Advances in tungsten-armored plasma facing components

Abstract

High-Z armor is appropriate for use on plasma facing components (pfcs) subjected to very high heat loads and low plasma edge temperatures. During the past several years much progress was made on the development of tungsten rod armor bonded to water-cooled heatsinks. These pfcs can endure heat fluxes near 25 MW/m/sup 2/ typical of high density burning plasmas without thermal stress cracking, melting or debonding of the armor. Tungsten rod armor is considered for use on portions of the ITER-FEAT divertor and is the reference design for the FIRE divertor. This year, three 40-cm-long, dual-channel, water-cooled, tungsten rod-armored pfc mock-ups were fabricated by Plasma Processes, Inc. and tested at the Plasma Materials Test Facility at Sandia National Laboratories. The 32-mm-wide armor was fabricated by plasma spraying copper onto the back of a hexagonal close-packed array of 3-mm-diameter tungsten welding rods with an exposed height of 10-mm. In one of the mock-ups, designated PW-8, the armor was joined to a copper heat sink by hot isostatic pressing using a Ni interlayer. In another type of mock-up, designated PW-14, full-penetration electron beam welding was used to join the tungsten and plasma-sprayed copper substrate to the heatsink. The mock-ups were tested with 4 MPa, 20/spl deg/C water at 15 m/s using a rastered electron beam system. The highest absorbed heat flux, 24 MW/m/sup 2/ over a 10-cm heated length, brought the rod ends to the melting point. Fabrication issues, thermal fatigue performance at 20 MW/m, and the results of surface analyses of the rods also are reported. These test results help qualify the pfc design for use in the FIRE divertor.