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

What are the MDI issues? 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

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

Ohuchi for S-KEKB

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

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

The source of HOM power: Collimators Novokhatski for PEPIII

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

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

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

Basic Design 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 NEG Strips Fight against HOM ----Never ending story told by Suetsugu

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. [Collaboration with VAT Co.] Fingers: Ag plated SS Teeth: Cu Suetsugu for S-KEKBI

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

Beam Duct with Ante-chamber _6 Electrons in the beam channel –Photoelectrons decreased by factors at high current (I b  mA). –The reduction was by orders at low current (I b  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. Limit of measurement [Linear Scale][Log Scale] Repeller Voltage = -30 V 3.77 buckets spacing Suetsugu for S-KEKBI

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)

Sullivan for PEPIII

2.5cm

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.

SR, downstream magnet (QCS) origin 1.Downstream final focus magnet (QCS) generate high energy SR (E crit ~ 40 keV) 2.SR photons are scattered at downstream chamber (~9m) 3.Backscattering photons enter to the detector (E eff ~ 100 keV) SVD ~ 1/3 of bkg CDC ~ 1/3 of bkg BG  I HER SR from QCS backscattering

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 Tajiama for S-KEKB

Radiative Bhabha origin Main BG source for KLM Negligible for others BG  Luminosity

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 IP –Possible shield to reduce further Simulation studies including several nuclear reaction for neutron production. (  Robertoson)

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

Rad. Bhabha BG sim. for Super-KEKB FWD EndCap BWD EndCap Barrel L=10 34 /cm 2 /s ~4 % of total BG L=25x10 34 /cm 2 /s Expected BG from other sources with heavy metal total 1~2 ton Realistic design based on discussion with QCS group Tajima for S-KEKBI

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

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

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

Hara Vertexing degradation due to HIGH occupancy

B→  +  - recon. Efficiency ~high momentum tracking /cm 2 /s For simplicity, assuming relation btw luminosity and BG level is linear: Current CDC config. 130x10 32 /cm 2 /s (x1), 260 (x2), 390 (x3) Old CDC config. 90x10 32 /cm 2 /s (x1), 450(x5) No degradation found in high momentum tracking eff. upto x3 BG of that in current operation condition. B→  +  - rec. eff (w/ geom. eff.) Single track eff. (square root of left value) MC study Sumisawa

D* + D* - (both D*  (K3  )  s )  high multiplicity case loose mass for D 0,D* -,and B 0 cut are only required. 3  BG : eff. loss = 32.9% (1  BG : eff. = 4.05  0.14%, 3  BG : eff. = 2.72  0.11%) updated T0 recon. narrow window of drift time. new readout electronics for 2 more layers. eff. loss = 18.7 % (+14.2% gain) new readout electronics for all layers eff. loss = 12.1 % (+6.6% gain) case2 case3 case4 case1 Sumisawa

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.