Development of a beam imaging system for the European spallation source tuning dump

To provide essential beam diagnostics for the spallation target and for the tuning dump of the European Spallation Source (ESS) with its high-power, low-emittance proton beam, optical imaging systems have been developed allowing remote viewing of the beam profiles, using scintillation light from coatings on the proton beam window (PBW) at the accelerator exit and the target entry window (TW), and insertable interceptive screens at the tuning dump (TD). In this paper, we present the techniques used and the main parameters in the design of the TD system, including the optical configurations modelled in the software Zemax OpticStudio (ZOS). We also present the design principles for reflective optics which can transmit high-quality images, showing the performance of the imaging systems as predicted by ZOS and by prototyping. We take account of the requirements for initial alignment and ongoing maintenance of the optical system. Studies of the radiation and thermal environments, which impact on sensitive optical components such as cameras and mirrors, are also described, as are mechanical considerations for the vacuum vessels and screen actuators. Finally, comments are made on the applicability of similar optics to diagnostic systems at other neutron sources and accelerators