Prototype screen monitor for XFEL/SPring-8

A prototype screen monitor for XFEL/SPring-8 is developed and verified at the SCSS test accelerator. The imaging apparatus has a high-resolution (<10um) optical system with variable magnification of 1.2x-4x. In order to change the magnification ratio by remote control, a lens and an imaging device are mounted on motorized stages. The screen actuator can hold two screen targets, an OTR target and a fluorescent plate target, and can switch them by an air cylinder. We developed a thin OTR target made of 100um-thick stainless-steel foil in order to reduce demagnetization of undulator magnets due to scattered particles at the target. We performed a beam experiment of the prototype screen monitor with the thin OTR target at the SCSS test accelerator and we appropriately obtained an electron beam profile. (author)