Spiral orbit charged particle accelerator and its acceleration method

• US 20060175991A1
• Filed: 04/03/2006
• Published: 08/10/2006
• Est. Priority Date: 07/21/2004
• Status: Active Grant

• Current Assignee: National Institute of Radiological Sciences
• Original Assignee: National Institute of Radiological Sciences
• Inventors: Fujisawa, Takashi
• Granted Patent: US 7,262,565 B2
• Time in Patent Office: Days
• US Class Current: 315/501
• CPC Class Codes: H05H 13/00 Magnetic resonance accelerators; Cyclotrons strophotrons, turbine tubes H01J25/62
• CPC Class Codes: H05H 15/00 Methods or devices for acceleration of charged particles not otherwise provided for , e.g. wakefield accelerators

Abstract

According to the present invention, a non-isochronous magnetic field distribution in which the magnetic field increases as the radius increases is formed and a distribution of fixed-frequency accelerating RF voltage is formed, said non-isochronous magnetic field distribution and said distribution of fixed-frequency accelerating RF voltage being formed so that a harmonic number defined as a ratio of the particle revolution period to the period of the accelerating RF voltage decreases in integer for every particle revolution.

Claims

1. A spiral orbit charged particle accelerator comprising means for forming a non-isochronous magnetic field distribution in which the magnetic field increases as the radius increases and means for forming a distribution of fixed-frequency accelerating RF voltage, said non-isochronous magnetic field distribution and said distribution of fixed-frequency accelerating RF voltage being formed so that a harmonic number defined as a ratio of the particle revolution period to the period of the accelerating RF voltage changes in integer for every particle revolution.

2. A spiral orbit charged particle accelerator described in claim 1 wherein said means for forming a distribution of fixed-frequency accelerating RF voltage maintains the magnitude of the accelerating RF voltage at constant regardless of the radius and said means for forming a non-isochronous magnetic field distribution increases the magnetic field as the radius increases so that the harmonic number decreases in integer for every particle revolution.

3. A spiral orbit charged particle accelerator described in claim 1 wherein said means for forming a non-isochronous magnetic field distribution forms an averaged magnetic field B_R at trajectory radius R given by Equation of B_R=B_Ri(R/R_i)^m where R_i is an injection radius and B_Ri is an averaged magnetic field at the injection point and said means for forming a distribution of fixed-frequency accelerating RF voltage modifies the magnitude of the accelerating RF voltage as the radius increases so that the harmonic number decreases in integer for every particle revolution.

4. An acceleration method used in a spiral orbit charged particle accelerator, said method comprising steps of forming a non-isochronous magnetic field distribution in which the magnetic field increases as the radius increases and forming a distribution of fixed-frequency accelerating RF voltage, said non-isochronous magnetic field distribution and said distribution of fixed-frequency accelerating RF voltage being formed so that a harmonic number defined as a ratio of the particle revolution period to the period of the accelerating RF voltage changes in integer for every particle revolution.

5. An acceleration method described in claim 4 wherein said step of forming a distribution of fixed-frequency accelerating RF voltage includes a step of maintaining the magnitude of the accelerating RF voltage at constant regardless of the radius and said step of forming a non-isochronous magnetic field distribution includes a step of increasing the magnetic field as the radius increases so that the harmonic number decreases in integer for every particle revolution.

6. An acceleration method described in claim 4 wherein said step of forming a non-isochronous magnetic field distribution includes a step of forming an averaged magnetic field B_R at trajectory radius R given by Equation of B_R=B_Ri(R/R_i)^m where R_i is an injection radius and B_Ri is an averaged magnetic field at the injection point and said step of forming a distribution of fixed-frequency accelerating RF voltage includes a step of modifying the magnitude of the accelerating RF voltage as the radius increases so that the harmonic number decreases in integer for every particle revolution.