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Central Fiber Tracker Light Guide Performance

Central Fiber Tracker Light Guide Performance. Thomas Nunnemann Fermilab 90 days before RunII … (a.k.a. 12/01/00). Optical Readout of Scintillating Fibers. Light Yield and Trigger Efficiency. discrimination of signal from Visual Light Photon Counters (VLPC) with SIFT chip:

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Central Fiber Tracker Light Guide Performance

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  1. Central Fiber Tracker Light Guide Performance Thomas Nunnemann Fermilab 90 days before RunII … (a.k.a. 12/01/00)

  2. Optical Readout of Scintillating Fibers

  3. Light Yield and Trigger Efficiency • discrimination of signal from Visual Light Photon Counters (VLPC) with SIFT chip: • provides trigger information • threshold of 1 photo electron (p.e.) signal anticipated (mayor challenge) • average p.e. yield measured in Lab3 cosmic ray test: 7 p.e. (with 11m light guide) • contribution of 0 p.e. and 1 p.e. peak (Poisson), i.e. inefficiency of single layer at threshold of 1.5 p.e • 7 p.e. average: 0.7% • 5 p.e. average: 4.0% • Note: CFT has doublet layers! • We cannot afford any additional light attenuation! Optical transmission from SciFi to VLPC has to be optimal!

  4. CTT Single Track Efficiencies • Central Track Trigger (CTT) requires a hit in all 8 axial CFT layers (8 out of 8) • for highest p-t bin (p-t > 10 GeV): 7 out of 8 • MC simulation based on 7 p.e. yield, not including compromised fibers (Alan Bross): (-0.5<h<0.5) But: Hit efficiency (doublet layer) in cosmic ray test was estimated to be approx. 98% (Brian Smith). Additional inefficiencies in CR test? Some naïve estimates:

  5. 152 Light Guides on Each Side of CFT Light guide with curved connector CFT installed in central cryostat

  6. Light Guide Routing 1 VLPC CRYOSTAT FORWARD DETECTORS ECS INSTALLATION FORWARD PRE-SHOWER SEPT 98 ICD LEVEL ZERO WAVE GUIDE FIBER BUNDLE INSTALLATION CFW CFE TRACKER CENTER CABLING SLOT BEAM WAVE GUIDE PATCH PANEL VLPC CASSETTE VLPC CASSETTE VLPC CRYOSTAT VLPC CRYOSTAT SILICON TRACKER POWER SUPPLIES 2-FRONT

  7. Light Guide Routing 2

  8. Light Guide Routing 3

  9. Light Guide Testing 1 • Scintillating fibers can be illuminated with LED panels. • Each ribbon (256 fibers) is covered by 3 panels on both ends respectively. • LED panel designed for calibration purpose (no absolute calibration possible, coupling LED panel – SciFi non-uniform and unknown) • provides a measurement of light attenuation (LG quality) Photo peaks in the ADC spectrum of single fibers: Poisson fit (smeared by Gaussians) provides a measure of the average p.e. yield for a fiber channel (scintillating fiber + clear fiber + VLPC chip [quantum efficiency]). p.e. yield with LED system: 0.5–2.5 p.e. depends on light coupling into scint. fibers

  10. Light Guide Testing 2 • CFT Front-End: 4 production cassettes, any 2 integrated in the read-out (limited by electronics) • LED pulser data taken with primary DAQ (L3) • CFT is currently primary DAQ user • hundreds of runs with millions of events • provides thorough test of DAQ and data logging system • online/offline analysis using examine and stand-alone kumac/fortran code • online: direct feedback to installation team • mapping SVX channels – fibers not provided in DØ offline framework (stereo boards) • LG are tested with 2-3 different LED settings. • provides a partial cancelation of LED panel effects • P.e. yield can be determined with 7% accuracy on average. • But non-uniform coupling LED panel – SciFi can fake losses. • classification of LGs based on uniformity of p.e. yield distributions • can be compared to ribbon and LG QC with radio-active source (Lab3)

  11. QC: Light Guide with Uniform Response dead electronics LED panel edge LED panel edge

  12. QC: Light Guide with Crack Structure The worst LG so far! Even-odd structure indicates crack in curved connector in between doublet layer. To minimize cracks curved connectors (LG to ribbon) are now glued with temporary clamps. Glue is strong enough to stop evolution of cracks (tested independently).

  13. CFT Curved Connector

  14. QC Summary: LG on Axial Ribbons • Problematic LGs were detected during QC: • easy: wrong labels, wrong pinning of connectors coupled to cassettes • severe: several LG reglued, 5 LG entirely replaced (cracks) • Classification of the 152 LG (axial side), multiple class. allowed: • low gain means < approx. 75%, LED effects not entirely cancelled, performance of whole system including scintillating fibers • good uniformity: 43 • edge fibers with low gain: 25 • drop at edge (<20%): 30 • drop at edge (>20%): 16 • Indication of crack: 17 • several (>3) low gain fibers: 9 • structure (period 32): 21 • bad: 1 (shown in QC example) • marginal: 20

  15. QC Summary: LG on Stereo Ribbons • 82 out of 152 LG installed and glued, QC completed for 69 LG • On average LGs on stereo side have a better performance than those on axial side: • due to less handling? initial routing now close to final route • only 1 replacement candidate up to now • Ironically optimal performance is much more crucial for LGs on axial side, since stereo layers are not included in CTT. • Installation and QC anticipated to be finished 12/11 • 2 additional checkouts of optical/electronic read-out system needed before RunII • after LG connection to final cassette • after installation of AFE boards • What I haven’t mentioned: • only limited QC of CPS LGs possible due to non-uniform LED response (by design to account for large dynamic range) • FPS LGs not yet produced

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