On Thursday, June 7, we began beam profiling the NSTTF field heliostat beam. Using the “Hot 80” heliostats aimed at a single aimpoint on a vertical target, the peak flux was 192 W/cm2. Using the remaining 128 heliostats (the Cool 128) aimed at a single aimpoint on a vertical target, the peak flux was 152 W/cm2. (Six of the 214 field heliostats were not operational the day of this test.) By summing these two flux readings, the estimated peak flux, from these 208 heliostats aimed at single aimpoint would be 344 W/cm2. Currently, we do not have a target that can be accept this flux. For comparison, an exposure in 2008 using all 200 operational heliostats aimed at a single aim point yielded a peak flux of 204 W/cm2.
The Hot 80 are heliostats that are closest to the tower and have facets were focused using the Sandia Optical Fringe Analysis Slope Tool (SOFAST). These heliostats were canted using the Heliostat Facet Alignment and Canting Technique (HFACET). Only the center facets on The Cool 128 were focused using SOFAST, since SOFAST was not fully operational for use on these heliostats. HFACET was used to focusing and cant these heliostats.
Additional beam profiling is planned. (Cheryl Ghanbari, email@example.com, 505-845-3426)