San Diego, California, 17-19 June 2002

Studies of Solid DT in IFE Targets

J. Hoffer

Los Alamos National Laboratory

Los Alamos, NM 87545

hofferlanl.gov

We discuss ongoing work at Los Alamos to study the feasibility of cryogenic targets for IFE applications. These include:

• an experiment to measure the modulus and yield strength of solid DT,

• experiments to measure the response of a cryogenic, DT- layered target to a rapid temperature transient, and

• measurements of the solid DT surface spectrum following beta- layering over a layer of foam.

These topics address the general problem of cryogenic target survivability during injection into the reaction chamber. For instance, the yield strength of solid DT may well prove to be too low to support the high g- loads being proposed for target acceleration. Because the reaction chamber walls will be very hot, the therma l load on the target is high. Most of the energy absorption occurs in the thin plastic outer shell of the target, which then slowly heats the inner solid DT fuel layer via conduction. When this heating is sufficient to cause the fuel layer to sag or roughen, ignition is no longer possible. Knowing the expected practical 'lifetime' of the target then puts an upper bound on the necessary injection speed that in turn affects the injector length and/or accelerative g- loading.

Intermediate foam layers complicate the problem of target lifetime. On the one hand, the foam plastic also absorbs heavily in the infrared. However, the presence of fine-grain-sized foam may allow the inner, pure DT fuel layer to form with a smoother inner surface, delaying the time whe n unacceptable roughening would occur.