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Design and optimization of the RF input-coupler for a low-frequency, split-coaxial RFQ

Journal Article · · Journal of Instrumentation
 [1];  [2];  [3]
  1. Massachusetts Inst. of Technology (MIT), Cambridge, MA (United States); Brookhaven National Lab. (BNL), Upton, NY (United States)
  2. Massachusetts Inst. of Technology (MIT), Cambridge, MA (United States)
  3. Bevatech GmbH, Frankfurt am Main (Germany)
+ Show Author Affiliations
The Isotope Decay-At-Rest experiment (IsoDAR) is a proposed underground experiment which is expected to be a definitive search for sterile neutrinos. In order to be decisive within 5 years, high rates of neutrinos must be produced, by impinging a 10 mA continuous wave proton beam at 60 MeV on a high power target. Due to space restrictions, a compact cyclotron was chosen as an accelerator to produce this driver beam. To overcome space charge limitations during injection, H2+ ions are accelerated and later stripped into protons by means of a carbon foil. IsoDAR uses an especially designed low-frequency (32.8 MHz) split-coaxial Radio-Frequency Quadrupole (RFQ) to effectively bunch H2+ ions before injecting them into this cyclotron. The RFQ will be embedded vertically in the cyclotron yoke, facilitating a very compact design. This puts stringent limits on RFQ size, type, and accessibility. Here, we present the design and optimization of the low-frequency (32.8 MHz) RF input-coupler for the IsoDAR RFQ. The design is challenging due to the necessarily small diameter of the RFQ (28 cm) and the split-coaxial type, as well as limited access to the RFQ. We have determined the optimal position and shape for the coupler, leading to a low power consumption of < 6 kW for an inter-vane voltage of 22 kV. Finally, the highest calculated fields are safely below the Kilpatrick limit for this structure.
Research Organization:
Brookhaven National Laboratory (BNL), Upton, NY (United States)
Sponsoring Organization:
Bose Foundation; National Science Foundation (NSF); USDOE Office of Science (SC), Nuclear Physics (NP)
Grant/Contract Number:
SC0012704
OSTI ID:
1813965
Alternate ID(s):
OSTI ID: 23165278
Report Number(s):
BNL--222024-2021-JAAM
Journal Information:
Journal of Instrumentation, Journal Name: Journal of Instrumentation Journal Issue: 08 Vol. 16; ISSN 1748-0221
Publisher:
Institute of Physics (IOP)Copyright Statement
Country of Publication:
United States
Language:
English

References (9)

High intensity cyclotrons for neutrino physics
  • Winklehner, Daniel; Bahng, Jungbae; Calabretta, Luciano
  • Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, Vol. 907 https://doi.org/10.1016/j.nima.2018.07.036
journal November 2018
Where are we with light sterile neutrinos? journal September 2020
Criterion for Vacuum Sparking Designed to Include Both rf and dc journal October 1957
Preliminary design of a RFQ direct injection scheme for the IsoDAR high intensity H2+ cyclotron journal February 2016
Optimizing the 8 Li yield for the IsoDAR Neutrino Experiment journal March 2019
The shielding design concept for the ISODAR neutrino target journal July 2020
Proposal for an Electron Antineutrino Disappearance Search Using High-Rate Li 8 Production and Decay journal October 2012
Transverse-longitudinal coupling by space charge in cyclotrons journal November 2011
Solar Neutrinos: A Scientific Puzzle journal January 1976

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Related Subjects

43 PARTICLE ACCELERATORS
IsoDAR
RF-power
RFQ
loop coupler