High-Current H₂⁺ Beams from a Compact Cyclotron using RFQ Direct Injection

Analyzing beam-gas interactions in an H2+ cyclotron beam

“…The Isotope Decay-At-Rest (IsoDAR) experiment [1][2][3] aims to perform unique searches for sterile neutrino oscillations and non-standard neutrino interactions by developing a novel cyclotron-based neutrino source. The IsoDAR accelerator [3][4][5] will deliver 60 MeV protons that impinge on a 9 Be target, producing neutrons that diffuse through a sleeve containing highly enriched 7 Li, thereby creating a high intensity 8 Li β-decay-at-rest antineutrino source. Coupled with a large high-efficiency inverse beta-decay detector like the 2.6 kt LSC at Yemilab in South Korea, IsoDAR will make several measurements of high interest [6,7]: test the sterile neutrino hypothesis, collect ne -e − scattering events for weak mixing angle and nonstandard-interaction measurements, and search for axion-like particles (see figure 1 for a schematic layout of IsoDAR@Yemilab).…”

“…Additionally, this accelerator was proposed as an injector for the DAEδALUS experiment, a two-cyclotron acceleration complex focused on studying CP-violation in the neutrino sector [13][14][15], but also aimed to be used for accelerator-driven systems (ADS) [16]. The 10 mA proton beam is obtained from an isochronous cyclotron that will accelerate + H 2 ions to the full energy of 60 MeV/amu, operating in continuous wave (CW) mode [5,17,18]. The beam will be produced by a reliable, high-intensity multicusp ion source [19] and then injected into the cyclotron through a compact low energy beam transport line (LEBT) and a novel radio-frequency quadrupole (RFQ) buncher [20,21], partially embedded in the cyclotron yoke.…”

“…Then, an RF system at a fixed frequency accelerates the particles, and the magnetic field causes the ions to follow spiral orbits with radii increasing with energy. For vertical focusing and isochronicity, the pole faces are cut into four sets of wedges, alternating high-field 'hill' regions, where the gap between the poles is small, having a maximum mid-plane field of 1.48 T; with low-field 'valleys' where the poles are very far apart, resulting in a minimum value of 0.5 T. The beam dynamics have been optimized making use of vortex motion, an effect that can stabilize beam growth and leads to clean extraction [5]. On the last turn, the beam can be extracted with an electrostatic deflector that diverts the beam into specialized magnetic channels designed to direct the beam to an extraction pipe.…”