M. WeaverPEP-II MAC Review, Dec 04  Operational issues  radiation aborts  radiation-dose and background monitoring  Background characterization  characterization experiments  long-term projections & vulnerabilities  Simulations  G4 development status  collimation studies  Other background developments Machine-Detector Interface (MDI) report Presented by M. Weaver, SLAC

M. WeaverPEP-II MAC Review, Dec 04 Run-4 radiation-abort history B. Petersen ~ 1.7/day (Sep 03-Jul 04) ~ 0.6/day, 1-31 Jul 04

M. WeaverPEP-II MAC Review, Dec 04 Run-4 radiation-abort history Run-4 radiation-abort history (cont’d) Since 1 March /332 = 52% sympathetic aborts ~ 1/day...but ~ ½ of these are probably sympathetic! B. Petersen L. Piemontese / S. Foulkes

M. WeaverPEP-II MAC Review, Dec 04 Run-4 radiation-dose history HER trickle starts Outgassing storms B. Petersen Vacuum valve ROD increase probably instrumental

M. WeaverPEP-II MAC Review, Dec 04 Injection- & trickle- background history EMC trigs (always on) LER trickle EMC trigs (always on) HER trickle DCH trigs LER trickle DCH trigs HER trickle Monitor using injection-gated triggers (1  s x 15 ms) HER injection-quality monitor LER LER injection-quality monitor

M. WeaverPEP-II MAC Review, Dec 04 Stored-beam background history SVT  =  (LEB-sensitive) 20% DCH current normalized to Jan 04 background data I DCH, msrd/pred 10% 04 DCH ocp’cy DCH L1 rate Dead time HEB sensitive

M. WeaverPEP-II MAC Review, Dec 04 Background sources in PEP-II  Synchrotron radiation  Synchrotron radiation (this bkg negligible in PEP-II, but not in KEKB)  Beam-gas (bremsstrahlung + Coulomb)  HEB only: B Hbg ~ I H * (p H 0 + P H Dyn * I H ) Note: p 0 = f(T) !  LEB only: B Lbg ~ I L * (p L 0 + P L Dyn * I L ) Note: p 0 = f(T) !  beam-gas x- term: B LHbg ~ c LH * I L * I H (LEB+HEB, out of collision) (?)  Luminosity (radiative-Bhabha debris) – major concern as L   B P ~ d P * L (strictly linear with L)  Beam-beam tails  from LER tails: B L, bb ~ I L * f L (  L,H +/- )  from HER tails: B H, bb ~ I H * f H (  L,H +/- )  Trickle background: B Li, B Hi  Trickle background: B Li, B Hi (injected-beam quality/orbit + beam-beam)  Touschek: B LT  Touschek: B LT (signature somewhat similar to bremstrahlung; so far small)

M. WeaverPEP-II MAC Review, Dec 04 Background characterization measurements Step 1: Beam-current scans  single-beam terms Data: Jan 04 (bef. therrmal outgassing crisis)

M. WeaverPEP-II MAC Review, Dec 04 SVT occupancy (FL1 M01-  ) EMC cluster multiplicity Beam-beam term present in all subdetectors fluctuations, short - & long-term  parametrization optimistic ? Step 2: L & beam-beam terms Total occupancy -HER single beam - LER single beam

M. WeaverPEP-II MAC Review, Dec 04 Step 3: Background Parametrizations  DCH example: total current & occupancies Step 4: Background Extrapolations I DCH = PEP-II parameter projections Tracking efficiency drops by roughly 1% per 3% occupancy DCH LER contribution very small 60 L

M. WeaverPEP-II MAC Review, Dec 04 DCH + TRG When combined, higher trigger rates and long read-out time leads to unacceptable deadtime, driven by the DCH 3-step strategy  DCZ trigger (ready)  Waveform decimation (was implemented Summer ’04)  DCH DAQ upgrade (Summer 05) +DCZ

M. WeaverPEP-II MAC Review, Dec 04 LER  It has been realized that in the SVT (but not in other subdetectors), a large fraction of the “Luminosity” background is most likely due to a HER-LER beam-gas X-term (but: similar extrap’ltn). SVT Integrated dose will be more than 1 Mrad/year by 2007 Backward: Forward: TopEastWestBottom TopEastWestBottom NOW Background now is ~75% HEB [LEB negligible (!)] In 2007, it will be 50% HER, 50% L Background strongly  - dependent By 2007 predict 80% chip occupancy right in MID-plane In layer 1, 10% will be above 20% occupancy

M. WeaverPEP-II MAC Review, Dec 04  Given that future backgrounds have serious implications for detector performance, can anything be done to mitigate them?  Beam-gas backgrounds : manage residual gas pressure  Luminosity backgrounds : learn how to shield  Beam-beam backgrounds : learn how to collimate  How will the IR upgrade affect each of these?  Need to turn to simulation to improve our understanding and test mitigation strategies.

