1. A Fast Orbit Feedback for the Elettra Storage Ring 1. Fast Global Orbit Feedback Tango Control System … … BPM Server BPM Server Corrector Server Corrector Server User Space Shared Memory Schematics of one of the 12 Local Stations RTAI Kernel Space From N-1 GOF Station F.O. Links To N+1 GOF Station Real-Time Thread Local Station CPU Reflective Memory DACs 7 Horizontal GE Driver DAC Driver RM Driver Differential Analog Links to Corrector Power Supplies Master Station 7 Vertical Control System Network Corrector Setting DC Setting Ethernet Switch Gigabit Ethernet Links Control System Network 4. Operations and Performance 3. Automatic Procedures and Operator Panels Libera Libera Libera Libera Libera Libera Libera Libera BPM Buttons BPM Buttons BPM Buttons BPM Buttons BPM Buttons BPM Buttons BPM Buttons BPM Buttons M. Lonza, D. Bulfone, V. Forchi’, G. Gaio, L. Pivetta, Sincrotrone Trieste, Trieste, Italy Abstract A fast global orbit feedback using digital Beam Position Monitor (BPM) detectors has been installed and commissioned at Elettra. The system uses 96 BPMs and 82 steerer magnets to correct closed orbit errors at a 10 kHz repetition rate. The feedback processing is performed by twelve VME stations equipped with commercial CPU boards running the Linux operating system with real-time extension and connected to each other by a low-latency fiber optic network. The system is fully controlled by a Tango based control system. The operational experience and the achieved results are presented. Plans for further improvements of the orbit stability are also discussed. 2. Software Architecture • 96 BPMs and 82 Correctors • Old BPM detectors upgraded with Libera Electron (by Instrumentation Technologies d.o.o.) • 12 Local Stations and 1 Master Station (VME PPC boards with Linux+RTAI) • Data collected at 10kHz rate throguh UDP packets on a dedicated Gigabit Ethernet network • Data shared through Reflective Memory in a fiber optic ring (GE-Fanuc PMC-5565) • Feedback processing executed in the Local Stations Libera Electron integration into the Elettra control system • Embedded Tango device server running in Libera Electron, interfaced through a 100Mbit/s Ethernet interface • Dedicated Gigabit Ethernet interface provides position data at 10 KHz to the fast feedback system Local Station software architecture • RTAI kernel space: • Device drivers (DAC, Gigabit Ethernet, Reflective Memory) • Real-Time thread (collects and share data, computes and applies corrections) • Shared memory between user and kernel space: contains 200 Mbytes of buffers for data recording • Users Space: Tango device servers for BPMs and correctors Master Station • Master Station receives from the Local Stations synchronous BPM and correction data at 10 kHz through the Reflective Memory and stores them into memory buffers • Master Station sends to the Local Stations commands and configuration parameters: • set point (reference orbit) • inverted response matrix • feedback configuration parameters (PID, digital filter coefficients, etc.) • feedback control commands: close/open loop, freeze/unfreeze • time stamps • output values to drive the corrector power supplies with arbitrary waveforms Software architecture of a local station Real-time performance • Libera Electron latency: 300 ms • transmission time from 10 Libera Electron to local station CPU: <10ms • reflective memory data sharing between 13 stations: 25 ms • feedback processing time: 21 ms Total delay ~450ms • CPU load ~80% (real-time tasks 60%, user-space tasks 20%) The fast orbit feedback system is in operation during users shifts since the beginning of September 2007 • the feedback loop can run even with a number of faulty BPMs • in the presence of output saturation or severe system malfunctioning, the loop is immediately opened • a slow loop running in the Master Station with a period of ten seconds executes the following automatic actions: • adjusts the machine RF to correct for horizontal orbit distortions due to beam energy changes (dispersion loop) • in case of beam loss, opens the loop and prepare BPM detectors and feedback system for a new injection • checks if the feedback DACs are close to saturation and, if so, transfers their values to the corrector control system DACs or freezes the feedback DACs and opens the loop Average beam position rms (mm) with feedback off/on in the 0‑5 Hz and 0‑200 Hz frequency ranges Average beam position rms using 10 Hz data of all the BPMs. The feedback is switched on at 270 mA Expert panels Feedback system synoptic Operator panel Orbit error rms with respect to a reference orbit with feedback on in a time period of 7 hours after injection and energy ramping to 2GeV BPMs monitor panel Correctors monitor panel ICALEPCS'07, Knoxville, October 15-19, 2007