1. Libera and ELETTRA Marco Lonza, Giulio Gaio, Vincenzo Forchi’
Sincrotrone Trieste – ELETTRA

2. Booster Injector
shut down of ELETTRA since October 2007 for the connection of the new Booster Injector to the storage ring
users operations restarted the 3rd of March
2.5 GeV Booster allows for full-energy and top-up injection
former injector based on a 1 GeV Linac will be available for the Free Electron Laser
site
Booster
Old Linac
Storage Ring

3. Booster Installation and Commissioning
booster installation 26th April 2007 – 3rd August 2007
Linac 100 MeV
: 0.8 GeV extraction
– connection of the booster to the storage-ring
: 2.0 GeV extraction
: 2.0 GeV injection into Elettra
Linac beam profile
Booster Ring
100 MeV Booster Linac

4. Accumulated current in “frequent injection” mode
Booster Status
the booster is currently operating at 2.0 GeV 1 Hz (specified 2.5 GeV 3 Hz)
limitation due to bending and quadrupoles power supplies (max current, repetition rate and ripple)
power supplies refurbishing program: 2.4 GeV 3 Hz by beginning of April, reduced ripple by August 2008
present operation: full energy injection at 2.0 GeV, injection once a day on top of the stored current, max injection rate 0.4 mA/s (specified 1 mA/s)
“frequent injection” mode successfully tested
first top-up tests foreseen in the next run, top-up operation not before autumn 2008
Accumulated current in “frequent injection” mode

5. Libera at Elettra 107 Libera Electron purchased in 2006, 100 installed
release 1.42 used up to end of March, 1.82 installed during last shutdown
not decided yet whether to buy the 2.0 release or not
not real need (at the monet) for new features such to justify the expense
same considerations for Libera Brilliance
behavior of Libera is good, apart from:
steps in the position readings when changing attenuators
frequency components at 70 Hz: to be investigated
one Libera used for tune measurement in the Booster
no Libera used for multi-bunch feedback systems (still using the old systems with DSPs)

6. Global Orbit Feedback Architecture
96 rohmboidal + 4 low-gap BPMs all equipped with Libera Electron
82 corrector magnets per plane
12 VME stations with Motorola 6100 CPU boards running Linux (Tango control system) and RTAI real-time extension (feedback processing)
feedback stations acquire position data at 10 kHz from Libera Electron through Gigabit Ethernet links
data shared in real-time through Reflective Memory fibre optics
10 kSample/s D/A converters generate the analog correction signals sent to the corrector power supplies
Master Station connected to the reflective memory for feedback supervision and data acquisition
Event system: 1 EVG, 12 EVR, Libera Clock Splitters and fibre optics to distribute MC, SC, PM and Trigger signals

7. Differential Analog Links to Corrector Power Supplies
Global Orbit Feedback Architecture
From N-1 GOF Station
F.O. Links
To N+1 GOF Station
GOF Station
CPU
Reflective Memory
DACs
7 Horizontal
Differential Analog Links to Corrector Power Supplies
7 Vertical
±400 mA
±48/70 mrad
Control System Network
Corrector Setting
DC Setting
Ethernet
Switch
Gigabit Ethernet Links
Control System Network
Libera
Libera
Libera
Libera
Libera
Libera
Libera
Libera
BPM Buttons
BPM Buttons
BPM Buttons
BPM Buttons
BPM Buttons
BPM Buttons
BPM Buttons
BPM Buttons

8. Control Algorithms
PID dedicated to low frequency (0-150 Hz) noise components
Harmonic Suppressors damp periodic noise components: 50, 100, 150, 200, 250 and 300 Hz
50 Hz and harmonics
Feedback OFF
Feedback ON
Amplitude spectrum of the horizontal beam position

9. Fast Global Orbit Feedback operator Panel
Milestones of the feedback project
the existing RF BPM detectors have been replaced with Libera Electron:
March March 2007
installation of the feedback system: finished in February 2007
loop closed in March 2007
since beginning of September 2007 the feedback is routinely used during users shifts
operations stopped in October 2007 and re-started in March 2008
still work to be done to:
optimize PID and Harmonic suppressors
optimize singular values
use weights for BPMs (and correctors?)
Fast Global Orbit Feedback operator Panel

