A multi-species powder dropper for magnetic fusion applications

Abstract

We present a device for controlled injection of a variety of materials in powder form. The system implements four independent feeder units, arranged to share a single vertical drop tube. Each unit consists of a 80 ml reservoir, coupled to a horizontal linear trough, where a layer of powder is advanced by piezo-electric agitation at a speed proportional to the applied voltage, until it falls into a drop tube. The dropper has been tested with a number of impurities of low (B, BN, C), intermediate (Si, SiC), and high Z (Sn) and a variety of microscopic structures (flakes, spheres, rocks) and sizes (5-200 μm). For low Z materials, drop rates ∼2-200 mg/s have been obtained showing good repeatability and uniformity. A calibrated light-emitting diode (LED)-based flowmeter allows measuring and monitoring the drop rate during operation. The fast time-response of the four feeders allows combination of steady and pulsed injections, providing a flexible tool for controlled-dose, real-time impurity injection in fusion plasmas.

Active conditioning of ASDEX Upgrade tungsten plasma-facing components and discharge enhancement through boron and boron nitride particulate injection

“…The Impurity Powder Dropper as described in [10] The IPD was installed in sector 14 on the top of AUG and connected to the main vessel through a 2.5 m long drop tube. An image of the installation as well as a cutaway drawing of the interior of the powder dropper assembly can be seen in figure 1.…”

Observation of a novel reduced-turbulence regime with boron powder injection in a stellarator

“…The impurity powder dropper (IPD) is a device for injecting controlled amounts of sub-millimeter powder grains into the plasma under the action of gravity [3]. Its main applications is to perform a real-time boronization by injecting B powder (and B composites such as BN and B 4 C) into the plasma.…”

A horizontal powder injector for W7-X

“…A continuous layer of powder, 1-2 mm thick, is fed under the paddle wheel by a vibratory feeder, the design adapted from the piezoelectric feeder used on vertical powder droppers [3]. A side mounted tray with an 80 ml volume cylindrical funnel/reservoir mounted at the opposite end of the paddle is vibrated causing powder to flow out of the 2mm gap between the funnel output and delivery tray bottom toward the paddle wheel.…”

“…See figure 1 for the MPM overall view, and figure 2 for pictures of the PMPI assembly. If the first experiments successfully confirm the potential of powder injection for conditioning W7-X, then a vertical drop unit, with multiple larger reservoirs would be considered, similar to other units presently deployed on AUG, DIII-D, EAST and KSTAR and [3].…”