LHCb Vertex Detector System: Status Report J.F.J. van den Brand Subatomic Physics Group, VUA - NIKHEF

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LHCb Vertex Detector SystemStatus Report
J.F.J. van den BrandSubatomic Physics Group,
VUA - NIKHEF

• Milan design
• Optimized design
• mechanics
• vacuum system
• cooling system
• Summary

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Mechanics TP design
top half bottom half
See LHCb 99-042/VELO
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Milan design

• VELO Design
• Single flange
• XY table
• CO2 cooling
• WF suppressors
• Second. vacuum
• Studied
• assembly
• alignment
• To do
• further design
• FEA

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Detector and support frame

• both halves on same side
• VD easier to mount and
• position in the tank
• install complete VD at once
• the two halves are no
• longer interchangeable

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Vacuum vessel

• Employ top flange
• Easier installation
• Shorter cables
• Length 2000 mm
• Width 1200 mm

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Top flange

• Length 1500 mm
• Distance from ceiling 1900 mm
• Install using wires
• Baking to 60o C?
• Regenerate NEGs after every access to Si detectors

1900
770
Lift 600
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Optimized System

• Two detector boxes
• Baking up to 150o C
• Decouple access to Si detectors

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Support system

• Microswitches at out position
• LVDTs
• Steel frame
• Alignment
• 2 planes
• 3 points each
• define IP

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Support system

• Alignment pins for reproducible coupling
• reproducible positioning

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Vessel Installation

• Move bellows to in-position
• Install vessel from top
• Align vessel
• Mount vessel to frame
• Mount bellows
• Pump-outs visible

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Install 2nd-Vacuum Vessel

• Remove upstream flange
• Need 2 m access
• Rectangular bellows
• 60 mm stroke
• normal 35 mm
• lateral 6 mm
• Fabrication
• Palatine, Bird
• Calorstat, MB
• cost

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Vacuum vessel / Positioning system
Secundary vacuum

• Moving parts not in vacuum
• Thin vacuum container
• Special bellows construction

Primary vacuum
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After installation

• Detector system separated from vacuum system
  functionality
• Mount positioning system to detector housing
• Install
• pump-out, valves
• turbos, damping

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Connect inner system to motion drives

• Mount M8 through side flanges

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Detector Installation

• Install detector halfs from sides
• Decouple detectors from box
• Tooling needed

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VELO Assembly

• Detectors mounted

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Wakefield suppressors

• Mount screens after mounting 2nd vacuum container
• Mount through top flanges
• seal with view ports?
• Upstream mount with large flange off

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Wakefield suppressor downstream

• Up/downstream suppressors are identical
• Material CuBe
• Length 179 mm
• Thickness 100 ?m
• 16 segments
• Mounting to box non-trivial

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Wakefield suppressors

• Segments deform differently during movement
• Coating needed on suppressors
• Press-fit to beam pipe structure
• Anneal CuBe, deform, harden at 400o C

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Detector Mounting
Install Modules 3D alignment Mount References
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Thin Vacuum foil

• Beryllium expensive k 500 per container
• Aluminum
• welding 250 ?m Al is possible
• press-shaping being developed
• FEA ongoing

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Thin Vacuum foil

• Labour intensive press, anneal, etc.
• welding 250 ?m Al is possible
• Extensive prototyping program

CP?!
Chiel Bron
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Thin Vacuum foil

• Increase radius 10 ? 20 mm to avoid folding
• Crystal structure is affected
• Employ Al with magnesium alloy
• Deform at higher temperature 150 - 200o C

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Foil design ongoing (continued)
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Foil design ongoing
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Control of Vacuum System

• Group active with experience at former NIKHEF
  accelerator
• Propose meeting in Q1 2001

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Vacuum Tests

• Self-regulating valve behaves as advertized
• Various gas flows have been characterized

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Vacuum constraints
(rough!)
See LHCb 99-045/VELO

• LHC
• beam life time
• static density of 10-7 mbar ? 2 m (H2 300K) ?
• 0.01 of LHC limit for integrated
  density
• ( 2.7 106 cm ? 1.6 109 molecules/cm3
  )
• beam stability dynamic effects must be taken
  into account
• LHCb
• 10-7 mbar ? 1.2 m (H2 300K) ? 1.5 of LHCb
  nominal luminosity
• Difficult to achieve with silicon detectors,
  electronics and signal wires
• directly in LHC vacuum ! ? differential pumping.

