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Background characterization: MD plan. W. Kozanecki. MD goals Background sources & parametrization Operational procedures Open questions. MD goals. Characterize beam-current dependence of machine-induced backgrounds all BaBar ‘detectors’: SVT, DCH, EMC, DIRC, IFR + TRG, ODF

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background characterization md plan
Background characterization: MD plan

W. Kozanecki

  • MD goals
  • Background sources & parametrization
  • Operational procedures
  • Open questions
md goals
MD goals
  • Characterize beam-current dependence of
    • machine-induced backgrounds
      • all BaBar ‘detectors’: SVT, DCH, EMC, DIRC, IFR + TRG, ODF
      • dedicated background monitors (pins, CsI counters, collim. BLMs)
    • beam-beam performance (& backgrounds)
      • specific luminosity
      • vertical & horizontal spot sizes in LER & HER
      • loss rates @ collimators in PR12 (HER), PR04 + PR02 (LER)
proposed baseline parametrization
Proposed baseline parametrization

B = BP + BL + Bbb + BHbg + BLbg + BLHbg + BI [+ BLT]

= BP(from no-beam data)

+ dP * L (from colliding-beam data)

+ Bbb (IbL, IbH) (from colliding-beam data)

+ aH*IH + bH*IH2 + cH*IH4 (from single-beam HER data)

+ aL*IL + bL*IL2 + cL*IL4 (from single-beam LER data)

+ cLH * IL * IH (from 2-beam, non-colliding ?)

+ BI (differential, trickle – coasting ?)

[+ BLT] (LER only, vary VRF?)

proposed baseline parametrization1
Proposed baseline parametrization

B = BP + BL + Bbb + BHbg + BLbg + BLHbg + BI [+ BLT]

= BP(from no-beam data)

+ dP * L(from colliding-beam data)

+ Bbb (IbL, IbH) (from colliding-beam data)

+ aH*IH + bH*IH2 + cH*IH4 (from single-beam HER data)

+ aL*IL + bL*IL2 + cL*IL4 (from single-beam LER data)

+ cLH * IL * IH(from 2-beam, non-colliding ?)

+ BI(differential, trickle – coasting ?)

[+ BLT](LER only, vary VRF ?)

background characterization measurements

Data: Jan 04 (bef. therrmal outgassing crisis)

Background characterization measurements

Step 1: Beam-current scans

 single-beam terms

slide6

Data: Jan 04

  • Total occupancy
  • HER single beam
  • LER single beam
  • Beam-beam term
  • present in all subdetectors
  • reproducibility!

Step 2: L & beam-beam terms

EMC cluster multiplicity

SVT occupancy (FL1 M01-f)

