alisonBates

The LHCb VELO: Status and Upgrade Developments: 

The LHCb VELO: Status and Upgrade Developments Alison G Bates on behalf of the LHCb VELO Group CERN (Geneva), EPFL (Lausanne), NIKHEF (Amsterdam), University of Glasgow, University of Heidelberg, University of Liverpool Overview The LHCb detector and the VELO VELO sensor performance Possible upgrade solution Czochralski Silicon Current status

LHCbAim: to study CP violation in B meson systems: 

LHCb Aim: to study CP violation in B meson systems Detector at the LHC analysing 14 TeV proton-proton collisions ~1012 bb pairs produced every operational year Angular acceptance 15 - 300mrad Proton interaction region RICH 2 RICH 1 Forward spectrometer Trigger tracker

VErtex LOcator - Vertex reconstruction is a fundamental requirement for LHCb : 

VErtex LOcator - Vertex reconstruction is a fundamental requirement for LHCb 21 silicon tracking stations placed along the beam direction 2 retractable detector halves for beam injection periods (up to 30 mm) 21 stations Retractable detector halves

VELO Sensor design: 

VELO Sensor design 2 sensor types: R and F R measuring gives radial position F measuring gives an approximate azimuthal angle Varying strip pitch 40 to 102 mm (R – sensor) 36 to 97 mm (F – sensor) First active silicon strip is 8.2 mm from the beam line n+-on-n DOFZ silicon minimises resolution and signal loss after type inversion Double metal layer for detector readout

VELO in the Vacuum: 

Double sided modules (1 x R and 1 x F sensor) Cooling contacts Carbon fibre paddle TPG* substrate with carbon fibre frame 16 Beetle chips Silicon Sensor Secondary vacuum Chamber Retracting Detector Half Silicon operating temperature -7oC *Thermalised Pyrolytic Graphite VELO in the Vacuum

VELO environment: 

VELO environment VELO sensors operate in a harsh non-uniform radiation environment fluence to inner regions 1.3 x 1014 neq./cm2 fluence to outer regions 5 x 1012 neq./cm2 Estimated to survive 3 years

May 2004 test beam results: 

May 2004 test beam results 300mm S:N =18:1 200mm S:N =12:1 300mm n+-on-n R sensor 16 readout chips (Beetle 1.3) Prototype hybrid (K03) spillover: signal at 25ns after peak in % of the peak signal 30% (100V bias) (30% is the maximum before displaced vertex trigger performance degraded.)

Possible upgrade choices for 2010n+-on-p, pixels, 3D, …many possibilities : 

Possible upgrade choices for 2010 n+-on-p, pixels, 3D, …many possibilities Magnetic Czochralski silicon Standard industrial method of producing silicon Cheap Naturally high Oxygen content more radiation hard? Test beam at the CERN SPS of a MCz detector* before and after irradiation LHC speed electronics (40 MHz) (3 SCTA (analogue) chips) p+-on-n MCz material Area read out = 6.1 x 1.92 cm 380 mm thick, 50 mm pitch *Many thanks to the Helsinki Institute of Physics for the MCz detector

MCz test beam results: 

MCz test beam results S / N > 23.5 + 2.5 (380 mm thick) Depleted the detector (~550 V) (CV measured Vdep ~ 420 V) 1.3 x 1014 24 GeV p/cm2 S/N = 15 4.3 x 1014 24 GeV p/cm2 S/N = 11 (under depleted) 7.0 x 1014 24 GeV p/cm2 S/N = 7 (under depleted) Signal [ADC Counts] Bias Voltage [V]] Signal [ADC Counts] Bias Voltage [V]]

Further MCz benefits: 

Further MCz benefits The VELO currently uses n+-on-n DOFZ silicon detectors This is necessary because we want material where the high field side is always on the strip side in order to prevent loss of resolution and signal However, n+-on-n is expensive and restricts the choice of processing company (requires double-sided processing) We have found that MCz does not type invert using the Transient Current Technique (measured to 5 x 1014 p/cm2)* *Work performed under the PH-TA1/SD group, CERN (A Bates & M Moll)

