A. R. Raffray, F. Najmabadi, and the ARIES Team
University of California, San Diego
raffray
fusion.ucsd.edu
The ARIES-IFE effort is focused on a broad-based assessment of chamber options and related technologies relevant for both laser and heavy ion drivers. This effort includes an assessment of the key issues and of operating parameter windows for chamber design concepts. These can be classified into three primary categories: (1) dry chambers; (2) solid wall chambers protected with a "sacrificial zone" (such as liquid films); and (3) neutronically thick liquid walls. Each class of chamber embodies a different characteristic set of issues and constraints and in order to maintain focus, each of these chamber classes is examined sequentially. The activities on dry chamber walls were carried out in 2001, followed by activities on thin liquid films which are about to be concluded and followed by activities on the thick liquid walls.
For the solid armor configuration (dry wall), lifetime is a key issue and the candidate armors must provide high temperature resistance and accommodate the operating conditions with minimal erosion. Past studies indicated the need for a protective gas to prevent unacceptable wall erosion. The ARIES-IFE effort has provided a more detailed assessment of dry chamber wall based on ion and photon spectra from direct-drive targets proposed by NRL and an indirect-drive target from LLNL. Several material options were considered including carbon and tungsten flat wall and a high-porosity fibrous carbon configuration to maximize the incident surface area and help accommodate the energy deposition. Detailed analyses using very fine meshes were performed for both the energy deposition from the photons and ions and the thermal behavior of the wall. The time of flight effect for both the photons and ions were included, whereby the photon energy reaches the wall faster than the ion energy, and a dramatic effect on the wall thermal and erosion behavior was observed when compared to the previously-assumed instantaneous energy deposition case.
In thin liquid film configuration, the film protects the structural wall by absorbing most of the energy from the incident photons and ions and re-transmitting it by conduction over a longer time to the coolant. Major issues include: the need to re-establish the film for complete wall coverage following each shot, which would be affected by the supply method (e.g injection from the back through a porous layer or film flow along the wall surface); and the need to provide an acceptable environment to satisfy target injection and driver requirements which is dependent on aerosol formation and behavior and on the rate of vapor recondensation.
This presentation summarizes the key chamber engineering issues and analysis carried out as part of the ARIES-IFE study on dry walls and thin liquid films and discusses their implication on IFE chamber and reactor design.
