A New Family of High-Current Cyclotrons
Date
2023
Authors
Alonso, Jose R.
Winklehner, Daniel
Conrad, Janet
Villarreal, Joshua
Waites, Loyd
Journal Title
Journal ISSN
Volume Title
Publisher
ORCID
Type
Conference Presentation
Degree Level
Abstract
We have developed a new family of compact cyclotrons capable of 10 mA of protons at energies up to 60 MeV. Designed for the IsoDAR neutrino experiment [1], the x10 current increase could find important applications in isotope production, for products with long half-lives (68Ge) or low cross sections (232Th(p,X)225Ac). A recent development has been use of the breakup of 40-MeV deuteron ions forming an intense fast-neutron field suitable for 226Ra(n,2n)225Ra --> 225Ac, a highly-efficient channel for 225Ac production. Achieving and Using High Currents Beam current limits on today’s isotope cyclotrons arise from extraction foil lifetime and central region erosion from inefficient injection. Our cyclotrons accelerate H2+ ions, reducing the effect of space charge, and bunch 90% of the beam into the RF acceptance window with an RFQ. A beam-dynamics effect discovered at PSI called “vortex motion” translates space charge forces in the cyclotron magnetic field into lateral motion that stabilizes the individual RF beam packets into compact bunches. Halo is generated but is collimated in the first turns. Stable packets are formed in about the first few MeV (~5 turns), allowing for adequate turn separation to enable clean septum extraction of the H2+ ions without use of a stripper foil. Using these principles we can build cyclotrons for energies ranging from a few MeV up to 60 MeV. Turn separation above 60 MeV is lower, but use of structure resonances may enable extending the energy to higher values. Q/A of H2+ is 0.5, so cyclotrons are suitable for D+, He+, C6 ions at the same energy/nucleon. At present, the H2+ ion source and RFQ are ready, the 1.5 MeV Demonstrator is being built, the IsoDAR experiment will be deployed in 5 years. x10 current means x10 beam power. Developing high-power targets will enable the most efficient utilization of the available beam. In the interim, splitting the beam onto as many as 10 target stations is feasible, by employing either RF kicking of bunches into separate beam lines, and/or by insertion of stripper foils into the edges of the extracted H2+ beam to peel off adjustable amounts of protons using a dipole right after the stripper. Conclusions Our designs represent a paradigm shift in cyclotron performance, shattering the beam-current barrier, and opening the door for novel applications. In addition to isotope production, these machines are compact high-flux MeV-range neutron generators; planned uses extend from neutrino production to cost-effective IFMIF-style fusion reactor materials testing platforms. References 1 J.Alonso et al (2022) Neutrino Physics Opportunities with the IsoDAR Source at Yemilab. Phys. Rev. D, 105, 075150. https://doi.org/10.1103/PhysRevD.105.052009
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Keywords
Cyclotron, High-Current, High-Power, deuteron