Lessons from LEP

1. Lessons from LEP • Brief reminder • LEP Challenges – beam related • LEP challenges – controls • What helped in the way of controls • Control group myths • LHC? • Conclusions Lessons from LEP

2. LEP - The largest particle accelerator to date… 1989 First turn 1989-1995 The Z-years (precision studies) 1996-1999 The W-years (precision studies) 2000 The Higgs-year (almost a discovery?) Nov 2000 Start of dismantling Circumference: 27 km Energy range: 20 – 104.5 GeV Lessons from LEP

3. LEP challenges • Multi-cycle injection • Stability of lines, steering • Accumulation: resonances, coherent tune shifts, wigglers, radiation in experiments, etc. etc. • Ramp between 22 GeV and 104 GeV • Tune, chromaticity and orbit control (particularly the start), resonances, bunch length, wigglers • Squeeze between * = 20 cm and * = 5 cm. • Tune, chromaticity and orbit control • Physics • Beam-beam, control of tune, chromaticity, orbit, beam crossings, coupling, lifetimes • Background optimisation - collimation • Continual optimisation to maximise delivered luminosity. Lessons from LEP

4. LEP challenges • 27 km of equipment and instrumentation to keep running • 700 or so power converters, • 1000s of magnets: 8 of which superconducting • 20 or so electrostatic separators • Huge RF system • Lots of Collimators • Kickers, beam dumps • 250 BPMs, BCTs, Q-meter, BST, profile measurements, beam loss monitors etc • A few interlocks • Communication with the experiments All held together with a rudimentary control system Lessons from LEP

5. 1989 - commissioning • 14th July: first beam • 23rd July: circulating beam • 4th August: 45 GeV • 13th August: colliding beams These people are to blame for what followed Lessons from LEP

6. LEP – difficult teething • Fractured high level control system • It was slow (even in 2000 it took 15s to acquire a closed orbit) • Poor measurement facilities • Beam instrumentation lived in a world of its own. Very little integration. • Essential signals not available e.g. no beam lifetime, for example • Poor data management • Inflexible communication with experiments • No easy way of closing the measure/correct loop • Poor and unreliable, incoherent data acquisition systems • After commissioning and 2 years of operations we were faced with just wanting to get the beam up the ramp occasionally. Operations a real struggle (turn around was around 7 hours back then) Lessons from LEP

7. 1999 253 pb-1 BORING! Lessons from LEP

8. Performance LEP2 LEP1 Continual improvement even for same peak luminosity! Lessons from LEP

9. So what went right? • Things clearly got a lot better: • Turn around • Injection efficiency • Transmission through the ramp and squeeze • Performance, in spite of limited current and the huge RF system Lessons from LEP

10. Settings management • Need to drive machine through a reproducible cycle • Handle all modifications to settings in a sensible way • Be able to roll back some or all changes • Exert control in a appropriate way Lessons from LEP

11. Settings • Took around 20 minutes to fill LEP, a lot of fiddling around with tunes, orbit and stuff. • Changes need to be incorporated to ramp in an appropriate way without screwing the ramp up • Ramp (always a rocky start) and squeeze • Driven by current functions downloaded to power converters (and RF and separators) • Control in terms of Tune and chromaticity and corrector strengths • Plus stops in ramp or squeeze, fiddle around and then carry on… Lessons from LEP

12. Parameters Ability to control beam in terms of appropriate parameters • Trim synchrotron tune, calculate total voltage change, trim total voltage. • Trim tune calculate changes in Kqf, Kqd, Iqf, Iqd, and send to hardware - where in fact the current is delivered by 8 power converters • Trim integrated B-field in wiggler, Calculate associated orbit correction, calculate associated optics change, calculate current changes in wigglers, wiggler compensation coils, orbit correctors and insertion quads. • Plus user-definable KNOBS, e.g. orbit bumps, beta*squeeze etc etc For either functions in the ramp or at steady state – provide trim history, rollback, consistency etc… and the ability to carrying on ramping Note: The ability to set a current is not considered sufficient. Lessons from LEP

13. Combined controls/operation project Controls provided fellows & support for the old system Redesigned and re-implemented high level control system (on-line ORACLE controls database) Successfully solved serious data management problem Lessons from LEP

14. Trim History All changes recorded on database. Rollback of any or all systems possible Lessons from LEP

15. Databases KEY FEATURE - THE USE OF DATABASES • Measurement database • beam, equipment, experiments, max rate 0.25 Hz, year’s worth of history, • Controls database • All settings, machine parameters, configuration, optics etc • All trims are recorded • Logging database • many years, sparser than measurements plus environment etc etc • RF logging database Extremely useful, providing as they do… Consistency, back-up, support of relational model, access mechanism, a lot of neat stuff, data management, etc…, CENTRAL RESPOSITORY Lessons from LEP

16. Series of applications accessing data via database ORACLE database provides central repository System dependent black boxes pushing data up at appropriate rates Experiments’ communication system Lessons from LEP

17. DATA EXTRACTION - JAVA GUILS Lessons from LEP

18. DATA EXTRACTION  POST RUN ANALYSIS With historical data on the database, reasonably easy to extract and analyze off-line Lessons from LEP

19. Statistics Data hauled from database automatically at end of fill Lessons from LEP

20. Fixed Displays Generic data driven application + dynamic SQL + backgrounds, radiation, beam-beam tune shifts, bunch currents, angle and positions, beam sizes, luminosities from various sources... Lessons from LEP

21. Typical view of LEP control room Fixed Display Operator Lessons from LEP

22. Scans – tie it together Dedicated program: standard calls to perform trims Measurements from Database • Separator voltages • Beam sizes • Beam angle • & results Lessons from LEP

