The design of thermionic electron source is developed by the radiation source ELBE (Electron Linac for beams with high Brilliance and low Emittance) project- HZDR (Helmholtz-Zentrum Dresden-Rossendorf) at Dresden and still in operation ( The mechanical design of gun for TARLA is obtained from HZDR within the collaboration.

The injector system which consist of a thermionic triode DC electron gun, two buncher cavities operating at 260 MHz and 1.3 GHz, five solenoid lenses, and one dipole magnet is based on fully normal conducting technology delivers beam with energy of 250 keV, a bunch charge of 120 pC and a repetition rate of 13 MHz, that corresponds to an average beam current of 1.5 mA at CW mode. The repetition frequency is the 100th fraction of the working frequency of the main accelerating frequency of 1.3 GHz. The electron bunches are created at grid modulated tungsten dispenser cathode with length of ˜500 ps. The bunches have energy of 250 keV when they leave the gun and they will be compressed in the drift following the energy modulation obtained in the subharmonic buncher (SHB) and fundamental buncher (FB) in order to have optimum longitudinal (temporal) waist inside the first cell of the first SC cavity. The beam can additionally be modulated by a macro-pulse mode with a macro-pulsing system installed on injector.