Post on 19-Jan-2016
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1/19/2006 Frank LenkszusAdvanced Photon Source
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ILC Timing
Frank Lenkszus
Controls Group
Advanced Photon Source
Argonne National Lab
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Timing Functions
• Master oscillator distribution (1.3 GHz)
• 5 Hz timing fiducial distribution
• Programmable triggers for field hardware
• Mechanism to synchronize software processing to timing events
• Time fiducials for synchronized timestamps for software and hardware events.
• Develop pulse ID number to identify pulses within the 1 millisecond pulse train
– ID number will accompany data relating to individual pulses
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Key Parameters that Influence Timing
Bunch Compressor Phase Tolerance
0.03 to 0.1 degrees at 1.3 GHz
Inter-linac timing tolerance 100 femto-seconds
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Timing Global Specifications
• Timing Phase locked to RF System– Stability at the point of RF measurement and control: ~10 picoseconds– Short Term Stability for Bunch Compressor: ~100 femtoseconds
• Timing phase reference will be distributed via active phase stabilized redundant fibers in star configuration to sectors
– Fiber cable has temperature coefficient: ~10 ppm/ C• Timing phase reference to be dual redundant with auto failover
– Timing phase reference distribution will use active phase stabilization• Phase shifter will be based on fiber in a temperature controlled oven• Will build on prior work for NLC and TELSA
• Local distribution (~500 meters) will be via coax• Active phase stabilization scheme• Phase averaging scheme
• 5 Hz timing fiducial will be encoded on timing phase reference by momentary phase shift
– Others have used Amplitude Modulation.
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Timing Global Specifications (Cont.)
• Required timing triggers and other frequencies will be developed locally at sector locations from the distributed phase reference
• Local timing triggers will be developed by counting down phase reference• Graded approach to timing trigger generation
– High precision: (pico-second)– Medium precision (nano-second)– Low precision (microsecond) (Event System)
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Prior Work On Phase Reference Distribution
• TELSA– “First Generation of Optical Fiber Phase Reference Distribution System for
TESLA”, Krzysztof, C., et al, TELSA Report 2005-08• NLC
– A High Stability , Low Noise RF Distribution System”, Frisch, J., et al, Proceedings of 2001 PAC, Chicago, pp 816 – 818
– “R&D for the ILC Phase/Timing Distribution System”, Frisch, J. 10/20/04• KEK
– KEK (“RF Reference Distribtution Using Fibre-Optic Links for KEKB Accelerator”, Natio, T. et al, PAC2001)
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TELSA Reference Distribution Specifications
• Short Term Stability (phase noise) << 1 ps, (10 fs at XFEL)• Short term stability (minutes) < 1 ps at RF frequency (0.5 @ 1.3 GHz)• Long term stability (days) < 10 ps (5.0 @ 1.3 GHz)• System Length: up to 15 km• Distributed frequencies 9-2856MHz (Tests done at1.3GHz)• High Reliability
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TESLA Features
• Use 1550 nm DFB Laser– Temperature controlled to 25 C
• Use SMF-28 fiber (Corning)– Loss < 0.22dB/km @ = 1550 nm => 4.4 dB for 20 km fiber
• Phase Shifter– 5km fiber inside an oven with 30 C temperature range
• Compensates for phase changes induced by 10 C temperature change of 15 km link
• Digital PID controller– Only PI gains used
• Transmit 1.3 GHz reference
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TESLA
RF Signal In
DFB LaserFO Tx
FO RX
RF Phase Detector
CirculatorPhase Shifter
Directional Coupler
FO RX
Controller
Long Link
FO RX
OutPut
Directional Coupler
Optional
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TELSA System Performance
• Integrated system test had problems– Had to reduce PID P gain to make system stable
• Caused by phase shifter dead-time– Couldn’t run tests for more than 5 -15 hours because of software malfunction
• Stability– Short Term Stability 0.3 psec– Long Term Stability 2 psec
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NLC Requirements
• Transmission length : 15 km• Noise 10 sec to 10 kHz: < 0.12 psec RMS• Stability < 1 hour: +/- 1 psec• Stability Long Term:+/- 5 psec• Temperature Stability: < 2x10-8/C
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NLC Prototype Features
• Use 1550 nm DFB Laser– Laser pulsed at 3125 Hz to avoid interference between forward and reflected
power.• Use SMF-28 Single-mode fiber 15 km long• Phase Shifter
– 6km fiber inside an oven– Oven continuously cooled by TEC cooler and heated by a wire grid.