proposed operational procedure general guidelines
Proposed operational procedure: general guidelines
  • BaBar taking data!
  • Perturb as adiabatically as possible
    • start with stable machine in delivery mode
    • avoid acrobatics (delivery  collisions bkg  pedestals  single-beam  non-colliding  pedestals)
  • At each current setting
    • optimize tunes
      • on luminosity (in collision, coasting so lifetime reasonable)
      • on lifetime (single beam, minimize Touschek for beam-gas measurement)
    • reset vertical IP angles in both rings
    • check SLM, SXM & interferometer settings
    • start a new run (also at trickle-coasting transition)
  • Pedestal runs
      • no beam
  • Reproducibilty: if beam(s) lost, redo last setting
time request
Time request
  • 2 components
    • setup & tuning: hard to estimate - make appropriate arrangements!
      • at least 5\' per setting when changing only 1 beam current (requires BaBar shifter "on the ball")
      • first setup, state changes & aborts more time-consuming (need MCC ops "on the ball")
    • Babar data taking
      • in 2004: 7\' per setting (no trickle), dominated by pin-diode stabilization needs
      • can we shorten it?
        • what do diamonds need?
        • what does data taking need?
        • what do pin diodes need?
  • From actual experience
    • in 2004:
      • planned 8h for data taking & BBR transitions only (w/o setup & mishaps)
      • used 16 h, but with more complicated procedure
    • 2006 request: comparable DAQ time  RQ 2 shifts (8:30 am - 12 am)
      • recovery should be easier than from an acc. phys. MD
to be clarified
To be clarified
  • Prerequisites
    • stabilized vacuum
      • in particular: is PR02 NEG 8020 really quiet ?
      • Babar encouraged to sample single-beam data whenever possible in the next few days (+ analyze it quickly)
    • ‘routine’ running in LER & HER with fulll RF complement
    • decent stored-beam & trickle backgrounds during preceding owl shift
  • Minimize data-taking time
    • diamond/diode settling time?
    • best trigger rmix to enhance background fraction ?
  • When (not) to trickle?
  • Need volunteer(s) to analyze data - incl. CsI & BLM!
proposed operational procedure colliding beam measurements
Proposed operational procedure: colliding beam measurements
  • Setup: save configs & orbits; check fbcks; change BBR L1 config.
  • Keep IL ~ constant, vary IH (> 0.25 A, 0.25 A steps)
    • 2 regimes (to help separate Lumi & beam-beam contributions)
      • IL ~ 1.6 A (60% of peak LER current, moderate beam-beam)
        • no trickle (coast during data taking, trickle LER back up while filling HER)
        • ~ 7’ steps (dominated by pin-diode stability?)
      • IL ~ 2.7 A (or max. LER current that can be sustained stably)
        • to measure trickle contribution differentially, for each HER current setting:
          • trickle LER + HER (~ 5’)
          • coast LER + HER (~ 5’)
  • Keep IH ~ constant, vary IL (> 0.30 A, 0.35 A steps)
    • 2 regimes (to help separate Lumi & beam-beam contributions)
      • IH ~ 1.0 A (60% of peak HER current, moderate beam-beam)
        • no trickle (coasting during data taking, trickle HER back up when filling LER)
      • IH ~ 1.6 A (or max. sustainable HER current, assuming full RF complement)
        • to measure trickle contribution differentially, for each LER current setting:
          • trickle LER + HER (~ 5’)
          • coast LER + HER (~ 5’)
  • Pedestal run
proposed operational procedure single beam measurements
Proposed operational procedure: single-beam measurements
  • Vary IH : 0.25-1.6 A, 0.25 A steps, no LEB
      • no trickle at low current, 7’ per setting
      • at topmost (or 2 topmost) HER current(s), trickle then coast (5+5\')
  • Vary IL : 0.3-2.7 A, 0.35 A steps, no HEB
      • no trickle at low current , 7’ per setting
      • at topmost (or 2 topmost) LER current(s), trickle then coast (5+5\')
  • Reproducibility check on single beam scans (esp. pins)
      • repeat middle & top points of previous two scans (HER, then LER)
  • Non-colliding scan (sparse)
    • Keep IH ~ constant (1.35 A), vary IL (> 0.30 A, 0.6 A steps)
    • Keep IL ~ constant (2.35 A), vary IH (> 0.25 A, 0.5 A steps)
    • Operational aspects
      • Separate beams: X = 2 * 1 mm, Y = 2 * 400 microns ?
      • 7’ per setting, no trickle (measure HEB lifetime change)
  • Pedestal run
total time estimates only data taking bbr on off 690
Total time estimates (ONLY data taking + BBR on-off): 690\'
  • Setup 15’
  • Collision scan @ fixed LER current 160’
    • IL = 1600 mA, vary IH 7 x 10’
    • IL = 2700 mA , vary IH 7 x 13’
  • Collision scan @ fixed HER current 190’
    • IH = 1000 mA , vary IL 8 x 10’
    • IH = 1600 mA , vary IL 8 x 13’
  • Pedestals 5’
  • HER single-beam scan 5 x 10’ + 2 x 13\' 80’
  • LER single-beam scan 6 x 10’ + 2 x 13\' 90’
  • Repeat middle & top points of single-beam scans (H, L) 50’
  • Non-colliding scans 90’
    • IH = 1350 mA , vary IL 5 x 10’
    • IL = 2350 mA , vary IH 4 x 10’
  • Pedestals 5’
background sources
Background sources
  • Luminosity (radiative-Bhabha debris) – major concern (DCH future)
    • BP ~ dP * L (strictly linear with L)
  • Beam-beam tails
    • from LER tails: BL, bb ~ bL,bb*IL + fL(xL,H+/-)
    • from HER tails: BH, bb ~ bH,bb*IH + fH(xL,H+/-)
  • Beam-gas (bremsstrahlung + Coulomb)
    • HEB only: BHbg ~ aH*IH + bH*IH2 (aH , bH > 0)
    • LEB only: BLbg ~ aL*IL + bL*IL2 (aL , bL > 0)
    • beam-gas cross term: BLHbg ~ cLH * IL * IH (LEB+HEB, out of collision)
  • BI: LER injection (trickle) background
  • BLT (exp. signature somewhat similar to bremsstrahlung)
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