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An Operations Model of the Tevatron Complex

An Operations Model of the Tevatron Complex. Elliott McCrory Fermilab/Accelerator Division 13 October 2005. Outline. Fermilab Overview of the Operations Model Data input to the Model SDA: Database indexed by store number Optimization Strategies Optimizations with Future Improvements

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An Operations Model of the Tevatron Complex

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  1. An Operations Modelof theTevatron Complex Elliott McCrory Fermilab/Accelerator Division 13 October 2005

  2. Outline • Fermilab • Overview of the Operations Model • Data input to the Model • SDA: Database indexed by store number • Optimization Strategies • Optimizations with Future Improvements • Quick transfers • 24 mA/hr • Electron Cooling (3E12 pbars) Elliott McCrory, Fermilab/AD

  3. Elliott McCrory, Fermilab/AD

  4. Elliott McCrory, Fermilab/AD

  5. Elliott McCrory, Fermilab/AD

  6. Fermilab Overview Linac Tevatron Booster Pbar Source Main Injector & Recycler Elliott McCrory, Fermilab/AD

  7. Fermilab Terminology • Stack • The antiprotons in the Accumulator • Stash • The antiprotons in the Recycler • Shot • The process of transferring antiprotons to the Tevatron • Done during a “Shot Setup” • Store • Proton/antiproton collisions in the Tevatron • Begins at the end of the Shot Setup • Transfer • AccumulatorRecycler antiproton transfer and its associated setup time Elliott McCrory, Fermilab/AD

  8. Fermilab Operations • Stacking • Antiproton production in DebuncherAccumulator • Every 2 to 3 seconds • 15E10 per hour • AccRecycler transfers • Three or four time per store, today • Depends on stacking rate • Shot Setup • Each step is 10 to 60 minutes • Tuning • Transfer protons into Tevatron • Transfer antiprotons into Tevatron • Accelerate • Squeeze/scrape • Collisions • 20 to 40 hours • Between stores … Elliott McCrory, Fermilab/AD

  9. The Operations Model

  10. One Week of Operation Recycler Stash Luminosity Accumulator Stack Elliott McCrory, Fermilab/AD

  11. One Simulated Week of Ops Recycler Stash Luminosity Blue: recycler Stash [E10] Red: Luminosity [1/(cm2 sec)] Green: Accumulator Stack [E10] Accumulator Stack Hours Elliott McCrory, Fermilab/AD

  12. Operations Model • Phenomenological representation of the Tevatron Complex • Mostly non-analytic & randomized • Monte Carlo (randomizations) • Complexity is replaced by randomizations • Online and offline data are used to match model to reality • This model’s genesis: • To develop intuition and provide guidance for optimizing luminosity • Now: • Extrapolations/”What If”, based on today’s performance • The effect of Recycler improvements Elliott McCrory, Fermilab/AD

  13. Complexity  Randomness • Downtime • For the Tevatron, stacking and the PBar Source • Variations in all realistic parameters • For example • Transmissions during a shot, • Luminosity lifetimes, • Extraction efficiency from antiproton sources, • Shot setup time, • Downtime for each sub-system, • Etc… Elliott McCrory, Fermilab/AD

  14. Model Assumptions • Performance does not improve • Random fluctuations around a specific set of parameters • Performance determined largely by these parameters • No shutdown periods • “Shot data” & Ops Summaries are accurate • Supplemented and supported by other sources Elliott McCrory, Fermilab/AD

  15. Luminosity • One average proton and 36 antiprotons are tracked • Proton bunches are all the same • Recycler & Accumulator antiprotons are different • Li(t=0) = K H Np(0) NPBar, i(0) [єp(0) + єPBar, i(0)] • L(t) = L(0)e-t/τ(t) • τ(t) = τ(0) + C1 t C2 • τ(0) depends on L(0) and is adjusted to fit Real Data • C1= 3 ± 2 • C2 = f(C1) Elliott McCrory, Fermilab/AD

