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.a[ zv / yv].u]darmytisned tnerruC[ 505005055005Fig. Transverse velocity distributions of a single negative ion beam produced by a cesium-seeded negative ion source. The multi-components, each of which has a particular velocity distribution, compose a resultant asymmetric profile of the single beam. This finding has been well described in our previous publication 1), which was selected as Featured. The cause of such multi-components has not yet been identified, and further investigation will follow. 1) Abundance ratio of multiple velocity distribution components in a single negative ion beamlet produced by a cesium-seeded negative ion source, AIP Advances, 12, 035223 (2022). https://doi.org/ 10.1063/5.00833002) Nonuniform plasma meniscus modelling based on backward calculation of negative ion beamlet, Nuclear Fusion, accepted manuscript (2022). https://doi.org/10.1088/1741-4326/ac86043) Characterisation of negative ion beam focusing based on phase space structure, New Journal of Physics, 22, 023017 (2020). https://doi.org/10.1088/1367-2630/ab6d414) Response of beam focusing to plasma fluctuation in a filament-arc-type negative ion source, Jpn. J. Appl. Phys., 59, SHHA01 (2020). https://doi.org/10.35848/1347-4065/ab74735) Development of a dual beamlet monitor system for negative ion beam measurements, Rev. Sci. Instrum., 89, 123303 (2018). https://doi.org/10.1063/1.505626010-5-10-10-5vx / vz [mrad]15013011090705030Yasuaki Haba is a research assistant at the Department of Electrical and Electronic Engineering, College of Industrial Technology, Nihon University. He received his BSc in physics from Aoyama Gakuin University in 2003, and his MSc in particle physics and astrophysics at Nagoya University in 2006. From 2006 to 2017, he worked at private high schools. After receiving his PhD in particle physics and astrophysics in 2020 at Nagoya University with his research on “Negative ion beam focusing based on phase space structure,” he moved to Nihon University. His major research topic aims to provide a better characterization of beams extracted from cesium-seeded negative ion sources that are utilized for advanced applications such as boron neutron capture therapy, experimental particle physics, and plasma heating for nuclear fusion. Concentrating on the investigation of beams in terms of transverse velocity distributions, a compact negative ion source equipped with a single extraction hole, including beam diagnostics, is being developed at Nihon University. Insights into the velocity distributions depending on the geometries of beam acceleration electrodes with cesium adsorption as well as magnetic fields to remove coextracted electrons will be revealed. Dr. Haba is a member of the Physical Society of Japan. 10-5-1010-10-5vx / vz [mrad]101501301109070503010-5-10-10-5vx / vz [mrad]1015013011090705030－　　－8Research AchievementsYasuaki HABAResearch Assistant, Department of Electrical and Electronic Engineering