Design, fabrication and relative bunch length measurement of S-band pre-buncher

A 10 MeV, 3 kW RF electron linear accelerator (linac) is in operation at EBC, Kharghar. A new horizontal linac rated for 10 MeV, 5 kW has been planned to be developed at EBC, Kharghar. The components of 10 MeV linac beam line consists of electron gun, a standing wave (SW) single cell pre-buncher cavity and a SW main linac cavity of length 0.9 m. In order to enhance the beam capture efficiency and to reduce the energy spread a pre-buncher cavity along with focusing elements will be introduced between the electron gun and the main linac cavity section. In this work the design simulation, fabrication, RF measurements and beam experimental trials of the 2856 MHz low Q, wide band pre-buncher cavity is presented. The measured RF parameters of pre-buncher cavity are f0=2854.4 MHz in air, QL=600, tuning range ±2.5 MHz. Electron beam transmission efficiency of 99% is achieved with minimum relative bunch length obtained at 400W of input RF power. •Low Q, high band width pre-buncher cavity for stable beam operation.•Measurement of relative bunch length from beam current modulation.•99% beam transmission in pre-buncher beam line.