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The LCLS Timing & Event System - An Introduction – John Dusatko / Instrumentation & Controls - EIE. Outline. Introduction to LCLS Some background on SLAC Timing The SLAC Linac Timing System The LCLS Timing System Comments / Future Directions. Introduction. LCLS Introduction.

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  1. The LCLS Timing & Event System- An Introduction –John Dusatko / Instrumentation & Controls - EIE

  2. Outline • Introduction to LCLS • Some background on SLAC Timing • The SLAC Linac Timing System • The LCLS Timing System • Comments / Future Directions

  3. Introduction

  4. LCLS Introduction • The Linac Coherent Light Source is a tunable X-ray FEL based on the SLAC Linac: • 1.0nC, 14-4.3 GeV e- are passed thru an undulator, a Self Amplifying Stimulated Emission process produces 1.5-15 Angstrom X-Rays. • LCLS is an addition to the existing SLAC Linac: it uses the last 1/3 of the machine • This is important to note because we have to integrate the New LCLS Timing System with the Existing Linac (SLC) Timing System.

  5. The LCLS – Schematic View (ignoring photon beamline) Single bunch, 1-nC charge, 1.2-mm slice emittance, 120-Hz repetition rate… 250 MeV z  0.19 mm   1.6 % 4.54 GeV z  0.022 mm   0.71 % 14.1 GeV z  0.022 mm   0.01 % 6 MeV z  0.83 mm   0.05 % 135 MeV z  0.83 mm   0.10 % Linac-X L =0.6 m rf= -160 rf gun Linac-1 L 9 m rf  -25° Linac-2 L 330 m rf  -41° Linac-3 L 550 m rf  -10° new Linac-0 L =6 m undulator L =130 m 21-1b 21-1d 21-3b 24-6d 25-1a 30-8c X ...existing linac BC-1 L 6 m R56 -39 mm BC-2 L 22 m R56 -25 mm DL-1 L 12 m R56 0 LTU L =275 m R56  0 research yard SLAC linac tunnel (RF phase: frf= 0 is at accelerating crest)

  6. LCLS Timing – Some Definitions • The LCLS Timing System can be viewed as consisting of three parts: • Part 1: ‘Standard’ Accelerator Timing • 10ps Triggers for Acceleration and Diagnostics • Part 2: S-Band Timing • 2856MHz LCLS RF Phase Reference Distribution • Part 3: Ultra-Precise Timing • 10fs Synchronization for Experiments (LBL System)

  7. LCLS Timing – Some Definitions • The LCLS Timing System can be viewed as consisting of three levels: • Part 1: ‘Standard’ Accelerator Timing • 10ps Triggers for Acceleration and Diagnostics • ‘Triggers’ are signals from the timing system used by HW to accelerate & measure the beam • Part 2: S-Band Timing • 2865MHz RF Phase Reference Distribution • Part 3: Ultra-Precise Timing • 10fs Synchronization for Experiments (LBL System)

  8. LCLS Timing – Performance Requirements

  9. Requirements Comparison • Timing Reqmts for earlier SLAC systems: Original Linac: (~1968) • Resolution: 50 nSec - Jitter: 15 nSec - Main Trigger Line Waveform: + / - 400 Volts PEP – II: (~1998) - Resolution: 2.1 nSec - Jitter: 20 pSec - NIM Level Waveform: 0 to –0.7 V into 50 Ohms

  10. Background

  11. SLAC’s Timing Systems • In order to explain the New LCLS timing system, we first need to understand how the old SLAC timing system works – i.e. how we got from there to here • The SLAC Accelerator complex consists of several machines: Linac, Damping Rings, Stanford Linear Collider, PEP-II, FFTB, NLCTA / each with its own timing sub-system • The overall timing system consists of incremental add-ons to the original system • Design Challenge for LCLS Timing System was that it had to know about and work with the existing system

  12. (pre-LCLS) SLAC Accelerator Complex(Lots of Pieces)

