A Method for Enhancing Axial Focusing in the Central Region of a Cyclotron

Abstract

The invention discloses a method for enhancing axial focusing in a central region of a cyclotron. Through a special magnet structure, a magnetic field of which the field strength slightly decreases with the radius is constructed in 5-15 circles of a beam trajectory, and the negative gradient of the magnetic field is utilized to provide an axial focusing effect of the magnetic field; by changing aDEE plate and a Dummy DEE profile within the range of 1-5 circles of the beam trajectory, the positions of acceleration gaps are further moved, the phase where a beam enters each acceleration gap is changed, so that the beam enters the acceleration gaps when an alternating electric field reaches a peak value and leaves the acceleration gaps at a falling edge of the alternating electric field, andthus an axial focusing effect of the electric field is generated. The method disclosed by the invention has a simple principle, and by reasonably planning the cyclotron structure, the cyclotron can construct a proper electromagnetic field distribution, and the axial focusing in the central region of an isochronous cyclotron can be effectively enhanced.

Description

technical field [0001] The invention belongs to the field of cyclotrons, and in particular relates to a design method for enhancing beam current axial focusing in the central area of ​​an isochronous cyclotron. Background technique [0002] In a classical cyclotron, the magnetic field strength decreases with increasing radius due to the need for axial focusing. At the same time, as the energy of the particle increases, the mass of the particle increases due to the relativistic effect. The cyclotron period of the particle is proportional to the mass of the particle and inversely proportional to the strength of the magnetic field. The final result is that the cyclotron period of the particle becomes longer, the cyclotron frequency decreases, and the acceleration phase will slip during the particle motion process, which cannot maintain resonance acceleration with the accelerating electric field. , limiting the particle energy to further increase. [0003] The isochronous cycl...

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Problems solved by technology

[0004] However, in the central area of ​​the isochronous cyclotron, due to the compact structure, the modulation degree and the helix angle of the magnetic field are very small, and the axial focusing effect of the particles brought by the modulation degree and the helix angle is very weak, and the particles will be unable to Sufficient axial focusing is lost in the central region, so it is particularly important to provide an isochronous method of axially focusing particles in the central region of the cyclotron for the design of the cyclotron

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