M. WeaverPEP-II MAC Review, Dec 04 Evolution of HER single-beam background, B Petersen N. Barlow M. Cristinziani/T. Glanzman J. Malcles Jan 2004 Apr 2004 Feb 2002 SVT occupancy Jan 2004 EMC clusters Apr 2004 Regularly activating NEGs & TSPs does help ! We should continue to take advantage of single beam opportunities to monitor the background.

M. WeaverPEP-II MAC Review, Dec 04 Turtle Simulation : e + e -  e + e -  Background M. Sullivan P. Roudeau, A. Stocchi, W.K. (preliminary) 10 9 L = z (m)

M. WeaverPEP-II MAC Review, Dec 04 EMC default digi map: luminosity background (N. Barlow) W FwdBkwd  index E E  index Electromagnetic shower debris or…

M. WeaverPEP-II MAC Review, Dec 04 Neutrons J. Va’vra Measurements appear consistent with Turtle radiative Bhabha simulation + GDR cross sections. Projected neutron rates may affect detector electronics – depends upon neutron energy spectrum.

M. WeaverPEP-II MAC Review, Dec 04 Turtle Level Simulations Beam-gas background from the HER (and LER) Where do scattered e - hit? Where do scattered e - come from ? R. Barlow

M. WeaverPEP-II MAC Review, Dec 04  Determining detector response requires Geant level simulation  Beam line up to Q5 implemented in Geant4 simulation of BaBar detector  Considering re-implementation for robustness but carrying on w/o  Added e-N,  -N and neutron transport to physics processes  Detector background analyses integrated for data and simulation alike  First full G4 simulation output of 2004 geometry recently available  Single beam background comparisons look good (normalization?)  Post-2005 configuration (IR upgrade) Turtle not ready Q2 Q4 Q5 B1 Q1 Geant4 Simulations

M. WeaverPEP-II MAC Review, Dec 04 Z location where particles are lost. Colors correspond to upper plot. Starting x, x’ coordinates of particles lost along the beamline. x/  x x’/  x; Z [m] IP Beam-Beam Collimation Study Large X-Emittance: Phase Space Plot

M. WeaverPEP-II MAC Review, Dec m from IP LER m from IP X [mm] xxxx  x [m]  x [2  ] +25 m m Results are based on an older LER deck (’98) with a tune of 0.57 (in x).

M. WeaverPEP-II MAC Review, Dec 04 Beam-beam collimation study: summary  Large-amplitude, horizontal b-tron tails originating at the IP can be effectively curtailed at + 25 m ...at least in the simulation  basically because of the phase-advance relationships reduce this to a one- turn problem, and assuming the impact on LEB lifetime remains manageable.  This study should be redone with the new LER deck & current x-tune of  Vertical tails are not an issue (in the LER)  Pre-trickle collimator-scan data remain to be analyzed.  However, the +25 m collimator  can’t replace existing PR04 collimators in some corners of phase space  provides no protection against Coulomb scatters between PR04 and PR02  Both horizontal and vertical b-tron tails will be studied for the HER

M. WeaverPEP-II MAC Review, Dec 04  Major background source: thermally-enhanced beam-gas  in incoming LER straight  Sensitive to LER current; several time constants in a time-dependent mix  Action: removed several NEGs and collimator jaws  Pressure at low currents may be worse now, but less susceptible to heating   SVT dose + occupancy (E-MID); minor impact on dead time  in incoming HER straight  sensitive to HER current, very long time constants   BaBar dead time + SVT occupancy (W-MID)  in (or very close to) the shared IR vacuum system  sensitive to both beam currents; at least 2 time constants  suspect: NEG + complicated IR ‘cavity’ (Q2L  Q2R) + HOM interference   BaBar dead time + SVT occupancy (W-MID + E-MID)  HOM dominant heating mechanism  mostly long to very long time constants (30’-3 h): suggests low power  sensitive to: bunch pattern, V RF, collimator settings, Z(IP), hidden var’s Outgassing storms

M. WeaverPEP-II MAC Review, Dec 04  Background analysis & mitigation  Background analysis & mitigation [BP, MC/TG, NB, JM/JV, RM, LP, WK/GW]  Background simulations  Background simulations [RB, MB, GC, WL, SM, PR/AS, WK + SLAC (TF/GB)]  Fast monitoring of machine backgrounds  available online in PEP-II CS  Fast monitoring of machine backgrounds  available online in PEP-II CS [MW, C’OG, AP, GDF,...]  injection & trickle quality variables: SVT, DCH, EMC  subdetector occupancies: SVT, DCH, EMC, DIRC  BaBar dead time  more operator-friendly displays (& controls) of radiation inhibits/aborts  BaBar-based machine diagnostics  time distribution of injection triggers [LP, BP,...]  Online centroids & sizes of luminous region using BaBar ,ee [C’OG, BV, AP, IN, MB,...] Continued BaBar involvement in Accelerator Performance Improvements (I)

