1. SOLEIL Fast Orbit Feedback System
First results and optimization
Nicolas HUBERT
Synchrotron SOLEIL
On behalf of Diagnostics group
3-4/04/2008
2nd Libera Users Meeting, ALBA

2. 2nd Libera Users Meeting, ALBA
Summary
System properties
System efficiency
What has to be done before using it in operation?
3-4/04/2008
2nd Libera Users Meeting, ALBA

3. 2nd Libera Users Meeting, ALBA
FOFB properties
Modularity: choice in the number of involved BPMs (from 1 to 120)
2 configuration have been used:
48 BPMs (straight sections BPMs)
120 BPMs (all of them)
Correction is applied at 10 KHz to 48 dedicated power-supplies and air-coil correctors (located at each side of the straight sections).
For the moment the correction is done from DC, (SOFB system is OFF)
Integrative coefficient of the PI controller is equal to 1:
IN = ΔIN + IN-1 => simple accumulator
3-4/04/2008
2nd Libera Users Meeting, ALBA

4. 2nd Libera Users Meeting, ALBA
FOFB efficiency
The frequency range were the FOFB has an influence can be divided in 3 area:
1 Hz to Hz : fast beam perturbations
0.01 Hz to 1 Hz : Insertion devices perturbations
DC to Hz : slow drifts
3-4/04/2008
2nd Libera Users Meeting, ALBA

5. 2nd Libera Users Meeting, ALBA
FOFB efficiency (0-500 Hz)
3-4/04/2008
2nd Libera Users Meeting, ALBA

6. 2nd Libera Users Meeting, ALBA
FOFB efficiency (0-100 Hz)
3-4/04/2008
2nd Libera Users Meeting, ALBA

7. 2nd Libera Users Meeting, ALBA
Effect on the perturbations caused by the insertion devices (vertical plane)
NO OFB
SOFB
FOFB 48*48
FOFB 120*48
3-4/04/2008
2nd Libera Users Meeting, ALBA

8. 2nd Libera Users Meeting, ALBA
FOFB efficiency on slow drifts
Values in µm and µrad
DESIRS (UV)
Hard X ray
Soft X ray
Bending magnets
sx /10
Dx pp (fofb off) 3.5h
Dx pp (48x48) 2h
Dx pp (120x48) 3h 32 12 18 10
0.5 39 15
0.3 ?
4.5
1.5
0.2
s'x /10
Dx’ pp (fb off) 3.5h
Dx’ pp (48x48) 2h
Dx’ pp (120x48) 3h
4.6
3.4
2.5
0.1 11
0.9
sz /10
Dz pp (fb off) 3.5h
Dz pp (48x48) 2h
Dz pp (120x48) 3h 6 4
0.6
6.5
5.8
0.55
3.2 17
4.1
s'z /10
Dz’ pp (fb off) 3.5h
Dz’ pp (48x48) 2h
Dz’ pp (120x48) 3h
4.2
1.6
0.52
5.3
3-4/04/2008
2nd Libera Users Meeting, ALBA

9. 2nd Libera Users Meeting, ALBA
Soleil particularity
Slow correctors are located inside the sextupoles.
Vacuum chambers are in Aluminum because of NEG coating
=> Necessity to have different correctors for the Fast Feedback (over stainless steel bellows)
SOFB and FOFB systems are operating with different correctors
3-4/04/2008
2nd Libera Users Meeting, ALBA

10. 2nd Libera Users Meeting, ALBA
Should the FOFB correct to DC?
Slow and Fast Feedback are not compatible at the moment
Option 1: Make a dead-band to separate both system S O F B
FOFB
0.1 1 10
100
Frequency (Hz)
+ Both systems are independent
- Some perturbation caused by insertions will not be corrected
Development of a high pass filter
=>
Option 2: Make the FOFB efficient to DC
FOFB
0.1 1 10
100
Frequency (Hz)
Verification that the FOFB can work alone during at least 8 hours without saturation
Elaboration of a communication between the 2 feedbacks
External treatment of the correction applied on the RF
+ All low frequency perturbations can be damped
- SOFB should from time to time relieve the fast correctors from their DC part.
=>
3-4/04/2008
2nd Libera Users Meeting, ALBA

11. 2nd Libera Users Meeting, ALBA
To be solved before operation
Spikes on the correction:
FOFB 48*48
FOFB 120*48
SOFB
NO OFB
Visible on both plane: 60 µm in horizontal
1 µm in vertical
3-4/04/2008
2nd Libera Users Meeting, ALBA

12. 2nd Libera Users Meeting, ALBA
Spikes
3-4/04/2008
2nd Libera Users Meeting, ALBA

13. 2nd Libera Users Meeting, ALBA
Spikes
3-4/04/2008
2nd Libera Users Meeting, ALBA

14. 2nd Libera Users Meeting, ALBA
Schedule
Loop closed for the first time in December 2007
First use in operation foreseen for September 2008
Special thanks for their collaboration to
I. Uzun and G. Rehm (Diamond Light source)
E. Plouviez (ESRF)
3-4/04/2008
2nd Libera Users Meeting, ALBA