Post on 29-Jan-2016
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)
14th September 2006 4Martin van Beuzekom, STD6
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)
14th September 2006 5Martin van Beuzekom, STD6
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
14th September 2006 6Martin van Beuzekom, STD6
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
14th September 2006 7Martin van Beuzekom, STD6
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