Synchrocyclotron

Abstract

A synchrocyclotron comprises a ferromagnetic structure (4) with a pair of poles (5, 5'), which have a generally circular cross section of radius R which are placed on either side of a mid-plane (2) and centred on a central axis (1). These poles (5, 5') are separated by a gap forming a cavity (9) having a profile substantially symmetrical with respect to the mid-plane (2). The height of this gap varies radially and the profile of the gap comprises, in succession, starting from the central axis (1): a first portion (6, 7) of circular section with a radius R2, which is centred on the central axis (1), the height of the gap at the centre thereof being equal to Hcentre, and which includes an annular subportion (7) in which the height of the gap progressively increases up to a maximum height Hmax at the radius R2, and a second portion, of annular section (8), which surrounds the first portion (6, 7) and in which the height of the gap progressively decreases down to a height Hedge at the edges of the poles (5, 5'). The height Hcentre is greater than 10 cm and the ratio of the maximum height Hmax to the height Hcentre is between 1.1 and 1.5.

Description

technical field [0001] The present invention relates to synchrocyclotrons. Background technique [0002] A synchrocyclotron, like a cyclotron, is a particle accelerator with a magnet structure with two magnetic induction coils radially surrounding a cavity for particle acceleration between two magnetic poles with a central axis, the center plane extends in the cavity perpendicularly to said center axis. Particles are produced in a particle source located near the central axis in the cavity, and are discharged from the particle source so that the accelerating electrode powered by a high-frequency AC voltage generator is accelerated along a helical trajectory in the central plane. Such synchrocyclotrons are increasingly being used in hadron therapy. [0003] Unlike a cyclotron where particles are accelerated at the same frequency, in a synchrocyclotron the frequency of the electric field applied to the accelerating electrodes is modulated to compensate for the increase in re...

AI Technical Summary

Problems solved by technology

However, increasing the magnetic field beyond 6 tesla, as proposed in the aforementioned patent, has adverse effects

Therefore, it becomes impossible or very difficult to design the central region of the cyclotron because the very high magnetic field causes the radius of the first orbit that the particles follow to be reduced so that the particles cannot bypass the ion source in the first loop

The second disadvantage of magnetic fields above 6 Tesla is that the implementation of the extraction device becomes very complicated

A third disadvantage of magnetic fields above 6 Tesla in the center of the cyclotron is that for such fields the magnetic fields in the coils exceed those for which niobium-titanium alloys can be used

This lack of space requires a short distance between the accelerating electrode and the transmission line, thereby increasing the capacitance (capacité) between these two elements

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