Reference Artifacts for NDE

Abstract

Two reference artifacts will be fabricated for this study. One of the artifacts will have a cylindrical geometry and will contain features similar to those on an SNRT target. The second artifact will have a spherical geometry and will contain features similar to those on a Double Shell target. The artifacts were designed for manufacturability and to provide a range of features that can be measured using NDE methods. The cylindrical reference artifact is illustrated in Figure 1. This artifact consists of a polystyrene body containing two steps and a machined slot, into which will fit a tracer made of doped polystyrene. The polystyrene body contains several grooves and can be fabricated entirely on a diamond turning machine. The body can be machined by turning a PS rod to a diameter slightly greater than the finished diameter of 2 mm. The part can be moved off-axis to face it off and to machine the steps, slot, and grooves. The tracer contains a drilled hole and a milled slot, which could be machined with a single setup on a milling machine. Once assembled, the artifact could be placed in a Be tube or other structure relevant to target assemblies. The assembled artifact will contain many features that could be measured using various NDE methods. Some of these features are: Diameter; Maximum height; Step height; Dimensions of upper step; Radius at the union of the bottom of step and the vertical wall; Sizes of the grooves; Distance from step to groove; Slot width; Slot height; Location of the groove beneath the tracer; Diameter and location of drilled hole in tracer; and Size and location of slot in tracer. The spherical reference artifact is illustrated in Figure 2. This artifact is intended to replicate a double shell target, which consists of concentric polymer spheres separated by aerogel. The artifact consists of an upper hemispherical shell composed of 1% BrCH, which mates via a step joint with a hemispherical component made of polystyrene. This lower component contains a replica of an inner capsule from a double shell target. The ''inner capsule'' and the bottom portion of the artifact are fabricated as a single piece to ensure dimensional stability. The area between the upper and lower components is filled by a machined piece of CRF aerogel that contains several intentional defects. Each of the components of this artifact can be fabricated on a diamond turning machine. The assembled artifact will contain several features that could be measured using various NDE methods. Some of these features are: Outer and inner diameters of the upper hemispherical shell; Diameter of the inner sphere; Concentricity of outer and inner spheres; Step joint characteristics; Total width of step in the lower polystyrene component; Size of air gap at the top of the CRF; Size of air gap below the CRF; and Size and location of groove in the CRF.