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Design and fabrication of a four-rod radio frequency quadrupole with a variable aperture

Journal Article · · Nuclear Instruments and Methods in Physics Research. Section A, Accelerators, Spectrometers, Detectors and Associated Equipment
 [1];  [2];  [2];  [2];  [2];  [2];  [3];  [4];  [5];  [6]
  1. Institute of Science, Tokyo (Japan)
  2. Brookhaven National Laboratory (BNL), Upton, NY (United States)
  3. Nagaoka University of Technology (Japan)
  4. GSI-Helmholtz Centre for Heavy Ion Research, Darmstadt (Germany)
  5. TIME Co., Ltd, Tokyo (Japan)
  6. Columbia Univ., New York, NY (United States)
+ Show Author Affiliations
Radiofrequency quadrupole (RFQ) linear accelerators with variable aperture cell parameters offer an effective means of accelerating high-intensity ion beams exceeding 100 mA and have been implemented in various RFQ designs. However, in a four-rod RFQ, the use of dielectric perturbation methods to measure the voltage distribution behind the rod electrodes is not applicable when implementing variable aperture geometries, because changes in the rod shape influence the electric field at the location of the perturbation element. Therefore, it was necessary to design the rod profile for each cell such that the electric field distribution behind the rods remains unaffected by changes in the aperture. In this study, we present a method to adjust the voltage distribution by modifying the geometry of the rod electrodes according to each cell's aperture parameters. This design approach enables the integration of variable aperture cells into a four-rod RFQ linac, significantly enhancing the achievable beam current. To ensure uniform capacitance and maintain a constant rod-electrode voltage despite variations in the average aperture radius, we developed a systematic method for shaping the rod electrodes. This method was refined using two-dimensional (2D) and three-dimensional (3D) electromagnetic field simulations to optimize the electrode cross-sectional profiles. The fabricated rod electrodes were then installed in a four-rod RFQ, and the electric field distribution was measured using the perturbation method and tuned by adjusting the base plates. As a result, the measured variation of ±1.1 % confirms that this design methodology can produce a sufficiently uniform voltage distribution for high-current beam acceleration. These results demonstrate the practical feasibility of a variable-aperture four-rod RFQ linac.
Research Organization:
Brookhaven National Laboratory (BNL), Upton, NY (United States)
Sponsoring Organization:
USDOE Office of Science (SC), Basic Energy Sciences (BES)
Grant/Contract Number:
SC0012704
OSTI ID:
3018627
Report Number(s):
BNL--229425-2026-JAAM
Journal Information:
Nuclear Instruments and Methods in Physics Research. Section A, Accelerators, Spectrometers, Detectors and Associated Equipment, Journal Name: Nuclear Instruments and Methods in Physics Research. Section A, Accelerators, Spectrometers, Detectors and Associated Equipment Vol. 1085; ISSN 0168-9002
Publisher:
ElsevierCopyright Statement
Country of Publication:
United States
Language:
English

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Carbon beam acceleration using a simple injection method into an RFQ
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Beam dynamics studies on a 200 mA proton radio frequency quadrupole accelerator
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journal February 2008
The beam commissioning of a CW high charge state heavy ion RFQ
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journal September 2015
The CERN PIXE-RFQ, a transportable proton accelerator for the machina project journal November 2019
Research opportunities with compact accelerator-driven neutron sources journal October 2016
Demonstration of an intense lithium beam for forward-directed pulsed neutron generation journal August 2022
Direct plasma injection scheme in accelerators (invited) journal January 2008
Laser ion source with solenoid field journal November 2014
Development of a radio frequency quadrupole linac implemented with the equipartitioning beam dynamics scheme journal December 2019
Electromagnetic design and tuning of the four-vane radio frequency quadrupole with nonuniform intervane voltage profile journal November 2020

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43 PARTICLE ACCELERATORS