A horizontal powder injector for W7-X

Injection of low-Z powders into fusion plasma has been used to improve wall conditions, similar to the standard boronization process using diborane. Powder injection has the advantage of being much simpler, non-toxic, and efficient. The W7-X stellarator is planning on utilizing powder injection in l...

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Bibliographic Details
Published in:Fusion engineering and design 2019-09, Vol.146, p.1403-1407
Main Authors: Nagy, Alexander, Bortolon, A., Gates, D., Gilson, E., Killer, C., Klinger, T., Lunsford, R., Maingi, R., Mansfield, D., Mauzey, D., Nazikian, R., Roquemore, L., Wolfe, E.
Format: Article
Language:English
Subjects:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY
Actuators
Biocompatibility
Boronization
Diborane
High temperature environments
Horizontal
Impurity
Injection
Injectors
Magnetic fields
MATERIALS SCIENCE
Piezo feeder
Polyether ether ketones
Powder
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Summary:Injection of low-Z powders into fusion plasma has been used to improve wall conditions, similar to the standard boronization process using diborane. Powder injection has the advantage of being much simpler, non-toxic, and efficient. The W7-X stellarator is planning on utilizing powder injection in long pulse discharges; a proof-of-principle test for horizontal injection into the plasma was conceived, a Probe Mounted Particle Injector (PMPI). The PMPI concept is developed using a polyetheretherketone (PEEK) paddle wheel hub that is driven by a piezo motor, due to the high magnetic fields, that rotates at 100 deg/s. This small PMPI fits into an envelope of 120 mm diameter × 150 mm long, a standard size for Multi-Purpose Manipulator (MPM). The device is housed in a carbon cup mounted on a retractable probe that can be placed near the plasma edge, enabling powder injection ˜4–8 cm radially into the boundary plasma. The feed for the paddle is via piezo electric actuator that vibrates a funnel filled with powder into a trough for the paddle to push. The 8 paddle arms, 35 mm long and 10 mm wide, are made from 0.38 mm thick PEEK which drag slightly along the powder-filled trough bottom, becoming a spring-loaded paddle which accelerates the powder upon release. Design challenges are the high ambient magnetic field, vacuum compatible materials, high temperature environment, limited rotary-drive options, and compact space. The design and testing of this new device will be presented.
ISSN:0920-3796
1873-7196
DOI:10.1016/j.fusengdes.2018.12.099