1. LLRF & Synchronization System + Roadmap
On behalf of the LLRF
and
Laser based Synchronization team
Presented by H. Schlarb 1

2. LLRF upgrades and developments at FLASH
Outline
LLRF upgrades and developments at FLASH
- Decision to keep MO frequency at 9MHz
=> Software & Hardware will be identical to XFEL
=> Implementation of uTCA based system at FLASH 2011/2012
=> XFEL software development has basically started!
Highlights from FLASH operation
Overview on synchronization
+ some recent results
Roadmap (Tuesday …) 2

3. ~ ~ Overview on LLRF systems at FLASH Station until 2009
Laser ~ ~
BC3
Gun
ACC1
3rd
BC2
ACC2
ACC3
ACC4
ACC4
ACC4
ACC7
A 
A 
A 
A 
A 
A 
LLRF
LLRF
LLRF
LLRF
LLRF
LLRF
Station
until 2009
After upgrade 09/10
Shutdown 11/12
RF gun
Simcon3.1
SimconDSP
uTCA
ACC1
SimconDSP (250kHz)
ACC39 -
(54MHz)
ACC23
DSP
(250kHz)
ACC45
DSP/ATCA
(250kHz/54MHz)
(semi-dist.)
ACC67 3

4. Upgrade of LLRF system
Upgrade of all RF stations using SimconDSP controller
Gun/ACC23/ACC45/ACC67
IF=250kHz, IQ-sampling scheme
Sampling rate 81MHz (use averaging)
RF control for 3.9GHz
Probe, forward and reflected signals
New RF down converter & LO generation with
IF=54MHz, non IQ-sampling, LO = 3954MHz
Sampling rate 81MHz
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10 Channel 14bit ADCs
81 MHz clock rate
8 DAC, 14 bits
2 Gigalinks
FPGA: XILINX Virtex II pro 4 4

5. Upgrade of LLRF system
Upgrade of all RF stations using SimconDSP controller
RF control for 3.9GHz
New cabling in injector racks
MO1 & MO2 cabling completed
New rack & cabling for RF gun
New rack & cabling for ACC1/ACC39
Enclosed racks for better temperature stability
Parallel cabling for development system
Careful noise investigation and power level
adjustment of LO and RF signals
RF gun
ACC39
ACC1 MO
ACC39 DWC
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6. Upgrade of LLRF system
Upgrade of all RF stations using SimconDSP controller
RF control for 3.9GHz
New cabling in injector racks
Upgrade & unified FPGA controller firmware
Multiple feed forward table (main/beam loading/correction)
Multiple setpoint table (main/beam based correction)
Model based Multiple In Multiple Out (MIMO) controller
Charge correction & intra-train beam based feedback
Exception & Error handling, limiters
Error and status displays
Scheme of LLRF RF controller
Feed forward table architecture
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7. Upgrade of LLRF system
Upgrade of all RF stations using SimconDSP controller
RF control for 3.9GHz
New cabling in injector racks
Upgrade & unified controller firmware
Unified and new control software
New C++ architecture for front end server
LLRF library based on SysML approach
Unified naming convention
Automatic firmware downloads
Finite State Machine for automation
High level software: diagnostics, calibration…
DAQ integration
Model based learning feed forward (LFF)
Loop phase/gain correction
Piezo control for cavity detuning comp. …
Voltage [MV]
Phase [deg]
LFF off
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LFF on
1st bunch 7 7

8. Upgrade of LLRF system
Upgrade of all RF stations using SimconDSP controller
RF control for 3.9GHz
New cabling in injector racks
Upgrade & unified controller firmware
Unified and new control software
Beam signals integrated
Charge signals
Bunch Arrival time
Pyro signal
Real time FB with matrix
Limiter on Ampl/Phase corr.
IIRF filters
Rep. rate adaption
Charge scaling of beam load
compensation table
Control software ~ 90 % completed
Most of features are commissioned
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9. Upgrade of LLRF system
Upgrade of all RF stations using SimconDSP controller
RF control for 3.9GHz
New cabling in injector racks
Upgrade & unified controller firmware
Unified and new control software
Beam signals integrated
Piezo drivers
new driver for ACC1 / ACC7
DAQ server for detuning measurements
Several piezo studies performed
Active compensation of ringing
DC voltage added for static detuning
Control software ~ 80 % completed
But many features not fully commissioned 9