M. WeaverPEP-II MAC Review, Dec 04  Beam dynamics  beam-beam simulations [IN (Caltech), YC (Slac ARD), WK]  beam-beam experiments, monitoring of beam-beam performance [WK]  ,  *,  z measurements using , ee  Instrumentation  Gated camera: now operational in both in LER & HER [DD, Slac Exptl Grp C]  LER interferometer software [AO, Orsay]  Installation of an X-ray beam-size monitor for the LER [Caltech + LBL + SLAC]  SVTRAD sensor & electronics upgrade [BP et. al. (Stanford); MB/DK et. al. (Irvine) (initiated & funded by BaBar)]  CsI background sensors, n detectors & shielding [JV, Slac Exptl Grp B]  Forward end Fe shielding wall (may allow better collimation elsewhere) BaBar involvement in Accelerator Performance Improvements (II)

M. WeaverPEP-II MAC Review, Dec 04 Summary (I)  Stable-beam (genuine) radiation aborts are down to ~ 1/day  Injection backgrounds under control, expect even better in Run5  Stored-beam bgds (dose rate, data quality, dead time)  OK most of the time –watch for thermal outgassing, esp. HER  Background characterization experiments  Highly valuable in identifying the origin, magnitude & impact of single- & two-beam backgrounds – be opportunistic  Maintain a measure on the projected backgrounds – impacts detector remediation/upgrades with long lead times  G4 Simulation progressing; anticipate better understanding and correlation of sources with detector response  Collimation simulations can direct future background improvements

M. WeaverPEP-II MAC Review, Dec 04 Summary (II)  In the medium term ( ), the main vulnerabilities are  beam-gas backgrounds from HOM-related thermal outgassing as I +,-   high dead time associated with DCH data volume & trigger rates (addressed by DCH elx upgrade)  high occupancy and radiation ageing in the mid-plane of the SVT,  possibly leading to a local loss of tracking coverage.   reduce the HER single-beam background back to 2002 levels (/1.5-2) ?  a high flux of ~ 1 MeV neutrons in the DCH (wire aging from large pulses, possibly also contributions to occupancy)  Background simulations  large investment in reviving/updating tools + rebuilding the group  ‘almost’ ready to evaluate backgrounds in IR upgrade  manpower limited  BaBar-based accelerator performance enhancement  common BaBar-PEPII diagnostics greatly improved, starting to pay off  very significant involvement of BaBarians in beam instrumentation & simulation

M. WeaverPEP-II MAC Review, Dec 04 MDI abstracts submitted to PAC05  Predicting PEP-II Accelerator-Induced Backgrounds Using TURTLE  R. Barlow, W. Dunwoodie, W. Kozanecki, S. Majewski, P. Roudeau, A. Stocchi, T. Fieguth & J. Va’vra  Modelling Lost-Particle Accelerator Backgrounds in PEP-II Using LPTURTLE  T. Fieguth, et al.  GEANT4-based Simulation Study of PEP-II Beam Backgrounds in the BaBar Detector at the SLAC B-Factory  W. Lockman, D. Aston, N. Barlow, N. Blount, M. Bondioli, G. Bower, G. Calderini, B. Campbell, M. Cristinziani, C. Edgar, W. Kozanecki, B. Petersen, S. Robertson, D. Strom, G. Wormser, D. Wright  Beam-induced Neutron Fluence in the PEP-II Interaction Region  G. Bower, W. Lockman, J. Va'vra, D. Wright  Measurement of the Vertical Emittance and beta Function at the PEP-II Interaction Point Using the BaBar Detector  J. M. Thompson & A. Roodman  Measurement of the Luminous-Region Profile at the PEP-II IP, and Application to e+/- Bunch-Length Determination  B.Viaud, W. Kozanecki, C. O’Grady, M. Weaver  Experimental Study of Crossing-Angle and Parasitic-Crossing Effects at the PEP-II e+e- Collider  W. Kozanecki, Y. Cai. I. Narsky, M. Sullivan & J. Seeman

M. WeaverPEP-II MAC Review, Dec 04  Measurement of the Vertical Emittance and beta Function at the PEP-II Interaction Point Using the BaBar Detector  J. M. Thompson & A. Roodman  Measurement of the Luminous-Region Profile at the PEP-II IP, and Application to e+/- Bunch-Length Determination  B.Viaud, W. Kozanecki, C. O’Grady, M. Weaver  Experimental Study of Crossing-Angle and Parasitic-Crossing Effects at the PEP-II e+e- Collider  W. Kozanecki, Y. Cai. I. Narsky, M. Sullivan & J. Seeman