14th September 2006 1Martin van Beuzekom, STD6

Outline:• Introduction to LHCb and VErtex LOcator (VELO)• Status of VELO• Beamtests• Upgrades• Summary

LHCb Vertex Locator: present and future

Martin van Beuzekom

On behalf of the LHCb VELO group

Liverpool University

14th September 2006 2Martin van Beuzekom, STD6

LHCb overview

Large Hadron Collider• pp collisions: √s = 14 TeV• bunch crossing every 25 ns

LHCb• Studies physics of b-flavoured hadrons (CP violation)• B-hadrons produced at small angles

– -> Single arm forward spectrometer• 10 – 300 (250) mrad in bending plane (non bend.)• Luminosity 2·1032 cm-2 s-1

interaction region

14th September 2006 3Martin van Beuzekom, STD6

Vertex Locator

• 2 retractable detector halves– Range 3 cm each

• 23 silicon microstrip modules / side • Silicon modules in secondary vacuum

• Modules separated from beam vacuum (10-9) by 300 m Alu foil (RF box)– Maximum allowed diff. pressure 5 mbar– Shield against beam induced EMI

• Innermost strip 8 mm from beam

(2 mm)

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Silicon sensor details

42 mm8 mm

• 300 m thick sensors• n-on-n, DOFZ wafers• 42 mm radius• AC coupled, double metal• 2048 strips / sensor• Pitch from 40 to 100 m• Produced by Micron Semiconductor

-measuring sensor(radial strips with a stereo angle)

R-measuring sensor(45 degree circular segments)

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Module construction

Kapton hybrid

Carbon fibre

Thermal Pyrolytic Graphite (TPG)

• 4 layer kapton circuit• Heat transport with TPG• Readout with 16 Beetle chips

• 128 channels, 25 ns shaping time, analog pipeline• 0.25 m CMOS• no performance loss up to 40 Mrad• Yield > 80 %

Beetle

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Silicon microstrip modules

• 21 stations with R- geometry – Fast R-Z tracking in trigger farm– Overlap of right and left det. halves – Total of 176k strips

• 2 stations with R-sensor for PileUp trigger

VELO sensors

PileUp sensors

RF-foil

Fine pitch kapton cables

Carbon fibre base

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n = # pp interactions/crossing

Pile Up (veto) trigger

LHCb luminosity

• PileUp system detects multiple interactions• Vetoes Level-0 trigger

– Increases physics output– Multiple interactions complicate Level-1 trigger (CPU-farm)

• Factor 3 reduction in #crossings with multiple interactions

• 2 R-sensors, prompt binary readout– Combine 4 strips in 1 to reduce # inputs– 2048 “bits” @ 40 MHz = 80 Gbit/sec– Special hybrids (4 times #signals)

BPV

APV

B

A

ZZ

ZZ

R

Rk

14th September 2006 8Martin van Beuzekom, STD6

PileUp continued

• Each vertex bin corresponds to a small wedge in the RA-RB correlation plot

• Each “track” is represented by a point

• Histogramming of Z-vertex– determine # vertices with FPGAs– find 1st peak, mask hits,

find 2nd peak– Algorithm highly pipelined ( ~ 80 Bunch crossings)

true tracks all combinations

2 vertices

14th September 2006 9Martin van Beuzekom, STD6

LHCb status

Installation progressing, first collisions expected in fall 2007

14th September 2006 10Martin van Beuzekom, STD6

Status @ Interaction point

• Vacuum vessel installed May 2006– Vacuum controlled by PLC– Movement system controlled by PLC

• Thin (2 mm) exit foil mounted in Aug 2006• Vacuum qualification ongoing• Detector installation early 2007

14th September 2006 11Martin van Beuzekom, STD6

CO2 cooling

T=-30 ºC

T ~ -5 ºC

• 2 phase CO2 cooling system• Low mass• Radiation hard• Non toxic

• Silicon modules in parallel • 1 mm Ø stainless steel capillaries • Pressure up to 70 bar

• Large T over TPG + interface

• heat load max. 30W

14th September 2006 12Martin van Beuzekom, STD6

Testbeam performance

2004: • Single sided module with 200 m sensor• Characterized (final) sensor + (final) Beetle

• S/N 16• Spillover @25 ns < 25 %• Resolution ~4 m

November 2006• Aim for a complete detector half (21 mod.)• Module production in Liverpool at full speed

• Delivery 4 modules per week• Major effort!

August 2006• 3 double sided modules• Full electronics chain with final electronics

• ADCs, Timing, Fast & Slow Control• Data taken for many sensor and chip settings

•Analysis ongoing

Beetle Frontend pulseshape

14th September 2006 13Martin van Beuzekom, STD6

VELO Upgrades

Why:• Limited lifetime of VELO due to high radiation dose

– (1.3x1014 neq/cm2/year)• Improve (impact parameter) resolution

– Displaced vertex trigger• Increase statistics

– Readout of complete LHCb detector @ 40 MHz

How:• Different sensor technology/geometry• Reduce material in VELO• Move closer to beam

– Currently 8 mm, goal 5 mm (min. allowed by accelerator)– Up to 36% resolution improvement

• Increase luminosity (not SLHC)– Level-1 computing power

14th September 2006 14Martin van Beuzekom, STD6

Radiation environment

Radiation environment for current design• Strongly non-uniform • Dependence on radius and z-position• Max fluence 1.3x1014 neq/cm2/year

Define as 1 LHCb-year• Expected (useful) lifetime ~3 years

• assuming nominal luminosity• no accidents

Far station

Middle station

With upgrades• 5 mm strip radius -> 2.5x increase • Luminosity to 1x1033 -> 5x increase• Fluence 1.7x1015 neq/cm2/yearOnly possible with• Different sensor technology• and/or smaller strips or pixels (Syracuse group)

14th September 2006 15Martin van Beuzekom, STD6

Radiation Hard Technologies

5..6 LHCb-years

• p-on-n MCz • Assume required CCE min. 60 %• Single sided processing• R&D by Glasgow group

Magnetic Czochralski

14th September 2006 16Martin van Beuzekom, STD6

Radiation Hard Technologies- II

n-on-p

Presentation by Gian-Luigi Casse

> 20 LHCb-years

• High resistivity p-silicon • Single sided processing• Very high bias voltage• R&D by Liverpool group

14th September 2006 17Martin van Beuzekom, STD6

Radiation Hard Technologies- III

3D - sensors

• Extremely radiation hard• Low bias voltage• Very promising• Complex processing• R&D by Glasgow group

14th September 2006 18Martin van Beuzekom, STD6

Reduce material in VELO

• BTeV planned sensors in primary vacuum

• Beam (mirror) current via wires/strips • Cryo pumping against outgassing

• Totem (@LHC) • 150 m Inconel (Ni-Cr) foil 1 mm from beam

• Radiation length of total VELO: 19 % X0

• Largest contribution from RF-foil and sensors• Thin sensors (200 m) already tested extensively • Thinner RF-foil is under investigation

14th September 2006 19Martin van Beuzekom, STD6

Summary

• Construction of LHCb VErtex LOcator is well underway– Mechanics, vacuum, motion system installed– Cooling system steadily progressing– Silicon module production at full speed

• Next deadline is half detector for November testbeam– Detector (sensors) installation early 2007

• Already starting to think about upgrades– Limited lifetime of VELO– More radiation hard sensors– Reduce material to improve performance