Present Status of Orbit Stabilization at SPring-8 H. Tanaka (JASRI/SPring-8) On behalf of SPring-8 Project Team for Beam Orbit Stabilization I would like to present our experience of interdivisional collaboration at SPring-8, which means the collaboration among accelerator scientists, beamline scientists and end-users aiming at the performance upgrade. 2019/5/3

1. Progress in These Two Years Cycle by cycle reproduction of ID photon beam axes by XBPM Sep’03 Introduction of top-up operation May’04 Increment in the number of Steering magnets in SOFB (24->48) Sep’04 In general, accelerator scientists take the initiative in the process of the machine-performance upgrade. Here in SPring-8, most of the upgrades, stored current increase, beam emittance reduction, beam orbit stabilization, etc. are this style, top-down one. On the other hand, users’ leading upgrade is rare, we have had only one upgrade relating to the optics change of the storage ring. 2019/5/3

2. Present Performance Fast orbit stab. (0.1Hz ~ 200Hz) Hori. r.m.s. ~4um @ID’s H.size=360um Vert. r.m.s. ~1um @ID’s V.size=5~6um Slow orbit stab. (<0.1Hz) Hori. r.m.s. 1~2 micron / week Vert. r.m.s. 2~3 micron / week Energy drift ~2x10-5 (full width) What is the problem in the accelerator-leading upgrade? The answer is following. In this kind of the upgrade, users can’t clearly predict what happens by the upgrade and can’t clearly understand the merit given by the upgrade. A lack of information makes users extremely conservative, negative to any modification. 2019/5/3

2.1. Fast Orbit Stability 2019/5/3 What is the problem in the accelerator-leading upgrade? The answer is following. In this kind of the upgrade, users can’t clearly predict what happens by the upgrade and can’t clearly understand the merit given by the upgrade. A lack of information makes users extremely conservative, negative to any modification. 2019/5/3

2.2. Slow Orbit Stability 2019/5/3 What is the problem in the accelerator-leading upgrade? The answer is following. In this kind of the upgrade, users can’t clearly predict what happens by the upgrade and can’t clearly understand the merit given by the upgrade. A lack of information makes users extremely conservative, negative to any modification. 2019/5/3

2.3. Beam Energy Stability 2019/5/3 What is the problem in the accelerator-leading upgrade? The answer is following. In this kind of the upgrade, users can’t clearly predict what happens by the upgrade and can’t clearly understand the merit given by the upgrade. A lack of information makes users extremely conservative, negative to any modification. 2019/5/3

3. Merit of Top-up X-ray beam stabilization at experimental stations Purpose of beam orbit stabilization X-ray beam stabilization at experimental stations Improvement of X-ray optics stability Reduction of current-dependent noise in beam orbit variation To break this situation, we have applied a new approach to a top-up project at SPring-8. The mission of the project is to introduce the top-up operation in user-service time. Firstly, the combined taskforce was composed of accelerator scientists, beamline scientists, and end users. Secondly, two leaders were assigned in the taskforce. One covers the accelerator relating problems and the other covers beam line and experiment relating problems. Thirdly, all information, that is, discussion process and decision, progress of R&D and situation of the problem to be solved, etc were opened by the dedicated Web page to build the common understanding of the project progress. 2019/5/3

3. Merit of Top-up (Con’t) Example: Quality-improvement of Diffraction Data Diffraction data especially at higher 2, which need relatively large integration time, was improved in accuracy Deviation between two scanned patterns Top-up Diffraction pattern from Pse glass @E=61.6keV To break this situation, we have applied a new approach to a top-up project at SPring-8. The mission of the project is to introduce the top-up operation in user-service time. Firstly, the combined taskforce was composed of accelerator scientists, beamline scientists, and end users. Secondly, two leaders were assigned in the taskforce. One covers the accelerator relating problems and the other covers beam line and experiment relating problems. Thirdly, all information, that is, discussion process and decision, progress of R&D and situation of the problem to be solved, etc were opened by the dedicated Web page to build the common understanding of the project progress. Conventional 2019/5/3