10. Upgrade of LLRF system
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11. LLRF Control Tables – software philosophy -
Process control via FSM
Operator & FSM & LLRF expert
Setpoints: A, & Parameters: timing, …
- As larger impact on
cavity/coupler
the more restriction
on table/table generation
- Separation of physics
cause of effect
- Easier exception handling
Static detuning
correction
Dyn. detuning
SP filling correction
Resonance filling
Slow BBF correction
VM offset corr.
DCW calibration
BLC adaptation
Beam based
SP correction
Model based
FF & SP tables
ratio ≤
Learning
Feed forward
Bunch
Pattern
SP_BBF
table
SP_USER
table
SP_CORR
table ≤ SP
table FF
table
FF_CORR
table
FF_BLC
table ≤ ≤ ≤
Slow FB loops for parameter
optimization Q
MPS + + Q -
Beam signals
a b
c d
Rot
FF-total
table
Loop
G/
MPS ≤ - +
Field detection
Controller
Rot ≤
DAC
DAC 11

12. On-crest acceleration phase
Definition and adjustment (min. energy spread/ max acceleration)
Drifts of down converter + cables (~1-2deg) > hardware changes
Difference between Setpoint and Vectorsum > software done
To some extend drifts from laser arrival time + conv. -> hardware changes
On-crest phases a dominated by operation set-point (support panel)
Remark:
1% ACC1 gradient change
 3.5 phase difference for all
downstream modules
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13. FLASH results: Learning Feed Forward13

14. FLASH results: Learning Feed Forward
4 ps
0.5 ps 14

15. FLASH results: with MIMO (ACC39)
Value
Repetitive error (aver. 100 macro-pulses)
Pulse to pulse (each time stamp)
Abs.
Rms
PKPK
Limited by ADC bit noise
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LFF off 15 15

16. FLASH results: Performance LLRF
Arrival time measurements
Typically values
60-100fs rms from injector
60-80fs rms behind BC2
50-60fs rms exit LINAC
Pulse to pulse
about factor of 2 better
than last year
Across bunch train
dA/A~7e-4
(LFF was off
RMS timing jitter
400fs
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17. FLASH results: Gradient stability ACC1/ACC39
shutdown
shutdown 17

18. Intended working point
FLASH results: Performance at 4.5mA operation
Beam Current (mA) 1 2 3 4 5
Gradient change over 400us (%) -3 -5 +3 +5
Gradient Tilts vs Beam Current (ACC7)
Intended working point
~2.5%
Characterisation of solution by scanning beam current
model benchmarking
Flat gradient solution achieved
4.5 mA beam

19. FLASH results: Performance at 4.5mA operation
15 consecutive studies shifts (120hrs), and with no downtime
Time to restore 400us bunch-trains after beam-off studies: ~10mins
Energy stability with beam loading over periods of hours: ~0.02%
Individual cavity “tilts” equally stable
Energy stability over 3hrs with 4.5mA
~0.02% pk-pk
9 Feb 2011
Concept with toroid based BLC scaling worked excellent
(at least up to 4.5mA) 19

20. ~ ~ FLASH results: Beam base FB (with MIMO & LFF)
Laser ~ ~
BC3
Gun
ACC1
3rd
BC2
ACC2
ACC3
ACC4
ACC7
Latency of system
Exit of linac & out-of-loop
Both intra-train FB on
MIMO controller
Repetitive pkpk deviation < 100fs
< 22 fs 20

21. Open software developments:
Next steps (till end of FLASH run)
Firmware & Software for RF gun (consistent to SRF)
Automation and permanent usage of DC/AC piezo operation
MIMO controller including BBF
Setpoint correction during filling / resonance filling using phase slopes
Forward peak power reduction
Improved error handling
Rapid VS calibration
Improved DAQ implementation and long term statistics
Error budget management & optimization of loops for LLRF parameters
LO table correction

22. Layout of uTCA LLRF system
1. Project phase (19“ modules, uTCA without backplane)
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Complicated cable management - LLRF RTM backplane concept 22 22

23. Layout of uTCA LLRF system
2. Project phase (19“ modules, uTCA with backplane)
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Higher risk of signal degradation … (for main linac eventually only)
TT Interne Diskussion
Frank Ludwig, Tomasz Jezynski, DESY 23 23

