Beam dynamics in 10 MeV S-band LINAC for Container Inspection System

The Beam dynamics of S-band 10 MeV electron LINAC for Container Inspection System (CIS) was carried out with beam dynamics code E-GUN[1] and PARMELA[2]. This S-band LINAC is consists of DC-gun injector, side-coupled accelerating structure, waveguide power coupler, klystron with modulator, vacuum device, water cooling and control system. The DC-gun is produce 20 kV electron beam with 0.5 A beam current and 4.9 mm-mrad emittance. The accelerating structure consists of bunching section and accelerating section. The bunching section consists of one pre-bunching cell with β=0.50.65 and one bunching cell with β=0.7-0.9. The accelerating section consists of 10 accelerating cells with β=1 respectively. In addition to this, the side coupled cavities are also involved, it provides a 3% coupling coefficient from cell to cell coupling. A taped waveguide power coupler is used to provide RF power for exciting π/2 mode of the structure. In order to reduce electron beam size and increase electron capture coefficient, a solenoid is placed ahead the accelerating structure to generate axial magnetic field for beam focus. The 10 MeV beam energy with 1 kW beam average power has a beam size less than 5 mm, 30 πmm-mrad normalized emittance with the energy spread less than 5%. The operation radiofrequency and macro-pulse duration are set to 2856 MHz and 4 us, respectively. The designed beam peak current and average current are 125 mA and 0.1 mA.