Oxygen Profile Determination in NIF GDP Capsules Using Contact Radiography

CH capsules, produced with glow discharge plasma coating, pick up oxygen continuously and irreversibly during storage. The added X-ray opacity from this oxygen affects the shock velocity during target implosion, requiring compensation in the shock timing. We developed a radiography technique that nondestructively characterizes the oxygen profile and have used it to track the evolution of the oxygen profiles in various types of storage conditions. Modified storage protocols have reduced the amount of pickup, and our database enables estimation of the oxygen profile at shot time such that the impact on target implosion performance can be minimized.