Patent ID: 9099271
Filing Date: 2015-08-04
Classification: H01J,H05H

Abstract:
1. A method of configuring an electron gun for generating and injecting an electron beam into a linac accelerating waveguide operating in magnetic fringe fields of an MRI scanner in the absence of a magnetic shield, comprising: a) providing an in-line MRI-linac configuration with no magnetic shielding; b) determining an anode drift tube diameter at an injection point of a linac of said in-line MRI-linac configuration, using an appropriately programmed computer, wherein said anode drift tube diameter is according to a value of a magnetic field from an MRI scanner of said in-line MRI-linac configuration and according to a predetermined current density, wherein said magnetic field comprises an isocenter, wherein twiss parameters are used by said appropriately programmed computer to determine a length of said anode drift tube, wherein said twiss parameters are according to axial position and capture efficiency of said linac; c) determining a transverse diameter of a Type M cathode in an electron gun, using said appropriately programmed computer, wherein said transverse diameter of said cathode is according to said anode drift tube diameter and said current density; and d) minimizing a value of emittance in an electron beam of said electron gun at an entry point of said anode drift tube, using said appropriately programmed computer, wherein said minimization comprises optimizing the distance between said cathode and said anode, wherein said electron beam is directed proximal to an axis of symmetry of said MRI magnetic field, wherein an electron gun is configured for generating and injecting an electron beam into a linac accelerating waveguide operating in magnetic fringe fields of said MRI scanner in the absence of said magnetic shield.