3D field simulations for cyclotron magnet systems


Completed orders:

Flerov Lab, Joint Institute of Nuclear Research, (Dubna, Russia) - cyclotron DC-60
Flerov Lab, Joint Institute of Nuclear Research, (Dubna, Russia) - cyclotron U-400
Flerov Lab, Joint Institute of Nuclear Research, (Dubna, Russia) - cyclotron DC-72
Efremov Institute (St. Petersburg, Russia) - cyclotron CC12
Efremov Institute (St. Petersburg, Russia) - cyclotron 18/9


The specially developed 3D calculation models enable precision calculations of the "influence functions" for different components in order to adjust magnet system geometry and provide a desired field distribution. The models are developed with regard to fabrication/maintenance/cost saving requirements. There is a possibility of modelling of non-linear magnetic properties and complex geometry of ferromagnetic and conducting elements. Simulated field maps are applicable for the trajectory analysis. Calculated EM loads are presented in a format suitable for the stress analysis. Solving the tripled problem makes it possible to form a closed iterative adjustment of the required field distribution.

The promising method of field formation in cyclotrons is to combine simulations of 3D field distribution and sector profiles with magnetic measurements in the median plane. The simulated and measured data are then used for sector shimming to adjust the field [2].

An important aspect to provide a desired field distribution in the cyclotron is shimming [3]. The basic shimming methods are

- axial shimming by adjusting the sector thickness near the median plane;
- axial shimming by adjusting the sector thickness near the pole;
- azimuthal shimming by varying the azimuthal sector length with the radius.

In particular, a set of application programs have been developed specifically for cyclotron modelling:

- a mesh generator based on a parametric calculation of the cyclotron magnet system implemented in a specialised programming language;
- additional modules for the mesh generator to enable parametric calculations of complex curved surfaces, such as profiled sector surfaces;
- an interpolator for field calculations at any given point, specifically useful for field mapping with given angular, radial, and vertical steps;
- tools for a calculation of integral field parameters, such as radial distributions of an azimuthally averaged field, flatter and harmonics.

The additional tools allow effective synthesis of the cyclotron magnet systems.
An analysis of the influence functions made it possible to assess influence of manufacture/assembly tolerances on a field distribution in the working zone of a cyclotron.
A comparison between the magnetic measurements and simulated results suggests that numerical simulations of magnet systems is a promising alternative for building a prototype cyclotron, offering much more cost- and time-effective, yet accurate, results in any cyclotron design.



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