4. Facing Problems -A 4.1. Precise measurement of X-ray beam axes during user operation Measured data by XBPM have gap and phase dependences Measured data by rfBPM up- and down-stream of ID have at least gap, stored current, and filling dependences This new approach worked well and we have successfully introduced the top-up operation, which meets the users requirement, keeping the time-schedule. The merits of the approach are following two. The users’ demand was reflected in the accelerator development and as the second, users can fully utilize the merit by the upgrade from the beginning of the new operation. This approach will be standard in the mission of the performance upgrade and construction of a new challenging beam-line. These prevent “hard correction” 2019/5/3

4. Facing Problems -A (Con’t) Counter-measures: New BPM chamber with bellows and cooling channels Improvement of BPM support rigidity Introduction of narrow path-band filters to electric circuit (under investigation) This new approach worked well and we have successfully introduced the top-up operation, which meets the users requirement, keeping the time-schedule. The merits of the approach are following two. The users’ demand was reflected in the accelerator development and as the second, users can fully utilize the merit by the upgrade from the beginning of the new operation. This approach will be standard in the mission of the performance upgrade and construction of a new challenging beam-line. 2019/5/3

4. Facing Problems -A (Con’t) BPM ID ID Support Bellows This new approach worked well and we have successfully introduced the top-up operation, which meets the users requirement, keeping the time-schedule. The merits of the approach are following two. The users’ demand was reflected in the accelerator development and as the second, users can fully utilize the merit by the upgrade from the beginning of the new operation. This approach will be standard in the mission of the performance upgrade and construction of a new challenging beam-line. Beam test for global + local correction will start in next year 2019/5/3

4. Facing Problems -B 4.2. Clear one-day (periodic) orbit slow variation After introducing top-up operation, clear one day orbit variation appears Season-dependence Strange correlation between STs In general, accelerator scientists take the initiative in the process of the machine-performance upgrade. Here in SPring-8, most of the upgrades, stored current increase, beam emittance reduction, beam orbit stabilization, etc. are this style, top-down one. On the other hand, users’ leading upgrade is rare, we have had only one upgrade relating to the optics change of the storage ring. 2019/5/3

4. Facing Problems -B (Con’t) 2004 2004 Vertical Horizontal In general, accelerator scientists take the initiative in the process of the machine-performance upgrade. Here in SPring-8, most of the upgrades, stored current increase, beam emittance reduction, beam orbit stabilization, etc. are this style, top-down one. On the other hand, users’ leading upgrade is rare, we have had only one upgrade relating to the optics change of the storage ring. 2019/5/3

4. Facing Problems -B (Con’t) In general, accelerator scientists take the initiative in the process of the machine-performance upgrade. Here in SPring-8, most of the upgrades, stored current increase, beam emittance reduction, beam orbit stabilization, etc. are this style, top-down one. On the other hand, users’ leading upgrade is rare, we have had only one upgrade relating to the optics change of the storage ring. 40 min. period 2019/5/3

4. Facing Problems -B (Con’t) We have been trying to find out these perturbation sources and mechanism of this orbit variation We hope to report the complete story in next IWBS In general, accelerator scientists take the initiative in the process of the machine-performance upgrade. Here in SPring-8, most of the upgrades, stored current increase, beam emittance reduction, beam orbit stabilization, etc. are this style, top-down one. On the other hand, users’ leading upgrade is rare, we have had only one upgrade relating to the optics change of the storage ring. 2019/5/3

4. Facing Problems -C Q: Is fast orbit feedback (FOFB) necessary at SPring-8 or not ? A: Although the answer depends on the mode in higher frequency regime, SOFB seems to meet the condition rather than FOFB In general, accelerator scientists take the initiative in the process of the machine-performance upgrade. Here in SPring-8, most of the upgrades, stored current increase, beam emittance reduction, beam orbit stabilization, etc. are this style, top-down one. On the other hand, users’ leading upgrade is rare, we have had only one upgrade relating to the optics change of the storage ring. 2019/5/3

5. Summary By introducing top-up operation, slow orbit drift was reduced to some extent To request for further slow orbit stability, the local feedback loop will be provided BL by BL We will be continue source-hunting to reduce the fast orbit variation lower than 200Hz without FOFB In general, accelerator scientists take the initiative in the process of the machine-performance upgrade. Here in SPring-8, most of the upgrades, stored current increase, beam emittance reduction, beam orbit stabilization, etc. are this style, top-down one. On the other hand, users’ leading upgrade is rare, we have had only one upgrade relating to the optics change of the storage ring. 2019/5/3