Plasma experiments on electron cyclotron resonance heating (ECRH) using a high-power optical vortex beam (OVB) have been demonstrated for the first time in the Heliotron J stellarator/heliotron device. The OVB is generated by a spiral phase plate in a 70 GHz ECRH system. Plasmas are successfully sustained up to the second harmonic extraordinary (X) mode cut-off density. Virtually identical performance in terms of stored energy and density limits confirms the injection of the OVB as a heating tool comparable to Gaussian beams. These first results showed that the OVB is a possible method for the research on wave and plasma physics in magnetically confined fusion systems.
For about 120 years, the Atomic Spectroscopy Group at the National Institute of Standards and Technology (NIST) was one of the world leaders in experimental and theoretical atomic and plasma spectroscopy, production of standard reference data for atomic parameters, and development of atomic databases. Nonetheless, in early 2025 the group was abruptly terminated due to the apparent change of priorities for NIST research. Fortunately, the whole ASG scientific and engineering team was soon adopted by NASA Goddard Space Flight Center and the University of Maryland College Park which allowed us to preserve its rich legacy and offer new opportunities. We will briefly describe the achievements and status of the group at this pivotal moment of its history as well as its research plans for the near future. (c) 2026 The Japan Society of Plasma Science andNuclear Fusion Research
This study investigated the effects of heavy-ion beam (HIB) pulse waveform and irradiation time on the implosion process of a multilayer fuel target designed for heavy-ion inertial fusion (HIF). Achieving high beam intensity, beam quality, and precise timing synchronization is challenging owing to the space charge effect. Multilayer fuel targets with low-density foam layers may alleviate these beam condition requirements and help achieve robust, uniform implosion. Using a 1-D spherical coordinate hydrodynamic model, this study evaluated implosion dynamics and variation using the coefficient of variation. Results showed that multilayer targets offer enhanced robustness against beam irradiation time variations compared to conventional designs. The Pb pusher configuration consistently demonstrated superior stability, attributed to the high density and atomic number of Lead that influences transport and hydrodynamics. The foam layer also plays a crucial role in mitigating the adverse effects of timing fluctuations. These findings suggest that multilayer fuel targets, particularly with a Pb pusher, provide a compelling advantage for practical applications by offering improved robustness and simplifying parameter optimization procedures compared to conventional HIF targets. (c) 2026 The Japan Society of Plasma Science andNuclear Fusion Research
A tomography system in the PANTA device found fluctuation pattern distortion during a cycle of the solitary wave oscillations, and global moment vector analysis quantified the degree of the distortion successfully. The method can be refined by help of Fourier-Rectangular Function Expansion to analyze local property of the distortion. This article present the method, called the local moment vector analysis, which can evaluate the local distortion of fluctuation patterns, with the results obtained by applying the local method to the solitary wave oscillations. (c) 2026 The Japan Society of Plasma Science andNuclear Fusion Research
To properly study plasma fluctuations and to develop new plasma processing technologies, precise calibration of probes is required. We exploit plasma fluctuations properties to develop a novel simple method for calibrating the radial position of a probe in a linear magnetized plasma device. We determine the probe radial position with respect to the plasma column axis by using a previously calibrated reference probe. This study provides the experimental evidence that plasma fluctuations can be used not only to investigate plasma physics but also to determine the radial position of probes. (c) 2026 The Japan Society of Plasma Science andNuclear Fusion Research
