Removal of GDP Mandrels from Sputter-Coated Beryllium Capsules for NIF Targets

Ablative targets for the National Ignition Campaign (NIC) have been fabricated by sputter coating spherical mandrels made of glow discharge polymer (GDP) with graded copper doped beryllium (Be) layers. The inner mandrel must be completely removed to meet specific ignition design requirements. The process of removing the mandrel requires elevated temperature in the presence of oxygen. However, elevating the temperature in air also oxidizes the Be and can cause blistering on the inner surface of the Be shell. This paper will discuss a refined technique, which removes the GDP mandrel without compromising the integrity of the inner Be surface. The oxygen gradient that develops during the mandrel removal and the impact of its presence will also be discussed.