ILC Phase Reference Distribution R&D Frank Lenkszus Controls Group Advanced Photon Source Argonne National Lab 2/8/2006 Frank Lenkszus Advanced Photon Source

Advanced Photon Source RF Phase Stability The main technological issue for the RTML is likely to be the required RF system phase stability, which is a few percent of 1 degree of L-band. This phase stability must be maintained for a period which is long enough for a beam-based feedback to determine that an unacceptable phase change has occurred, as indicated by variation in the beam arrival times at the IP; thus, a stability period of a few seconds is probably sufficient. (From the RTML BCD) 2/8/2006 Frank Lenkszus Advanced Photon Source

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 0.5 degrees is 1 psec at 1.3 GHz 2/8/2006 Frank Lenkszus Advanced Photon Source

Reference Distribution (General) Use point-to-point fibers Fiber cable has temperature coefficient: ~10 ppm/ oC Fiber dispersion: 10ps/nm/km Use active phase stabilization for fibers Dual Redundant system with auto fail-over Short haul (~500 meters) distribution through conventional coax Active phase stabilization Phase average scheme Phase Stable Coax 2/8/2006 Frank Lenkszus Advanced Photon Source

Advanced Photon Source Prior Work 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) DESY/MIT “High-Precision Optical Synchronization Systems for X-Ray Free Electron Lasers”, Winter, A et al, Proceedings of the 27th International Free Electron Laser Conference, 8/21/05 – 8/26/05, Stanford CA. 2/8/2006 Frank Lenkszus Advanced Photon Source

Advanced Photon Source Results of Prior Work TELSA (15 km cable, 1.3 GHz) Short Term Stability (~1 minute) 0.3 psec Long Term Stability (5-15 hours) 2 psec NLC (15 km cable 375 MHz chopped at 3125 Hz) System Phase stability: 10 femtosecond per degree C per kilometer Phase Noise 0.1Hz to 10 kHz: 0.1 psec RMS Stability < 1 hour: +/- 0.75 psec Stability Long Term (1 month) : +/- 1 psec KEK ( 4.8 km PSOF cable, 508.8 MHz) Phase stability: ~ 2 degrees DESY/MIT (XFEL) (500 meters, 100 MHz repetition rate Mode locked laser, dispersion compensated fiber links) 50 fsec (0.1 Hz to 20 MHz) 2/8/2006 Frank Lenkszus Advanced Photon Source

Active Phase Stabilized Link 2/8/2006 Frank Lenkszus Advanced Photon Source

Redundant Reference Transmission with Failover 2/8/2006 Frank Lenkszus Advanced Photon Source

Advanced Photon Source 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 Temperature stable Coax . 2/8/2006 Frank Lenkszus Advanced Photon Source

Local (IntraSector Reference Distribution) Reference: Frish, J. “R+D for the ILC Phase/Timing Distribution System”, 10/20/04 2/8/2006 Frank Lenkszus Advanced Photon Source

Work to be done on Phase Distribution Establish stability/phase noise budget Master Oscillator Long haul distribution Local (Intra Sector distribution) (From 1/17/06 LLRF mtg at Fermi) 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 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 Failure Effects and Analysis 2/8/2006 Frank Lenkszus Advanced Photon Source

Advanced Photon Source R&D Proposals Update Active Phase Stabilization design and prototype Trench test of fiber system (vs coil in oven) Evaluate whether to Chop or not Chop. Prototype Sector Distribution scheme Evaluate phase averaging scheme Issue directional couplers required at each pick crate. active phase stabilization Stabilize end to end Is temperature uniform enough across a sector. phase stable cable. Prototype Two-channel phase reference receiver comparator scheme Is there a credible low-cost way of building a vcxo with sufficient performance? Evaluate beam derived reference for locking phase reference to beam. Pursue HOM phase detector scheme. Investigate different schemes to meet the bunch compressor requirements. Investigate the wavelength tuneable lasers to replace phase shifters over realistic temperature range. 2/8/2006 Frank Lenkszus Advanced Photon Source

Phase Stabilization R&D Update Active Phase Stabilization design and prototype Pick site to install fiber Want both head and tail ends at same physical location so direct end to end measurements can be made Full 15 km fiber length is highly desirable Trench Test? Can’t control fiber environment Expensive. At APS could rap 15 km fiber around SR cable tray (1.1 km) Integrate with Fermi ILCTA Chop or not to chop Select directional coupler with low crosstalk Prototype in chopping that can be disabled to evaluate performance with and without. Evaluate effect of chopping on VCXO. Evaluate low phase noise VCXO’s for receiver end. 2/8/2006 Frank Lenkszus Advanced Photon Source