1. 5 months of experience with 8 units of Libera Brilliance
- generally good performance (stability & resolution)
also high quality Sum signal (resolution & stability) --> charge measurements
1 unit (c14) broke down due to faulty board /connections
resolution disturbed by (real) 22KHz vertical beam motion ?
resolution disturbed by non-equal phased RF inputs (different cable lengths)
resolution much disturbed by partial fill (i.e. 30%) and single (4 & 16) bunch fills
But : offset-tuning offers a solution to all these disturbances (or not ?)
also : the fine-tuning of certain (FA) filters can also help to suppress aberations
Status now :
1) performance under 1, 4 & 16 bunch (and 30% fill) need close investigations
2) this with various values of offset-tune & cleverly designed filters
3) while analyzing the (spectrum of) FA (10KHz) data

2. Once optimum timing adjusted
inject 1/3 fill in SR and kick it out
after 1 single Turn :
One single Turn should be seen on
the SUM signal, without smearing
Conclusion :
the modified DDC filter works well

3. Situation with standard DDC filter
‘smearing’

4. 22KHz component of ~15um pk-p in Vert. Plane,
+ strong DSC Libera-switching (at 27 TbT-intervals) (C8)

5. DSC OFF (0)
DSC ON (2)
2 um

6. Tuned (MC=SR)
PMO-Tuned (MC~SR)
1 um
DSC ON (2) all the time

7. DSC ON
DSC OFF
DSC ON
DSC OFF
DSC ON
500nm
DSC ON : ~ 12 nm rms
‘perfect-stable’
beam
DSC OFF : ~110 nm rms

8. Tuned
(MC=SR)
Poor Man’s Offset-Tuning
(MC~SR, only few (milli-)Hertz offset)

9. For a certain time we believed some aliasing effect between the
13 KHz DSC mechanism & the 22KHz real beam motion was
responsible for the resolution degradation.
Seemed plausible
In fact, later it was found that simply non-equal phased input signals
(because of different cable lengths) are enough for a Libera Brilliance
resolution degradation. (when tuned)
Seemed surprising
this is the ‘Brilliance’ that does not even need offset-tuning
according to official IT documents

10. tuned
~350nm
DSC off
off-tuned (20)
DSC on
CW RF signals from splitter (equal ampl. & phase) into the 4 Libera inputs

11. tuned
DSC on
DSC off
off-tuned (20)
~2um
CW RF signals from splitter into the 4 Libera inputs, but with 11cm extra cable for D

12. Degradation with partial fill and 1, 4, 16 bunch fills
output after the 40MHz wide BPF
that the ESRF puts just in front
of the Libera RF inputs

13. tuned off-tuned (20) DSC on DSC off
Libera fed with button & beam signals in 16 bunch fill,
but going through Sum & Split. (i.e. stable beam) after 40MHz BPFs
the max. ADC values are strong but well below saturation (i.e. <30K)

14. TUNED
~7 um
DD-decimated, 10Ksa=1.8sec

15. OFF-TUNED (20)
~7 um
DD-decimated, 10Ksa=1.8sec

16. Transition : from off-tuned (20) to tuned
DD-decimated, 10Ksa=11sec

17. Spectrum from FA output 16 bunch, offset-tune=20
Beam. Hor.
Stab.Hor.
Stab.Vert.
Beam. Vert.
Spectrum from FA output
16 bunch, offset-tune=20

18. Beam. Hor.
Stab.Hor.
Stab.Vert.
Beam. Vert.
Spectrum from FA output
16 bunch, offset-tune=20

19. Beam. Hor.
Off-tune=30
Beam.Hor.
Off-tune=20
Beam.Vert.
Off-tune=20
Beam. Vert.
Off-tune=30
Spectrum from FA output
16 bunch, offset-tune=20 & 30

20. When tuned, what is causing the poor performance of the Liberas ??
40MHz
5.7MHz
SAW-Libera
15MHz
ADC signals with
16 bunch fill i.e.
side bands at 5.7MHz
5MHz
Blue : with 40 MHz BPF (and the internal SAW 15MHz BPF)
Red : with 5 MHz BPF

21. * ? 40MHz 5.7MHz ‘Leaking SAW’ ‘Leaking SAW’ ADC signals with
16 bunch fill i.e.
side bands at 5.7MHz
5MHz
Blue : with 40 MHz BPF (and the internal SAW 15MHz BPF)
Red : with 5 MHz BPF

22. Blue : 16 Bunch with 40 MHz BPF & the internal SAW 15MHz BPF
SAW-Libera
15MHz
7 X fsa – 2 X frf
created by Libera itself
Blue : 16 Bunch with 40 MHz BPF & the internal SAW 15MHz BPF
Black : CW RF with 40 MHz BPF & the internal SAW 15MHz BPF

23. offset=20units offset=10units
Another Libera artefact appears in SA data with offset-tuning :
a slow 200nm pk-pk oscillation, the period is determined by the value of the offset
data taken under 16 bunch, ‘perfect stable’ beam (Sum & Split)

24. The slow 200nm pk-pk oscillation in SA data can be minimized by
playing with the switching delay parameter,
data taken under 16 bunch, ‘perfect stable’ beam (Sum & Split)

25. offset=20units offset=10units offset=40units
Another Libera artefact appears in DD t-b-t data with offset-tuning :
~ 12um pk-pk oscillation in vert. plane, the period is determined by the value of the offset
data taken under 16 bunch,
with ‘perfect stable’ beam (Sum & Split)
offset=40units

26. offset=20units offset=10units offset=40units
Another Libera artefact appears in DD t-b-t data with offset-tuning :
~ 25um pk-pk oscillation in vert. plane, the period is determined by the value of the offset
data taken under 16 bunch,
with real beam (Cell 8, BPM 3)
i.e. including the ESRF’s 15um 22KHz vertical beam motion, (just about visible in 1rst graph)
offset=40units

27. Numbers in the ESRF Libera
[ in units of fsr ]
ESRF harmonic : ,202,600 Hz
ADC sample freq. : ,933,055 Hz
T-b-T : ,043 Hz
DSC mechanism : / ,150 Hz
T-b-T decimated : / ,548 Hz
FA output : / ,862 Hz
SA output : / 36 x Hz
Just note :
304 = 19 x 16
4 x 27 = 108 = 3 x 36
I-Tech, being confronted with our findings, is re-thinking the 304 and 36 design

28. What’s next :
At the ESRF :
- close investigations under 1, 4 & 16 bunch (and 30% fill)
- this with various values of offset-tune & cleverly designed (FIR-FA) filters
- while analyzing the (spectrum of) FA (10KHz) data
At I-Tech :
re-produce the ESRF findings (1, 4 & 16 bunch) with ultra-short pulse generator
find the optimized offset-tune values and FIR filters to satisfy all ESRF operation
study the impact of different numeric designs ( 304  305,  35 )