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Giovanni Petri University of Pisa/INFN Pisa/SLAC 29 August 2005

Study of TEM errors. Giovanni Petri University of Pisa/INFN Pisa/SLAC 29 August 2005. Lost in Translation. Introduction. Can the LAT produce errors during data acquisition? Choice of Error Type How often does it happen? Under what condition does it happen ?

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Giovanni Petri University of Pisa/INFN Pisa/SLAC 29 August 2005

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  1. Study of TEM errors Giovanni Petri University of Pisa/INFN Pisa/SLAC 29 August 2005

  2. Lost in Translation Introduction • Can the LAT produce errors during data acquisition? • Choice of Error Type • How often does it happen? • Under what condition does it happen? • What is the impact of these Errors on-orbit?

  3. How does it happen??? A particle hits the tower Tracker Readout starts from the BOTTOM!!! Trigger Primitives fired by subsystems TEM collects them, checks 3-in-a-row and (if TKR triggers) sends it to GEM Calorimeter GEM opens window on first trigger type and waits for others to arrive (Coincidence Window) Tower Electronic Module After few ticks CW closes and TAM is sent back to the readout controller to start readout Glt Electronics Module Tower Subsystems Overview

  4. 1 cable stores up to 128 hits 8 cables per Tower 128 x 8 = 1024 hits per tower Other Buffer Limits: Readout controller: max of 64 hits allowed Plane: max of 128 hits allowed (64x2) How: Cosmic showers e.g. Let’s call an event with FIFO error “BAD” TEM CC FIFO Error Si Planes Cables Tracker Sketch FIFO Definition

  5. 2 Towers Runs: # Runs: 48 (all!!) # Register Config: 19 # Events: 9,564,116 # Bad Events: 915 4 Towers Runs: # Runs: 31 (B type) # Register Config: 2 # Events: 1,084,655 # Bad Events: 93 How Often? Statistics Summary • 6 Towers Runs: • # Runs: 62 (B type) • # Register Config: 3 • # Events: 15,346,394 • # Bad Events: 1760 • 8 Towers Runs: • # Runs: 81 (B type) • # Register Config: 3 • # Events: 22,391,000 • # Bad Events: 2900

  6. Error Rates for B type Runs: 2 Towers: 7.4 · 10-5 B2: 8.3 · 10-5 B10: 7.1 · 10-5 B13: 7.5 · 10-5 4 Towers: 8.66 · 10-5 B10: 8.40 · 10-5 B13: 8.79 · 10-5 6 Towers: 1.13 · 10-4 B2: 1,15 · 10-4 B10: 1.09 · 10-4 B13: 1.20 · 10-4 Among 2 Towers runs (not B type) 135002057-2103 Single RC Right/Left ER 2 · 10-4 135002166-2168 Single RC R/L + Overlay 10 KHz 2,1/2,7 · 10-4 135002107 Only Cal Trigger 5.9· 10-3 What’s that? 2 orders of magnitude? How Often? Bad Events Rates B2: Flight Settings B10: Cal 4 range B13: Zero Suppression OFF Can we explain this?

  7. RC on one side only: Max hits per plane is 64 RC try to read its entire plane! An event that had 70 hits on a plane now saturates the plane! It’s easier to have more hits on the same Cable!! 30 40 Single RC ER Anomaly 70 Planes • The factor 2-3 of difference is not so strange!! • This can be a first order explanation!! Cables

  8. CAL LE has more probability to be triggered by high energy events. Energetic events have more probably high hits occupancy Is it enough to explain the big difference? No other runs to compare rates!! The run has few events: 3000 instead of 300,000! NOT STRANGE!! • ER = 5.9· 10-3 • We can REPRODUCE that!!! • Cut on CAL LE triggered Events!! BUT... What comes out is ER ~ 3.6 · 10-3!!! Do you believe me? Cal Only Trigger Anomaly • # Events: 3048 • # Bad Events:18

  9. Which primitive triggers are there? GemConditionsWord When do they arrive? Are there temporal patterns? Is a Bad Event influenced by the previous one? GemDeltaEventTime How are hits distributed? Are there odd configurations? You understand “odd” later Stay tuned… When do Bad Events happen to good people? Bad Events Topology!! Trigger Hits Occupancy You clearly recognize Eduardo when he’s been working late in the night

  10. Good Bad Trigger Topology B10 runs 2 towers • GemConditionsWord: • Tells which primitive triggers arrived in the CW • Possible combinations: • TKR (2) • CAL LE (4) • CAL HE (8) • TKR + CAL LE (6) • TKR + CAL HE (10) • CAL LE + CAL HE (12) • TKR + both CAL (14) • No 8s, 10s, 12s: • This was expected!! • Bad Events are “big”! • High Multiplicity Trigger Types

