@article{hossain_regev_shah_laggner_ammons_mazzeo_kallenberg_davda_crowley_scoville_et al._2026, title={Fluid-kinetic modeling of a high power density radio frequency inductively coupled positive hydrogen ion source}, url={https://doi.org/10.1088/1361-6595/ae3cbf}, DOI={10.1088/1361-6595/ae3cbf}, abstractNote={Abstract High power density radio-frequency (RF) inductively coupled positive ion sources are attractive candidates for next-generation neutral beam injection (NBI) systems, where higher injected power and longer pulse lengths are desired without sacrificing source reliability. Operating at absorbed power densities of order <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:mo>></mml:mo> <mml:mn>1</mml:mn> <mml:mtext> </mml:mtext> <mml:msup> <mml:mrow> <mml:mi mathvariant="normal">W</mml:mi> <mml:mstyle scriptlevel="0"/> <mml:mi>cm</mml:mi> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>3</mml:mn> </mml:mrow> </mml:msup> </mml:mrow> </mml:math> places these sources in a regime with stronger gas heating, higher dissociation, and non-Maxwellian electron energy distributions. The Large Uniform Plasma for Ionizing Neutrals (LUPIN) is an RF inductively coupled plasma source designed to explore this high power density regime and to provide guidance for a positive ion source upgrade for the DIII-D NBI system. LUPIN is designed to operate at up to 20 kW of RF power at 2 MHz, coupling energy through a cylindrical quartz vessel to achieve target ion current densities of <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:mn>2100</mml:mn> <mml:mstyle scriptlevel="0"/> <mml:msup> <mml:mrow> <mml:mi mathvariant="normal">A</mml:mi> <mml:mstyle scriptlevel="0"/> <mml:mi mathvariant="normal">m</mml:mi> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>2</mml:mn> </mml:mrow> </mml:msup> </mml:mrow> </mml:math> . This paper presents fluid-kinetic modeling of LUPIN using the hybrid plasma equipment model where electrons are treated kinetically, and the simulations reveal that electron energy distribution function transitions from nearly Maxwellian in the core to bi-Maxwellian towards the edge. Parametric simulations investigate the effects of RF power, gas pressure, and frequency on plasma density, ion flux, and uniformity. Parametric sweeps reveal that increasing power shifts the primary ionization channel from molecular to atomic with diminishing flux gains due to skin-depth contraction and gas rarefaction. Higher frequency localizes heating and increases <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:msubsup> <mml:mrow> <mml:mi mathvariant="normal">H</mml:mi> </mml:mrow> <mml:mn>2</mml:mn> <mml:mo>+</mml:mo> </mml:msubsup> </mml:mrow> </mml:math> and <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:msubsup> <mml:mrow> <mml:mi mathvariant="normal">H</mml:mi> </mml:mrow> <mml:mn>3</mml:mn> <mml:mo>+</mml:mo> </mml:msubsup> </mml:mrow> </mml:math> delivery to the grid, while elevated pressure boosts ionization yet hinders ion transport due to increase in collisionality.}, journal={Plasma Sources Science and Technology}, author={Hossain, Md Sazzad and Regev, Tom and Shah, Miral A and Laggner, Florian M and Ammons, Keanu J and Mazzeo, Arthur and Kallenberg, Evan and Davda, Kirtan M and Crowley, Brendan and Scoville, John T and et al.}, year={2026}, month={Jan} }
 @article{davda_laggner_kallenberg_ammons_crowley_scoville_hossain_lietz_shannon_mazzeo_et al._2025, title={AMAROK: A Novel Single-Turn Multi-Coil Antenna Demonstration Setup for DIII-D Neutral Beam Injector Upgrade}, DOI={10.1109/ppps56198.2025.11248474}, abstractNote={The Advanced Multi-turn Adaptive Radio-Frequency (RF) source on Kinetic Neutrals (AMAROK) is a novel full-scale RF-Inductively Coupled Plasma (ICP) source producing positive ions designed to upgrade and enhance the heating power of the DIII-D Neutral Beam Injection (NBI) system. AMAROK features a racetrack-shaped dielectric tube measuring 40 cm in length, with a turn diameter of 28 cm at the curved ends, and a height of 30 cm. It is designed to operate with deuterium at a flow rate of 15 Torr-L/s to match the conditions in the NBI injector at the DIII-D, with an operating pressure ranging from 0.1 to 10 Pa. This configuration aims to create a homogeneous plasma source across a potential extraction area of 48 cm by 12 cm. A water-cooled racetrack-shaped Faraday shield was designed to minimize the erosion of the dielectric window, and commercially available solid-state RF generators provide up to 200 kW of power. The optimal frequency for efficient power coupling is currently being explored between <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$2-4 \text{MHz}$</tex>, with the goal of achieving an ion density of approximately <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$10^{18} \mathrm{m}^{-3}$</tex> that is needed to sustain the required ion density to extract a 85 A positive ion beam. AMAROK is expected to explore innovations in single-turn multi-coil antennas, dubbed as the wolverine coil, to study the neutral dynamics within the source for better extraction of the neutrals. AMAROK will also investigate interactions of neutrals with Faraday shields, power coupling, density uniformity, and RF frequency sweeps.}, author={Davda, K. M. and Laggner, F. M. and Kallenberg, E. and Ammons, K. J. and Crowley, B. J. and Scoville, J. T. and Hossain, M.S. and Lietz, A. M. and Shannon, S. C. and Mazzeo, A. G. and et al.}, year={2025}, month={Jun} }
 @article{mazzeo_laggner_ammons_hossain_kallenberg_king_davda_shah_shannon_lietz_et al._2025, title={Design and Engineering of LUPIN: A Test-Bed Radio-Frequency Ion Source for Enhanced Neutral Beam Injection on DIII-D}, volume={6}, url={https://doi.org/10.1080/15361055.2025.2498216}, DOI={10.1080/15361055.2025.2498216}, journal={Fusion Science & Technology}, author={Mazzeo, Arthur and Laggner, Florian M. and Ammons, Keanu J. and Hossain, Sazzad and Kallenberg, Evan and King, Liam and Davda, Kirtan and Shah, Miral and Shannon, Steven C. and Lietz, Amanda M. and et al.}, year={2025}, month={Jun} }
 @article{kallenberg_crowley_scoville_laggner_mazzeo_ammons_hossain_king_lietz_shannon_2025, title={Design and Study of Inductively Coupled Plasma Chamber Components Using the SupRISE Test Device at DIII-D}, volume={8}, url={https://doi.org/10.1080/15361055.2025.2515323}, DOI={10.1080/15361055.2025.2515323}, journal={Fusion Science & Technology}, author={Kallenberg, Evan and Crowley, Brendan and Scoville, John T. and Laggner, Florian M. and Mazzeo, Arthur and Ammons, Keanu J. and Hossain, Md. Sazzad and King, Liam and Lietz, Amanda M. and Shannon, Steven C.}, year={2025}, month={Aug} }