About radiative temperature measurement with a Streaked Optical Pyrometer

The simple-flux platform at OMEGA [1] was designed to observe ablation-fronts and shock-fronts simultaneously because their interplay is instrumental to ICF design. It is an indirect-drive experiment with one halfraum pluged to a shock tube. The X-ray framing camera (XRFC) was set to visualize both shocked and ablated regions in the tube. The streaked optical pyrometer (SOP), used in an unconventional manner (side-on with respect to the shock propagation), was turned on to probe the location of the shock [1].
Recent analysis of these SOP images have shown surprising results. First, the SOP is sensitive to visible light only and yet, it captured a signal along the whole tube during the nanosecond laser pulse (illuminating the inside of the halfraum) whereas only hard X-rays (>2 keV) are supposed to travel throughout the tube. Second, the power 1/4 of the profile of the SOP signal with respect to time collapses very well, during the nanosecond pulse, with the radiative temperature given by DANTE (which was also turned on) and with the radiative temperature predicted by the hydro-radiative code FCI2.
The relation between these results and the experimental potential will be explained in this talk.

[1] O. Poujade, M. Ferry and I. Geoffray, Phys. Plasmas 24, 102105 (2017)