Frank Lenkszus

1
ILC Timing

• Frank Lenkszus
• Controls Group
• Advanced Photon Source
• Argonne National Lab

2
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

3
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
4
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/ oC
• 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.

5
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)

6
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
• RD 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)

7
TELSA Reference Distribution Specifications

• Short Term Stability (phase noise) ltlt 1 ps, (10
  fs at XFEL)
• Short term stability (minutes) lt 1 ps at RF
  frequency (0.5o _at_ 1.3 GHz)
• Long term stability (days) lt 10 ps (5.0o _at_ 1.3
  GHz)
• System Length up to 15 km
• Distributed frequencies 9-2856MHz (Tests done
  at1.3GHz)
• High Reliability

8
TESLA Features

• Use 1550 nm DFB Laser
• Temperature controlled to 25 oC
• Use SMF-28 fiber (Corning)
• Loss lt 0.22dB/km _at_ l 1550 nm gt 4.4 dB for 20
  km fiber
• Phase Shifter
• 5km fiber inside an oven with 30 oC temperature
  range
• Compensates for phase changes induced by 10 oC
  temperature change of 15 km link
• Digital PID controller
• Only PI gains used
• Transmit 1.3 GHz reference

9
TESLA
10
TELSA System Performance

• Integrated system test had problems
• Had to reduce PID P gain to make system stable
• Caused by phase shifter dead-time
• Couldnt run tests for more than 5 -15 hours
  because of software malfunction
• Stability
• Short Term Stability 0.3 psec
• Long Term Stability 2 psec

11
NLC Requirements

• Transmission length 15 km
• Noise 10 sec to 10 kHz lt 0.12 psec RMS
• Stability lt 1 hour /- 1 psec
• Stability Long Term /- 5 psec
• Temperature Stability lt 2x10-8/oC

12
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.

13
NLC Test Setup
14
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 lt 1 hour /- 0.75 psec
• Stability Long Term (1 month) /- 2 psec
• Later report of /- 1 psec
• Temperature Stability lt 10-8/oC

15
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/oC (-10 to 30 oC)
• 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

16
Active Phase Stabilized Link
17
Redundant Reference Transmission with Failover
18
Sector Timing Distribution
19
Sector Timing Controller
20
Other Frequencies

• Other generated frequencies will be syncd 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)

21
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

22
Numerology

• Items that influence flexibility in bunch pattern
  choice
• Ratio of ML to DR RF (1300/500 gt 13/5)
• DR Harmonic number
• Linac bunch spacing (nominal 308 nsec gt 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.

23
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 dont 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
• .

24
Local (IntraSector Reference Distribution)
Reference Frish, J. RD for the ILC
Phase/Timing Distribution System, 10/20/04
25
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

26
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

27
Timing Requirements

• Gather list of devices requiring timing
• Develop table

Device Quantity Range Resolution Jitter Stability Accuracy



28
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 _at_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

29
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
• RD 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.