Timing and Event System for the LCLS Electron Accelerator

1
Timing and Event System for the LCLS Electron
Accelerator
See Remi Machet and Steve Lewis for LCLS photon
event system plans.
2
Outline

• Introduction
• Architecture and Pictures
• Issues and Tasks

3
LCLS Introduction

• The Linac Coherent Light Source is an X-ray FEL
  based on the SLAC Linac
• 1.0nC, 14GeV e- are passed thru an undulator, a
  Self Amplifying Stimulated Emission process
  produces 1.5 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.

4
(pre-LCLS) SLAC Accelerator Complex(Lots of
Pieces)
5
Existing SLAC Timing System

• The Linac is a Pulsed Machine (get a packet of
  beam per pulse) runs at a max of 360Hz (120Hz)
• 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)
• Existing system used for RF modulator triggers.

6
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 its own master oscillator
  (PLL syncd with Linac MO) and local phase
  reference distribution system at S20
• LCLS Electron Accelerator is VME based (most CPUs
  are MVME6100), using High-Speed digital serial
  links to send Clock, Trigger and Data all on one
  optical Fiber to timing clients. Uses commercial
  hardware (MicroResearch Finland)
• So far for the electron side, there are gt80 EVRs
  (mostly PMC) and gt10 fanout modules.

7
LCLS Timing/Event System Architecture
Linac main drive line

Low Level RF
FIDO
PDU
Raw 360 Hz
LCLS Timing System components are in RED
LCLS Timeslot Trigger
476 MHz
LCLS Master Oscillator
Sync/Div
Linac Master Osc
119 MHz
360 Hz
System is based around the EVent Generator and
EVent Receiver
SLC MPG
P N E T
F A N
I O C
E V G
LCLS events
SLC events
fiber distribution
Precisionlt10 ps

EPICS Network
Digitizer LLRF BPMs Toroids Cameras Wire
Scanner SLC klystrons
D E V
E V R
I O C
TTL

P N E T
m P
P D U
TTL-NIM convert.
SLC Trigs
MicroResearch
8
LCLS Systems Master Timing Rack
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
9
LCLS Timing System BPM Client
BPM Crate w/VME-EVR
Rx FODU Fanout Crate
Rear of BPM Crate / Showing Trigger Rear
Transition Module
10
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
11
Event System Requirements

• Event Generator IOC
• Send out proper event codes at 360Hz based on
• PNET pattern input (beam code and bits that
  define beam path and other conditions)
• Add LCLS conditions such as BPM calibration on
  off-beam pulses , diagnostic pulse etc.
• Future event codes also based on new MPS and
  user input
• Send out timing pattern, including EPICS
  timestamp with encoded pulse in nsec. part on
  timing fiber
• Manage user-defined beam-synchronous acquisition
  measurement definitions

12
Event System Requirements, cont

• Event Receiver IOC
• Set trigger delays, pulse widths, and
  enable/disable via user requests (not yet done on
  a pulse-by-pulse basis)
• Set event code per trigger (triggering done in HW
  when event code received)
• Receive timing pattern 8.3 msec before
  corresponding pulse. Provide EPICS timestamp to
  record processing.
• Perform beam-synchronous acquisition based on
  tags set by EVG in the timing pattern.
• Process pre-defined records when specific event
  codes are received not used much yet.

13
EVR IOC Time Line 1 Beam Pulse (B0)
Record processing (event, interrupt)
Hardware Triggers
Receive pattern for 3 pulses ahead
Triggering Event Codes
Beam
Kly Standby
Event Timestamp, pattern records, and BSA ready
Start
End
Acq Trigger
Kly Accel
Fiducial Event Received
Fiducial
Fiducial
B0
F0
F1

40
0
500
1023
2778
100
0.3
110
Time (usec)
14
Issues and Tasks

• Modifications to EVG HW and firmware for 119MHz
  clock input and AC line input.
• Had to power cycle a fanout module after an EVG
  power cycle.
• Changing an event code for a specific trigger
  requires a change in the delay to trigger at the
  same time need database to automate the change.
• Trigger Storms Due to LCLS Master Osc
  unlocking / Fix New MO / De-Couple LCLS Timing
  Sys from it (connect direct to MDL).
• Need interface to MPS over private UDP at 360hz.
• Need global kicker control (single-shot, burst)
  done by EVG instead of locally.
• Record processing at beam rate (up to 120hz)
  some processing delays seen
• Too many records in one lockset.
• Some records pick up wrong timestamp when delayed
  too long and data cannot be correlated with other
  data on other IOCs.
• Some records need to have TSE field properly set.
• Too many CA clients monitoring PVs at beam rate
  instead of snapshot PVs provided at a slower
  rate.
• Not an issue but interesting - some beam
  diagnostic (ie, BPM) IOC engineers choosing to
  trigger at max possible rate and then use the
  timing data to decide if record processing
  required or to set record severity.

15
Linac Upgrade List

• When 2 event codes trigger a device on the same
  pulse, the second event restarts the delay. The
  second event must be ignored instead.
• Interrupt from the EVG on fiducial trigger (AC
  line trigger).
• Diagnostics from the fanout modules.
• Need status of the RF clock into the control
  system.
• Upgrade front end timing hardware.
• Move functions from the old timing system master
  pattern generator to the EVG IOC.

16
End of Talk Thank you!
17
Timing Requirements