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A Monte Carlo Model of Tevatron Operations

A Monte Carlo Model of Tevatron Operations. Elliott McCrory Fermilab/Accelerator Division 13 October 2005. Where is Fermilab?. ~50 km. Fox River. Fermilab Overview. Linac. Tevatron. Booster. Pbar Source. Main Injector & Recycler. Outline. Overview of the Operations Model

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A Monte Carlo Model of Tevatron Operations

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  1. A Monte Carlo Model of Tevatron Operations Elliott McCrory Fermilab/Accelerator Division 13 October 2005

  2. Where is Fermilab? Elliott McCrory, Fermilab/AD

  3. ~50 km Elliott McCrory, Fermilab/AD

  4. Fox River Elliott McCrory, Fermilab/AD

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

  6. Outline • Overview of the Operations Model • Monte Carlo ≡ Randomizations • SDA • Sequenced Data Acquisition • Shot Data Analysis • Model Observations and Predictions • Effects of Future Improvements • Note: • Several “extra” concepts relating to current Tevatron performance. May have to skip some. Elliott McCrory, Fermilab/AD

  7. Definitions of “Model” • Curiously subtle shades of meaning! • An example for imitation or emulation • “My brother is a role model for my son” • Person who serves as a subject for an artist or a fashion designer • A Structural Design • “We need a business model” • A type or design of a product • “I own a Volkswagen.” “Which model?” “Jetta.” • Something built to represent reality in a simplified way • “Model Airplane, 1:32 scale” • Here: 5 Elliott McCrory, Fermilab/AD

  8. 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 • Often used interchangeably with shot • Transfer • AccumulatorRecycler antiproton transfer and its associated setup time Elliott McCrory, Fermilab/AD

  9. Fermilab Operations: Basics • 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 • 100 to 200 minutes • 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

  10. The Recycler • An antiproton Storage Ring • Main bends are permanent magnets • Transfers into Recycler every few hours • Offloading antiprotons from Accumulator • Advantages over Accumulator • Electron cooling and Stochastic cooling • Emittances are better • 4π smaller transverse emittance • Longitudinal emittances are consistent and smaller • Transfers into Tevatron are better • Transmission efficiency is higher • Brighter antiprotons bunches at collisions • Can hold more antiprotons • Stacking rate into Accumulator is better at smaller stacks Elliott McCrory, Fermilab/AD

  11. Fermilab Operations: Update • Averaging 18 pb-1 delivered per week to our two experiments • 107 ± 27 hours/week in collisions • 10 E10 antiprotons/hour • Initial luminosity world record set on 4 October • 1.42E32 [cm-2 sec-1] • Main Injector • Slip stacking • Recycler • Electron cooling achieved on July 9 • Implemented for >50% of transfers to Tevatron in last 4 weeks • Cool by 70 eV-sec in 80 minutes, 250E10 particles • I am, by no means, an expert on these topics! • An intelligent observer, perhaps Elliott McCrory, Fermilab/AD

  12. Recycler Electron Cooling Beam current: 250E10 Transverse emittance Longitudinal emittance Cool 70 eV-sec in 80 minutes 53 min Elliott McCrory, Fermilab/AD

  13. Tevatron Operations Status • BPM Upgrade completed • New lattice implemented last month • 28 cm beta-star • Practical understanding of coupled machine • Partially equalized luminosity at 2 experiments • Reduced beta-beating in arcs between 2 experiments • Increase luminosity by ~15% • Previous lattice change • December 2004 • 30% improvement in luminosity • Extra • Orbit stabilization • Crystal Collimator demonstration? Elliott McCrory, Fermilab/AD

  14. Orbit Stabilization EXTRA Elliott McCrory, Fermilab/AD

  15. Crystal Collimator Study EXTRA Elliott McCrory, Fermilab/AD

  16. The Operations Model

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

  18. 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

  19. Basic Idea • Phenomenological representation of the Tevatron Complex • Mostly non-analytic • Monte Carlo (randomizations) • Complexity is replaced by randomizations • Downtime • For the Tevatron, stacking, PBar Source, etc. • Real data: 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

  20. Complexity  Randomness • 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… • Model Assumptions • Performance does not improve • Random fluctuations around a specific set of parameters • Performance determined largely by these parameters • Better performance? Change parameters and run again. • No shutdown periods Elliott McCrory, Fermilab/AD

