Magnetic field generating assembly

• US 4,968,915 A
• Filed: 06/15/1989
• Issued: 11/06/1990
• Est. Priority Date: 01/22/1987
• Status: Expired due to Term

• Current Assignee: Oxford Instruments PLC
• Original Assignee: Oxford Instruments PLC
• Inventors: Kruip, Marcel J. M., Wilson, Martin N.
• Primary Examiner(s): DeMeo, Palmer C.
• Application Number:
  US07/366,355
• Time in Patent Office: 509 Days
• Field of Search: 328/234, 313/62, 313/154, 335/214, 335/301, 315/8
• US Class Current: 313/62
• CPC Class Codes: H01F 6/00 Superconducting magnets; Superconducting coils magnetic resonance assemblies using superconducting coil systems G01R33/3815
• CPC Class Codes: H05H 13/00 Magnetic resonance accelerators; Cyclotrons strophotrons, turbine tubes H01J25/62
• CPC Class Codes: H05H 7/04 Magnet systems , e.g. undulators, wigglers free-electron laser H01S3/0903; Energisation thereof

Abstract

A cyclotron includes a magnetic field generating assembly defined by a pair of main, superconducting coils mounted about the axis of the cyclotron on a former. The coils are surrounded by an ion shield positioned within a cryostat. Radially outwardly of the shield are positioned a pair of coils which guide most or all of the magnetic flux due to the coils leaking out of the shield back into the shield.

Claims

1. An assembly for generating a magnetic field within a volume, said assembly including a hollow substantially tubular ferro-magnetic shield with axial ends, a first magnetic field generating means, and second magnetic field generating means, said volume being defined by the ferro-magnetic material of the shield and the hollow space within the shield, said first magnetic field generating means positioned within said ferro-magnetic shield and positioned and adapted to generate substantially all of said magnetic field within said volume, said second magnetic field generating means comprising a first set of auxiliary coils mounted around and along said shield and connected in series with said first magnetic field generating means and a second set of auxiliary coils mounted at opposite axial ends of the shield, said second magnetic field generating means positioned substantially about and along said tubular shield and further positioned and adapted so as to guide magnetic flux of said magnetic field leaking from said volume back into said volume so as to optimize the quantity of flux from said first magnetic field generating means which is guided through said shield.

2. An assembly according to claim 1, said first magnetic field generating means comprises at least one cylindrical, electrical coil.

3. An assembly according to claim 1, wherein said shield is an iron shield.

4. An assembly according to claim 1, wherein said shield is tubular, said first magnetic field generating means being positioned within said shield

5. An assembly according to claim 4 wherein said shield has inwardly projecting flanges at each end.

6. An assembly according to claim 1, wherein said second magnetic field generating means comprises at least one electrical coil.

7. An assembly according to claim 6, wherein said second magnetic field generating means comprises at least one electrical coil mounted closely to said shield.

8. An assembly according to claim 1, further comprising a cryostat, and wherein said first magnetic field generating means comprises a superconducting magnet defined by at least one coil positioned within said cryostat.

9. An assembly according to claim 8, wherein said shield is positioned within said cryostat.

10. A cyclotron comprising an evacuated chamber;

radio frequency energy generation means for generating radio frequency energy in the evacuated chamber; and

an assembly for generating a magnetic field within a volume, said assembly including a hollow substantially tubular ferro-magnetic shield with axial ends, a first magnetic field generating means, and second magnetic field generating means, said volume being defined by the ferro-magnetic material of the shield and the hollow space within the shield and including said evacuated chamber, said first magnetic field generating means positioned within said ferro-magnetic shield and positioned and adapted to generate substantially all of said magnetic field within said volume, said second magnetic field generating means comprising a first set of auxiliary coils mounted around and along said shield and connected in series with said first magnetic field generating means and a second set of auxiliary coils mounted at opposite axial ends of the shield, said second magnetic field generating means positioned substantially about and along said tubular shield and further positioned and adapted so as to guide magnetic flux of said magnetic field leaking from said volume back into said volume so as to optimize the quantity of flux from said first magnetic field generating means which is guided through said shield, said first magnetic field generating means being further positioned and adapted so as to generate a magnetic field which guides ions within said chamber, said radio frequency energy generation means generating radio frequency energy so as to accelerate said ions guided by said magnetic field generations assembly.

11. A cyclotron according to claim 10, said cyclotron having an ion beam outlet passing radially through said magnetic field generating assembly, and further comprising a slidably mounted holder adapted to be moved across said ion beam outlet so as to bring a selected foil of a plurality of foils mounted to said holder into alignment with said ion beam, said foils being adapted to convert the polarity of said ions causing them to be ejected from said cyclotron.

12. An assembly for generating a magnetic field within a volume, said assembly including a hollow substantially tubular ferro-magnetic shield with axial ends, a first magnetic field generating means, and second magnetic field generating means, said volume being defined by the ferro-magnetic material of the shield and the hollow space within the shield, said first magnetic field generating means positioned within said ferro-magnetic shield and positioned and adapted to generate a magnetic field within said volume, said second magnetic field generating means comprising a first set of auxiliary coils mounted around and along said shield and connected in series with said first magnetic field generating means and a second set of auxiliary coils mounted at opposite axial ends of the shield, said second magnetic field generating means positioned substantially about and along said tubular shield and further positioned and adapted so as to guide magnetic flux of said magnetic field leaking from said volume back into said volume so as to optimize the quantity of flux from said first magnetic field generating mean which is guided through said shield.