Machine Detector Interface (MDI) Summary: Key Issues, Solutions & Background in Beam Physics

1. Machine/Detector interface (MDI)Summary J. Haba KEK

2. IP beam pipe Vertex resolution HOM/wall current Pick-up noise (not small for short bunch small bp?) Background IR magnets and beam ducts Interference in space Detector solenoid field compensation Background Vacuum and SR fans Background Cooling Communication between ACC. and EXP. Information exchange  Luminosity, vertex point, beam profile  Orbit information, vacuum, background control by movable mask What are the MDI issues?

3.  Not covered here.  Not covered here. 10 nice contributions. Not in this order.

4. Ohuchi for S-KEKB

5. Ohuchi for S-KEKB Compensation solenoid (ESL) indispensable for HIGH luminosity (Oide)

6. Ohuchi for S-KEKB Request to modify the Pole tip.

7. The source of HOM power: Collimators Novokhatski for PEPIII

8. Novokhatski for PEPIII IP HOM Power Insufficient cooling cause high vacuum pressure (high beam background), then melting and vacuum leak….

9. Other than HOM, we have wall current Comparison of 2.5, 1, and 0.5 cm pipes. Novokhatski for PEPIII This is only resistive-wall power!

10. Wake field Evidence from PEP-II • Shielded fingers of some vacuum valves were destroyed by breakdowns of intensive HOMs excited in a valve cavity. Novokhatski for PEPIII

11. Fight against HOM ----Never ending story told by Suetsugu Basic Design NEG Strips • Proposed basic designs for arc are: • Beam duct: • Copper beam duct with an ante-chamber • Distributed pumping by NEG strips • Inner surface with low SEY or/and solenoid [e+] • Bellows and gate valves: • with comb-type RF shield (Low impedance, high strength) • Connection flange: • MO-type flange (little step) [or RF bridge + Vacuum seal] • Movable mask (collimator) • Invisible mask head [no concrete design yet] • · · · · · Beam SR

12. Suetsugu for S-KEKBI Gate Valve _1 • Gate valve has the same problem to bellows chamber. • Application of comb-type RF-shield to gate valve is studied. • A test model (circular type) was manufactured and installed in LER last winter. • The temperature of body decreased to ½. Fingers: Ag plated SS Teeth: Cu [Collaboration with VAT Co.]

13. Better vacuum, less PE. Suetsugu for S-KEKBI Beam Duct with Ante-chamber _2 Uniform pumping speed • Pumps in Q and SX LER • 1 NEG channels 3 strip each • Conductance = 0.4 m3/s/m • 25 – 45 % up in average • 2 NEG channels 1 strip each • 0.1 m3/s lumped pumps at both sides of magnets • Conductance = 0.36 m3/s/m/channel

14. Suetsugu for S-KEKBI Beam Duct with Ante-chamber _6 • Electrons in the beam channel • Photoelectrons decreased by factors at high current (Ib1 000 mA). • The reduction was by orders at low current (Ib  100mA). • Multipactoring seems to become important at higher current. • Combination with solenoid field, and an inner surface with a low SEY will be required at higher current. Repeller Voltage = -30 V [Linear Scale] [Log Scale] 3.77 buckets spacing 3.77 buckets spacing Limit of measurement

15. Where background comes from? • SR from magnets. • Spent particle from beam- residual gas in the upstream • Radiative Bhabha  the last WS found • Touchek interaction in LER • (more frequent top-up injection to compensate very short life time of beam)

16. Sullivan for PEPIII

17. Sullivan for PEPIII 2.5cm

18. Sullivan for PEPIII No strong separtion bend. SR from Q is now main concern Evaluation of the beam tail Is very important, however, simulation may be very tough, Measurement should be done. Reflection should be Considered next.

19. SR from QCS backscattering SR, downstream magnet (QCS) origin SVD ~ 1/3 of bkg CDC ~ 1/3 of bkg BGaIHER • Downstream final focus magnet (QCS) generate high energy SR (Ecrit ~ 40 keV) • SR photons are scattered at downstream chamber (~9m) • Backscattering photons enter to the detector (Eeff ~ 100 keV)

20. Tajiama for S-KEKB Radiative Bhabha : inner detectors • Actually, BaBar has large BG for inner detectors while it is negligible at Belle BaBar DCH We should consider because higher lum gives higher BG

21. Radiative Bhabha origin Main BG source for KLM Negligible for others BGaLuminosity

22. Radiative Bhabha background • First identified in the last Joint workshop (2004-Jan.) • Confirmed in the following BBB task force • Extrapolation of PEPII background to super Bfactory invalidated. • No separation bend @ IP • Possible shield to reduce further • Simulation studies including several nuclear reaction for neutron production. ( Robertoson)

23. Difference of magnet position is the reason Shower caused by over bend particle Pointed out by M.Sallivan in 6th HLWS (Nov,2004) Tajiama for S-KEKB Originally from Sullivan

24. Tajima for S-KEKBI Rad. Bhabha BG sim. for Super-KEKB Barrel BWD EndCap FWD EndCap Realistic design based on discussion with QCS group Expected BG from other sources with heavy metal total 1~2 ton L=25x1034/cm2/s ~4 % of total BG L=1034 /cm2/s

25. Tajima for S-KEKBI My optimistic Average Vacuum 2.5x10-7 Pa KEKB Super-KEKB design at Now!! Suppressed by Neutron shield BGx33 (several MRad/yr)!? (sim. for particle shower) Beampipe radius 1.51cm 1st layer

26. Tajima for S-KEKBI Does the background scale with luminosity or just beam current ? CDC leak current We don’t have to be too psimistic Lum. (/ub/sec)

27. Effect of background • Radiation damage • Performance degradation due to high occupancy • Lower efficiency • Worse resolution in vertexing/tracking/clustering

28. Vertexing degradation due to HIGH occupancy Hara

29. B→p+p- recon. Efficiency~high momentum tracking Sumisawa B→p+p- rec. eff (w/ geom. eff.) Single track eff. (square root of left value) MC study 1032/cm2/s MC study 1032/cm2/s For simplicity, assuming relation btw luminosity and BG level is linear: Current CDC config. 130x1032/cm2/s (x1), 260 (x2), 390 (x3) Old CDC config. 90x1032/cm2/s (x1), 450(x5) (reported@HL05(Nov.2004)) No degradation found in high momentum tracking eff. upto x3 BG of that in current operation condition.

30. D*+D*- (both D*(K3p)ps) high multiplicity case Sumisawa loose mass for D0,D*-,and B0 cut are only required. case2 3BG : eff. loss = 32.9% (1BG : eff. = 4.050.14%, 3BG : eff. = 2.720.11%) case1 updated T0 recon. narrow window of drift time. new readout electronics for 2 more layers. case3 eff. loss = 18.7 % (+14.2% gain) new readout electronics for all layers case4 eff. loss = 12.1 % (+6.6% gain)

31. Should be done soon… • Understand the current status further (BBB task force) • Detector solenoid strength • Optimize for better lower mometum track? • Cut off in pt • Less degradation in tracking/vertexing • Less constrarints among the IR components and the detector. • IP beam pipe radius 1cm? • Better vertex with smaller r. • Tough (impossible) optimization of SR. • Much higher background even for outer detector. • Cooling against severe HOM/wall current? • Mechanical robustness? Feed back from Physics target is the key for optimaization.