  13. SLAC Linac Timing System

  14. Old SLAC Timing System We’ll talk a little about the existing SLAC Linac Timing System (PEP-II Timing was very similar): • The Linac is a Pulsed Machine (get a packet of beam per pulse) runs at a max of 360Hz • Three Main Timing Signals: • 476MHz Master Accelerator Clock (runs down 2mile Heliax Main Drive Line cable) • 360Hz Fiducial Trigger (used to ‘tell’ devices when the beam bunch is present) / encoded onto the 476MHz master clock • 128-Bit PNET (Pattern Network) Digital Broadcast (contains trigger setup, beam type & rate information)

  15. Some More Details • Why 360Hz? • Original design rate of the Linac / derived from the 3-phase, 60Hz AC power line frequency: want to trigger devices (Klystrons, etc.) consistently so as to not create huge transients on the Power Line Sync’d to 476MHz • PNET Broadcast • A special computer called the Master Pattern Generator (triggered by the 360Hz fiducial) broadcasts a 128-bit digital message containing information (conditions, rate, charge, etc.) about the beam • This is used by the Trigger Generator computers to set up triggers and their delays • Sent over SLAC coax cable TV network

  16. How The 360Hz is Generated The Sequence Generator creates a 360Hz signal as well as 6 Timeslot pulses (used for further synchronization) Source: SLAC Blue Book c.1962

  17. Timing HW at Head-End of Linac For Phase Stabilization Source: D. Thompson

  18. Generation of The Linac Timing Signal (AM Modulator) • The 360Hz Signal is Amplitude Modulated onto the 476MHz Accelerator Clock and propagated down the Main Drive Line. • The AM process is not ideal and some FM occurs; in addition, the signal gets more dispersed as it heads down the 2 mile MDL

  19. Linac RF Phase Reference Distribution • This slide is to give you an idea of how the Linac Phase Reference is used Each sector (30 total) taps off the MDL, to extract the RF clock This is just the Phase Ref, trigger generation is accomplished by a different set of HW

  20. CAMAC Trigger Generation Timing CAMAC Crate • Old Timing System (CAMAC based) generates triggers by combining the RF Clock, 360Hz Fiducial and PNET Data (processed by local micro) • 476MHz is divided/4 to get 119Mhz + fiducial by another system / This is because the older technology HW could not run at 476MHz PNET Data on Serial Link • The Programmable Delay Unit (PDU) Module generates the triggers. It contains digital counters that get set with delay values from PNET and started when the Fiducial Pulse comes along

  21. The LCLS Timing System

  22. Finally – The LCLS Timing System • Old CAMAC System is no longer viable for new Systems (performance limited, obsolete) • Seek to implement a new Timing System that has similar functionality, better performance, and can be laid atop the old system, working alongside it • In addition, LCLS has have its own master oscillator (PLL sync’d with Linac MO) and local phase reference distribution system at S20 • LCLS System is VME based, using High-Speed digital serial links to send Clock, Trigger and Data all on one optical Fiber to timing clients

  23. The LCLS Timing System • New Timing HW: • Event Generator (EVG): Similar to the MPG • Event Receiver (EVR): Similar to the PDU • Timing is more closely integrated into each sub-system: • Each Subsystem has its own EVR (living in VME crate with an IOC) • Compared to SLC timing which had multiple types of devices served by one PDU typically • LCLS Timing is architected as a Star network with one master broadcasting to many clients

  24. Timing Compare/Contrast • SLC Timing: • CAMAC Based • Copper data cable @ 5Mb/s • PDU Triggers: • NIM-Level • Width: Fixed @ 67ns • Polarity: Fixed NIM level • Delay Range: 0…2.7ms (5.4ms) • Step size: 8.4ns (100ps w/VDU) • 16 outputs per PDU • One PDU per CAMAC crate • SCP-Based • LCLS Timing: • VME Based • Fiber data & clk cable @ 2.38Gb/s • EVR Triggers: • TTL-Level (can have others) • Width: Adjustable: 8.4ns…550us • Polarity: Selectable Pos/Neg • Delay Range: 0…36 seconds • Step size: 8.4ns (420ps w/EVR-RF) • 14 outputs per EVR • Can have multiple EVRs per VME Crate • EPICS-Based

