David C. Harper

High-Heat-Flux Testing of Irradiated Tungsten-Based Materials for Fusion Applications Using Infrared Plasma Arc Lamps

Abstract Testing of advanced materials and component mock-ups under prototypical fusion high-heat-flux conditions, while historically a mainstay of fusion research, has proved challenging, especially for irradiated materials. A new high-heat-flux–testing (HHFT) facility based on water-wall plasma arc lamps (PALs) is now introduced for materials and small-component testing. Two PAL systems, utilizing a 12 000°C plasma arc contained in a quartz tube cooled by a spiral water flow over the inside tube surface, provide maximum incident heat fluxes of 4.2 and 27 MW/m2 over areas of 9×12 and 1×10 cm2, respectively. This paper will present the overall design and implementation of a PAL-based irradiated material target station (IMTS). The IMTS is primarily designed for testing the effects of heat flux or thermal cycling on material coupons of interest, such as those for plasma-facing components. Temperature results are shown for thermal cycling under HHFT of tungsten coupon specimens that were neutron irradiated in HFIR. Radiological surveys indicated minimal contamination of the 36-× 36-× 18-cm test section, demonstrating the capability of the new facility to handle irradiated specimens at high temperature.

High-Density Infrared Cladding of Ta on Steel

The addition of tantalum to the inside diameter of a gun barrel would reduce erosion during firing of medium and large caliber guns. In this work, chemical vapor deposited (CVD) Ta was bonded to A723 Steel. High-density infrared (HDI) heating was employed to bond Ta to steel at 1440°C while maintaining bulk steel temperatures below the 357°C threshold for retaining beneficial compressive stresses (autofrettage). Through-thickness temperature evolution modeling was performed. Metallographic evaluation of claddings is reported. Characterization of the interface showed that metallurgical bonding occurred while keeping bulk temperatures low.

HIGH DENSITY INFRARED PROCESSING OF WC/Ni–11P COMPOSITE COATINGS

Abstract A new high density infrared based coating process has been developed to produce wear resistant coatings on AISI 4340 steel substrates that are of commercial interest. The process combines infrared heating, with power densities up to 35 MW m -2, with room temperature precursor spray deposition processes to rapidly form wear resistant coatings. Here, the process is demonstrated using a 20 vol.-%WC reinforced coating in a Ni-11 wt-%P binder on a AISI 4340 steel substrate, to produce a smooth, high density, 10 μm thick coating with minimal degradation of the WC reinforcement or base steel and a hardness seven times greater than that of the substrate.

Facility for high-heat flux testing of irradiated fusion materials and components using infrared plasma arc lamps

A new high-heat flux testing (HHFT) facility using water-wall stabilized high-power high-pressure argon plasma arc lamps (PALs) has been developed for fusion applications. It can accommodate irradiated plasma facing component materials and sub-size mock-up divertor components. Two PALs currently available at Oak Ridge National Laboratory can provide maximum incident heat fluxes of 4.2 and 27 MW m−2, which are prototypic of fusion steady state heat flux conditions, over a heated area of 9 × 12 and 1 × 10 cm2, respectively. The use of PAL permits the heat source to be environmentally separated from the components of the test chamber, simplifying the design to accommodate safe testing of low-level irradiated articles and materials under high-heat flux. Issues related to the operation and temperature measurements during testing of tungsten samples are presented and discussed. The relative advantages and disadvantages of this photon-based HHFT facility are compared to existing e-beam and particle beam facilities used for similar purposes.

Flexible solar cells in milliseconds: Pulse Thermal Processing of CdTe devices

Materials for a CdTe solar cell (ITO/CdS/CdTe/Cu/Pt) were sputtered at room temperature onto kapton, then transformed from resistive layers into a working solar cell by Pulse Thermal Processing (PTP), a novel radiant heat treatment developed at Oak Ridge National Laboratory (ORNL). Unlike conventional device fabrication approaches, the solar cell was a complete device, front-to-back contact, prior to heat treatment. In this proof-of-concept approach, the I-V curves for the as-deposited sputtered materials demonstrate little measurable photovoltaic (PV) activity, but achieved a Voc of 634 mV after PTP. Based on process simulations, its estimated that the material/device transformation occurred in under 30 ms, while maintaining the kapton substate at temperatures below 250 °C.