• Prototype operated at 375 MHz carrier• RF signals mixed down to 25 kHz IF and digitized at 200 kHz.• Phase measured digitally in PC.• PID loop implemented in PC to drive phase shifter• All RF components and optical components were mounted in a temperature
controlled oven. • Test output signal filtered with 100 Hz bandwidth VCXO phase locked loop to reduce
broadband noise.
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NLC Test Setup
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NLC Prototype Performance
• System Phase stability: 10 femtosecond per degree C per kilometer
• Phase Noise 0.1Hz to 10 kHz: 0.25 psec RMS– Later report of ~0.1 psec
• Stability < 1 hour: +/- 0.75 psec• Stability Long Term (1 month) : +/- 2 psec
– Later report of +/- 1 psec• Temperature Stability: < 10-8/C
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Variations
• KEK (“RF Reference Distribtution Using Fibre-Optic Links for KEKB Accelerator”, Natio, T. et al, PAC2001)
– Used Phase Stabilized Optical Fiber (PSOF) : 0.4ppm/C (-10 to 30 C)– Used WDM (1310 (Forward) and 1550 (Reflected) nm to avoid crosstalk
• Avoids RF chopping– Distributes 509MHz – Temperature stabilized phase shifter
• Electronically controlled varactor diodes– Phase stability: ~ 2 degrees for 4.8 km PSOF cable
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Active Phase Stabilized Link
RF Signal In
DFB LaserFO Tx
FO RX
RF Phase Detector
CirculatorPhase Shifter
Directional Coupler
Mirror
FO RX
Controller
Long Link
FO RX
OutPut
Directional CouplerDf
Transmitter Phase
Feedback
TemperatureStabilized
TemperatureStabilized
RF Phase Detector
Optional DFB Phase
Stabilization
Controller
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Redundant Reference Transmission with Failover
Master Oscillator
Secondary
Master OscillatorPrimary
Frequency Lock
Main Timing Control and
Fiducial Generator
Stable Fiber Transmitter
Line Reference
5 Hz Fiduical
Stable Fiber Transmitter
Stable Fiber Transmitter
Stable Fiber Transmitter
Stable Fiber Transmitter
Stable Fiber Transmitter
Stable Fiber Transmitter
Stable Fiber Transmitter
Stable Fiber Receiver
Stable Fiber Receiver
To Other Sectors
To Other Sectors
Phase Comparator Unit
(Narrow Band PLL)
Detects fast phase changes and noisy
channelsContains narrowband
VCXO to clean-up phase noise
Phase Reference
Fiduicial
Use phase reference from adjacent sector to aid in detecting phase wander
“Head/Tail” scheme
MPS Trip
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Sector Timing Distribution
Redundant Fibers from Main Timing
Redundant Active Phase Stabilizer Tail
End
Sector Timing ControlMaster
Oscillator to LLRF
5 Hz Fiduicial
Phase Reference to LLRF and Timing
Event System
GPS
Global Event System
LO to LLRF
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Sector Timing Controller
5 Hz Fiduicial
Phase Reference to LLRF and Timing
Event System
GPS
Global Event System
5 Hz FiduicialPhase
Reference
Event Receiver
Event Generator
Local Event List
Diagnostics
Processor
52 MHz
LO to LLRF
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Other Frequencies
• Other generated frequencies will be sync’d to 5 Hz timing fiducial• 3.25 MHz Injector (1/400 1.3GHz)
– Reference: BCD2005 General Parameters: 308 ns Linac Bunch Interval.• 6.5 MHz Injector (Low Q option) (1/200 1.3 GHz)
– Reference: BCD2005 General Parameters: 154 ns Linac Bunch Interval• 500 MHz DR (5/13 1.3 GHz)• 46.3 kHz Electron (6 km) DR Revolution Clock (500MHz/Harmonic #)• 23.15 kHz Positron (12 km) DR Revolution Clock (500MHz/Harmonic #)• 54 MHz Mode Locked Lasers (1/24 1.3 GHz)
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Event System
• Bit serial system sends event codes• Synchronous to 5 Hz and sub harmonic of 1.3 GHz • Possible events
– Start of Bunch Train– 5 Hz– MPS Trip– Pulse Tic– Revolution Clock(s) (DRs)– GPS Clock Tick
• Event Receivers– Generate interrupt to processors to synchronize software processing– Time stamp counter– Low grade timing triggers on occurrence of specified events
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Numerology
• Items that influence flexibility in bunch pattern choice– Ratio of ML to DR RF (1300/500 => 13/5)– DR Harmonic number– Linac bunch spacing (nominal 308 nsec => 3.24 MHz)
• References that explore the relationships.– “Basic Timing Requirements for TELSA”, Kriens, W. TELSA Report– “Some Timing Aspects for ILC”, Ehrlichmann, H, DESY, Presented at GDE
Freascati, December 2005.