24. Activities and milestones scheduled for Jan. 11 -> Jun. 11
Main components of uTCA based LLRF system:
Typically 2-3 revision required for each, 3-6 month per revision
Components With whom Status Expected
uTCA crate (EMI/PS noise/…)* indu./indu. rev1/prod. Jun/Jan11
ADC board (16bit/10Ch)* with industry revision 1 Mar
Low noise DCW* in-house/indu. start rev 1. May 2011
Vector modulator* collaboration routing Mar. 2011
AMC controller collaboration production Feb
LO generation (19’’)* collabr./in-house design May 2011
LO distribution (19’’) collabr./in-house design Mar. 2011
LO generation (RTM)* industry contacted Aug. 2011
Calibration unit (19’’)* collabr./in-house design Apr. 2011
uTCA back plane* collabr./indu. production May 2011
Piezo driver board collabr. design June 2011
* Indicates ultra high performance (<150dBc/Hz , clk ~200fs , <10fs stab., -80dB cx-talk) usually not available in industry (close collaboration / exchange important / few companies)

25. Software developments uTCA
2011
Most important is the transition from SimconDSP -> uTCA!!!
Firmware & Communication protocols & Front-end server
Middle layer server can be move to front-end CPU
Implementation of new Timing/Clock
2012
New software developments feasible
Down-converter calibrations (directly into performance)
Make us of Pfor/Pref within controller (e.g. real time quench det./model)
30Hz operation with 9MHz tables & 96 channels (DSP???)
AMTF software developments for routine measurements
Upgrade of beam base feedbacks …
2013/2014
Control software for 25 RF stations XFEL
Energy management …

26. uTCA based LLRF Systems & schedule
2011
REGAE (May-July) 1 Crate (8)
FLASH ACC1/ACC39 (June-Sep) 1 Crate (24/12) Shutdown
PITZ TDS (Aug-Sep) 1 Crate (8)
CMTB (Sep) 1 Crate (24)
FLASH ACC23/ACC45 (Sep-Dec) 2 Crates (48/48) DWC/ADC?
2012
Freeze final LLRF design
FLASH ACC Crate (48)
FLASH ACC Crate (48) Semi-distr.
AMTF (March) 3 Crates (24/24/24)
Final revision (Oct.)
Start mass production
2013
XFEL L Crates (36/36)
2014
XFEL L1-L Crates (96)

27. ~ ~ ~ Synchronization system approaches t f = t f 1) RF distribution
f ~ 100MHz …GHz ~
2) Carrier is optically ~
MZT
f ~ GHz
3) Carrier is optically + detection ~
f ~ 200 THz
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4) Pulsed source
f ~ 5 THz
OXC
Mode locked
Laser 27 27

28. Hybrid system for FEL facilities
Reliability
RF System
CW optical
Pulsed system
Performance
Costs
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29. Layout of XFEL Synchronization System
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30. Optical synchronization system
EDFL, soliton, t~200fs, f=216MHz
SESAM, P > 100mW,
phase noise < 5fs (1kHz)
Laser
MLO
MO-RF
Narrow
Band.
Free space distribution
+ EDFA
Distribution
Dispersion comp.,
Polarization contr.,
Collinear bal. opt.
cross-corr.
Optical link
Optical link
Optical link
<5fs
<5fs
<5fs
Other lasers
Direct
End-station
LO-RF
Two color bal.
Opt. cross-corr.
EOMs/
Seeding
Direct/
Interferometer
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Laser pulse
Arrival beam/laser
DWC/Kly FB
A &  cavity
Desired point-to-point stability ~ 10 fs
Main issue: robustness, stability and maintainability  Prototype at FLASH
, Daresbury, “Rule of lasers in particle beam research”
Holger Schlarb, MSK, DESY 30 30

31. Optical Synchronization System Installation at FLASH
Master Laser Oscillator (RF locked to MO)
Free space distribution system to 16 ports
Optical Links: 6 stabilized using OXC & 1 passive
Front-ends
4 Bunch arrival time monitors (BAM)
OXC for INJ / TiSA lasers
RF locked for TiSA (HHG) (not yet completed) 31

32. Bunch Arrival Monitor Detector32

33. Bunch Arrival Monitors Front-end Electronics
Top view
to LLRF
Bottom view 33

34. Fiber Link Stabilization (RF based)
Time domain
Frequency domain
Every odd harmonic
destructively interfere
Amplitude detection
with mixer (sign) of
high harmonics (45th)
allow to measure link
delay variations
Scheme RF link
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35. Fiber link stabilization (RF based)
Optics section
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LO generation
In-loop
Detector branch
Digital FB loop
Out-of-loop
Detector branch 35 35