  16. The Other 200 Parameters Elliott McCrory, Fermilab/AD

  17. Match Model to Reality • Data Sources • SDA (Shot Data Acquisition) • The “Supertable” • Other data tables • Data loggers • Weekly summaries from operations • Goal • Appropriate range of values for important parameters • Correlations among the parameters Elliott McCrory, Fermilab/AD

  18. SDA Sequenced Data Acquisition or Shot Data Analysis

  19. SDA: Defined • Overloaded definitions • Sequenced Data Acquisition • Defines alternate “clock” for recording data • Extends definition of what can be stored • Shot Data Analysis • Look at Sequenced Data Acquisition database • Look at conventional data loggers • Create summaries • Do certain types of calculations • More complicated (transmission efficiencies) • Time dependent (Emittances) • Observe/alert Elliott McCrory, Fermilab/AD

  20. More relevant “clock” Shot/store number Today: store # 4410 Case Collider shot: 15 main cases Proton Injection Porch Proton Injection tune up Eject Protons Inject Protons Pbar Injection Porch Inject Pbars … Before Ramp Acceleration Flattop Squeeze Initiate Collisions Remove Halo HEP Pause HEP Set Each case may have one or more sets For example: “What happened at 4401, Inject Protons, second bunch injection [a.k.a. Set 2]?” Other common processes use this clock abstraction AccumulatorRecycler transfers Pbar Transfers to Tevatron Sequenced Data Acquisition Elliott McCrory, Fermilab/AD

  21. Sequenced Data Acquisition (2) • Data collection abstraction • All types of data can be acquired • Implemented as a Java interface • SDA Database • Detailed information • Often, 36 bunch data • Often, raw data from front ends • Indices: • Store Number (**Most widely used**) • Accumulator to Recycler Transfer Number • 30 GB today • Data Loggers • Not strictly part of this, but very relevant • Store <timestamp, value> pairs in relational DB • Essentially Unix + milliseconds timestamp • 70+ instances at Fermilab • O(100 GB) Elliott McCrory, Fermilab/AD

  22. Shot Data Analysis • Data mining applications • Example • Sequenced Data Acquisition cross-checks • Summary tables on the web • The Supertable • A summary of key information, mostly from SDA database • Excel, HTML, AIDA/JAS • One row = one store • Over 200 columns for each store • http://www-bd.fnal.gov/sda/supertable Elliott McCrory, Fermilab/AD

  23. SDA Database Example Elliott McCrory, Fermilab/AD

  24. http://www-bd.fnal.gov/sda/supertable Elliott McCrory, Fermilab/AD

  25. Supertable Example Elliott McCrory, Fermilab/AD

  26. SDA Examples Relevant to Model • Initial Luminosity versus Number of Antiprotons • Initial Luminosity versus Initial Luminosity Lifetime • Antiproton Emittances • Uncertainty at the IP • Beta-star changing?? Elliott McCrory, Fermilab/AD

  27. Initial Luminosity vs. # PBars Elliott McCrory, Fermilab/AD

  28. Initl Lum Vs. Init Lum Lifetime Elliott McCrory, Fermilab/AD

  29. PBar Emittance at Extraction Accumulator Recycler Elliott McCrory, Fermilab/AD

  30. PBar Emittance at Extraction Real Emittances from Recycler Model generated Emittances Elliott McCrory, Fermilab/AD

  31. Better emittance measurements Better lattice understanding Better instrumentation Uncertainty at the IP Luminosity / (all known factors) β* = 28 cm Elliott McCrory, Fermilab/AD

  32. Tevatron Failure Rate Time Between Tevatron Failures; Real Data Model data for Tevatron Failures f(t) = e - t σ = < t > = 1/ e - t R ≈ 1 - Δt Δt = 42 hours  = 0.975 / hour Elliott McCrory, Fermilab/AD

  33. Failure Rate: Interpretation •  is “Tevatron Up Time” •  is measured directly from real data • < t > = σ = 1/  • Probability of having stores of: • 1 hour: 0.975 • 2 hours: (0.975)2 = 0.951 • 10 hours: (0.975)10 = 0.776 • 20 hours: 0.603 • 30 hours: 0.459 • Failures are Independent of Time • This is a random process!! Elliott McCrory, Fermilab/AD

