SPUTTER-DEPOSITED BE ABLATORS FOR NIF TARGET CAPSULES

We have performed a series of preliminary experiments to determine whe ther sputter deposition of doped Be is a practical route to producing NIF target capsules with Be ablators. Films ranging in thickness from 7 to similar to 120 mu m have been deposited on spherical polymer mand rels using a bounce pan to ensure uniform coating. With no voltage bia s applied to the pan, relatively porous coatings were formed that were highly permeable to hydrogen. The surface finish of these films range d from similar to 250 nm rms for 13-mu m-thick films to a minimum of s imilar to 75 nm rms for an 80-mu m-thick film. Application of a voltag e bias was found to significantly modify the film morphology. At a bia s of 120 V, 7-mu m-thick films with a dense, fine-grained microstructu re were produced. These capsules had a reflective surface with a 50 nm rms roughness. Finally, to demonstrate the ability to produce a grade d dopant profile, a coating was produced in which the concentration of added Cu was varied from 2.5 atom % at the beginning to zero after 40 mu m of deposition.