Manufacturing Technologies for Ultra-High-Vacuum–Compatible 10 MW/m2 High Heat Flux Components for Application in Fusion Devices

Abstract

High heat flux components form the primary interface for thermal management of injectors in fusion devices. The requirement for such application varies from 1 to 10 MW/m2. Ultra-high-vacuum compatibility is the inherent characteristic of such components, and manufacturing processes involve the development of specific materials, process qualification of special processes like electron beam welding (EBW), and component performance validation. One such component of active thermal management in a neutral beam injector is the hypervapatron-based heat transfer element (HTE), which is designed to absorb heat flux as high as 10 MW/m2. The route to realization is through a prototype and a one-to-one model and evaluating their performance. The development route of HTEs includes several important areas. One area is development of precipitation-hardened CuCrZr material characterized for its fatigue life (more than 100 000 stress-controlled cycles); mechanical properties at ambient temperature [ultimate tensile strength (UTS) >384 MPa, elongation >13%] and at operational temperature, i.e., 350°C (UTS >263 MPa, elongation >14%); and restricted chemical composition range of Cr, Zr, Cd, and O2 to enhance the precipitation effect and weldability of the component. A second area is similar material (CuCrZr to CuCrZr) and dissimilar material (CuCrZr-Ni-SS316L) joining by an advanced technology like EBW in a controlled environment to enhance the localized high heat input over a large weld penetration depth with minimal distortion and thereby overcome the effect of thermal diffusion by typical copper during welding. A third area is validation of these weld joints with respect to international codes/standards. Successful realization of this route establishes HTEs as main baseline components of the high heat flux system or neutral beam system. Similar application areas can be identified in various fusion devices. The paper presents the implementation of this realization route of prototype HTEs including details of the assessment carried out with respect to application.