  34. Reliability of Tevatron Today • Low Beta: ~0.988 • 20 hours: 0.785 • 30 hours: 0.696 • Preparation for store: ~0.95 • Ramping & squeezing: 0.88! • Recovery time from unexpected failure is severe for superconducting machine • ∴ Longer stores • Tevatron is more reliable in collisions Elliott McCrory, Fermilab/AD

  35. Details on ModelImplementation

  36. State Machinery • All machines are implemented as Finite State Machines • Vary in complexity • Proton source: 5 states • Ready, Down, Sick, Studies, Access • Accumulator/Debuncher: 7 states • ReadyStacking, ReadyShot, ReadyRecTransfer, Down, Recovery, Sick, Studies • Tevatron: 17 states • Ready, 7 shot-setup, 4 luminosity, Failure, Studies, Access, Recovery, Turn-Around • Recycler: 12 states • Ready, 4 transfers (2 in, 2 out), 2 down, recovery, 2 studies, access, cooling, turn-around. Elliott McCrory, Fermilab/AD

  37. Elliott McCrory, Fermilab/AD

  38. How does this work? Step size = 0.1 hours “Listeners” provide connections among State Machines Main program guides time progression & venue for main decisions Stack Do transfer to Recycler? “End-store” criterion satisfied? Start shot setup. Repeat for N weeks, dumping lots of relevant data. Input parameters Output handler Lots of data files can be dumped C++/Linux 800 weeks/minute On 1.8 GHz Celeron 220+ parameters Program Structure Elliott McCrory, Fermilab/AD

  39. Linux drand48( ) Random Numbers RandomLikely(-2, 12, 8) Product of these two distributions RandomLikely(0, 5, 2) Elliott McCrory, Fermilab/AD

  40. Decisions • Same as reality • Store • When to end the store • When to begin a store after a failure • Answer: Wait for accumulation of antiprotons • Antiprotons • When and how much to transfer from Accumulator to Recycler • Combination • How many antiprotons to get from two sources • Recycler only, Accumulator only, Combined Source Elliott McCrory, Fermilab/AD

  41. Some End-Store Criteria • Store Duration • Number of Antiprotons we have available • How low L can the experiments use • Best: Combination of last two: • Np  expected luminosity • R = Expected Luminosity / Actual Luminosity • This criterion works very well algorithmically, but there are other considerations in Real Life • Nowadays, the Run Coordinator ends a store based on this factor and many other factors, e.g., time of day. • If Model is believable • Can change the performance • See how the End-Store criteria respond • Find the Best criterion for ending stores for lots of parameters Elliott McCrory, Fermilab/AD

  42. Best End-Store Criterion? • How to decide which is the “Best” criterion? • It integrates lots of luminosity • It insensitive to natural fluctuations in parameters • Some of these changes may be unnoticed • Random fluctuations or improvements?! • It is simple • Everyone can understand it! • Some effective but complex schema have been rejected Elliott McCrory, Fermilab/AD

  43. Minimum Luminosity Criterion • Show typical week Elliott McCrory, Fermilab/AD

  44. Show optimization plot Elliott McCrory, Fermilab/AD

  45. Show duration plot Elliott McCrory, Fermilab/AD

  46. Target Ratio Criterion • Show typical week Elliott McCrory, Fermilab/AD

  47. Show optimization plot Elliott McCrory, Fermilab/AD

  48. Store Duration End store when Ratio=4 Remake this? dN/dt [stores/1 hour bin] 5 6 8 Store Duration [hours] Elliott McCrory, Fermilab/AD

  49. Ratio: End at R>4; R(t) Elliott McCrory, Fermilab/AD

  50. Decisions Involving Recycler • More degrees of freedom/choice with Recycler • When to shoot from Acc to Recycler? • How? • How much to take from each? • Emittances from Recycler are smaller than from Accumulator • Better coalescing efficiency Optional slides?? Elliott McCrory, Fermilab/AD

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