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HIGH POWER 15/20 KW CO2 LASERS FOR MATERIALS PROCESSING

Objective


2 Laser modules, one in the turbulent axial flow DC discharge (TAF) and one in the radiofrequency discharge (RF) approach are fully operational at an output power of 10 kW. The RF laser has also achieved 30 kW of peak power in the superpulse mode. Successful power extraction has been demonstrated with an aerodynamic window Good beam quality has been obtained experimentally which compares favourably with the predictions of 2 different computer codes developed by each partner, respectively.
In the present technology the TAF approach is not scalable to powers well beyond 15 kW. However, a medium frequency excitation scheme which has yet to be validated makes higher powers accessible. The power density in the RF approach is already high (15 W/cm{3}) and thus, scalability to powers well in excess of 15 to 20 kW will be achieved by appropriate combination of laser modules.

The general objectives of the research were to establish the basic technology of 2 alternative approaches for second generation high power carbon dioxide lasers;
large volume axial flow discharge with turbulent aerodynamic flow (TAF) stabilization;
large volume transverse flow radio frequency (RF) discharge with capacitive coupling.

The major tasks of the project were basically related to scaling properties of the electrical discharge and the active gas medium and to characteristics of the radiation field and its extraction from the laser device. A final technical evaluation of a 15 to 20 kW laser design was completed including manufacturing aspects.

It was found that both approaches have their merits, especially if the evaluation is extended to the whole laser system. Wall plug efficiencies between 5% and 7% and beam qualities better than 1.5 times diffraction limit were achieved for continuous wave powers of up to 12 kW and peak powers of 20 kW.

The 10 kW TAF laser module was shown to be rather cumbersome and a practical power scaling beyond 15 kW was not possible with present excitation technology which is limited to a maximum power density of 5 watts per cubic centimetre. Power densities in excess of 30 watts percubic centimetre were reached in the 10 kW RF laser module. The present concept is scalable to laser output powers well in excess of 15 kW by appropriate combination of individual modules.
THE MAIN OBJECTIVES OF THE PROJECT ARE TO ESTABLISH THE BASIC TECHNOLOGY OF 2 ALTERNATIVE APPROACHES FOR THE SECOND GENERATION HIGH POWER CO2 LASERS, NAMELY: THE TURBULENT AXIAL FLOW DC-DISCHARGE (TAF) AND THE RADIOFREQUENCY DISCHARGE (RF).
FURTHERMORE THE TECHNICAL POTENTIAL OF THE TWO APPROACHES HAS TO BE EVALUATED WITH RESPECT TO MAIN CRITERIA SUCH AS EFFICIENCY, BEAM QUALITY, MODES OF OPERATION AND COMPACTNESS. FINALLY, THE VALIDATION OF THE RESULTS SHOULD LEAD TO THE DESIGN OF A 15-20 KW LASER FOR INDUSTRIAL APPLICATION, ESPECIALLY FOR LARGE AREA SURFACE TREATMENT.

Funding Scheme

CSC - Cost-sharing contracts

Coordinator

GERMAN AEROSPACE CENTRE
Address
Linder Höhe
51147 Koeln
Germany

Participants (2)

Compagnie Générale d'Electricité (CGE)
France
Address
Route De Nozay
91460 Marcoussis
Institut Méditerranéen de Technologie
France
Address
Technopôle De Château-gombert
13451 Marseille