ITERATIVE METHOD FOR MODELING OF STEADY OPERATION MODES OF MULTIPURPOSE ISOCHRONOUS CYCLOTRONS

I.V. Amirhanov¹, G.A. Karamysheva¹, I.N. Kiyanª¹, J. Sulikowski², R. Taraszkiewicz²

¹Joint Institute for Nuclear Research, Dubna, Russia

²Instytut Fizyki Jądrowej Polskiej Akademii Nauk, Kraków, Polska

Abstract

The mathematical and computer modeling of operation modes of multipurpose isochronous cyclotrons is based on calculation of currents in trim coils of correction of the basic magnetic field at a certain level of current in the main coil. The calculation is made for a given extraction energy or rotation frequency of particles. The results of the calculation allow a required magnetic field to be formed with a certain accuracy in the range from the ion source to the extraction radius of particles. The method derives its name from iterative calculation of extraction energy, current in the main coil, and isochronous magnetic field with allowance for influence of the trim coil contributions on the flutter of the basic magnetic field. The essentially new algorithm of excluding some of the involved trim coils from the calculation is based on consecutive selection them. The input of solution in frameworks of the given boundary conditions are carried out step by step. The use of interpolation both inside and between the measured maps of magnetic fields allows interpolating the resulting maps of magnetic fields instead of measuring them. In turn, it allows to replace calculating-experimental iterations for formation of the required magnetic field only calculating. A series of physical experiments carried out in 2007 at the multipurpose isochronous cyclotron AIC144 (INP PAS, Krakow) confirmed legitimacy of this replacement. The essentially new algorithm of excluding some of the involved trim coils from the calculation has allowed stability of the resulting magnetic field to be improved; That is, the influence on the quality of the calculated operation modes of a lot of the factors (the accuracy of the measurement of the source magnetic field maps, the features of the start-up algorithm of the cyclotron at a certain operation mode, the stability of the used power supplies, etc.) became less significant. A series of numerical experiments on calculation of the basic operation mode of AIC (p, 60 MeV / 26.25 MHz) confirmed the necessity of including the evaluation of the solution stability into the calculation.

ª – corresponding author

Paper 

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