A New Injection System for an Electron/positron Linac

For the Linac II, which supplies the accelerator chain at DESY with electrons and positrons, a new injection system is planned. It is supposed to ensure reliable operation and to avoid the beam loss of about 60% before the positron converter and the associated activation. The main components are a 6 A/100 kV triode gun, buncher and a dispersive section for energy collimation. The output energy is 5 MeV. The new buncher structure is a hybrid of a standing wave and traveling wave structure and allows a compact design and good electron capture. Its main part is a traveling wave structure in 2π/3 mode, to which one capture cell is coupled in π mode. The function of the injector components, the entire injection system and the acceleration in the linac sections were optimized in simulations. In addition, the design is analysed in a test rig before final installation. Test rig and subsequent injector are equipped with extensive diagnostics. Besides the design of the injection system results of simulations and measurements on the test rig will be presented.