Closing plenary summary of working group 4 instrumentation and controls for ERL2011

Working group 4 was charged with presentations and discussions on instrumentation and controls with regards to Energy Recovery Linacs (ERL). There were 4 sessions spanning 3.5 hours in which 7 talks were delivered, the first being an invited plenary presentation. The time allotted for each talk was limited to 20-25 minutes in order to allow 5-10 minutes for discussion. Most of the talks were held in joint session with working group 5 (Unwanted Beam Loss). This format was effective for the purpose of this workshop. A final series of discussion sessions were also held with working group 5. Summary of the working group 4 activities, presented in the closing plenary session. We had a plenary presentation on operational performance, experience, and future plans at the existing ERL injector prototype at Cornell. This included instrumentation data, controls system configurations, as well as description of future needs. This was followed by four talks from KEK and RIKEN/SPring-8 that described electron beam instrumentation already in use or under development that can be applied to ERL facilities. The final talks described the ERLs under construction at KEK and BNL. The format of having joint sessions with working group 5 was beneficial as there were a significant number of common topics and concerns with regards to the causes of beam loss, instrumentation hardware, and techniques used to measure and analyze beam loss

Vertical instability with transient characteristics in KEK-Photon Factory electron storage ring

A vertical instability of the KEK-Photon Factory electron storage ring was observed in a multibunch mode with empty buckets (bunch gap) using a bunch-by-bunch beam diagnostic system that consisted of a high-speed light shutter and an optical betatron oscillation detector. It was clearly seen that vertical betatron frequencies of individual bunches varied along a bunch train. The dependence of the betatron frequencies on the bunch positions in the train was explained by modulation of trapped-ion density caused by passage of the beam. Agreement between experimental results and the theoretical prediction was quite good