LHC Real-time requirements.ppt

1、TC 25th October,1,LHC Real-time requirements,What is real-time?,What is latency?,The time between asking for something to be done and it being done,The violation of one or more temporal constraints causes a loss of functionality. If it takes too long it dont work. It aint necessarily speed.,TC 25th

2、October,2,Implications,Front-ends Field bus Gateway Network Workstation,Widely available industrial standards: ATM, WorldFIP, LynxOS, PowerPC which would satisfy LHC requirements (and in fact are already in use, planned to be used, or being used in prototypes.),E.g: Full ATM for LHC: 2M CHF,Power co

3、nverters Beam Instrumentation Reference magnets,Real time,To allow real time control/access of:,But note: things are moving quickly out there,TC 25th October,3,Why bother?,150 units of Q,Large but reproducible, will clearly have to be measured,Energy during injection plateau,Orbit,1. Multipole error

4、s,TC 25th October,4,Control: assumptions,Snap-back and low energy provide the challenge Nominal is the worse case. The “multipole factory” takes care of at least 80% of the effect i.e. magnetic measurements non-linear models on-line reference magnets Characteristic frequency of snap-back slow & not

5、changed by feed-forward from “multipole factory”,Corrections to: horiz. orbit correctors (b1) & tuning quads. (b2) sextupole (b3) and decapole (b5) spool pieces,Characteristic frequency is low,70 s,TC 25th October,5,Beam parameter changes,TC 25th October,6,Beam based feedback,max rate db3/dt 0.067 u

6、nits/second, 3 - 5 units Q/second 1 unit per second given the 80% from the magnet factory (NB out of tolerance in 1 second) Chromaticity is NOT an easy measurement and is not likely to be available for the physics beams (emittance growth). Available for pilots reproducibility (again),Tune & orbit we

7、 can do but b3: caveat.,TC 25th October,7,So we have large multipole swings during the injection plateau and snapback. Beam stability will depend totally on feed-forward from the reference magnets feedback on the key beam parameters tune, orbit, energy, chromaticity Have to make a phase jump in our

8、expected performance of a control system: at present it is in the stone-age have a look at synchrotron light sources to get an idea of what is possible. We will need similar to deal with multipoles, tight physics constraints & the low tolerance to beam loss.,TC 25th October,8,LEP Orbit,Maximum sampl

9、ing frequency 0.067 Hz,LHC Orbit,Proposed sampling frequency 10 Hz,The stone age.,TC 25th October,9,RT Requirements,Reference magnets feed-forward of corrections to machine Feedback-loops Global Orbit Local Orbit - e.g. orbit stability at collimators Tune Chromaticity Real-time knobs typically tune,

10、 orbit bumps extension of feedback, operator close loop, need. Display Orbit Beam loss (not for abort, but display & possible feedback) Luminosity, Beam sizes, Lifetimes Timing like actions (possibly) e.g post-mortem trigger,TC 25th October,10,RT requirements II,Response limited by PC/magnet,TC 25th

11、 October,11,Work in progress,Power converters: WordlFip 2.5 Mb/s + PowerPC/LynxOS gateway already planning RT capabilities up to 100 Hz BPM/BLM work in progress but use of RT functionality assume ATM prototyping SPS Q-loop LHC orbit correction simulation Requirements elucidated: LHC report 221 “Requ

12、irements for real time correction” CO/OP forum LHC-CP workshop here.,TC 25th October,12,SL-BI,Two classes of instrumentation: global & local The global systems e.g. orbit and beam loss will provide the main control challenges:- Orbit: 10 Hz RT connection to PCR BLMs: 10 Hz RT connection to PCR (NOT

13、to decide on beam abort) Local systems such as tune & chromaticity will be involved in RT feedback Proposed Architecture VME World FIP for RT Ethernet for off-line retrieval & Post-mortem,Under discussion,TC 25th October,13,Gateway,Gateway,Gateway,Gateway,MCCS Server,80 Gateways,1700 Digital Control

14、lers,Up to 30 Digital Controllers Per WorldFIP fieldbus,RT LHC Network,Major system - all magnets - set, ramp, trim etc. etc. Offering RT control at 100 Hz (whether you need it or not!) Digital controllers:- CERN design, manufactured by industry. Prototypes for String II. Gateways:- standard SL-CO -

15、 Power PC running LynxOS Fieldbus: WorldFIP from CEGELEC Timing: via an IRIG-B receiver card,Power Converters,TC 25th October,14,Reference magnets,C,MCCS Gateway,Multipoles Factory,DB,I,SM18 Magnet Test Benches WorldFIP fieldbus,Real-time LHC controls network,FB,Power Converter,Real-Time LHC Control

16、 System,Instrumented Magnet,3-10Hz,TC 25th October,15,SL-CO-FE - Real Time,Investigating RT architectures Front-ends, Networks Prototype WorldFIP, FIP running LynxOS, ATM SPS as test-bed Q-loop LHC orbit correction simulation,TC 25th October,16,Conclusions,Demonstrable need for real-time control at

17、the LHC Essential requirements established. Foresee dual system: real-time for purposes outlined above non-deterministic but high bandwidth for non-critical monitoring, command flow, post-mortem etc. etc. Accept RT is necessary, form WG under auspices of LHC-CP, ask them to investigate possible architectures Much work already done in prototyping possible system, howev