Afterglow Studies

1. Afterglow Studies Eric Torrence University of Oregon 183nd LMTF Meeting 10 October 2013

2. Overview • Test afterglow model by single-bunch addition • Originally studied by Mika • Will need to be used for 25 ns operations • Try to test assumptions in method • Afterglow is universal with time and μ • Afterglow is additive to the prompt luminosity signal(not true if there are migration effects) • Look at expected afterglow levels in 2015(using 2012 templates) • Look at 2012 25 ns fills

3. Fills • Single-bunch templates • r200804 - 2 bunches, μ~20, first fill of 2012 • r206717 - 1 bunch, μ~50, high-mu test • Test runs • r212529 - 6 bunches in mini-train • r214651 - 50 ns physics fill - during BCM noise period • r215541 - 50 ns physics fill - after BCM noise period • r216399 - 25 ns fill - 97 bunches • r216432 - 25 ns fill - 373 bunches Large range in mu, 3 months apart

4. Details • Looked only at OR algorithms (simpler), mainly: • BcmH_EventOR • BcmV_EventOR • Lucid_HitOR • No absolute calibrations applied, everything scaled to some relative luminosity • Simple log formulas, no complicated Lucid mu dependence L = -ln(1-Rate)

5. BCMV single-bunch response r206717 - BcmVOR Colliding bunch Afterglow Noise Single-bunch, high μ Peak = 1, used to normalize relative response Afterglow falls below noiselevel after ~500 BCIDs

6. BCMV single-bunch response r206717 - BcmVOR Afterglow Reflections Single-bunch, high μ Averaged over many LBs More plots in appendix...

7. Stability over short time BCMV: http://physics.uoregon.edu/~torrence/BcmVOR.mov Lucid: http://physics.uoregon.edu/~torrence/r200804_LucORA.mov

8. Stability over long times BcmVOR r206717 r200804 ~ identical over x2 in muand three months!

9. Lucid HitOR r200804 No reflections Short-term falloff Similar mid-term slope Longer tail (or just lower noise?)

10. Single-beam Templates BCM - 500 BCIDsto reach ~10-7 level r200804 LucidHit - 1500 BCIDsto reach ~10-7 level(ran into next bunch) Constant background subtracted from -100 BCIDs

11. Maximum BCM afterglow Just add 500 copies of this template (without peak), each shifted by 1 BCID Asymptotic value 0.8% reached in ~200 BCIDs

12. Maximum Lucid Hit afterglow Even with longer tail, less ‘integral’ afterglow (no reflections) Asymptotic value 0.3% reached in ~300 BCIDs

13. 50 ns limits 0.4% is half of 25 ns limit (expected) BCID-1 worksfor BCM in 2012! (coincidental,only for BcmV) Afterglow under collisions ~ 10-3 Difference w/ BCID-1 ~ 1 x 10-3(worse in 2011) bcid ± 1 colliding

14. Realistic 25 ns fill pattern 2604 bunches colliding in P1/5 Mostly saturated(except at start-of-train) 25ns_2604b_2592_2288_2396_288bpi12inj.sch 14

15. Data subtraction procedure (per LB) • Start with raw luminosity by BCID for each lumi block • Identify colliding bunches, and divide out average colliding luminosity from full distribution • not strictly necessary, but useful for averaging over LBs • also avoids need for calibration, everything relative... • Build model of afterglow by adding up templates, one template per collision BCID, weighted by relative lumi • Subtract this afterglow from raw luminosity in all BCIDs • Iterate if desired (practically makes little effect) • Measure residual background in abort gap (last 50 BCIDs) • Subtract background as well to produce corrected lumi

16. Example 6 colliding bunches (normalized response) Raw Luminosity After.+Bgd. Prediction constant term ‘fit’ here 500 BCIDtemplate length

17. Example Zoomed 6 colliding bunches under collisions rather excellent agreement between predicted and observed afterglow

18. Lucid artifacts constant term ‘fit’ here 1500 BCIDs Finite Lucid template leads to (small)artifacts with few bunches

19. Lucid HitOR Prediction close to luminous bunches looks right on (high μ template, 28 tubes)

20. Lucid - 50 ns fill Works fine withfull fill pattern Remember: simple logformula applied, no mu dependence

21. BcmV noise comparison During BCM noise period << 10-3 discrepancies After BCM noise period

22. 25 ns runs Can’t prove afterglow under collisions is correct, but procedure seems to work fine

23. 25 ns runs Can’t prove afterglow under collisions is correct, but procedure seems to work fine Same train length and gap expected in 2015

24. Lucid reduced HV Lucid ran with reduced HV for most runs from r215433, includes all 25 ns runs Template clearly not accurate

25. Lucid reduced HV 2 Scale up fast component (BCID+1, 2) by ~30% Seems to work fine!

26. 25 ns Lucid Hit OR slight mismatch normalized background error Use scaled template to look at 25 ns Lucid data Much larger afterglow (~2%) due to HV settings

27. 25 ns comparison Compare afterglow-subtractedrelative luminosity collisions only Shape looks familiar, butmagnitude is larger...

28. 50 ns comparison Similar to Benedetto’s plots? Remember, no complicated Lucid corrections, just log formula 28

29. Trigger Counters • Special-purpose counters to look at 6 L1 items before and after veto to study deadtime by BCID • Can try to use before veto as a proxy for luminosity • Triggers available • Counter 0 is trigger 93 L1_MU11 • Counter 1 is trigger 85 L1_EM30 • Counter 2 is trigger 102 L1_J50 • Counter 3 is trigger 128 L1_FJ75 • Counter 4 is trigger 118 L1_XE50 • Counter 5 is trigger 97 L1_J10 • Must be skeptical, many trigger-related issues with bunch train position... • Trigger rates ~1% error per BCID (over many LBs) Most linear with lumi

30. 50 ns run L1_EM30 L1_MU11 L1_MU11 low at start of train (retriggering?) L1_EM30 rises in early train (calo noise?)

31. 50 ns run L1_EM30 Now referenced to Lucid, L1_MU11 looks pretty OK...

32. 25 ns run Back end of bunch train seems to be more consistent with BcmV

33. 25 ns run Really had to draw any conclusions from this

34. Conclusions • Single-bunch template method seems to work for 2012 • Templates quite universal over all 2012 • Afterglow error using BCID-1 appears smaller than 2011for BcmVOR • No evidence of anything weird in BCM noise period • 25 ns data shows larger (as expected) but manageable afterglow levels, Lucid larger due to HV settings • First look at Lucid/BCM ratios is rather alarming, but probably lots to understand here • Trigger rates don’t seem to help

35. Appendix A Single-bunch plots Run 200804 2 bunches, μ ~ 20

36. Lucid Hit OR

37. Lucid OR

38. Lucid OR A

39. Lucid OR C

40. Lucid AND Raw rate only!

41. BcmH OR

42. BcmV OR

43. BcmH OR A From Rates: A + C = OR + AND

44. BcmV OR A From Rates: A + C = OR + AND

45. BcmH OR C

46. BcmV OR C

47. Appendix A Single-bunch plots Run 206717 1 bunch, μ ~ 40

48. Lucid Hit OR

49. Lucid AND Raw rate only!

50. BcmH OR