An injector study for electron cooling at PETRA using a bunched beam

An increase in the luminosity of circular hadron–lepton collider HERA may be achieved via electron cooling of hadrons in the PETRA-preaccelerator. The cooling of high-energy (15–20 GeV) protons requires a high electron beam current (few amperes) with low emittances (<4 π mm mrad normalized) to reach reasonable cooling times of <10 min. For this purpose a linac-based scheme has been considered. Electron bunches from a magnetized thermal cathode are longitudinally compressed, accelerated in a traveling wave structure and, after reducing their energy spread, subsequently debunched to match the bunch length in PETRA. The entire electron accelerator, as well as the cooling section, is immersed in a kG magnetic field; matching is provided for the technically unavoidable gaps in the solenoidal field. This paper presents the status of the development of the magnetized gun, accelerating structure and different variants of the debuncher.