1) Optimization of the cyclotron magnet design
1a) Parametrized tools have been developed for automatic generation of FEM models of the magnet and its extraction magnetic elements.
1b) The magnet design has been optimized to ensure a perfect 2-fold rotational symmetry, an isochronous magnetic field during beam acceleration, a radial and axial (vertical) focusing of a beam during acceleration and the possibility to install all cyclotron subsystems.
1c) The extraction path in the magnet has been improved compared to the prototype: i) the groove acting like a sort of magnetic septum is now replaced by a ”plateau” to improve the extracted beam quality, ii) now the iso-gap contours follow equilibrium orbits.
2) Optimization of the central region design
2a) Parametrized tools have been developed for automatic generation of FEM models of the central region.
2b) The central region design has been optimized to ensure 2-fold rotational symmetry, good beam centering and vertical electric focusing, good RF phase acceptance and energy gain and beam collimation to remove unwanted particles.
3) Space charge simulations in the cyclotron central region
A quantitative self-consistent approach has been developed for simulation of a space charge dominated beam in the central region. This method consists of three steps:
- the central region model is solved by using the SCALA space charge solver of Opera3D to find the plasma meniscus and the beam properties on it.
- the central region model is solved again by using the TOSCA solver of Opera3D. In this model the meniscus surface is put at ground potential. This provides the 3D electric field map everywhere in the central region, including the source-puller gap.
- The beam extracted from the meniscus is simulated in the 3D field map using AOC, the IBA space-charge tracking code. This code has been extended to also simulate the bunch formation process in the first gap, including space charge.
4) Beam tracking simulations including space charge
Beam tracking in the simulated 3D electric field and magnetic field of the self-extracting cyclotron has been carried out for:
- Optimization of the magnet, extraction magnetic elements and central region design.
- Study of the dependence of the extraction efficiency and beam quality on the beam intensity.
- Study of the effect of the dee-voltage ripple on the extraction efficiency and beam energy spread.
5) Optimization of the extraction process
5a) A permanent magnet gradient corrector has been designed. It provides radial focusing to the extracted beam.
5b) Harmonic coils that are used to optimize the beam extraction have been included in the FEM model.
5c) Parametrized tools have been developed for automatic generation of FEM models of the harmonic coils.
5d) A dedicated program has been written to find the cyclotron settings that give the maximum extraction efficiency.
Data generated during the design study of the InnovaTron cyclotron has been shared with the worldwide specialized accelerator community by publications openly accessible on the Internet. The main simulation results have been presented at multiple accelerator conferences and the proceedings have been published on the public accessible JACOW website. They have also been presented at the annual congress of the Italian Physical Society, specialized workshops and seminars in high schools and universities.
