Why don't you talk to NASA they developed the ceramics for use on space craft.I'm with Todd here. Here is everything I could find you saying about this tube.
A 30 meter long tube was filled with atmospheric value gases. The tube was constructed such that the tube itself was not reactive to LWIR and was insulated to stop energy loss to the room. The ends were opaque and thermo-couplers (accurate to 0.001 Deg C +/-0.003) were positioned throught the length of the tube.They were shielded from LWIR to make sure there were no erroneous readings obtained.
As for the tube, it was made of ceramics which was non-LWIR reactive. So it did not warm with the amount of LWIR we were directing through it. IT was our attempt at keeping the only thing which could warm was the atmosphere in the tube. Ceramics, when warmed, take very little convective energy to warm or cool so they will not adversely affect the outcome of the experiments. Insulating was made much easier as well.
The design of the structure, to do testing, was such that LWIR did not warm it. This was by design to stop convective and conductive interference allowing us to see exactly how the atmosphere reacts.
It exited the tube without causing warming.. We measured the output of the tube to determine how much was being passed through the coulomb. essentially its like putting a spotlight at one end of a tunnel, then watching the light exit the tunnel onto a wall (receptor pad) at the other end.
I know of no transparent or even translucent ceramics. Detectors, by design, would be completely opaque. Where did the energy go?
Tell us something. Could you show us the relationship between CO2 levels and the amount of LWIR received at the end of the tube? For example, with CO2 at 10%, what were the received levels at the far end of the tube from the moment your energized your LW source till you considered the run complete.
Did space craft ceramics make heat disappear? Or just your ceramics?