w. kozaneckiir summary, bes-iii workshop interaction region: a terse summary accelerator issues ...
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W. Kozanecki IR summary, BES-III workshop
Interaction Region: a terse summaryInteraction Region: a terse summary
Accelerator issuesAccelerator issues Parameter comparison with PEP-II/KEKB
IR layout
Particle-loss mechanisms
Thermal issues
Detector issuesDetector issues Machine background predictions
Detector radiation-protection & beam-abort
Luminosity monitor
Subdetector-specific issues (DCH, trigger, TOF)
Summary: Summary: thethe most critical/urgent studies most critical/urgent studies
Conveners: K. Trabelsi, W. Kozanecki
A very lively & productive interchange between BEPC & BES experts!
W. Kozanecki IR summary, BES-III workshop
IntroductionIntroduction Experience in PEP-II & BaBar: Iimportance of
an integrated approach to
– Solving layout problemsSolving layout problems
– Predicting (now) & understanding (later) Predicting (now) & understanding (later) machine backgroundsmachine backgrounds
– IR heating issues (SR, HOM)IR heating issues (SR, HOM)
– Machine operation (injection, abort,...)Machine operation (injection, abort,...)
Accelerator issuesAccelerator 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, …
IR beam line layout(continued)
6040
25
.3
70 1
06
12
0
19001550
1150
360
7.2
606
_y max<120m(_y *=1.5cm)180m(_y
*=1cm), _x max<6m in s=0~1.9m
T: Xu Gang
Major implications for machine +
SR backgrounds
T: WK
W. Kozanecki IR summary, BES-III workshop
Accelerator issues (ct’d)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
W. Kozanecki IR summary, BES-III workshop
Accelerator issues (ct’d)Accelerator issues (ct’d) IR layout (cont’d)
Mechanical & vacuum interfaces “support tube” approach (BaBar) impractical
bec. of DCH conical shape
W. Kozanecki IR summary, BES-III workshop
Accelerator issues (ct’d)Accelerator issues (ct’d) Particle-loss mechanisms
Injection Injected e-: prob. OK
Injected e+: inj/stored ~10 ==> x-baam size x 3-4, ==> (present) clearance ~ 1 injected
– If confirmed, If confirmed, !! !!
– Need better understanding of injected Need better understanding of injected beam specs (A+D)beam specs (A+D)
– may need to collimate (“shave off”) may need to collimate (“shave off”) tails in linac, tails in linac, beforebefore injection 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)
Ring circumference
I bunch
Gap size driven by
kicker rise time
W. Kozanecki IR summary, BES-III workshop
Accelerator issues (ct’d)Accelerator issues (ct’d) Thermal issues: IR very sensitive
Synchrotron radiation
HOM losses
BaBar luminosity presently limited by heating here
W. Kozanecki IR summary, BES-III workshop
Detector issuesDetector 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
W. Kozanecki IR summary, BES-III workshop
Detector issues (ct ’d)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
W. Kozanecki IR summary, BES-III workshop
Detector issues (ct ’d)Detector issues (ct ’d) Detector radiation-protection & beam-abort:
consensus it is absolutely needed
SVT abort diode
Chronic dose trip level
1M trigger rate
W. Kozanecki IR summary, BES-III workshop
Detector issues (ct ’d)Detector issues (ct ’d) Luminosity monitor
Absolute: large- and/or medium angle BhaBhas
Relative: 0°-BhaBhas (e+ e- ) Water Cerenkov referred (Belle), 1/side
essential for
– Machine optimizationMachine optimization
– Beam-beam centering (feedback)Beam-beam centering (feedback)
– b-b vertical (y-z) alignmentb-b vertical (y-z) alignment
– IP beam size measurementsIP beam size measurements
– Bunch train diagnosticsBunch 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
Luminosity by bunch(HER) beam blow-up
W. Kozanecki IR summary, BES-III workshop
Summary: the top of the list….Summary: the top of the list….
IR layout : trade-offs betweenIR layout : trade-offs between Orbits
Backgrounds
Engineering
Injection !!Injection !!
Abort gap => kicker R&DAbort gap => kicker R&D
Background simulationsBackground simulations SR
Beam-gas
Touscheck
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