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Impurity powder injection experiments of boron powder

The impurity powder dropper (IPD) is a device for injecting controlled amounts of submillimetre powder grains into the plasma under the action of gravity. Its main application is to perform a real-time boronization by injecting B powder (and B composites like BN and B4C) into the plasma. The powder, penetrating the hot plasma, evaporates, and the resulting B ions are eventually deposited on the plasma-facing surfaces creating a thin boron layer. Advantages over the standard glow discharge bosonization include no need for the toxic diborane gas B2H6 or to interrupt the plasma operation. This technique has already been shown to improve wall conditioning in tokamaks. It reduces wall recycling and impurity content, which allows the plasma performances to be improved by accessing lower plasma collisionality, similar to the case of glow discharge bosonization.

Furthermore, as these experiments have been mainly performed in H-mode plasmas, the IPD has revealed itself to be an effective tool for the suppression of edge-localized modes, allowing access to an H-mode free of this violent bursts11. Nevertheless, a widespread turbulence reduction and temperature increase like the one reported in this Article has not been previously observed in the powder injection experiments performed on tokamaks or following a glow discharge bosonization. Conversely, edge turbulence is enhanced in the EAST tokamak by suppressing edge-localized modes with B powder injection. Recently, a pulsed injection of B4C powder has been employed on the W7-X stellarator, showing a transient confinement improvement with an increase in ion temperature. In contrast, the variation concerning the baseline level of electron temperature and stored energy assumes positive and negative values between consecutive powder injection pulses. The performance improvement is most likely due to the modification of the plasma profiles and a reversal of the radial electric field in the plasma core, switching from the electron-root regime to the better confining ion-root regime. If you are looking for high quality, high purity, and cost-effective Boron powder, or if you require the latest price of Boron powder, please feel free to email contact mis-asia.

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