  25. LCLS RF Front End LCLS Master Osc – slaved to Linac MO / Lower Phase noise req’d by LCLS

  26. LCLS Timing/Event System Architecture Linac main drive line ~ Low Level RF TRD Rx Fiber Cable FIDO PDU Linac Master Osc Raw 360 Hz LCLS Timeslot Trigger 476 MHz LCLS Master Oscillator Sync/Div TRD Tx TO: - Cav BPM - MPS BLM - MPS PIC - BCS 119Mhz + FID 119Mhz + FID Sq Wave on Coax Sq Wave on Coax 360 Hz 119 MHz TRD Rx SLC MPG P N E T I O C E V G F A N LCLS events SLC events fiber distribution Precision<10 ps * EPICS Network Digitizer LLRF BPMs Toroids Cameras Wire Scanner SLC klystrons I O C E V R D E V TTL * m P P N E T P D U System is based around the EVent Generator and EVent Receiver TTL-NIM convert. SLC Trigs *MicroResearch

  27. LCLS Timing/Event System Architecture Linac main drive line ~ Fiber Cable TRD Rx FIDO PDU Linac Master Osc Raw 360 Hz LCLS Timeslot Trigger LCLS Master Oscillator 476 MHz TRD Tx TO: - Cav BPM - MPS BLM - MPS PIC - BCS 119Mhz + FID Sync/Div 119Mhz + FID Sq Wave on Coax Sq Wave on Coax 360 Hz 119 MHz TRD Rx V M T G C P U E V G F A N 360Hz IRQ (Fiducial) Fiber distribution LCLS events IRQ Timeslot 60Hz Timeslot 1 Marker * Digitizer LLRF BPMs Toroids Cameras Wire Scanner Klystrons EPICS Network C P U E V R D E V TTL System Upgraded:  Removed Dependency on old MPS using new HW (VMTG) and SW * TTL-NIM convert.

  28. The Event System • Based on Commercial Hardware (MicroResearch Finland) • Which was based on a design from ANL-APS Timing System • Designed Around Xilinx Virtex-II FPGAs • Uses FPGA’s internal High-Speed 2.38 Gb/s Serial xcvr, which connects to a fiber optical transceiver • FPGA logic implements all of the timing functions • Uses 119MHz clock from Linac which get multiplied up to by FPGA internal PLL to 2.38GHz • EVG sends out 8-bit event code to EVRs along with clock and trigger information over one fiber • EVR Receives event code & with its associative memory, generates a trigger with a delay set by digital counters

  29. The Event System • Upon RX’ing a 360Hz Fid, the EVG sends out a stream of serial Data to the EVRs over a fiber link. The serial stream consists of 16-bit words sent every 8.4ns. • Each word contains an Event Code byte and some trigger setup data

  30. EVG contains a RAM that gets loaded with event codes, based on PNET data. 360Hz Fiducial causes the RAM to get sent out over the Serial fiber link to the EVRs. Event Generator

  31. Event Receiver • EVR contains another RAM that looks for matches of event codes to its contents. If match, it starts a counter running that generates a trigger

  32. EVG Hardware Event Generator VME-64x Module: Sits in Master Timing Crate with VME PNET receiver and Master Timing CPU. • Receives 119MHz reference and 360Hz master timing fiducial from SLC timing system. • Receives PNET pattern from SLC system. • Broadcasts timing system data in the form of a high-speed 2.38Gb/s serial data stream to the EVRs over an optical fiber.

  33. EVR Hardware Event Receiver • Comes in two flavors: VME and PMC. • Receives 2.5Gb/s serial datastream from EVR and generates triggers based on values of the event codes. • Also receives and stores PNET timing pattern, EPICS timestamp and other data and stores them in an internal data buffer. • Can output 14 total pulsed-output triggers and several more level-type • Triggers are output via a rear transition module (not shown) • Trigger delay, width, duration and polarity are fully programmable • Trigger signal level format is TTL • VME Version has 10ps jitter • PMC Version has 25ps jitter

