課件射波刀和tomo linac

1、Physics IntroductionLINAC Basics In the accelerator guide, RF energy from the magnetron produces rapidly changing fields These oscillating electric fields point along the accelerator axis The oscillating magnetic fields resonate within individual cavities The electron beam path passes through these

2、resonant cavitiesE-field/22 LINAC Basics Microwave (or RF) energy from the Magnetron is coupled to the accelerator via a waveguide The pattern of alternating electro-magnetic fields, standing waves, drive electrons down the acceleratorLINAC Basics The Electron Gun is the source of electrons for the

3、accelerator As the Cathode of the gun is heated, it emits a cloud of electrons This electron stream (entering the LINAC) is regulated by a Control Grid Cathode GridLINAC Basics - AccelerationRF is center fed (or side coupled) allowing for a shorter acceleratorStanding Wave Accelerator StructureRef:

4、I, USPAS Lecture 1, 11/21/01, pg. 11/22SF6 at 30 psiCavity 1RF InputCavity 2VacuumVacuumLINAC BasicselectronsRF energy varies sinusoidally0009290 MHzMagnetron output frequency is matched to LINAC cavity physical resonance dimensions Side cavities are used to couple the RF energy equall

5、y to all accelerator cavitiesLINAC Basics - Bunching The Electron Gun Control Grid is triggered on as RF fills LINAC Electrons enter the accelerator structure as a streamElectron Gune - CloudControl GridLINAC Basics - AccelerationElectron bunches are accelerated in phase as they reach each resonant

6、cavity by high power E-M fields oscillating in each cavity Tungsten targetX-raysLINAC Basics X-ray generationHigh energy electrons impact the Tungsten targetThe electrons interaction with the Tungsten nuclei cause a rapid deceleration of the electronsThis interaction produces high energy photons pho

7、tons in the X-ray spectrum with a nominal energy = 6 MeVLINAC Cross SectionSteering CoilsRef: I USPAC Lecture 1, 11,21,01 pg. 8 (see M. Weiss, Intro to RF linear accelerators. Vol 2, pp 913)Lenses are required for transverse stability (the RF cavities are transversely defocusing). RF CavitiesMagnetic Focusing LensParticle BeamSteering coilsTwo s