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