Transient Current Technique - experiment which probes the electric field inside the detectors type inversion in FZ silicon: 

Transient Current Technique - experiment which probes the electric field inside the detectors type inversion in FZ silicon F = 1.74x1013 24 GeV/c p F= 3.61x1014 24 GeV/c p

Slide12: 

TCT in MCz Time [ns] I [V/50Ohms] Low field High field MCz silicon always has the high field on the strip side of the detector => standard p+-on-n MCz detectors could replace the VELO n+-on-n DOFZ silicon, however, further investigation of the radiation tolerance of MCz is required 14

Status & Conclusions: 

Status & Conclusions The VELO is moving from the last prototype testing to sensor production first pre-production sensors are just arriving (October 2004) test beam of final module configuration in November 2004 R&D for possible upgrade solutions is continuing e.g. for MCz first operation of full size MCz sensor with LHC speed electronics in test beam further test beam studies planned non-inversion of MCz material under radiation demonstrated additional microscopic studies underway

TCT Review: 

TCT Review Illuminate front (p+) or rear (n+) side of detector with 660 nm photons Light penetrates only a few mm depth Ramo’s theorem dictates signal will be dominated by one type of charge carrier I(t) = q E(u(t)) u(t)drift e.g. hole dominated curent (hole injection) Illuminate rear (n+) side of detector Time [ns]

Signal treatment: 

Signal treatment Deconvolution of the true signal from the measured signal Measured signal = detector signal  transfer function Transfer function: I(t)=tTCT/R x dUosc(t)/dt + Uosc(t)/R R = 50W from input of preamp tTCT= RCd (Cd = detector capacitance)

Back up slide 2 – signal examples: 

Back up slide 2 – signal examples Black = signal as measured on the scope Red = Trapping corrected signal

IV/CV analysis: 

IV/CV analysis CV measurements - 10kHz Measurement at room temperature, then corrected to 20oC Guard rings grounded Annealed for 4 min / 80oC FZ (f2) DOFZ (W317) DOFZ (d1) MCz (n320) 24 GeV/c Proton Fluence [cm-2] 24 GeV/c Proton Fluence [cm-2] 24 GeV/c Proton Fluence [cm-2] 24 GeV/c Proton Fluence [cm-2] Vfd [V] Vfd [V] Vfd [V] Vfd [V]

TCT Diagram: 

Pulse duration min 1.5 ns FWHM Rise time of signal 1.5 ns Almost no detector shaping from electronics Custom written LabVIEW DAQ ROOT analysis of data TCT Diagram

MCz: 

MCz

Slide20: 

Beam Test: Setup Back up slide from D Eckstein, Vertex 2004

Slide21: 

Modules recently tested in Summer 2003: 200mm thick PR03 n-on-n R-sensor 1 Beetle1.2 on PCB 1 chip region read out in June 2004: 300mm thick PR03 n-on-n R-sensor fully populated K03 hybrid Beetle1.3 tested many regions read out Data with tracks in telescope single sample track data not yet analysed – use stand-alone 15 consecutive samples read out Back up slide from D Eckstein, Vertex 2004

Slide22: 

Beam Test 2003 – Results 300mm extrapolation 200mm measurement S/N and Spillover for a set of Beetle Bias settings S/N for 200mm at the lower side  test 300mm spillover: signal at 25ns after peak in % of the peak signal Back up slide from D Eckstein, Vertex 2004

Slide23: 

new 2004 Data- Results S/N for 300mm agrees with scaled 200mm the K03 hybrid (and other components in the chain) do not add noise S/N in agreement with requirements – should we use the thicker sensors? Back up slide from D Eckstein, Vertex 2004

Slide24: 

new 2004 Data- Results it is safer to run at ~100V Back up slide from D Eckstein, Vertex 2004