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A Pellet Injector and Associated Diagnostics for Performing Plasma Studies on the TJ-II Stellarator
| Content Provider | Semantic Scholar |
|---|---|
| Author | Mccarthy, K. J. Panadero, N. Arapoglou, Ioanna Combs, Stephen K. Caughman, J. B. O. Cal, Enrique A. De La Foust, C. García, Rafael A. Sanchez, Julio Hernandez Martin, Fujda Navarro, Mônica Pastor, Ignacio Rodriguez, Michael C. Velasco, Jose Luis |
| Copyright Year | 2015 |
| Abstract | A compact pellet injector has been installed and is now operating on the TJ-II stellarator. It is a four-pellet system equipped with a cryogenic refrigerator for in-situ hydrogen pellet formation, a fast propellant valve system for pellet acceleration (≤1200 m/s), in line diagnostics for determining pellet velocity and mass, and injection lines to the magnetically confined plasmas (ne(0) ≤5x10 m, Te(0) ≤1 keV, B(0) = 1 T, average minor radius = 0.22 m) created in this heliac device. It is intended for use on TJ-II as an active diagnostic for studying particle transport, suprathermal electron populations, magnetic field orientations, and rational surfaces as well as for plasma centre fuelling. For this, optical fibre coupled silicon diodes (or avalanche photodiodes), installed outside of nearby viewports, record the Balmer Hα light (λ = 656.28 nm) emitted from the neutral cloud that surrounds a pellet as it crosses the plasma. In this way, it is possible to follow the temporal evolution of the pellet ablation. In addition, an ultrafast-frame CMOS camera, equipped with a bifurcated coherent fibre bundle, is used to obtain multiple images of the neutral cloud. Finally, additional plasma diagnostics, e.g. Thomson Scattering, broadband bolometer arrays, Heavy Ion Beam Probes, combine to make the overall system a very powerful tool for plasma studies. In this paper, after providing a brief overview of the pellet injector and its associated plasma diagnostics, first injections into TJ-II plasmas are used to evaluate its overall capabilities to undertake and fulfil the objectives outlined previously. In particular, we assess the associated plasma diagnostics used to follow pellet ablation across the plasma radius, to locate particle deposition and to subsequently follow the plasma evolution along the discharge after injection. |
| File Format | PDF HTM / HTML |
| Alternate Webpage(s) | http://www.euro-fusionscipub.org/wp-content/uploads/2015/05/EFCP150208.pdf |
| Language | English |
| Access Restriction | Open |
| Content Type | Text |
| Resource Type | Article |
