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Fusion energy: Progress, partnerships, and the path to deployment
Over the past decade, fusion energy has moved decisively from scientific aspiration toward a credible pathway to a new energy technology. Thanks to long-term federal support, we have significantly advanced our fundamental understanding of plasma physics—the behavior of the superheated gases at the heart of fusion devices. This knowledge will enable the creation and control of fusion fuel under conditions required for future power plants. Our progress is exemplified by breakthroughs at the National Ignition Facility and the Joint European Torus.
M. S. Vorenkamp, A. Nagy, A. Bortolon, R. Lunsford, R. Maingi, D. K. Mansfield, A. L. Roquemore
Fusion Science and Technology | Volume 72 | Number 3 | October 2017 | Pages 488-495
Technical Note | doi.org/10.1080/15361055.2017.1335144
Articles are hosted by Taylor and Francis Online.
An impurity granule injector on the DIII-D tokamak (IGI) injects granules into the plasma to trigger Edge Localized Modes (ELMs). Impurities, such as lithium, carbon, and boron, are used. The IGI drops granules (0.3–1.0 mm diameter) from a four chamber segmented storage hopper into a down-tube. The downtube guides the granules into a spinning impeller, rotating at a maximum frequency of 170 hz. The granules’ collisions with the impeller propel the granules (maximum velocity 120 m/s) through a drift tube, through an open torus interface valve shield, and into the plasma. This device underwent substantial upgrades to improve its functionality, to minimize the device footprint, and to automate post injection analysis. Upgrades include: (1) a drop-tube positioner to account for impeller/granule collision trajectories; (2) a granule drop monitor using an LED and a photodetector in the drop-tube; (3) a photodiode based granule ablation monitor; (4) DC isolation from the DIII-D vacuum vessel; and (5) an electric motor impeller drive with an integrated rotational speed sensor. These modifications improved the operability and efficiency of the IGI, leading to the successful triggering of ELMs using gasless impurity injection. These recent upgrades are discussed in detail.