36. Fiber link stabilization (RF based)
Error between in-loop and out of loop ~ 0.8fs rms, 4.8 fs pkpk,
(30 m long fiber in laboratory, not stabilized, only monitored)
In-loop / 2
Out-of-loop
38 hours
difference
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overcomes AM-PM conversion in photo-detectors
several advantages compared to OXC link (low opt. power, monitoring possible, simple disp. comp.)
low cost version link with still high performance 36 36

37. ~ ~ ~ RF generation from optical pulses f = n*frep PD BPF frep
Time domain
Frequency domain
Phase noise
100fs
Photo Detector
Bandwidth PD
T = 5ns = 1/frep
frep
Direct conversion with photo detector (PD)
Low phase noise (to be proven at end-station)
Temperature drifts (0.4ps/C°)
AM to PM conversion (0.5-4ps/W)
Potential for improvement
(corporation with PSI)
laser pulses
f = n*frep PD
BPF ~ ~ ~ 
frep
f = n*frep
Sagnac loop interferometer
balanced optical mixer to lock RF osc.
insensitive against laser fluctuation
Very low temperature drifts
Results:
f=1.3GHz jitter & drift < 10 fs rms limited by detection
Remark: much easier at hire frequencies …
MZI based balanced RF lock
new scheme, under investigation 37 37

38. Results double balanced MZI-L2RF
Sensitive to
environment
2fs pkpk
But insensitive to
laser power
But 0.8 ps/K
temperature dependence 38 38

39. Thanks for your attention39

40. ~ ~ Beam Based Feedback Installation Beam Based Feedbacks:
Laser ~ ~
BC3
Gun
ACC1
3rd
BC2
ACC2
ACC3
ACC4
ACC7
Toroid
Toroid
Toroid
A 
A 
A 
A 
BAM
BAM
BCM
BAM
BCM
BAM
LLRF
LLRF
LLRF
LLRF
LLRF
Beam Based Feedbacks:
BAM before BC2 corrects phase in RF-Gun
BAM and BCM after BC2 simultaneously correct amplitude and phase in ACC1 and 3rd harmonic
BAM and BCM after BC3 correct amplitude and phase in ACC23
Results from BBF running at BC2 40

41. Master Laser Oscillator (MLO) Pulse generation and distribution
Promising: OneFive ORIGAMI-15
Repetition rate: 216,66MHz
Average power: > 100mW
Pulse duration: p < 150 fs
Integrated timing jitter < 5 fs
in the interval [1 kHz; 10MHz]
Mechanically robust, easy to maintain 41

42. Fiber Link Stabilization (optically)
216 MHz
Er-doped
fiber laser
Det 1
Det 2 -
Balanced optical cross-correlator
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J. Kim et al., Opt. Lett. 32, (2007) 42

43. Fiber Link Stabilization (optically)
3 generation of opto-mechanics
typical in loop jitter ~ 1-2 fs rms (also smaller)
Experience:
Operate reliably
Ampl. FB to be add
Smaller open questions
XFEL:
Dispersion management
need to be improved
Delay stage too short
for long links and large
temp. changes
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Courtesy: M. Bock 43 43

44. Low Level RF Control Systems Intra-train BBF Implementation
Toroid
LLRF Control Tables
Charge
Measurement
Qtoroid
ADC9
Pyro SP
Table
LLRF SP
Table
BCM I Q ΔU ΔΦ
Peak
Detection
Gating
Charge
Correction
ADC10 -
Transfer
Matrix
SP Signal
Modulation
BAM
tsample
Qnom
ΔA/A Δt
Optical
Link I Q
FPGA
MPS 44

45. BBF Calibration Transfer Matrix Determination
BC2
Gun
ACC1
ACC39 ?
BAM
Pyro
A/
A/ t
C/z
Actuators
Monitor system
scanning
measure
ACC1
ACC39
extract 45

46. Open issues: observation QL changes
Voltage change ACC45 from 67MV to 255MV (~4MV/m -> ~15MV/m)
ACC4
ACC5
Decay over time
No change at all
17MV/m
2.6 -> 3.0 (16%)
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2MV/m
10 min
10 min
Cause need to be investigated (likely main coupler antenna position change due to thermal expansion) 46 46

47. Open issues: Cavity pre-detuning using DC piezo voltage
Successfully used to change pre-detuning
10V 0V 0V
10V
Is accompanied with Ql changes => detuning via Lorenz force detuning
For some cavities orbit changes are observed
 reduces SASE, but simple corrector sufficient
 global orbit FB essential for reproducibility of machine operation
Several studies on detuning compensation during macro-pulse
Since 4 weeks PZT for ACC67 in operation (DC/AC)
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