The primary parabolic concentrator of 150cm diameter, 67 cm of focal length, 85% reflectivity was used. The light flux distribution at the focus of the primary parabolic mirror was mainly determined by its focal distance and by its rim angle. The accurate alignment of the primary parabolic mirror was considered essential for achieving the minimum focus spot. Since the focused on-axis and the defocused performances of a concentrator gave different flux distributions, the primary mirror was accurately aligned in order to obtain minimum light spot at the focus. Under these conditions, a detailed map of the light distribution was generated by a small aperture (1.0mm) radiometer scanned across the focal plane. Detailed results on and off the focus were obtained. A typical flux distribution at the focal plane of the primary concentrator is given in Fig.1.

The average solar insolation at the scan time was 800W/m2. A near-Gaussian type distribution was obtained, with the maximum solar flux being 25.6W/mm2. Based on the flux distribution at the focal plane, the total solar power of 1258W was calculated which matched well with experimental measurement.

THE FUSED SILICA LIGHT GUIDE ASSEMBLY

The fused silica light guide is a complex assembly composed of one straight light guide, four curved light guides and four more curved and twisted light guide. The light-coupling scheme from the light guides to the laser crystal within the flow tube can be observed in Fig.2.

The light-coupling scheme from the focus of a primary parabolic concentrator to the fused silica light guide assembly is given in Fig.3 an Fig.4, where the composition of nine light guides of 5X5mm square cross sections are of inward convex form. This unique spatial combination of the nine light guides permits the efficient light coupling of the divergent light energy to each light guide with small incident angles, facilitating the future light focusing to the laser crystal..

The packing of five principal light guides and the other four twisted light guides in diagonal positions (as shown in Fig. 5 and Fig.6) allowed an efficient coupling without extra loss.

Fig.6. The input end of one of the other four light guides in diagonal positions.