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LHC Timing. Sync or swim. RF. Revolution frequency (1&2) 40 MHz LHC bunch frequency (1&2) 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.

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LHC Timing


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lhc timing

LHC Timing

Sync or swim

LHC timing - operational perspective

slide2
RF
  • Revolution frequency (1&2)
  • 40 MHz LHC bunch frequency (1&2)
  • 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.

LHC timing - operational perspective

slide3
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.

LHC timing - operational perspective

slide4
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.

LHC timing - operational perspective

slide5
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.

LHC timing - operational perspective

slow timing

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

LHC timing - operational perspective

basic concepts
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 < 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

LHC timing - operational perspective

slide9
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 CERN’s 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

LHC timing - operational perspective

events
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

LHC timing - operational perspective

events1
EVENTS
  • Each event is a 32-Bit quantity…
    • Type of event 4-Bits
      • Timing=CTIM, 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 …

LHC timing - operational perspective

events2
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.

LHC timing - operational perspective

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

LHC timing - operational perspective

slide14

Data distribution

LHC timing - operational perspective

information on the lhc gmt cable
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 (1&2)
    • BPF (1&2)
    • SBF (1&2)
    • Mode
    • Beam permit (1&2)
    • Squeeze factor

LHC timing - operational perspective

information on the lhc gmt cable1
Information on the LHC GMT cable
  • Fill number
  • Basic-Period Number
    • Seconds since start of pre-injection
  • Particle type (1&2)
  • UTC

LHC timing - operational perspective

slide17

Julian Lewis

LHC timing - operational perspective

injection

INJECTION

LHC timing - operational perspective

injection 1
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.

LHC timing - operational perspective

injection 2
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]

LHC timing - operational perspective

injection 3
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.

LHC timing - operational perspective

rf injection
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

LHC timing - operational perspective

slide23

P. Baudrenghien

LHC timing - operational perspective

slide24

Pilot the LIC for LHC Filling

JL

LHC timing - operational perspective