ABSTRACT
The transportation of electron is inseparable from vacuum environment. The maintenance of the vacuum system of Elekta linear accelerator depends on two sputtering ionic pumps at the gun end and the target end. The traveling wave acceleration were used in Elekta linear accelerators. And the design of the electron gun filament is detachable. Because of these two reasons, the vacuum stability is relatively weak. Only two vacuum values are used to reflect the operation state of the whole vacuum system, which causes a few failures but will not trigger a the machine interlock. Considering the complexity of whole vacuum system, the problem of vacuum caused by the failure of various components in vacuum system is analyzed in this paper. It is hoped that some useful repairing experience and suggestions for the maintenance engineers of linear accelerator to solve the vacuum fault and rebuild the vacuum can be provided quickly.
Subject(s)
Electrons , Particle Accelerators , Radiotherapy Dosage , VacuumABSTRACT
Objective: To investigate the impact of MR fringe magnetic field on the electron beam characteristics of the electron gun in the MRI-guided radiotherapy (MRIgRT). Methods Electromagnetic field analysis software was used to simulate the beam characteristics of both Litton L2087 electron gun and Varian 600C electron gun under different magnetic field strengths for the in-line MRIgRT configuration. Results Two electron guns exhibited qualitatively similar behavior in the fringe magnetic field. As field strength increased, the current emitted by the cathode increased slowly, which could increase up to 2.72% and 1.93% from the original value without external magnetic field for Litton L2087 and Varian 600C electron gun, respectively. The current at the anode exit started to decrease after the initial plateau, and after reaching a minimum value, the current started to increase slowly, and the current loss could reach up to 80.25% and 73.48% of the initial value, respectively. At high values of the field strength, the beam radius changed periodically. Beam root mean square emittance fluctuated under different magnetic field strengths. Conclusion For in-line MRIgRT configuration, the fringe magnetic field can affect the trajectory of the beam and cause a large amount of current loss in the electron gun, and the beam RMS emittance varies greatly.