Author: Benitez, J.Y.
Paper Title Page
MOC2 A novel inductive oven design for the production of high current, metal ion beams 19
 
  • D.S. Todd, J.Y. Benitez
    LBNL, Berkeley, CA, USA
  
  Essential to the proposed search for element 120 at LBNL’s 88-Inch Cyclotron is the continual delivery of over a particle microamp of ⁵⁰Ti¹²⁺ for weeks-long campaigns spanning many months. The fully-superconducting ECR ion source VENUS will be the injector source for these runs, and we have developed a new inductive oven design that can survive VENUS’ high magnetic fields while injecting metallic gas into the plasma with high efficiency. The new oven employs a vertical susceptor to permit use with metals that melt before outgassing sufficiently, while also allowing a rotation of the oven’s material exit toward the plasma center for better conversion efficiency to the produced beam. The performance of VENUS with this oven has been outstanding: as reported here, 282 MeV ⁵⁰Ti¹²⁺ beams with stable currents between 1.0 and 1.5 pμA have been delivered for superheavy element searches over multiple ten-day runs.  
DOI • reference for this paper ※ doi:10.18429/JACoW-ECRIS2024-MOC2  
About • Received ※ 04 October 2024 — Revised ※ 10 October 2024 — Accepted ※ 29 January 2025 — Issued ※ 22 June 2025
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TUC3
 Microwave transmission measurements at the VENUS ECR ion source  
 
  • J.Y. Benitez, D.S. Todd, S. Holter
    LBNL, Berkeley, CA, USA
  
  The VENUS electron cyclotron resonance (ECR) ion source uses injected 18 and 28 GHz microwave power to resonantly energize electrons for plasma ionization. Waveguide antennas detecting 18 and 28 GHz microwaves located after the extraction electrode exit aperture of the source are used to measure the transmitted microwave power under different source and plasma conditions. In addition, an antenna is placed in the 28 GHz waveguide to measure 18 GHz microwaves that make it back out, during 18 GHz only operation. The relationship between the transmitted and reflected power is investigated. Measuring the transmitted power can aid in understanding how to efficiently couple the microwaves to the plasma so as to achieve the maximum source output. The transmitted power, which is inversely related to the absorbed power, is dependent on the neutral gas pressure, and the minimum magnetic field Bmin. The production of ¹⁶O⁶⁺ is also compared with the transmitted power.  
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WEB2 Applying machine learning techniques to the operation of the superconducting ECR ion source VENUS 152
 
  • D.S. Todd, A. Kireeff, H. Crawford, J.Y. Benitez, M. Salathe, V. Watson, Y.S. Lai
    LBNL, Berkeley, CA, USA
  
  Funding: This material is based upon work supported by the U.S. Department of Energy, Office of Science, Nuclear Physics program under Award Numbers DE-FOA-0002490 and DE-FOA-0002875
An operator of the superconducting ECR ion source VENUS tasked with optimizing the current of a specific ion species or finding a stable operating mode is faced with an operation space composed of ten-to-twenty knobs in which to determine the next move. Machine learning techniques are well-suited to multidimensional optimization spaces. Over the last three years we have been working to employ such techniques with the VENUS ion source. We will present how the introduction of computer control has allowed us to automate tasks such as source baking or to utilize optimization tools to maximize beam currents with no human intervention. Our more recent applications of Bayesian optimization and reinforcement learning to beam current maximization and the maintenance of long term source stability will also be presented. Finally, we will discuss control and diagnostic changes that we have employed to exploit the faster data collection and decision making abilities when VENUS is under computer control. 		 
DOI • reference for this paper ※ doi:10.18429/JACoW-ECRIS2024-WEB2  
About • Received ※ 04 October 2024 — Revised ※ 18 October 2024 — Accepted ※ 26 February 2025 — Issued ※ 24 May 2025
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THA3 Waveguide DC breaks with optimized impedance matching networks 162
 
  • M.K. Covo, B. Ninemire, D.S. Todd, D.Z. Xie, J. Cruz Duran, J.Y. Benitez, J.P. Garcia, L. Phair, M.B. Johnson, P. Bloemhard
    LBNL, Berkeley, CA, USA
  
  A custom 18 GHz waveguide DC break with a built-in impedance matching network, consisting of two inductive irises adjacent to a capacitive gap assembled around a quartz disk, was built for VENUS and simulated using the ANSYS High Frequency Structure Simulator, a finite element analysis tool. The DC break effectively doubled the RF power available for plasma production at the secondary frequency of 18 GHz while maintaining a DC isolation of 32 kV. Measurements of the forward and reflected power coefficients, performed with a network analyzer, showed excellent agreement with the simulations [1]. Additionally, an extended study was conducted to tailor the frequencies of 28, 35, and 45 GHz using WR-34, WR-28, and WR-22 waveguides with built-in impedance matching networks, aiming to predict performance for our upcoming 4th generation low-power, multi-frequency operation of the MARS-D ion source.
[1] M. Kireeff Covo et al., “Inductive Iris Impedance Matching Network for a Compact Waveguide DC Break”, IEEE Transactions on Microwave Theory and Techniques, early access 2024. doi:10.1109/TMTT.2024.3409470. 		 
slides icon Slides THA3 [1.702 MB]  
DOI • reference for this paper ※ doi:10.18429/JACoW-ECRIS2024-THA3  
About • Received ※ 13 September 2024 — Revised ※ 09 October 2024 — Accepted ※ 30 January 2025 — Issued ※ 18 May 2025
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