LHC Timing

1
LHC Timing

• Sync or swim

2
RF

• Revolution frequency (12)
• 40 MHz LHC bunch frequency (12)
• Pre-pulses
• Required in points SR2 and SR8 for LHC Injection
  Kickers.
• Generated by RF in SR4.
• Transmitted to PCR via optical fibre and then
  distributed from PCR by point-to-point optical
  fibre links.
• Extraction generated by SPS RF system,
• injection generated by LHC RF system.

3
TTC
Trigger, Timing and Control (TTC) system supplies
each experiment with accurate clocks.

• The 40.08 MHz LHC bunch-crossing clock and 11.246
  kHz orbit signals are broadcast over the same
  single mode optical fibres from RD12 high-power
  laser transmitters which have been installed in
  the Prevessin Control Room (PCR).
• The combined signals will be received at each of
  the 4 underground LHC experiment areas by a TTC
  machine interface (TTCmi) mini-crate containing
  an LHCrx module.
• The jitter of the received clock is reduced in
  the TTCmi to less than 10 ps rms by a narrow
  bandwidth PLL with a low-noise VCXO having low
  sub-harmonic feed-through.

4
BST
BST based on TTC technology and will use the
message capabilities of the TTC to encode machine
information, primarily for use by LHC beam
instrumentation.

• Convey signals, parameters and commands
  simultaneously to all instruments around the
  machine. All necessary real-time information is
  regrouped and transmitted in a so-called BST
  message.
• The complete BST system consists of
• a BST Master, used to broadcast the
  synchronisation signals and the BST messages
• the TTC system, used to encode and transmit the
  signals over an optical network
• a receiver interface, the BOBR, installed in each
  beam instrumentation crates recovers the BST
  messages and provides all timing signals required
  to synchronize instruments.
• Three operational BST systems and TTC networks
  are required
• one for each of the LHC rings and another for the
  SPS ring and its transfer lines.

5
BST
supplies the LHC beam instrumentation with
40MHz bunch synchronous triggers the 11kHz
LHC revolution frequency. In addition to these
two basic clocks, the TTC system also provides
the possibility of encoding a message which can
be updated on every LHC turn. This message will
mainly be used by the LHC instrumentation to
trigger and correlate acquisitions, but will also
contain the current machine status and values of
various beam parameters.
6
(No Transcript)
7
SLOW TIMING
LHC is not fast cycling Periods of tight
synchronisation of the loosely coupled hardware
and instrumentation systems Long periods when
the machine is coasting at a fixed energy
8
Basic concepts

• EVENTS
• Events arrive asynchronously and can be
  subscribed to
• 16 bit payload
• TELEGRAMS
• Sent out at fixed frequency, 1 Hz in the LHC
• A snapshot
• MULTIPLEXING
• Playing pre-loaded settings. Will multiplex on
  beam type in LHC
• CBCM
• Respond to commands from the LSA Sequencer LSEQ
  for LHC events in lt 100ms
• Provide an accurate UTC time reference
• Pilot the LHC Injector Chain LIC to fill the
  LHC
• Produce the LHC timing from external events and
  tables loaded by LSEQ
• Distribute the safe beam parameters and flags
  very reliably

9
CBCM

• The Central Beam and Cycle Manager CBCM
• (7 VME Crates Two racks of equipment) is a
  collection of hardware and software systems
  responsible for coordinating and piloting the
  timing systems of CERNs accelerators.
• In the LHC era, the CBCM will control Linac-II,
  Linac-III, the PSB, CPS, ADE, LEI, SPS and the
  LHCtiming systems. The CTF, although piloted
  using a similar system, runs on its own, on a
  completely separated timing network.
• The CBCM will also drive the Beam Synchronous
  Timing (BST) for LHC. There will be 3
  distributions R1, R2, Experiments.

