1. Be Coating on Spherical Surface for NIF Target Development H. Xu, J. Wall, and A. Nikroo General Atomics 3550 General Atomics Court San Diego, CA 92121

2. Beryllium Targets are essential for Inertial Confinement Fusion because of high x-ray absorption with stable implosions 300 eV design 1000 radii in µm (not to scale) 915 900 850 845 840 760 Cu dopant atom % 0% 0.35% 0.70% 0% DT 1 MJ graded Be:Cu design It requires ~160μm Be/Be(Cu) coatings. better stability for Be capsule

3. Magnetron Sputtering is One Way of Making Be Coatings on Sphere Mandrels - energetic deposition beam - low temperature - relative high rate

4. Be Coatings Characterized by X-ray Radiograph and SEM CH Be 27µ m X-ray radiograph shows ~100μm Be coating and inside CH mandrel. SEM showed columnar grain growth of Be coatings. 0.4-0.5μm/hr

5. Higher Coating Rates Lead to Twisted Grain Structure 0.75 μm/hr 0.5 μm/hr More directional beam at higher power plays a role here.

6. Be Coating Density Measurements Be shellsDensity (g/cc)+3% Be050325, 49μm1.74 Be041206-2, 95μm1.77 Be050414, 43μm1.74 Be050420, 53μm1.74 ρ = M/V 94-95% bulk density

7. TEM showed low void density and small void size voids Low void density and small void size are consistent with density measurements, which indicate Be films are a few percent from bulk density.

8. Roughness Evolution versus Thickness Roughness RMS ~ d β and β is 0.8-1.2, which is consistent with shadowing dominated roughening.

9. Evidence of Self-shadowing Striations seen at high magnification are consistent with shadowing effects. J. Appl. Phys. 91, 1963 (2002) 20º 40º 60º FIB cross section

10. Film Growth Structure Zone Model Microstructure of sputter-deposited coating At 3.7-10mTorr and deposition temperature of 130ºC-150ºC (T/T m ~0.25) microstructure of our Be film is consistent with a transition regime between Zone I and Zone II. Structure Zone Model (SZM) proposed by Thornton (1977) T/T m ~0.25

11. Challenge for full thickness capsule-beyond thin film regime High density up to 150μm thickness: repeatedly demonstrated at ~50μm; what will be the density at ~150μm? Some problems for getting thicker films (100-150μm): agitation, stoppage etc. power law predicts rougher surface with increasing thickness; one approach is to divide full thickness growth into a few thinner layer growth and apply polishing/ion etching at each interfaces. Smooth surface finish: polishing has been demonstrated to improve surface finish. High accuracy film density and doping level measurements. ~100μm coating with nodular growth~100μm coating with columnar grains

12. Summary Be coatings on sphere mandrels have been demonstrated. Columnar grain growth was obtained up to 100μm. Higher density columnar structure has been demonstrated repeatedly up to 50μm. Film roughening mechanism on spherical surface is analyzed and believed to be dominated by shadowing effect. Future efforts are focused on obtaining full thickness NIF capsule with high density and smooth finish.