Browsing by Author "Baricholo, Peter"

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    Dielectric barrier discharge CO2 TEA laser operated at frequencies up to 400 Hz
    (SA Institute of Physics, 2011) Baricholo, Peter; Stehmann, Timo; Rohwer, Erich G.; Collier, M.; Hlatywayo, Dumisani J.; Von Bergmann, Hubertus M.
    A dielectric barrier discharge CO2 TEA laser excited by a thyratron driven power supply has been developed and characterized. Laser output was observed at frequencies up to 25 Hz for an electrode separation of 10 mm with 1.8 mm suprasil glass covering the electrodes. At this gap separation, pulsed power output of about 9 W was detected for gas pressures between 100 and 400 mbar. The laser has a pulse duration was about 0.3 flS with a risetime of ~100 ns. Changing the electrode separation to 5 mm and using 1.4 mm suprasil glass dielectric increased the output power to 23 Wand enabled laser output to be observed at gas pressures up to 700 mbar and maximum pulse excitation frequencies of up to 400 Hz. The developed laser does not require water cooling since the system operates in burst pulse mode.
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    Influence of gas discharge parameters on emissions from a dielectric barrier discharge excited argon excimer lamp.
    (AOSIS Open Journals., 2011-11) Baricholo, Peter; Hlatywayo, Dumisani J.; Von Bergmann, Hubertus M.; Stehmann, Timo; Rohwer, Erich G.; Collier, M.
    A dielectric barrier discharge excited neutral argon (Ar I) excimer lamp has been developed and characterised. The aim of this study was to develop an excimer lamp operating at atmospheric pressure that can replace mercury lamps and vacuum equipment used in the sterilisation of medical equipment and in the food industry. The effects of discharge gas pressure, flow rate, excitation frequency and pulse width on the intensity of the Ar I vacuum ultraviolet (VUV) emission at 126 nm and near infrared (NIR) lines at 750.4 nm and 811.5 nm have been investigated. These three lines were chosen as they represent emissions resulting from deexcitation of excimer states that emit energetic photons with an energy of 9.8 eV. We observed that the intensity of the VUV Ar2* excimer emission at 126 nm increased with increasing gas pressure, but decreased with increasing excitation pulse frequency and pulse width. In contrast, the intensities of the NIR lines decreased with increasing gas pressure and increased with increasing pulse frequency and pulse width. We have demonstrated that energetic VUV photons of 9.8 eV can be efficiently generated in a dielectric barrier discharge in Ar.
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    The longitudinally excited continuous wave CO2 laser
    (LAP LAMBERT Academic Publishing, 2010-10) Baricholo, Peter