Data exchanged between the LHC machine and experiments
Data exchange is via DIP (Data Interchange Protocol) as described in https://edms.cern.ch/file/457113/2/DIPDescription.doc. DIP is maintained by IT/CO http://itcofe.web.cern.ch/itcofe/Services/DIP/welcome.html. The following chapters describe the items to be exchanged, their location and estimated availability.
Announcements of publication availability, new requirements, changes, etc. are announced through the lhc-exp-coms@cern.ch mailing list.
In the LHC machine environment all floating point data is typically produced as double (64-bit) and will be published as such. During the conversion some loss of precision may occur.
Machine to experiments
All publications from LHC are under dip/acc/LHC/ followed by the category of interest (Beam, RunControl, Safety, etc) and the publication items. The following tables depict the publication details. Additional information on some of the publications is available at http://ts-dep-lea-int.web.cern.ch/ts-dep-lea-int/dataexchange-DIP.htm
Available publications
Publications which are fully defined and currently published. They can still be subject to some small modifications.
dip/acc/LHC/Beam/Intensity/* (Beam1 and 2)/http://bdidev1.cern.ch/bdisoft/development/BDI-Domains/bdeyelids/bdeyelids.php?currentSelection=GI¤tDomain=LHC¤tInstrument=BCTDCLHC ExperimentAcquisition property - Please note that there are two redundant beam intensity publications and the one which is flagged as valid is published to DIP
K. Kostro
AB/BI, M.Ludwig
small
1 Hz
Individual bunch intensities
dip/acc/LHC/Beam/IntensityPerBunch/* (Beam1 and 2)/* (A and B) BI documentationExperimentAcquisition property - Please note that there are two redundant bunch intensity publications and the one which is flagged as valid is published to DIP
dip/acc/LHC/Beam/BLM/LSS*_thr Beam loss thresholds for 10us, 633ms, 1310ms for BLM monitors 260m around IP. Thresholds are calculated in the BLM concentrator and are adjusted by operation
K. Kostro
BLM concentrator, M.Misiowiec
400 doubles and monitor names
on change
HOR & VER Positions
dip/acc/LHC/Beam/BPM Vertical and horizontal positions from selected BPMs. Includes BPM names and error strings. They are published as arrays i.e. the position of a BPM which name is at index i will be at index i. If more BPMs are added, they will be added at the end but if you use it in a program, make a check if the name is at the expected position. Value may be not correct if the corresponding error string is not empty. Data is from beam orbit concentrator OFSU.LHC which itself gets it from closed orbit position measurement as descibed in http://bdidev1.cern.ch/bdisoft/development/BDI-Domains/bdeyelids/bdeyelids.php?currentSelection=GI¤tDomain=LHC¤tInstrument=BPMLHC The positions are given in micro-meter ('um') w.r.t. to the BPM center, which in usually about the same as the design orbit. The BPM misalignment errors are estimated to about 0.2-0.5 mm r.m.s. Note:positions from the 2 ATLAS Roman Pots are missing yet
K. Kostro
R. Steinhagen
48 doubles, status strings and monitor names
1 sec
Beam energy
dip/acc/LHC/Beam/Energy multiply by 120 to get MeV value
dip/acc/LHC/Machine/TEDPosition/* position from the Status property, position=2 means OUT (beam through), position=3 means IN (dump), other values: 0 (unknown), 1(installation), 4 (transport), 5 (undefined position)
K. Kostro
AB/ATB M. Donze
1 int
on change
Injection lines intensity
dip/acc/LHC/Beam/IntensityInj/* (TI2.29125, TI8.87750) The size of totalIntensityHigh is alvays one and unit is in charges with a unit-exponent of '10' so for example, the nominal LHC pilot (5E9 charges) would give "0.5". You have to check the value of cycleName as not all cycles are for LHC. The cycle names are assigned by operation and can change with time.
dip/acc/LHC/RunControl/CirculatingBunchConfig/* (Beam1 and 2) Circulating Bunch Configuration, per beam. Contains an array which encodes mapping of circulating bunches to RF buckets i.e. the first element contains the RF bucket number of the bunch 1 etc. If the value is 0 then there is no corresponding bunch.
K. Kostro
AB/OP M. Lamont
2808 integers
on change
Injection Bunch Configuration
dip/acc/LHC/RunControl/InjectionBunchConfig/* (Beam1 and 2) Injection Bunch Configuration, per beam. Contains an array which encodes mapping of injected bunches to RF buckets i.e. the first element contains the RF bucket number of the bunch 1 etc. If the value is 0 then there is no corresponding bunch. The 'ACTIVE' field will be set to true for the injected beam and to false for the other beam.
dip/acc/LHC/Safety/* (MaxSpsProbeBeamA and B) SPS Probe Beam Flag Threshold which gives the maximum beam intensity that can be injected into an empty LHC (probe beam). Value is in units of 1E8 charges.
dip/acc/LHC/Timing/PostMortem Postmortem Event. Typically postmortem request is delivered as HW signal but this software event allows to determine the timestamp of the last PM event to be included with the PM data
K. Kostro
AB/CO I. Kozsar
small
on change
Missing publications
Publications which are planned but delayed because equipment is not available yet or for other reasons
Whenever the same kind of publication is expected from several experiments, they shall follow the same naming schema and field definitions so that they can be used by LHC controls in a common way. For instance the same hanshake names and values are expected from all experiments. The following table defines this.
All publications used pricipally by LHC operation shall be under /dip/EXPERIMENT/LHC/. When a single field is published, the field name shall be the DIP default (__DIP_DEFAULT__). When several items which belong together it is preferred that they are published as a single DIP publication.
We will always try to prototype the publications with one experiment and others can follow then.
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