Transcript LHC Timing Sync or swim 01.11.06 LHC timing - operational perspective

LHC Timing
Sync or swim
01.11.06
LHC timing - operational perspective
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RF
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Revolution frequency (1&2)
40 MHz LHC bunch frequency (1&2)
Pre-pulses
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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.
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TTC
Trigger, Timing and Control (TTC) system supplies each
experiment with accurate clocks.
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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).
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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.
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The jitter of the received clock is reduced in the TTCmi to
less than 10 ps rms by a narrow bandwidth PLL with a lownoise VCXO having low sub-harmonic feed-through.
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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.
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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.
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The complete BST system consists of:
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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
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one for each of the LHC rings and another for the SPS ring and
its transfer lines.
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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.
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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
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Basic concepts
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EVENTS
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TELEGRAMS
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Playing pre-loaded settings. Will multiplex on beam type in LHC
CBCM…
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Sent out at fixed frequency, 1 Hz in the LHC
A snapshot
MULTIPLEXING
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Events arrive asynchronously and can be subscribed to
16 bit “payload”
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
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CBCM
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The Central Beam and Cycle Manager CBCM
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(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.
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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.
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The CBCM will also drive the Beam Synchronous
Timing (BST) for LHC. There will be 3 distributions R1,
R2, Experiments.
Julian Lewis
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Events
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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.
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Asynchronous events on request
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Trims etc
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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.
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Event tables
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EVENTS
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Each event is a 32-Bit quantity…
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Type of event 4-Bits
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Accelerator 4-Bits
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Event-Code, Telegram-Group …
Payload 16-Bits
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LHC, SPS, CPS, PSB, ADE …
Code 8-Bits
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Timing=CTIM, UTC-Time, Telegram ….
User, UTC, Telegram-Group-Value …
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Events
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Injection (B1, B2)
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Start ramp – PC, RF, Collimators
Abort ramp – PC, RF, Collimators
Power abort
RF events
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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
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T-100msec, T-20msec, 0, +10msec
Separate for First + All injections
Kickers - per-injection warning
Orbit/beam losses/BCT at pre-defined times in ramp, or on demand.
Synchronised kick and measure procedures.
Wire-scanners – fly wire.
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Event tables
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Pre-programmed tables of events
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Pre-loaded
Run on request
Loop on request
Run up to 16 event tables concurrently
Event
System
Time [ms]
Start Ramp
Power Converters
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Start Voltage Ramp
Radio Frequency
200
Start Frequency Ramp
Radio Frequency
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BLM acquisition
BLM
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BPM 1000 turn acquisition
BPM
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Start Ramp
Collimators
1000
BPM 1000 turn acquisition
BPM
10000
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No.
Requirement
R5
The machine mode shall be distributed as a safe beam parameter [2] at a frequency of 1
Hz or higher.
R6
The beam energy shall be distributed as a safe beam parameter at a frequency of 1 Hz or
higher.
R7
The LHC squeeze factors shall be distributed as a safe beam parameter at a frequency of
1 Hz or higher.
R8
Safe Beam Flag shall be distributed as a safe beam parameter at a frequency of 1 Hz or
higher.
R8
The circulating beam type shall be distributed at ~1 Hz at all times. It is possible to have
different beam types in ring 1 and ring 2.
(Beam type = intensity plus bunch structure. Syntax to be defined.)
The timing system shall change the beam type distributed at the moment of injection
(for example, in the over injection of a pilot by a nominal batch) with a latency of 100
ms. The timing system shall be informed via a dedicated LHC injection monitoring
process.
R9
Other parameters shall be distributed. These parameters shall include the RF frequency,
the total beam intensity for beam 1 & beam 2, the overall state of the collimator system
and the fill number.
R10
An API is required to input specified data into the timing system.
The latency shall be 100 ms.
R11
Other data items considered useful to LHC operations – as yet unspecified. E.g. bunch
pattern, beam position at IPs etc., run number.
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The incoming injected beam type shall be distributed (RF, BI). The RF position (bucket
number) of the batch to be injected beam shall be distributed.
The failure to transmit the SBPs will result in a beam dump. The fail over strategy in the
case of timing generator failure should be clearly established. Stale data must not be
sent out.
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Data distribution14
Information on the LHC GMT cable
Arrival Time & 1Hz
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Circulating beam type R1 & R2
RF parameters:
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Safe beam parameters
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Next injected beam type
Next injected bucket number
Next injected ring
Energy
Intensity (1&2)
BPF (1&2)
SBF (1&2)
Mode
Beam permit (1&2)
Squeeze factor
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Information on the LHC GMT cable
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Fill number
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Basic-Period Number
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Seconds since start of pre-injection
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Particle type (1&2)
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UTC
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Julian Lewis
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INJECTION
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Injection 1
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0. Preparation
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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.
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1. LHC makes request to CBCM with ring, bucket
number, beam type and number of PS batches.
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2. Beam injected into SPS, accelerated. Beam quality
checks on flat top.
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Injection 2
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3. SPS - decision to extract or not.
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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.
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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.
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4. Extraction. Beam down TI2/TI8.
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[checks on BLMs, trajectory]
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Injection 3
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5. Injection into LHC
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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.
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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.
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injection kickers having received warning timing events
& pre-pulse etc.
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.
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RF - injection
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LHC RF system expects the bunch number and the destination ring to be
delivered to SR4 by the LHC timing system.
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This would be delivered every SPS cycle whenever the LHC is in injection mode.
The LHC be the master for the SPS-LHC transfer.
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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.
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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.
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Signals for RF synchronization must be available in the PS about 450 ms
before extracting to the SPS.
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RF generates injection pre-pulses
sps
lhc
f rev
f rev
fc 
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P. Baudrenghien
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Pilot the LIC for LHC Filling
LHC
Pre-Injection plateaux
Ramp
Pilots
LHC Injection plateaux
1S
Status
Beam
Retry R1B1 2
Batch
1.2S
Decide on the next
Ring/Bucket
te
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Go for R1B2 3
Batch
Rephase
SPS RF
SPS
CPS
Batch 1
LHC Nominal
Batch 2
Batch 3
Batch 4
MD
LHC Nominal
MD
EastA
Batch 1
Batch 2
Batch 3
Batch 4
PSB
R1B1 2 Batch Nominal
LHC Filling scheme Table
Filling scheme: 234 334 334 334
Bucket Order: 123 456 789 10 11 12
Beam intensity: Nominal
Order: All Ring 1 then All Ring 2
On error: Repeat
Easta
Parasitic
Beam
R1B2 3 Batch Nominal
Nothing on this
side of the dead
line can depend
on the status of
the beam transfer
Dead Line
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Will be
driven into
spare
depending
on batch
number
LHC timing - operational perspective
Isold
Parasitic
BeamS
JL
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