interesting -- i wonder if they could have a 2 lens system where your overall system would look like: sun / outer lens / pressurized gas / quartz lens from dia

interesting -- i wonder if they could have a 2 lens system where your overall system would look like: sun / outer lens / pressurized gas / quartz lens from diagram / reactor you could adjust the pressurized gas chamber pressure to match that of the reactor so that you're subjecting the quartz lens to a net zero bending moment/tension. ideally you could then make the outer lens out of something tougher than quartz and it wouldn't need as much high temperature strength since it's farther away from the reactor.