Electric lamp and discharge devices: systems – High energy particle accelerator tube – Magnetic field acceleration means
Patent
1994-05-12
1996-05-28
O'Shea, Sandra L.
Electric lamp and discharge devices: systems
High energy particle accelerator tube
Magnetic field acceleration means
315507, 335216, 335299, H05H 1300, H01J 2300, H01F 100, H01F 500
Patent
active
055214690
DESCRIPTION:
BRIEF SUMMARY
SUBJECT OF THE INVENTION
The present invention relates to a cyclotron of novel design in which the particle beam is focused by sectors. More particularly, the present invention relates to an isochronal cyclotron comprising an electromagnet constituting the magnetic circuit which includes at least three pairs of sectors called "hills" where the air gap is smaller, these being separated by spaces in the form of sectors called "valleys" where the air gap has a greater dimension.
The present invention relates more particularly to a compact isochronal cyclotron, that is to say one energized by at least one pair of main circular coils surrounding the poles of the electromagnet.
The present invention relates both to superconducting and non-superconducting cyclotrons.
STATE OF THE ART
Cyclotrons are particle accelerators used in particular for the production of radioactive isotopes.
The cyclotrons are normally composed of three separate main assemblies constituted by the electromagnet, the high-frequency resonator and the vacuum chamber with pumps.
The electromagnet guides the ions over a trajectory representing approximately a spiral of radius which increases during the acceleration.
In modern cyclotrons of the isochronal type, the poles of the electromagnet are divided into sectors having, alternately, a smaller air gap and a larger air gap. The azimuthal variation in the magnetic field which results therefrom has the effect of focusing the beam vertically and horizontally during the acceleration.
Among isochronal cyclotrons, it is convenient to distinguish cyclotrons of the compact type which are energized by at least one pair of main circular coils and cyclotrons called separate-sector cyclotrons where the magnetic structure is divided into entirely self-contained separate units.
First-generation isochronal cyclotrons are cyclotrons which use circular coils of conventional type, that is to say non-superconducting coils. For these first-generation cyclotrons, the mean induction field obtained was limited to values of 1.4 tesla.
One particularly favourable embodiment for a cyclotron of this type is described in Patent Application WO-A-86/06924 where the air gap of the sectors called hills is reduced to a value close to the size of the accelerated beam, whereas the air gap of the sectors called valleys, which separate the hills, is very large so that the magnetic field y is approximately zero.
Another particularly favourable embodiment of an isochronal cyclotron focused by sectors is described in the document WO-A-91/07864 where the hills are coincident with the accelerator system by choosing their configuration and dimensions appropriately.
Both documents have constant air gaps between hills.
The document U.S. Pat. No. 2,872,574 describes an isochronal cyclotron whose air gap between hills has a profile which decreases linearly. This cyclotron is intended for accelerating particles up to a few tens of MeV proton.
The document IEEE Transaction on Nuclear Science (Vol. NS-32, No. 5/2, October 1985, NY-US, pp. 3316-3317) describes a compact isochronal cyclotron enabling H.sup.- particles to be accelerated up to an energy of 30 MeV for magnetic inductions between the hills of the order of 1.7 tesla, and in which the air gap between hills has a profile which increases up to a maximum value and decreases beyond that.
Over the last twenty years, cyclotrons called second-generation cyclotrons have appeared which use superconductor technologies. In these cyclotrons, the main coils are of the superconducting type and enable mean inductions lying between 1.7 and 5 tesla to be obtained, which makes it possible to deliver particle beams having magnetic strengths (Br) markedly greater than those delivered by first-generation cyclotrons.
However, because of the higher inductions obtained, the number of accelerating cavities had to be increased as far as possible so as to prevent the beam from having to execute too great a number of revolutions within the cyclotron. The reason for this is that, when the beam has to perform
REFERENCES:
patent: 4771208 (1988-09-01), Jongen
patent: 4943781 (1990-07-01), Wilson
Ning John
O'Shea Sandra L.
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