23. Tools e.g. Dataviewer Generic display & manipulation of data Lessons from LEP

24. Dedicated Video (FAST) Signals Data sampled at slower rate  database Vertical beam sizes – v. useful for luminosity optimization Life without lifetimes - impossible Lessons from LEP

25. 1000 Turns -  Beating BIG FILES!!! - Dedicated applications - Brain power Lessons from LEP

26. Turn around • Semi-automatic sequencer • Reproducibility • Reduced scope for error Typical 2000 turn-around: ~ 45 minutes Lessons from LEP

27. Optimisation • Reproducibility • Golden orbits including corrector settings • Procedures • Easy to perform measurement procedures • Coupling, beta*, dispersion… • Fast signals • Beam sizes, luminosity from lifetime… • Intellectual Property rights • DFS Lessons from LEP

28. & eventually the Q-loop Lessons from LEP

29. RF System – special mention Lessons from LEP

30. And other neat stuff 104.0 GeV 103.3 GeV Mini-ramp Beam lifetime: 9 hours 3 hours quantum lifetime Lessons from LEP

31. LEP COULD BE OPERATED BY ONE MAN! Lessons from LEP

32. Analysis and design In both LEP and SPS a major design effort was under taken • Method adopted (SASD) • the whole thing (e.g. operate LEP) • spent a long time in the analysis phase understanding the requirements • Data analysis & database design included • pragmatic but serious • CASE tool • documentation, focus, continuity and support of the method • Operations heavily involved • Same team throughout… • An appropriate user view… Vital in providing the “generic” tools outlined above Lessons from LEP

33. Interface(s) to Equipment • Specialised groups: power converters, RF, beam instrumentation, kickers, separators, vacuum, dedicated expertise (electronics, controls, hardware) • Both the SPS and LEP efforts accepted the existing equipment interfaces and buried the access to them in black boxes (“encapsulation”) • However it’s clear that the front-end system can compromised the high-level: • By not supplying appropriate functionality • The LEP low-level power converter s/w was probably it’s saving grace, but fixed approach to the start of the ramp, no RT knobs… • By being slow • By making life bloody awkward • Of course, we also have accept what ever the control group offers in the way of communication mechanisms. Again buried in the black boxes. Lessons from LEP

34. Components • Access system/Machine interlocks: always a problem • Alarms: dedicated system with a lot to deal with – worked well • Timing: Extremely important, few problems with the mtg’s but hardware infrastructure worked well • Gateways, networks, front-ends: flakey at first but things settled down • Reboot tool: always useful • Interlocks: not many Lessons from LEP

35. Control Myths • “The operator wants a unified standard MMI” • Maybe a similar look and feel but… • Speed, reliability and functionality are much more important • “A standard API to the equipment is vital” • Not a user requirement • And we can deal with it if it isn’t • “Accelerator consists of devices with properties” • “Not invented here…” • Some nice wheels (e.g. dataviewer) re-invented…. Lessons from LEP

36. Conclusions • Databases are useful • But need managing and designing properly • And everything doesn’t have to forced onto them • Settings management is key. • Control in terms of the right parameters is vital. • Fast, reliable signals of key beam parameters are vital. • Key feedback systems must be made to work ASAP • Anticipate closing the loop • Heterogeneous equipment access is a bit of a pain but hey… • If it ain’t ready in time, other solutions will be found (e.g. middleware) • Integration of, and maturing of BI took a long time. • Committed, aggressive, tool using individuals on the machine are, like, totally invaluable • Things evolve • We eventually ended up with some really cool stuff Lessons from LEP

37. Conclusions We didn’t solve all the problems and what we ended up with was a bit of a mish- mash but it did enable us to effectively exploit the machine. “The eventual efficiency with which LEP could be operated, even in the final years at the performance limits of the hardware system, was in large part due to the integration of a well designed control system using commercial databases.” Lessons from LEP

38. What did we miss? • Scripting environment • On-line model, the interface to MAD was a pain • Configurable feedback/control loops. • Machine protection/interlocks • Speed • Rigour Lessons from LEP

39. LHC - Operating challenges • Super-conducting magnets • multipoles, snap-back, persistent currents, key beam parameters affected, strong dependence on magnetic history • High energy, high intensity beams • extremely low tolerance to beam loss, quench protection collimation mandatory at all times • Machine design • 2 rings, 8 sectors, bits of the ring in common, cross-talk between the rings, small mechanical aperture, large energy swing large range in magnets and power converters. • Beam dynamics • Wide range of optics Beta* 18 m to 0.5 m • Dynamic aperture, limited by non-linear fields from magnet imperfections or beam-beam. Problem at injection where non-linearities are large and beam has large emittance. Tight constraints on beam parameters • crossing angle, beam-beam effects • Intra-beam scattering, synchrotron radiation, instabilities, electron cloud, PACMAN bunches, ghost bunches. beta beating … very tight orbit tolerances Lessons from LEP

40. LHC Inject, ramp, squeeze, collide… • Integrated measurements & control. Already see the need for tight coupling between controls, equipment, beam instrumentation, magnetic measurements. • Timing & synchronization (of measurements as well). • Speed • Protection/Interlocks • High-level data management • keeping track of trims, feed-forward, history, control in terms of relevant parameters, reproducibility, databases, analysis and design… • Feedback • Requisite low-level functionality in equipment controllers • Cross-system communications • Demands on controls high • high degree of automation, surveillance, post-mortem, diagnostics etc.. • powerful, flexible, rigorous, real-time, integrated, coherent, fast, safe, available on time Lessons from LEP

41. Last slide Databases, settings management, reproducibility, logical architecture LEP Real-time control Feedback Speed & Flexibility PEP II Rigour, diagnostics & protection LHC Lessons from LEP