PEOPLE · FACULTY

FACULTY

David R. Harding
Professor, Senior Scientist LLE
Ph.D. 1986, University of Cambridge (England)

250 E. River Rd, LLE
(585)275-5850
dhar@lle.rochester.edu

Courses

ChE 421: Thin Flims (alternating fall semesters)

Research Topics: Thin Film Deposition, Material Properties of films and composite structures, Developing cryogenic fuel capsules for nuclear fusion experiments

Research Overview: This research investigates the making of fuel capsules for use in fusion experiments at the University of Rochester's Laboratory for Laser Energetics. The immediate application of this work is to study high energy density physics; however, we also study how our materials are made to better understand the principles and mechanisms that give the materials the properties they exhibit.

The capsules we are endeavoring to make are small (1-mm in diameter), with exceedingly thin walls (1-mm), and each capsule has a thick layer of hydrogen-isotope ice (~100-mm) uniformly distributed around the internal perimeter. Making and diagnosing such an entity is a multi-disciplinary endeavor encompassing many aspects of physics, chemistry, and materials and chemical engineering. This research is also part of a small, but highly specialized, national and international research effort.

We have research activities in all the critical subjects required to make such a capsule: First, we make the high-aspect-ratio polymer capsules using thin-film deposition techniques. The processing conditions are optimized to maximize the strength, stiffness and permeability of the material over a wide temperature range (600K to 15K). Second, we have the specialized equipment required to permeate the hydrogen-isotope gas into the capsule (up to pressures as high as 22,000 psi), and then to freeze the gas to 17K to form a smooth spherical solid layer. Ensuring that the capsule survives this processing cycle requires sophisticated thermal modeling, precise control of the temperature and pressure, and accurate knowledge of the equation-of-state for hydrogen and its isotopes. Third, the need to control the distribution of hydrogen ice around the internal surface of the capsule involves research into the behavior of hydrogen as a condensed matter. Here, empirical measurements of the sublimation and condensation processes are combined with heat and mass transport models to develop a mechanism that describes how hydrogen behaves at temperatures where the solid, liquid and gas phases can co-exist. Finally, the cryogenic fuel capsule is imploded at the OMEGA laser facility to diagnose the correlation between the performance of the capsule and the capsule's properties.