No significant heating of the upper dome (which could cause pressure change and focus loss) was observed, as it was exposed to sunlight. No thermal problems of any kind were observed during the testing period.
The effect of the tracking motor movement on the beam shape and position is minimal. When a stepper motor is activated to keep the aim point of the heliostat on the target, there is an oscillation of the position of the beam on the target with an initial magnitude of less than plus/minus 1 inch (less than 0.1 deg) – the oscillation dies out within a couple seconds to the point where the displacement is not visible. There is no visible change in the shape of the beam on the target when a tracking motor pulse occurs. The small oscillation of the beam that occurs when the stepper motor is activated can be observed on the video that accompanies this report. The stepper motors are normally activated at approximately 30 second intervals.
In summary, good focused beam shape with concentration factors of 8.7 have been demonstrated. Beam shape is not affected by tracking motor motions, or other transient effects.
November 24, 2002