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Some Timing Issues
• Fiber oven phase shifters are large and consume significant power (~ 1kW/fiber)• Chop RF frequency or not – Avoid Circulator cross-talk
– NLC chopped at 3125 Hz– TELSA – cross talk constant so don’t worry about it– KEK used WDM (1300/1500 nm)
• Bunch Compressor – Required stability at the cavities not demonstrated when transmitted over long
distances• Local reference distribution
– Active Phase Stabilization• Can we assume temperature stable enough through ½ sector so phase
stabilizer not required for each local node.– Phase Averaging
• Requires directional couplers at each drop point
.
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Local (IntraSector Reference Distribution)
Reference: Frish, J. “R+D for the ILC Phase/Timing Distribution System”, 10/20/04
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Timing Questions
• Under what conditions should timing cause an MPS trip– Unrecoverable phase distribution error
• Interfaces/Timing Requirements:– MPS– BDS
• Timing Requirements for Accelerator Components– Table
• Number, Range, Resolution, Accuracy, Stability, Jitter– Kickers– Bpms– Laser Wire– Etc
• Bunch Compressor– Most stringent timing requirement
• Master Oscillator Specification
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Work to be done on Phase Distribution
• Establish stability/phase noise budget– Master Oscillator– Long haul distribution
• Bunch Compressor• All other
– Local (Intra Sector distribution)• Prototype phase stabilized link building on NLC/TELSA work• Extend prototype to redundant configuration
– Develop and test auto failover• Investigate options to distribute phase reference to Bunch Compressors
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Timing Requirements
• Gather list of devices requiring timing
• Develop table
Device Quantity Range Resolution Jitter Stability Accuracy
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Results of 1/17/2006 FERMI ILC RF and Controls Meeting
• LLRF LO to be 52 MHz (1.3GHz/25)• LLRF ADC sampling frequency 86.667 MHz (1.3GHz/15)• 2% loss in Luminosity is driving Bunch Compressor specs.• Bunch compressor (BC) requires a separate rf spec (0.03 deg, 0.08%) • Rest of the system:
– (+/-)0.5% energy error – brick wall limit!– 0.5 deg, 0.5% uncorrelated– 0.1 deg, 0.03% correlated
• For MO/phase reference distribution/reconstruction and no beam (pilot bunch) spec is– +/- 0.5 degrees rms (1 psec @1.3GHz) over 15 km over “long” time scale
• Beam based feedback (from cavity) will be used to stabilize locally distributed phase reference to the beam.
• Fermilab ILC Beam Test Facility Spec:– Rf specs for three cryomodules (24 cavities) powered by a single Klystron: 0.5%,
0.5 degree rms long term– Timing distribution jitter: 1 ps rms
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References
• “First Generation of Optical Fiber Phase Reference Distribution System for TESLA”, Krzysztof, C., et al, TELSA Report 2005-08
• “A High Stability , Low Noise RF Distribution System”, Frisch, J., et al, Proceedings of 2001 PAC, Chicago, pp 816 – 818
• “R&D for the ILC Phase/Timing Distribution System”, Frisch, J. 10/20/04• Larsen, R. S., Technical Systems Configurations – Electrical Subsystem:
Instrumentation – Timing, Rev. 1, March 23, 2001• “Basic Timing Requirements for TELSA”, Kriens, W. TELSA Report• “Some Timing Aspects for ILC”, Ehrlichmann, H, DESY, Presented at GDE Freascati,
December 2005.