Heliotron J is a plasma device designed to optimize the helical-axis heliotron configuration devised by Kyoto University researchers. Its physical design incorporates three elements: the concept of quasi-isomagnetic fields, the ability to control the bumpiness of the magnetic field, and a magnetic well that covers the entire confinement volume. These elements realize a high compatibility between particle confinement and MHD stability, which has been an obstacle in previous helical-axis heliotrons.
Since the initiation of plasma experiments in 2000, we have been steadily progressing towards demonstrating Heliotron J's high potential as a high-temperature plasma confinement system. We have improved our heating system and measuring equipment, generated high-temperature plasmas in regions with low collision rates (electron temperature of about 1 keV at the plasma center), and demonstrated good energy confinement (1.5 to 2 times greater than the ISS95 scaling value). Goals of the second mid-term plan for Heliotron J include (1) academic research of advanced helical configurations with an emphasis on understanding the unusual transport properties of helical systems with non-planar magnetic axes, (2) improving the plasma quality, especially by refining particle confinement and increasing the beta limit, and (3) developing Heliotron J into a nuclear fusion reactor. In addition to improving and expanding the experimental data infrastructure of Heliotron J, these goals will greatly contribute to the Numerical Test Reactor project and international collaborative research. We kindly ask for your guidance and support as we move forward in new research directions.