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Afterglow Studies Eric Torrence University of Oregon 183 nd LMTF Meeting 10 October 2013 Slide 2 Eric TorrenceSeptember 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 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 Slide 3 Eric TorrenceSeptember 2013 3 Fills Single-bunch templates r200804 - 2 bunches, ~20, first fill of 2012 r206717 - 1 bunch, ~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 Slide 4 Eric TorrenceSeptember 2013 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) Slide 5 Eric TorrenceSeptember 2013 5 BCMV single-bunch response r206717 - BcmVOR Single-bunch, high Peak = 1, used to normalize relative response Afterglow falls below noise level after ~500 BCIDs Colliding bunch Afterglow Noise Slide 6 Eric TorrenceSeptember 2013 6 BCMV single-bunch response r206717 - BcmVOR Single-bunch, high Averaged over many LBs Afterglow Reflections More plots in appendix... Slide 7 Eric TorrenceSeptember 2013 7 Stability over short time BCMV: http://physics.uoregon.edu/~torrence/BcmVOR.movhttp://physics.uoregon.edu/~torrence/BcmVOR.mov Lucid: http://physics.uoregon.edu/~torrence/r200804_LucORA.movcORA.mov Slide 8 Eric TorrenceSeptember 2013 8 Stability over long times r206717 r200804 BcmVOR ~ identical over x2 in mu and three months! Slide 9 Eric TorrenceSeptember 2013 9 Lucid HitOR r200804 No reflections Short-term falloff Similar mid-term slope Longer tail (or just lower noise?) Slide 10 Eric TorrenceSeptember 2013 10 Single-beam Templates r200804 BCM - 500 BCIDs to reach ~10 -7 level LucidHit - 1500 BCIDs to reach ~10 -7 level (ran into next bunch) Constant background subtracted from -100 BCIDs Slide 11 Eric TorrenceSeptember 2013 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 Slide 12 Eric TorrenceSeptember 2013 12 Maximum Lucid Hit afterglow Even with longer tail, less integral afterglow (no reflections) Asymptotic value 0.3% reached in ~300 BCIDs Slide 13 Eric TorrenceSeptember 2013 13 50 ns limits BCID-1 works for BCM in 2012! (coincidental, only for BcmV) Afterglow under collisions ~ 10 -3 Difference w/ BCID-1 ~ 1 x 10 -3 (worse in 2011) 0.4% is half of 25 ns limit (expected) colliding bcid 1 Slide 14 Eric TorrenceSeptember 2013 14 Realistic 25 ns fill pattern 14 25ns_2604b_2592_2288_2396_288bpi12inj.sch 2604 bunches colliding in P1/5 Mostly saturated (except at start-of-train) Slide 15 Eric TorrenceSeptember 2013 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 Slide 16 Eric TorrenceSeptember 2013 16 Example 6 colliding bunches (normalized response) 500 BCID template length constant term fit here Raw Luminosity After.+Bgd. Prediction Slide 17 Eric TorrenceSeptember 2013 17 Example Zoomed 6 colliding bunches rather excellent agreement between predicted and observed afterglow under collisions Slide 18 Eric TorrenceSeptember 2013 18 Lucid artifacts Finite Lucid template leads to (small) artifacts with few bunches 1500 BCIDs constant term fit here Slide 19 Eric TorrenceSeptember 2013 19 Lucid HitOR Prediction close to luminous bunches looks right on (high template, 28 tubes) Slide 20 Eric TorrenceSeptember 2013 20 Lucid - 50 ns fill Works fine with full fill pattern Remember: simple log formula applied, no mu dependence Slide 21 Eric TorrenceSeptember 2013 21 BcmV noise comparison During BCM noise period After BCM noise period