  11. Chained B10 runs 2 towers 1 tick = 50 ns ~80% TKR arrives soon!!! This is no surprise! The number of events goes down very rapidly!! Ticks • We expect that the TKR often arrives first! • TKR is big: high probability to • trigger first Trigger Topology Trigger Primitives Arrival Times

  12. Ticks Ticks Trigger Primitives Timing Trigger Topology • CAL LE should open when TKR is not the first: • CAL LE is faster than CAL HE! • # Times CAL LE opens CW is consistent!! 3 events This is odd!! Explanation??? Just a case? Remember Log Scale

  13. Temporal Correlations Trigger Topology The time between a Bad Event and the previous one is long!! The minimum Delta Time is longer than for Good events Just low statistics probably Bad Good 2000 ticks 1000 ticks

  14. Drittoni (big straight) “Recognizable track” Event Display Hits Occupancy Salt and Pepper 25% 50% Hits everywhere Cal lit up where “track” arrives Hits only in upper layers Cliffhanger No Cal 20%

  15. Puffettae Hits Occupancy Evt 135002052-268476 • Qualitatively: you can distinguish the single layers, one by one, from the other. • Hits are only on the borders and are uniformely distributed. Characteristic signature: everything’s FULL Readout Controllers Cables

  16. Puffettae • There is a Puffetta in 6 Towers Runs too!! • None found in 4 and 8 towers runs • It looks exactly the same as the 2 towers one. 135004119-115100

  17. Looking at Dumps you find this: 0040 (hex) = 64 (dec) For every single RC above 1 on every CC. 8 1 2 LDF Dump file Puffettae Dumps

  18. 2 Towers 6 Towers Are these energies consistent with showers that big? There is no obvious hint of electronics gone wild!! • Delta Times are long • GemDiscarded seems reasonable (TOT very long) Puffettae Data

  19. From Russia with… CAL! Energy (GeV) Asimmetry Layers Too good to be true!!!! CAL says: “Everything normal pal!! Just big shower!!”

  20. For Ep=105 GeV (for consistency with the observed rate) 350 GeV measured All strips hit ⇒ 104 particles in 6 towers 350GeV/10000 = 35 MeV per particle p 6 towers LAT • At sea level we see 10% of Ep (Tune) • From graph 106 e- at sealevel (Tune) High multiplicity shower of 10 MeV e- 10 MeV particles don’t go through the TKR!!

  21. There will be high-energy photons!! Will these be high multiplicity events in the TKR? Let’s see what MC has to say about this!! Used photons coming from 45°-60° from the vertical axis Energy of 300 GeV Searching for behaviours like those observed in FIFO errors Backsplash? 300 GeV What happens on-orbit? Total # MC photons 105 # Triggered Events 13006 #1 Towers Saturated: 38 NO PUFFETTAE!!

  22. Conclusions • The TKR works (poor me…) too well!! • FIFO errors are no mistery anymore!! • We know how to characterize AND understand them! • Rates are low: • 1 (lonely) bad guy every 100 thousands!!!! • No influence on other events!!! • Bad Events are consistent with showers • High energy photons MC needs to be further studied • What about reducing lower layers buffer bandwidth to improve recon??

  23. HIM ME Eduardo do Couto e Silva Favorite saying: THIS IS TOO COOL!!!! Anders Borgland TACK Favorite saying: “I told you NOT my Camaro!! Now I’m angry…” High energy Muon shower …trying to sneak home early… 1 AM…

  24. BACKUP SLIDES…hic sunt leones…

  25. EM Showers To be in the core area 3.14x4202=5.5x105 m2 Freq = 2 x 10-2/s(~4-8 e/ m2) To be in a 10 times denser area Freq ~ 2 x 10-3/s(~40-80 e/ m2) To be in a 100 times denser area Freq ~ 2 x 10-4/s(~400-800 e/ m2) 107 Gev To be in the core area 3.14x4202=5.5x105 m2 Freq = 2 x 10-4/s(~40-80 e/ m2) To be in a 10 times denser area Freq ~ 2 x 10-5/s(~400-800 e/ m2) To be in a 100 times denser area Freq ~ 2 x 10-6/s(~4000-8000 e/ m2) 108 Gev • Need ~ 104 particles • Total Energy ~ 350 GeV • <Ep> ~ 35 MeV • Let’s say initial total energy was 105-106 GeV • We get at sealevel ~ 106 particles • Assume for such initial energy, Freq ~ 2 x 10-4/s • The 6 tower data acquisition lasted ~ 1 day ~ 16 Puffettae (or like)

