IR Absorptive Properties of Plastic Materials Used in ICF Capsules

One approach to improving the quality of the DT ice layer on the inside of a NIF capsule target is to enhance the natural -layering process by heating the ice with infrared light (IR) tuned to a D₂ or DT excitation band. However to do this the IR must pass through the capsule wall, and absorption by the capsule material results in heat generation that is deleterious both in terms of reducing the energy input to the ice as well as increasing the difficulty of symmetrically cooling the capsule. In order to optimize the choice of wavelength we have measured the wavelength dependent transmission properties of IR through the plastic materials we are considering for capsule fabrication. We will present wavelength dependent extinction coefficient data for normal and fully deuterated plasma polymer and vapor deposited polyimide.