NIF is equipped with two target positioners (TARPOS), located at 90-239 and 90-015, which are capable of holding cryogenic and non-cryogenic (“warm”) targets, including gas targets. The TARPOS at 90-015 is designed to handle layered targets, including those containing tritium. It is commonly referred to as “cryoTARPOS,” though both TARPOS can field cryogenic (but not layered) targets. The cryoTARPOS has an in situ, three-axis x-ray viewing system and can handle large quantities of tritium for producing cryogenic layers of tritium– hydrogen–deuterium (THD) gas mixtures (see Section 5.4.3). Both TARPOS provide for positioning a target within ±5 cm of TCC. Translation in the vertical direction by ±5 cm is achieved by a combination of rotation about the gimbal and an opposite bend (“nod”) approximately 2 m from chamber center (see Figure 5-5). These same motions allow for up to a 1° tilt of the target axis. Translation in the horizontal direction is achieved by a rotation about the gimbal. An offset of 5 cm results in a rotation of approximately 0.5° about the vertical. No correction is provided in this direction. TARPOS also provides for ±14° rotation about the axis of the positioner itself; the limit is due to internal cabling. Each is outfitted with a cable harness that includes wires for temperature control of a cryogenic target system5, gas ll lines, fiber optics (90-239 only), and other power cables.
Figure 5-5. (Above) Diagram of the target positioner, showing the degrees of freedom for positioning a target.