  21. Luminosity Characterization • One average proton & 36 antiprotons are tracked • Proton bunches are all the same • Recycler & Accumulator antiproton bunches 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 onL(0)and is adjusted to fit Real Data • C1= 3 ± 2 • C2 = f(C1) ≈ 0.5 Elliott McCrory, Fermilab/AD

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

  23. SDA

  24. SDA: Overloaded Acronymn • 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

  25. More relevant “clock” Shot/store number Today: store # 4440 Case Collider shot: 15 main cases Proton Injection Porch Proton Injection tune up Eject Protons Inject Protons Pbar Injection Porch Inject Pbars (Defunct) 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

  26. Sequenced Data Acquisition • Data collection abstraction • All types of data can be acquired • Implemented as a Java interface • SDA Database • Detailed information • 36 bunch data • Raw data from front ends • Indexed by Store Number • 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

  27. 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 • 224 columns for each store • http://www-bd.fnal.gov/sda/supertable Elliott McCrory, Fermilab/AD

  28. SDA Database Example Elliott McCrory, Fermilab/AD

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

  30. Supertable Example Elliott McCrory, Fermilab/AD

  31. SDA Examples Relevant to Model • Using Excel • Initial Luminosity versus Number of Antiprotons • Initial Luminosity versus Initial Luminosity Lifetime • Antiproton Emittances • Uncertainty at the IP • Beta-star changing?? • Extras • Lifetime fits • Record luminosity vs. record integrated luminosity? • Antiproton Burn Rate • Tevatron failure rate • Not strictly SDA Elliott McCrory, Fermilab/AD

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

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

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

  35. PBar Emittance at Extraction Real Emittances from Recycler Emittance Model generated Emittances Number of Antiprotons Removed [E10] Elliott McCrory, Fermilab/AD

  36. Luminosity Decay Fits EXTRA http://mccrory.fnal.gov/tevatronDecayFits • Three types of fits • e(-t/tau) over first 2 hours • e(-t/tau(t)) like in the model • 1/t Elliott McCrory, Fermilab/AD

  37. Fit results for Stores 4332 EXTRA L(t) = L(0) exp(-t/τ(t)) τ(t) = τ(0) + c1 × t c2 τ(t) Fourth best initial luminosity Second Place for Integrated Luminosity Elliott McCrory, Fermilab/AD

  38. Fit results for Stores 4332 & 4431 EXTRA World record Initial Luminosity, 1.43E32 Third Place for Integrated Luminosity Elliott McCrory, Fermilab/AD

  39. Antiproton Burn Rate EXTRA • Calculated numerically using fitted results • Removes data noise • Cut:χ2/DOF < 30 • (error bars fixed: 0.05E9) • Luminosity Burn Rate [Rlum(t)] • dN(A) / dt [E9 particles/hour] = −0.252 × (LCDF + LD0) [E30/cm2sec] • CDF & D0 Luminosities taken from SDA, • Assumptions: • Emittances, tunes, orbits, etc. are bunch independent (?!) • See Beamdocs # 1408 • http://beamdocs.fnal.gov Elliott McCrory, Fermilab/AD

  40. Summary: 9/36 Bunches in Store 3744 EXTRA Burn Rate [E9 pbars/hour] Non-Luminosity Burn Rate Luminosity Burn Rate Total Burn Rate Elliott McCrory, Fermilab/AD Hours into the Store

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

  42. 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

  43. 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

  44. Reliability of Tevatron Today • Tevatron is two machines • Low beta: Higher reliability •  ~ 0.988 • 20 hours: 0.785 • 30 hours: 0.696 • Injection and ramping: Lower reliability •  ~ 0.88 to 0.95 • Recovery time • Severe for superconducting machine • Classes of failures? • Beyond the scope of this talk! • ∴ Longer stores • Tevatron is more reliable in collisions Elliott McCrory, Fermilab/AD

  45. Model Details and Predictions

  46. 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

  47. Elliott McCrory, Fermilab/AD

  48. C++/Linux 800 weeks/minute On 1.8 GHz Celeron 220+ parameters 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 Over200 input parameters to a model run Output handler Lots of data files can be dumped Program Structure Elliott McCrory, Fermilab/AD

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

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