20150109 DoE weekly summary.txt

A design study for an electron beam based in-situ materials diagnostic was presented by Harold Barnard on Monday, Jan. 6. This diagnostic, is conceptually similar to AIMS but uses an electron beam and silicon drift detectors (SDD) to perform energy dispersive X-ray (EDX) analysis in-vessel. EDX - commonly used in electron microscopy - will allow for quantitative in-situ elemental analysis of plasma facing materials with < 1cm spatial resolution to a depth of several microns with the ability to redily observe heavy elements (Mo, W, etc) and most low Z elements including Be, Li, B, C, O, etc. When AIMS is used to perform isotopic analysis of and deuterium retention studies, in-situ EDX can perform a complementary role by providing a versitile measurement technique of elemental composition of surfaces. For example, in Alcator C-Mod, changes in thickness of low-Z surface layers (e.g. from boronization) can be measured directly on the shot-to-shot timescale. Erosion and deposition of bulk wall material can also be measured with implanted depth markers. Furthermore, the overlap in beam physics, detection techniques, and established electron microscopy techniques will allow the development of in-situ EDX in tokamaks to draw from the development of AIMS and decades of EDX experience in the microscopy.