PROGRESS: The techniques required to concentrate solar light in order to obtain a resolution <10 mm for sintering were developed based on experience of the ESA-GSTP project.
A solar simulator had to be used since the solar oven, using the real sun, does not provide sufficient stability of light due to the change in the weather condition during the day. Two xenon lamps were therefore calibrated in a way that the focal point was as small as possible after reflection on the mirror.
Pictured is the Gaussian distribution of the flux density. Using more than two lamps was not possible due to the limited resistance of the mirror changing the light direction from horizontal to vertical.
The focal point could not be made smaller than 14 mm. A more concentrated light led to breakage of the mirror. In practice, since the sintering cannot always occur at the exact focal point, the sintering resolution in this stage is about 20-30mm.
Image: DLR Köln