Julian Lewis
10
Events

• Events will be sent out on a 1 ms boundary.
• 7 different events on a given 1 ms. boundary max.
• Latency of the system i.e. the time between a
  request being made by the user and its receipt by
  the equipment concerned should be of the order
  100 ms.
• Asynchronous events on request
• Trims etc
• Parallelism different trims overlapping in
  time. Power converters typically need to be armed
  for a given exclusive event, which might not be
  recognised by all other power converters.
• Event tables

11
EVENTS

• Each event is a 32-Bit quantity
• Type of event 4-Bits
• TimingCTIM, UTC-Time, Telegram .
• Accelerator 4-Bits
• LHC, SPS, CPS, PSB, ADE
• Code 8-Bits
• Event-Code, Telegram-Group
• Payload 16-Bits
• User, UTC, Telegram-Group-Value

12
Events

• Injection (B1, B2)
• T-100msec, T-20msec, 0, 10msec
• Separate for First All injections
• Kickers - per-injection warning
• Start ramp PC, RF, Collimators
• Abort ramp PC, RF, Collimators
• Power abort
• RF events
• during filling transverse feedback and
  longitudinal feedback functions during the
  injection process
• ramp
• before physics to synchronise rings.
• Synchronised collimator set, synchronised
  collimator ramp.
• Beam dump event to BIC (conditioning of BIC,
  eg, standard beam dump versus emergency beam dump
  not through timing system)
• Post mortem
• BI synchronised measurement acquisition
• Orbit/beam losses/BCT at pre-defined times in
  ramp, or on demand. Synchronised kick and measure
  procedures.
• Wire-scanners fly wire.

13
Event tables

• Pre-programmed tables of events
• Pre-loaded
• Run on request
• Loop on request
• Run up to 16 event tables concurrently

14
Data distribution
15
Information on the LHC GMT cable
Arrival Time 1Hz

• Circulating beam type R1 R2
• RF parameters
• Next injected beam type
• Next injected bucket number
• Next injected ring
• Safe beam parameters
• Energy
• Intensity (12)
• BPF (12)
• SBF (12)
• Mode
• Beam permit (12)
• Squeeze factor

16
Information on the LHC GMT cable

• Fill number
• Basic-Period Number
• Seconds since start of pre-injection
• Particle type (12)
• UTC

17
Julian Lewis
18
INJECTION
19
Injection 1

• 0. Preparation
• 0.1 Pre-warning to injectors that the LHC will be
  requiring beam manual/vocal/soft.
• 0.2 SPS training cycles request for beam from
  SPS. Check transfer lines, possibly beam to last
  TEDs. SPS master.
• 0.3 LHC to mode Filling. Change injection master
  to LHC.
• 1. LHC makes request to CBCM with ring, bucket
  number, beam type and number of PS batches.
• 2. Beam injected into SPS, accelerated. Beam
  quality checks on flat top.

20
Injection 2

• 3. SPS - decision to extract or not.
• The SPS extraction interlock system will have all
  the information on the state of beam dumps in the
  TLs, state of the LHC (beam injection
  interlocks summary) and status of extraction and
  line elements to take the appropriate decisions.
• If all elements are safe and the extraction
  timings events are distributed when the LHC USER
  is played, then the extraction kicker will be
  fired. The timing system will be sending out
  warning events the RF system, the pre-pulses.
• 4. Extraction. Beam down TI2/TI8.
• checks on BLMs, trajectory

21
Injection 3

• 5. Injection into LHC
• injection kickers having received warning timing
  events pre-pulse etc.
• The timing system does not play any role in the
  injection protection, with the exception of the
  safe parameter distribution.
• 6. Beam quality checks in LHC.
• BST triggered acquisition of first turn, beam
  loss, intensity, emittance.
• Destination (R1 or R2) required by BI
• Longitudinal feedback, transverse feedback and
  other RF settings are preloaded.
• Beam type dependent settings triggered by timing
  events at the point of injection. Clearly the
  events have to be set up in advance. The settings
  are explicitly pre-loaded before every injection.

22
RF - injection

• LHC RF system expects the bunch number and the
  destination ring to be delivered to SR4 by the
  LHC timing system.
• This would be delivered every SPS cycle whenever
  the LHC is in injection mode.
• The LHC be the master for the SPS-LHC transfer.
• The SPS receives a train of pulses at the SPS-LHC
  common frequency. With its bucket selector the
  LHC can select the position for transfer from the
  SPS.
• RF system updates the bucket selector and the
  phase of the 400 MHz sent to the SPS.
• Fine positioning of the beam injection phase in
  the LHC buckets is adjusted with the phase of the
  LHC RF signal sent to the injectors.
• Signals for RF synchronization must be available
  in the PS about 450 ms before extracting to the
  SPS.
• RF generates injection pre-pulses

23
P. Baudrenghien
24
Pilot the LIC for LHC Filling
JL
25
(No Transcript)
26
(No Transcript)