subjectTEA CO2 laseren_ZA
dc.subjectExcitationen_ZA
dc.subjectPreionizationen_ZA
dc.subjectPulse compressionen_ZA
dc.subjectElectronic excitationen_ZA
dc.subjectIonizationen_ZA
dc.subjectGas lasersen_ZA
dc.subjectCarbon dioxide lasersen_ZA
dc.subjectLaser pulses, Ultrashorten_ZA
dc.subjectUCTD
dc.subject.otherCorona (Electricity)en_ZA
dc.titleOptimized discharge excitation techniques for short pulse gas lasers : TEA CO2 laseren_ZA
dc.typeThesisen_ZA
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