Fill-tube-induced mass perturbations on x-ray-driven, ignition-scale, inertial-confinement-fusion capsule shells and the implications for ignition experiments

On the first inertial-confinement-fusion ignition facility, the target capsule will be DT filled through a long, narrow tube inserted into the shell. microg-scale shell perturbations Delta m' arising from multiple, 10-50 microm-diameter, hollow SiO2 tubes on x-ray-driven, ignition-scale, 1-mg capsules have been measured on a subignition device. Simulations compare well with observation, whence it is corroborated that Delta m' arises from early x-ray shadowing by the tube rather than tube mass coupling to the shell, and inferred that 10-20 microm tubes will negligibly affect fusion yield on a full-ignition facility.     

A semi-automated in-plane loader for materials testing

A universal testing machine is described for applying general in-plane loading as combinations of tension or compression, shear and in-plane rotation. It is composed of three computer-controlled hydraulic actuators connected to a movable head free to execute translation and rotation motions. Test specimens 1 in.×1.5 in. (25 mm×38 mm) are loaded through hydraulic grips for which the gripping pressure can be programmed. Other components include a mechanical specimen loader, a video digitizer for defining the specimen geometry, and a computer system that controls the test and gathers and stores the test data. A large number of tests can be conducted inexpensively over a broad range of loading conditions in this system, as opposed to the more generally available complex loading systems for which specimen costs are higher and testing time considerably longer. With rather limited changes, the system could be fully automated. The system has been used to characterize the fracture behavior of a series of carbon/epoxy composites over a broad range of in-plane loads.     

The photocurrent response of human cones is fast and monophasic

Background  

The precise form of the light response of human cone photoreceptors in vivo has not been established with certainty. To investigate the response shape we compare the predictions of a recent model of transduction in primate cone photoreceptors with measurements extracted from human cones using the paired-flash electroretinogram method. As a check, we also compare the predictions with previous single-cell measurements of ground squirrel cone responses.