Laser welding was carried out using a co-axial core-ring beam, with independent control of the power to the coreand the ring. The welding process was observed using high-power X-rays and high-speed imaging equipment.Adjusting the relative powers of the core and the ring beams was found to have profound effects on the shape ofboth the capillary created and the weld melt pool. Moderate laser power densities in the ring were found toincrease the top diameter of the weld pool and reduce fluctuations in the welding process. High laser powerdensities in the ring led to the creation of a second capillary which largely acted independently of the capillarygenerated by the laser power in the core. At high power densities and welding speeds the two capillaries werealmost completely separated in the direction of travel.
Zaiß et al. (Thu,) studied this question.