Upload
nhung
View
34
Download
4
Tags:
Embed Size (px)
DESCRIPTION
Machine/Detector interface (MDI) Summary. J. Haba KEK. 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. - PowerPoint PPT Presentation
Citation preview
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.