What is the potential impact of the IsoDAR cyclotron on radioisotope production: a review

Abstract

The IsoDAR collaboration is developing a high-current cyclotron for a neutrino search experiment. Designed to deliver 10 mA of 60 MeV protons, the current and power of this cyclotron far exceed those of existing accelerators, opening new possibilities for the production of radiopharmaceutical isotopes, producing very high-activity samples in very short times. The cyclotron can also be easily configured to deliver ions other than protons including 1 mA of alpha particles at 240 MeV: this flexibility gives a broad reach into new areas of isotope production. We explain how IsoDAR overcomes the beam limits of commercial cyclotrons, and how it could represent the next step in isotope production rates.

Keywords: 225Ac; 60-MeV-protons; 68Ge/Ga; Alpha-beams; Cyclotron.

Fig. 1

Schematic of the central region of a compact cyclotron. From Winklehner et al. (2017). This figure illustrates two-fold symmetry of the RF system. The IsoDAR cyclotron is designed with 4-fold symmetry, there are 4 RF “dees”

Fig. 2

Components of the IsoDAR cyclotron injection system mounted on the central axis of the cyclotron magnet. Adapted from Winklehner et al. (2018).

Fig. 3

Schematic of the stripper foil in an H⁻cyclotron

Fig. 4

Evolution of a space-charge dominated bunch from injection (turn 0) to turn 40 - about midway to extraction. From Yang et al. (2010)

Fig. 5

Simulated particle density in {y,r} plane for last few turns. Electrostatic extraction channel is shown, with field that bends beam away from cyclotron center (simulation courtesy of JJ Yang). (a) shows vertical beam size (mm) vs radius from center (also mm). The electrostatic deflection channel has a strong electric field between the plates that provides a kick to the last bunch to push it outside the cyclotron. Efficient operation requires that there be as few particles as possible in the space between the last two turns, to avoid damaging the thin septum plate. (b) shows the total particle count (plotted logarithmically) vs radius. The lower curve demonstrates how collimators placed close to the center of the cyclotron can help cleaning up the space between turns by absorbing halo particles. The beneficial effect of collimators is clearly seen (Yang et al. 2013)

Fig. 6

a Shadow stripper protects septum from halo particles. (Underlying simulations courtesy of JJ Yang). b Orbits of protons from shadow stripper avoid septum, and exit cleanly. Different orbits correspond to changes in stripper location in hill fringe field. c: 4-fold symmetry of magnetic field allows 4 locations for stripper foils to remove all beam from cyclotron via stripping. b and c Courtesy of L. Calabretta)

Fig. 7

Technique for sharing beam between many targets using sequential stations