  26. Is this consistent with Showers? Saturated tower: > 64 hits on each of the 4 bottom planes (both on x and y) =

  27. V.H.E. Cosmic Rays and Air Shower Profile proton Observation Step 1) Read off the flux of 107GeV proton rate Take a proton with Ep=107GeV=1016eV Flux is 6.8/E1.75per cm2, second, steradian and bin-width of E where E= 107GeV. We then get, Flux(Ep=107GeV)=3.8x10-12 /cm2/s/sr for a bin-width of 107GeV Step 2) Estimate the lateral distr. of particles Normalized density of 10-2 /X2 = 10-2 /(30m)2 X=Rad. length of atmosphere=36g/cm2=30m Distance from the core is about 14X = 420m

  28. Electron Component in Hadronic Shower Ne/E0 [1/GeV] For a 107GeV proton we get Number of e = 0.2x107 = 2x106 Step 3) Estimate the number of electrons in a 107GeV air shower at sea level. These are shower measured profiles for 105GeV proton. Since there is no measurement for 107GeV, we assume one sample profile from these. This gives highest number of electrons at sea level: use as an upper limit.

  29. Electrons and Gammas within an EM Shower Step 4) Calculate electron density per m2 From Step 3)Total number of electrons = 2x106 electrons From Step 2)Assume they are distributed uniformly in r=14X=420m of the core. Electron density is then 1.8x10-6 (1/m2) times 2x106= 3.6/m2 Uncertainty: a) Fluctuation: Trade-off with frequency. Can give a factor of 10-100? b) Low critical energy for LAT? Ec=10MeV > 1.5MeV: afactor of 2? (see Figure) Step 5) Calculate frequency: From Step 1)3.8x10-12 /cm2/s/sr From Step 2)core radius=14X=420m To be in the core area 3.14x4202=5.5x105 m2 Freq = 2 x 10-2/s(~4-8 e/ m2) To be in a 10 times denser area Freq ~ 2 x 10-3/s(~40-80 e/ m2) To be in a 100 times denser area Freq ~ 2 x 10-4/s(~400-800 e/ m2)

  30. Horizontal Air Shower? (1/2) Ref: S. Mikamo et al., ICR-Report-100-82-3 (1982) [Spires]; Lett. Nuovo Cimento 34 (1982) 273 Ordinary air shower initiated by protons and nuclei lose ~all energy for zenith ang. >50 deg. A different population “hirizontal” shower has been detected. If LAT is hit horizontally the electron multiplicity can be much lower. Step 6) Take horizontal air showers with Ne>104 Intensity = 2 x 10-13 /cm2/s/ster (see the right fig.) Likely zenith angle = 65, 75, 85 deg. (see the fig. in the next slide.) Overburden=1kg/cos(65,75,85deg)=2.4, 3.9, 11.5 kg = 67, 108, 319 X (the shower hist. may be shorter.) Typical lateral size: assume to be half the detector size of the Akeno exp. > radius=20m

  31. Horizontal Air Shower? (2/2) Ref: S. Mikamo et al., ICR-Report-100-82-3 (1982) [Spires]; Lett. Nuovo Cimento 34 (1982) 273 Step 7) Calculate frequency and electron density Core area = 1250m2 Electron density = >104/1250 = >8/m2 Freq = 2.5x10-6/s/sr To be in the core area (1250m2) Freq ~ 2.5 x 10-6/s(>8 e/ m2) To be in a 10 times denser area Freq ~ Prob. of 10 fold fluct. x 2.5 x 10-7/s(>80 e/ m2)

  32. Conclusion 1)Frequency of LAT being within the core radius (~420m for 107GeV) is high (~1/min) but average electron density is only ~4-8/m2. 2) Electron density probably fluctuate as much as 100 times, but the product of frequency and multiplicity remains constant for a given shower energy. Freq ~ 2 x 10-2/s(~4-8 e/m2) Freq (x 10) ~ prob. of 10 fold fluct. x 2 x 10-3/s(~40-80 e/m2) Freq (x 100) ~ prob. of 100 fold fluct. x 2 x 10-4/s(~400-800 e/m2) 3)Guestimatefor 108GeV protons: Frequency 1/100, multi. is 10 times. Freq ~ 2 x 10-3/s2 x 10-4/s(~40-80 e/m2) Freq ~ prob. of 10 fold fluct. x 2 x 10-5/s(~400-800 e/m2) Freq ~ prob. of 100 fold fluct. x 2 x 10-6/s(~4000-8000 e/m2) 4) Horizontal showers are likely to produce high multiplicity events than normal showers.

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