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 c

ompensation – 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.

Not covered here.

10 nice contributions. Not in this order.

Ohuchi for S-KEKB

Compensation solenoid (ESL) indispensable forHIGH 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 2 2

Incoherent Pow

(

er

) ( )b e eP k I I

P ar ameter s P E P - I I Super B

B unc h l ength [mm] = 13 1. 8

Los s f ac tor [V / pC ]= 0. 248 7. 224

LE R c ur r ent [A ] 2. 4 23

HE R c ur r ent [A ] 1. 5 10

B unc h s pac i ng [ns ec ] 4. 2 1. 05

P ower l os s (pul s e) [kW] 8. 36 4771. 34

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.

pipe Radius [m] 2.50E-02 1.00E-02 5.00E-03

Material Cu Cu Curesistivity [Ohm m] 1.69E-08 1.69E-08 1.69E-08S0 [m] 3.83E-05 2.08E-05 1.31E-05

bunch length [m] 1.80E-03 1.80E-03 1.80E-03Loss factor 0.009 0.022 0.045Bunch spacing [nsec] 1.05 1.05 1.05beam current [A] 23 23 23power [kW/m] 5.209 13.022 26.045

This is only resistive-wall power!

Novokhatski for PEPIII

Wake field Evidence from PEP-II• Shielded fingers of some vacuum valves w

ere 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]

– · · · · ·

BeamSR

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 m3/s lumped pumps at both sides of magnets– Conductance = 0.36 m3/s/m/channel

– 1 NEG channels 3 strip each

– Conductance = 0.4 m3/s/m

– 25 – 45 % up in average

Suetsugu for S-KEKBIBetter vacuum, less PE.

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.

Limit of measurement

[Linear Scale] [Log Scale]Repeller Voltage = -30 V

3.77 buckets spacing3.77 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)

e36 B-factory IR +/- 14 mrads RevD

0

10

20

30

-10

-20

-300 2.5 5 7.5-2.5-5-7.5m

cm

M. Sullivan Apr 16, 2005B3$E36_2_5M_8D_RL

200 kW40 kW

13 kW

83 kW3 kW

11 kW

QF5QD4 QF2

QD1QD1

QF2

QD4

QF5

LER

HER

Sullivan for PEPIII

physics window +/- 10 cm

2.5 cm radius beam pipe

e36 B-factory IR +/- 14 mrads RevD

M. Sullivan Apr 16, 2005B3$E36_2_5M_8D_RL

-1 -0.5 0 0.5 1

0

2

4

-2

-4

cm

m

Sullivan for PEPIII

2.5cm

10 15 20 25 30 355

100 100

10-3

10-6

10-9

10-3

10-6

10-9

Beam Sigmas

Y plane

X plane beam tails

PEP-II design beam tails

Tail #1

Tail #2

Beam Tail Distributions

M. Sullivan Apr. 17, 2005

Gaussian beam profile

Sullivan for PEPIII

No strong separtion bend.SR from Q is now main concern

Evaluation of the beam tailIs very important, however,simulation may be very tough,

Measurement should be done.

Reflection should beConsidered next.

SR, downstream magnet (QCS) originSR, downstream magnet (QCS) origin

1. Downstream final focus magnet (QCS) generate high energy SR (Ecrit ~ 40 keV)

2. SR photons are scattered at downstream chamber (~9m)3. Backscattering photons enter to the detector (Eeff ~ 100 keV)

SVD ~ 1/3 of bkgCDC ~ 1/3 of bkg

BG IHER

SR from QCS

backscattering

Radiative Bhabha : inner detectorsRadiative 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 g

ives higher BG

Tajiama for S-KEKB

Radiative Bhabha originRadiative Bhabha origin

Main BG source for KLMNegligible 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 Bfa

ctory invalidated.– No separation bend @ IP– Possible shield to reduce further

• Simulation studies including several nuclear reaction for neutron production. ( Robertoson)

87.57

6.56

5.5

4

3.532.5

21.51

0.5

4.55

HER Radiative Bhabhas

32.5

2 1.51

0.5

LER Radiative Bhabhas

-7.5 -5 -2.5 0 2.5 5 7.5

0

10

20

30

-10

-20

-30

m

cm

M. SullivanFeb. 8, 2004API88k3_R5_RADBHA_TOT_7_5M

3.1 G

eV

3.1 G

eV

9 GeV

9 GeV

PEP-II Radiative Bhabhas

LER radiative gammas

0.511.5

22.5

3

LER radiative bhabhas

HER radiative gammas

7654

0.5

1

2

3

HER radiative bhabhas

KEKB Interaction Region

0

10

20

30

-10

-20

-300 2.5 5 7.5-2.5-5-7.5m

cm

HER

LER

8 GeV

3.5 GeV

M. Sullivan Nov. 9, 2004 B3$KEK2_IR_RADBHA

Detector

Detector

CSL CSR

QCSL QCSR

CSL CSR

QCSRQCSL

Q1EL

Q1ER

Q2PL

Q2PR

0.5

11.5

22.5

3

LER gammas

0.5

12

3

4 5

6 7

HER gammas

Super KEKB IR

0

10

20

30

-10

-20

-300 2.5 5 7.5-2.5-5-7.5m

cm

M. Sullivan Nov. 13, 2004B3$_SUPER_KEK_RADBHA

HER

LER

8 GeV

3.5 GeV

Detector

QCSRQCSL

QC1LEQC2LE

QC2LP

QC1RE

QC2RE

QC2RP

Detector

Difference of magnet position is the reasonShower caused by over bend particle

Pointed out by M.Sallivanin 6th HLWS (Nov,2004)

Tajiama for S-KEKBOriginally from Sullivan

Rad. Bhabha BG sim. for Super-KEKBRad. Bhabha BG sim. for Super-KEKB

FWDEndCap

BWDEndCap

Barrel

L=1034 /cm2/s

~4 % oftotal BG

L=25x1034

/cm2/s

Expected BGfrom other

sources with heavy metaltotal 1~2 ton

Realistic designbased on discussionwith QCS group

Tajima for S-KEKBI

Average Vacuum 2.5x10Average Vacuum 2.5x10-7-7 Pa Pa

1st layer

Super-KEKB design at Now!!

My optimistic

Suppressed byNeutron shield

Beampipe radius 1.51cm

BGx33 (several MRad/yr)!?(sim. for particle shower)

KEKB

Tajima for S-KEKBI

Does the background scale with luminosity or just beam current ?

CD

C le

ak c

urre

ntLu

m. (

/ub/

sec)

Tajima for S-KEKBI

We

don’

t hav

e to

be to

o ps

imist

ic

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

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

0 100 200 300 400 500

pipipipi(old)

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

0 50 100 150 200 250 300 350 400 450 500

pipi singlepipi single(old)

1032/cm2/s

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.

B→+- rec. eff(w/ geom. eff.) Single track eff.

(square root of left value)

MC study

MC study

Sumisawa

D*+D*- (both D*(K3)s) high multiplicity case

loose mass for D0,D*-,and B0 cut are only required.

3BG : eff. loss = 32.9% (1BG : eff. = 4.050.14%, 3BG : eff. = 2.720.11%)

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.