  34. Fanout Hardware Fiber Fanout Module • Basic function is to receive one optical signal and generate copies of the same signal for transmission. • 1:12 way fanout (1 In  12 Out) • Contains Clock-Data Recovery (CDR) circuitry to re-generate & clean-up the signal • Fits into a VME crate, but ONLY uses power • Uses commercial SFP (Small Form-factor Pulggable) optical xcvrs • SFP units are hot-swappable • Front Panel LEDs indicate link health • No other diagnostics than this • There is one of these modules at each critical distribution point in the system / if one module fails, it takes timing out for a large group of clients

  35. System SW

  36. What Happens during one 2.8mS machine interval: Record processing (event, interrupt) Hardware Triggers Receive pattern for 3 pulses ahead Triggering Event Codes Start Beam Kly Standby Event Timestamp, pattern records, and BSA ready Acq Trigger Kly Accel Fiducial Event Received Fiducial B0 F3 18 500 0 1023 100 0.3

  37. LCLS Systems – Master Timing Rack  Located in LI20 RF Hut (Rack LKG-21) Master FODU Connects fibers to Long-Haul Trunks for entire machine Master Timing Crate Contains: • VME CPU • VME PNET Rx • EVG • Master Fanouts 119MHz Synchronizer Chassis

  38. LCLS Timing System – BPM Client  What you’d see in a typical service building (e.g. B105) … BPM Crate w/VME-EVR Rx FODU & Fanout Crate Rear of BPM Crate / Showing Trigger Rear Transition Module

  39. LCLS Timing System – Other Clients Toroid Crate w/PMC-EVR Profile Monitor Crate w/ (4) CPUs & PMC-EVRs MCOR Magnet Crate Rear of Toroid Crate / Showing Trigger Rear Transition Module

  40. Performance • The Event System Trigger Jitter was measured using an Agilent Infinium 54845A Digital Oscilloscope in Jitter Histogram Mode / data was collected for 30 minutes • The EVR output (shown) was measured against the system input trigger (360Hz fiducial) • The Actual jitter performance is much better after subtracting off the intrinsic jitter of the scope: Actual Jitter: JITTERsystem = [ (JITTERsys_meas)2 – (JITTERscope)2 ]1/2 Event System Jitter: JITTEREVR =[ (9.7472ps)2 – (6.3717ps)2 ]1/2 = 7.3763 ps EVR jitter w.r.t. fiducial 9 ps rms jitter

  41. Comments • Current LCLS Timing System has growing pains (integration w/old system, SW, HW) • Use of commercial HW doesn’t quite fit our needs / having to modify EVG & EVR • Problems Seen Thus Far: • “Trigger Storms”: Due to LCLS Master Osc unlocking / Fix: New MO / De-Couple LCLS Timing Sys from it (connect direct to MDL) • Dead Links: Fibers / Xcvrs / Still Troubleshooting

  42. LCLS Timing – Future Directions • MPG Replacement: • Planning on Moving the EVG Master Crate to MCC and Replacing the MPG Micro With it  COMPLETED Summer 2011 • Additional Diagnostics: • Designed & Built New Syncer Chassis with added diagnostics: Fiduciual Loss, Rate Monitors, RF Input Power, Clock Lock Detect, Clock Rate Monitors, etc. • Status: Chassis Installed / Need to wire up diagnostic readout HW and finish the SW • Would like to re-design the Fanout modules to take advantage to the built-in diagnostics (Tx & Rx optical power, temp, voltage, etc.) of the Fiber SFP modules • Additional Timing System Upgrades: • FIDO Replacement / New Fid Generation Scheme (future…) • Linac Sector 0 Timing Upgrade (future…)

  43. LCLS Timing – Future Directions • Eventual Goal: • Completely replace SLC Timing System in the Linac while retaining all of the legacy functionality and providing new features • Develop a timing system that is expandable & adaptable to new machines (e.g. PEP-X) • Challenges: • Temperature-induced phase drifts • Handling PEP Injection • Damping Ring Timing • Coming Soon….LCLS-II (First Light 2019)

  44. LCLS-II: Uses middle 1/3rd of Linac • New Injector • Re-purpose PEP-II Inj Line - 2 Undulators: - Hard X-Ray (2-13KeV) • Soft X-Ray (0.25-2KeV) First Light: Early 2018

  45. End of Talk

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