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Interaction Region: a terse summary

Interaction Region: a terse summary. Conveners: K. Trabelsi, W. Kozanecki. Accelerator issues Parameter comparison with PEP-II/KEKB IR layout Particle-loss mechanisms Thermal issues Detector issues Machine background predictions Detector radiation-protection & beam-abort

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Interaction Region: a terse summary

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  1. Interaction Region: a terse summary Conveners: K. Trabelsi, W. Kozanecki • Accelerator issues • Parameter comparison with PEP-II/KEKB • IR layout • Particle-loss mechanisms • Thermal issues • Detector issues • Machine background predictions • Detector radiation-protection & beam-abort • Luminosity monitor • Subdetector-specific issues (DCH, trigger, TOF) • Summary: the most critical/urgent studies A very lively & productive interchange between BEPC & BES experts!

  2. T: WK • Introduction • Experience in PEP-II & BaBar: Iimportance of an integrated approach to • Solving layout problems • Predicting (now) & understanding (later) machine backgrounds • IR heating issues (SR, HOM) • Machine operation (injection, abort,...) • Accelerator issues • Parameter comparison: BEPCII vs B-factories • Same beam-current & L regime • The joys & the pains of 2-ring machines • Some issues harder, a few easier • IR layout • orbits, BSCs, aperture constraints, … T: Xu Gang Major implications for machine + SR backgrounds

  3. Accelerator issues (ct’d) • IR layout (cont’d) • Mechanical & vacuum interfaces • Significant enginering “challenge” in accomodating necessary mechanical/vacuum interfaces in the heart of BESIII T: HUANG Nan

  4. Accelerator issues (ct’d) • IR layout (cont’d) • Mechanical & vacuum interfaces • “support tube” approach (BaBar) impractical bec. of DCH conical shape

  5. I bunch Gap size driven by kicker rise time Ring circumference • Accelerator issues (ct’d) • Particle-loss mechanisms • Injection • Injected e-: prob. OK • Injected e+: e inj/stored ~10 ==> x-baam size x 3-4, ==> (present) clearance ~ 1 sinjected • If confirmed,  !! • Need better understanding of injected beam specs (A+D) • may need to collimate (“shave off”) tails in linac, before injection • Beam abort: gap needed • Touscheck: need background calculation (A+D;Turtle!) • Beam-beam brems (aka radiative Bhabhas): where do the debris go? (Turtle!) • Need iterative vacuum calculations (bgd! A+D)

  6. Accelerator issues (ct’d) • Thermal issues: IR very sensitive • Synchrotron radiation • HOM losses BaBar luminosity presently limited by heating here

  7. Detector issues • Machine background predictions • Radiation tolerance of BES subdetectors • Most sensitive to injection: calorimeter • Most sensitive to stored beam: DCH • Numbers & criteria/specs needed! • Occupancy issues in BES subdetectors (esp. trigger) • Numbers & criteria/specs needed! • Background simulations • Belle experience • Early BES beam-gas & SR studies T: K. Trabelsi T:Jin Dapeng

  8. Detector issues (ct ’d) • Machine background predictions (ct ’d) • Background simulations (ct ’d) • Early BES beam-gas & SR studies T:Jin Dapeng Total power Total photon flux

  9. 1M trigger rate SVT abort diode Chronic dose trip level • Detector issues (ct ’d) • Detector radiation-protection & beam-abort: consensus it is absolutely needed

  10. (HER) beam blow-up Luminosity by bunch • Detector issues (ct ’d) • Luminosity monitor • Absolute: large- and/or medium angle BhaBhas • Relative: 0°-BhaBhas (e+ e-g) • Water Cerenkov referred (Belle), 1/side • essential for • Machine optimization • Beam-beam centering (feedback) • b-b vertical (y-z) alignment • IP beam size measurements • Bunch train diagnostics • Machine vs detector operation • Trigger: must accommodate easily arbitrary bunch patterns • TOF: consider separate timing signal from trigger (phase drift along train) • DCH: turn HV off/on afap

  11. Summary: the top of the list…. • IR layout : trade-offs between • Orbits • Backgrounds • Engineering • Injection !! • Abort gap => kicker R&D • Background simulations • SR • Beam-gas • Touscheck

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