The penetration of CO2-laser technology in industry is conditioned by a profound understanding of underlying physical which determine the laser's machining capability. Besides aspects linked with the beam delivery system, this processing capability is mainly a function of the laser beam quality and the fluctuations. The excitation and de-excitation of the vibrational-rotational levels of the CO2-molecule is extremely complex, since it is least to be considered as a 5 level system. This complexity is t origin of the lack of proper design and optimization criteria for the CO2-laser, despite the rater elementary constituent parts of the laser itself.
a) Evaluation of optimum frequency for the RF excited transverse laser carried out jointly by RFA and AEA was conclusive and showed 27.12MHz as an optimum choice.
b) Direct coupling of an RF generator to an electrode system without the use of a discreet RF impedance network was successfully accomplished. This could reduce overall RFsystem cost by up to 25%. The work also highlighted the need for a laser operating with fixed values for pressure and excitation power to enable effective operation of this type of system.
c) The digital feedback controller performed well and proved that phase delays through the whole system could be compensated and the output stabilised. True laser light closed loop output control with respect to a manual setpoint was achieved.
The main areas of investigations will comprise plasma engineering and flow conditioning, with the aim of ensuring laser operation to the required standards of beam quality for various laser processing functions. Flow visualization and evaluation of plasma parameters, will be combined with computer modelling of the turbulent gas flow to elucidate key features, with particular emphasis on time dependent effects, e.g. laser/plasma fluctuations vs. turbulence. The sources of critical frequencies in the fluuation spectra will be identified and, where possible, eliminated. This also includes the development of dedicated turbolowers with matched load lines.
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OX14 3DB Abingdon
S1 4ES Sheffield
BN22 8QL Eastbourne