Sample Preheating Capability for Dynamic Material Studies*$^{+}$

Coordinated analysis, design, software development, hardware fabrication, and testing activities have yielded a new control system and experimental load design for dynamic material studies on specimens heated to temperatures exceeding 650$^{\circ}$C prior to high-rate compression on a pulsed-power (e.g., Z machine) or gun platform. A proportional integral derivative controller supplies power for up to 16 resistive cartridge heaters mounted in a load assembly containing one or more test samples. The electrical output from this LabVIEW-based controller to each heater is continuously adjusted using feedback from thermocouples embedded in the load and in each heater. Experiments confirm steady temperature regulation to within $+$/-2$^{\circ}$C of the selected set point, as well as adequate surge protection from built-in electromagnetic pulse isolation circuitry. ANSYS thermomechanical simulations have guided the refinement of load design to minimize sample temperature gradients and thermal distortion. Improved thin-film coatings for the sample/window interface are being developed to ensure the viability of velocity interferometry measurements on preheated samples. *Sandia is a multiprogram laboratory operated by Sandia Corporation, a Lockheed Martin Company, for the U.S. Department of Energy's National Nuclear Security Administration under Contract DE-AC04-94AL85000; $^{+}$This work was done by National Security Technologies, LLC, under Contract DE-AC52-06NA25946 with the U.S. Department of Energy.