2D soft x-ray system on DIII-D for imaging the magnetic topology in the pedestal region

• Published in: Review of Scientific Instruments
• Main Authors: Shafer, M. W., Battaglia, D. J., Unterberg, E. A., Evans, T. E., Hillis, D. L., Maingi, R.
• Format: Article in Journal/Newspaper
• Language: English
• Published: AIP Publishing 2010
• Subjects: Instrumentation; Edge Island
• Online Access: http://dx.doi.org/10.1063/1.3481166; https://pubs.aip.org/aip/rsi/article-pdf/doi/10.1063/1.3481166/16038308/10e534_1_online.pdf

A new tangential two-dimensional soft x-ray imaging system (SXRIS) is being designed to examine the edge island structure in the lower X-point region of DIII-D. Plasma shielding and/or amplification of the calculated vacuum islands may play a role in the suppression of edge-localized modes via resonant magnetic perturbations (RMPs). The SXRIS is intended to improve the understanding of three-dimensional (3D) phenomena associated with RMPs. This system utilizes a tangential view with a pinhole imaging system and spectral filtering with beryllium foils. SXR emission is chosen to avoid line radiation and allows suitable signal at the top of a H-mode pedestal where Te∼1–2 keV. A synthetic diagnostic calculation based on 3D SXR emissivity estimates is used to help assess signal levels and resolution of the design. A signal-to-noise ratio of 10 at 1 cm resolution is expected for the perturbed signals, which are sufficient to resolve most of the predicted vacuum island sizes.