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Static pressure in VD
Consider outgassing by assuming outgassing
rates of (mbar l s-1 cm-2) ? 11 m2
Kapton (signal wires, pumped 40 hours) 10-7
H2O ? 2.3 m2 Al housing (per half) 10-10
H2 ? 1.5 m2 bellows (per half) 10-9 H2 ? 8
m2 SS vessel 10-10 H2 Pumps in detector
volume ? 140 l/s (per half) H2O Pumps in
tank ? 4000 l/s H2 Bypass tube 200 mm ? 4
mm pumped in the middle. Calculate using a
static flow model. Result 110-4 mbar in
detector volume 110-8 mbar in VD
tank 210-8 mbar l s-1 from det. vol. to VD
tank
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Outgassing measurements

Summary table (Data are approximate. QLHCb_total
estimate for the full vertex detector, i.e.
both halves.) Item Outgassing rate of
item QLHCb_total mbar l s -1 Kapton
foil, after 40 hrs pumping 1 E-7 mbar l s -1
cm-2 n/a sample Kapton flat cable QPI
3 E-5 mbar l s -1 130 E-4 male/female pair
of PEEK D-type 25-pin connectors 6 E-6 mbar l s
-1 / pair 50 E-4 male/female pair of
stand. D-type 25-pin connectors 1 E-5 mbar l s -1
/ pair 100 E-4 Liverpool carbon-fiber Si
support 1 E-8 mbar l s -1 cm-2 1 E-4
Continue measure all unknown outgassing rates of
components in a detector station
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Dynamic Vacuum
See Adriana Rossis presentation
Beam-induced particle bombardment ? desorption,
emission
Ions, photons, electrons energies up to keV

• Local pressure runaway (ion/electron-induced
  desorption)
• Local static charge increase (electron
  multipacting)

LHC beam instability
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Dynamic Vacuum (continued)

• Perhaps a solution
• use coating of surfaces by Ti
• advantages low ?SEY , low ?, local pumping
• Design issues
• better surfaces ? (NEG ?)
• in-situ coating required or not ?
• thickness of layer needed ?
• what re-coating rate ?
• affordable cathode temperature in-situ ?
• wake field / RF properties ?
• side effects ? (peeling, ...)

• We need ?, ? for
• different materials
• surface conditions (un)baked,
• saturated, activated, etc.
• different impact energy
• spectra
• Data available only in a
• few months ! (Mahner et al.)

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Cooling system with mixed-phase CO2

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CO2 Cooling Tests
Cooling system -30o C 40 W/module
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Mixed-phase CO2 Cooling system
See LHCb 99-046/VELO
CO2 gas-liquid storage tank 57.3 bar at 20 C
cool to 20 C
gas only
compresssor
heat to 20 C
pressure (temperature) regulating valve
CO2 supply line
flow restrictions
P W
cooling lines
P W
P W
supply line expansion valve
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CO2 Cooling Tubes
Cooling tubes 1.1 (0.9) mm S.St. Welding and
brazing
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FEA ongoing
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Tests ongoing
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RF tests at NIKHEF

• First 3 measured eigenmodes
• 220 MHz
• 270 MHz
• 380 MHz

Picture 1 of tank removed
Picture 2 of tank removed
Simulation with MAFIA

• Outlook
• Eigenmodes
• Short range effects Z/n
• Electric field inside secondary vacuum

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Wake field Suppressor
Central cooling line Temperature sensors (2 per
station, 4 wires per measurement
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Detector Modules
Liverpool delivers modules
44 pins, 440 / module
Discuss
Number of planes 25
40 W, 1 m cable, 50 isolation thickness, 10 -
15 K ?T, radiative cooling
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Summary

• Design is based on secondary vacuum system
• Beryllium option costly and uncertain
• needs approval for TDR
• Current design
• allows baking up to 150o C
• decouples Si detectors from primary vacuum system
• employs venting with Argon
• cooling based on CO2 in gas-liquid phase
• Self-regulating valves behave as advertised
• Wakefield excitation under study
• Need information on dynamic vacuum effects
• Propose meeting on control issues (e.g. NIKHEF)