D. Bittner, A. Bozek, N. Alexander, R. Petzoldt, L. Carlson, S. Grant, and D. Goodin

1. Target Layering: Characterization in a Fluidized Bed D. Bittner, A. Bozek, N. Alexander, R. Petzoldt, L. Carlson, S. Grant, and D. Goodin HAPL Project Review March 21-22, 2006 Oak Ridge National Laboratory

2. The MPLX is an eXperimental system for use in the development of Mass Production Layering processes. • “Layering” is a process for generating a uniform solid hydrogen layer on the inside of a capsule. • In “β-layering” one makes use of the volumetric heat generated by tritium β-decay to redistribute solid hydrogen inside of a capsule. LLNL layered target characterization system refrigeration system • Layering is intensely studied in the ICF program. • ICF uses “one-target” methods. • This IFE task is to show multi-target methods for mass-production. • Use IR as the volumetric heat source with D2. D2 capsule filling and layering

3. The MPLX characterization system will take advantage of the existing experience in ice layer analysis. fill tube aperture collection optics camera shell collimated or diffused rays LLNL layered target Existing experience is with mounted targets that are individually layered and characterized. • A shell either has a fill tube or is permeation filled. • Each shell is mounted and in its own layering chamber. • Layers are typically characterized using shadowgraphy.

4. Layers in shells are characterized using the brightband in shadowgraph images. actual layer thickness (μm) line of sight The brightband is due to reflection off gas/solid interface. 1 mm • Apparent image is more distorted for thin layers. • Apparent ice layer thickness is less than actual thickness. from work performed at LLNL

5. An analysis program extracts brightband profiles from the images and calculates the power spectra. lineout #n lineout #m extract a series of lineouts locate shell edge locate brightband unwrap lineouts rms = 1.4um ice layer perform FFT shell edge from work performed at LLNL

6. Raytrace simulations of shadowgraph images validated the diagnostic technique. • Ice surface described by spherical harmonic modal imperfections. • Images generated using a non-sequential numerical raytrace code. • Images analyzed with the same analysis program used for experimental images. J.A.Koch et.al., FST, vol 43, pg.55 (Jan. 2003) The analysis program-derived power spectra were found to be good indicators of the ice surface power spectra out to between modes 40 and 60. from work performed at LLNL

7. The MPLX characterization system will analyze “selected” capsules from the fluidized bed. • There is a set of system functions: • capsule selector • optics zoom out to grab a capsule • optics zoom in for characterization • There is a set of constraints: • refrigeration vibrations -> capsule motion • gas flow -> capsule motion • all characterization hardware and actuators outside the vacuum chamber Initial capsules will be transparent and nominally 4mm OD with 30um walls.

8. The characterization system will evolve in stages. • Bench top prototyping. • Solve problems outside the vacuum chamber. • Test grabbing shells with/without vibration. • Install prototyped characterization system on MPLX. • Test under actual operating conditions. • Success at this point is defined by being able to reliably grab capsules and watch as ice layers start to form. • Make final improvements to the system. • Improve shell handling, if necessary. • Add narrowband IR source. • Upgrade optics as layer quality improves.

9. Fabrication is underway on the MPLX. • Stand nearing final machining. • Vacuum vessels leak checked successfully. top plate

10. Tabletop design tests are being performed on components prior to cryogenic operation. We are prototyping capsule capture using a vacuum chuck in the process stream. It is easier to solve problems at room temperature than at 20K. Actuator and gripper tests are being performed for the remote handling manipulator. The fluidized bed seal is being optimized for material, size, shape, and drive.

12. A vacuum chuck can be used to reliably “grab” a capsule from a moving bed of capsules. vacuum chuck needle capsule vibrations capsule position operating range N2 gas flow • Tracked capsule with Poisson Spot detector. (see L. Carlson’s talk) • Std. deviation of ~1000 measurements in 1 min. • Initial measurements show no significant flow rate dependence. • Motion at detection system limit. • Polonium source overcame static issues. several layers of 3mm OD shells bed expansion ~ 2

14. Both grounding and polonium were used in evaluating static control. view aluminized mylar • 2mm OD, 200 Å Au-coated shells • Five shells pulled periodically • Surface did not significantly roughen. ground N2 gas flow 1cm diameter bed roughness spec 16 hr. estimated time in bed for power plant bed expansion = 2

15. Summary • A plan is in place for characterizing capsules in the fluidized bed. • We will make use characterization techniques developed in the ICF community.* • MPLX fabrication is progressing. • Prototype tests are underway: • characterization • static solutions * Opaque capsules will require the implementation of x-ray shadowgraphy D-T ice layer in a Be/Cu capsule LLNL/LANL target