Multichannel emission spectrometer for high dynamic range optical pyrometry of shock-driven materials

An emission spectrometer (450-850 nm) using a high-throughput, high numerical aperture (N.A. = 0.3)prism spectrograph with stepped fiberoptic coupling, 32 fastphotomultipliers and thirty-two 1.25 GHz digitizers is described. The spectrometer can capture single-shot events with a high dynamic range in amplitude and time (nanoseconds to milliseconds or longer). Methods to calibrate the spectrometer and verify its performance and accuracy are described. When a reference thermal source is used forcalibration, the spectrometer can function as a fast opticalpyrometer. Applications of the spectrometer are illustrated by using it to capture single-shot emission transients from energeticmaterials or reactivematerials initiated by km ⋅s−1impacts with laser-driven flyer plates. A log (time) data analysis method is used to visualize multiple kinetic processes resulting fromimpact initiation of HMX (octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine) or a Zr/CuO nanolaminate thermite. Using a gray body algorithm to interpret thespectral radiance from shocked HMX, a time history of temperature andemissivity was obtained, which could be used to investigate HMX hot spot dynamics. Finally, two examples are presented showing how the spectrometer can avoid temperature determination errors in systems where thermal emission is accompanied by atomic or molecular emission lines.

Source: Review of Scientific Instruments - October 12, 2016 Category: Physics Authors: Will P. Bassett and Dana D. Dlott Source Type: research