10. Libera Tango Device Server
Embedded Tango Device Server (by Nicolas Leclercq - SOLEIL) running in the SBC on top of the Generic Server (still not possible without it: thread problems?)
the Tango server is a “in house” modified version of the one developed for the 1.40 release but does not implement the new functionalities
the Tango server for the 1.82 is being developed by Nicolas
need for a closer coordination and collaboration between Tango/Libera users with respect to the development and maintenance of the Libera Tango Server
Giulio Gaio and Claudio Scafuri will take over from Vincenzo Forchi’ (resigning) the Libera Tango Server deployment at ELETTRA
Tango Device “inside” or “outside” Libera? What about Soleil, ESRF, ALBA, ...? The behavior of the Tango Server seems different! Tango Server needs debugging directly in the SBC

11. Closed Loop Performance
Integrated amplitude spectrum of the beam position noise measured by a BPM with feedback off and on

12. Closed Loop Performance
Average BPM rms in the 0-5 Hz and Hz frequency range with feedback off/on

13. Closed Loop Performance
Average beam position rms using 10 Hz data of all the BPMs. The feedback is switched on at 270 mA

14. “Out of the Loop” Performance
Horizontal beam position measured by a low-gap BPM not included in the loop with feedback off/on
Feedback OFF
Feedback ON

15. “Out of the Loop” Performance
Photon beam position measured by exit slits on the GasPhase beam line. The orbit is perturbed by continuous ID gap changes
Feedback ON
Feedback OFF

16. Operational Aspects
after a new injection and energy ramping an orbit correction program restores to required values the position and angle of the electron beam in the insertion devices and bending magnets
the feedback is eventually activated taking the corrected reference orbit as the set point for the loop: the AGC is switched off to avoid “steps” in the position reading
only the fast feedback operates to correct the orbit, no slow feedback working in parallel
correction algorithm: SVD with singular values reduction (48 s.v.)
a considerable part of the measured orbit drift is not due to real orbit distortions but to the movement of the BPMs driven by thermal drifts
the situation has considerably improved with full energy injection: expected further improvement when a more frequent injection or top-up will be performed

17. Control Room Panels
Expert Panels
Operator Panel

18. Open Issues and Perspectives
the feedback system is flexible, reliable and easy to use
further studies needed to optimize the respose matrix inversion (SVD)
modal analysis of orbit distorsion
optimization of singular value reduction
the global feedback minimizes the rms of the whole orbit, ID source points disadvantaged with respect to dedicated local correction
weighting of BPMs to privilege the correction at the IDs with respect to global one
rhomboidal BPMs are not adjacent to IDs, there are 2 correctors in between
Low-Gap BPMs with position measurement (better resolution and stability) already installed in straight section 2 and 7
necessity and feasibility of the installation of other Low-Gap BPMs to be evaluated
availability of integrated photon BPMs is extremely useful, both as complementary diagnostics and for a possible employment in-the-loop
ongoing activity to integrate a picoammeter current detector with fast digital interface into the global feedback
By Instrumentation Group
By Instrumentation and Detectors Laboratory

19. Real-time performance
Libera latency: 300 ms
Gigabit Ethernet transmission time: 10 ms
Ethernet switch latency: 1 ms
Reflective Memory Latency (BPMs and correctors data): 25 ms
matrix multiplication and 14 control channels (LP Filter + PID + 10 HS): 21 ms
DAC settings: 10 ms
all real-time tasks executed in ms
CPU Load (G4 1.3 GHz)
feedback processing under RTAI: %
8 TANGO servers (25 devices), control system interface, FFT of samples 20 times per second with transmission to the client: 20%

20. Diagnostic Features
Diagnostic capabilities for machine physics studies, investigation of beam noise sources, searching of malfunctioning machine components
Data recording:
Each local station stores:
8 seconds of 10kHz data (BPMs and correctors);
5 days of 1Hz data;
Master station stores:
5 seconds of 10kHz synchronous data of all BPMs and correctors
Post Mortem Analysis: buffers stop automatically under given conditions on BPM signals allowing beam dump detection
Arbitrary Waveform generation: driven by the master station, used to measure the corrector magnets transfer function
Horizontal Plane
BPM number
Frequency (Hz)