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High Precision Wire Chambers. at LHC. Historic remarks Wire chambers at LHC Precision tracking: ATLAS Muon Drift Tubes Precision timing: LHCb Muon Trigger Chambers. Werner Riegler, CERN. The Basic Objects. Tube Geiger- Müller, 1928. Multi Wire Geometry, in H. Friedmann 1949 .

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High precision wire chambers l.jpg
High Precision Wire Chambers

at LHC

  • Historic remarks

  • Wire chambers at LHC

  • Precision tracking: ATLAS Muon Drift Tubes

  • Precision timing: LHCb Muon Trigger Chambers

Werner Riegler, CERN

W. Riegler/CERN


The basic objects l.jpg
The Basic Objects

Tube Geiger- Müller, 1928

Multi Wire Geometry, in H. Friedmann 1949

G. Charpak 1968

  • These geometries are widely used at LHC

  • Basic elements are unchanged since many years

  • Electronics has changed considerably

W. Riegler/CERN

historic remarks


Detector electronics 1925 l.jpg
Detector + Electronics 1925

were quite different from today

‘Über das Wesen des Compton Effekts’

W. Bothe, H. Geiger, April 1925

  • Bohr, Kramers, Slater Theorie:

  • energy is only conserved statistically

  • testing Compton effect

‘ Spitzenzähler ’

W. Riegler/CERN

historic remarks


Detector electronics 19254 l.jpg
Detector + Electronics 1925

‘Über das Wesen des Compton Effekts’, W. Bothe, H. Geiger, April 1925

  • ‘’Electronics’’:

    • Cylinders ‘P’ are on HV.

    • The needles of the counters are insulated and connected to electrometers.

  • Coincidence Photographs:

    • A light source is projecting both electrometers on a moving film role.

    • Discharges in the counters move the electrometers , which are recorded on the film.

    • The coincidences are observed by looking through many meters of film.

W. Riegler/CERN

historic remarks


Detector electronics 1929 l.jpg
Detector + Electronics 1929

‘were not very different from today’

‘Zur Vereinfachung von Koinzidenzzählungen’

W. Bothe, November 1929

Coincidence circuit for 2 tubes

Geiger Müller Tubes, 1928

W. Riegler/CERN

historic remarks


1930 1934 l.jpg
1930 - 1934

Cosmic ray telescope 1934

Rossi 1930: Coincidence circuit for n tubes

W. Riegler/CERN

historic remarks


Atlas muon chamber 2000 l.jpg
ATLAS Muon Chamber 2000

looks fairly similar to 1934

W. Riegler/CERN

historic remarks


Wire chambers at lhc l.jpg
Wire Chambers at LHC

  • Cloud Chambers, Bubble Chambers, Spark Chambers … have disappeared but wire chambers are still popular.

  • While the principle detecting element has changed very little, the readout electronics integration has changed dramatically.

  • Situation can be compared to astronomy. Telescope mirrors haven’t changed much but detecting elements (CCDs etc.) improved a lot.

W. Riegler/CERN

wire chamber at LHC


Atlas l.jpg
ATLAS

  • Cathode Strip Chambers:

    • h=2.54mm, s=2.54mm

    • 67k cathode channels

    • Ar/CO2/CF4

    •   60m

  • Thin Gap Chambers

    • h=1.4mm, s=1.8mm

    • 440k cathode and anode channels

    • n-Pentane /CO2 45/55

    • : 99% in 25ns with single plane

  • Monitored Drift Tubes

    • R=15mm

    • 370k anode channels

    • Ar/CO2 93/7

    •   80m

  • Transition Radiation Tracker

    • R=2mm

    • 372k anode channels

    • Xe/CO2/CF4 70/10/20

    •   150m

Other than that - Silicon and RPCs

W. Riegler/CERN

wire chamber at LHC


Slide10 l.jpg
CMS

  • Cathode Strip Chambers:

    • 2h=9.5mm, s=3.12mm

    • 211k anode channels for timing

    • 273k cathode channels for position

    • Ar/CO2/CF4 30/50/20

    •   75-150m

  • Rectangular ‘Drift Tubes’

    • w=42mm, h=10.5mm

    • 195k anode channels

    • Ar/CO2 85/15

    •   250m

Other than that - Silicon and RPCs

W. Riegler/CERN

wire chamber at LHC


Slide11 l.jpg
LHCb

  • Cathode Strip Chambers:

    • h=2.5mm, s=1.5mm

    • 80k cathode and anode channels

    • Ar/CO2/CF4 40/50/10

    • t 3ns for two layers

  • Straw Tracker

    • R=2.5mm

    • 110k (51k) anode channels

    • Ar/CO2/CF4 75/10/15

    •   200m

Other than that - Silicon and RPCs

W. Riegler/CERN

wire chamber at LHC


Alice l.jpg
ALICE

  • TPC with wire chamber

    • 1.25-2.5mm wire pitch

    • 2 - 3 mm plane separation

    • 570k Readout Pads

    • Ne/CO2 90/10

    •   1mm

W. Riegler/CERN

wire chambers at LHC


Slide13 l.jpg

Precision tracking: ATLAS muon system

Precision timing: LHCb muon system

W. Riegler/CERN


Precision tracking atlas muon drift tubes l.jpg

Precision Tracking: ATLAS Muon Drift Tubes

  • Magnetic field

    • Toroidal magnetic field (0.5T) provided by 8 superconducting coils.

  • Three muon stations

    • ~1200 chambers,

    • Outer diameter ~20m,

    • Sagitta measurement  muons with pT=1 TeV/c will show a sagitta of ~500 µm

    •  for 10% momentum resolution we need a sagitta measurement accuracy of ~50 µm

  • Monitored Drift Tubes (MDT)

    • each chamber consists of 23 (24) layers of drift tubes ( 3cm)

    • chamber deformations monitored with in-plane alignment system

precision tracking


Principle of operation l.jpg
Principle of Operation Drift Tubes

  • Ionization

    • muon produces 100 clusters/cm with 2-3 e- (3 bars Ar/CO2 93/7)

  • Electron Drift

    • maximum drift-time ~800ns for baseline gas

  • Space-drift-time-relation  radius r

    • obtained by auto-calibration

W. Riegler/CERN

precision tracking


Drift chambers l.jpg

Drift Chambers Drift Tubes

  • Auto-calibration of the rt-relation

    • start with good estimate for rt-relation

    • track fit  residual distribution

    • rt-relation corrected with the mean of the residual distribution

    • convergence after a few iterations

    • muon tracks with an angular spread (~10°) are used to avoid systematic errors

    •  rt-relation with a typical accuracy of 10µm

precision tracking


Requirements l.jpg
Requirements Drift Tubes

  • Parameters

    • resolution < 80µm for a single wire

    •  3cm, 370 000 channels

    • rates up to 500 Hz/cm2 (400 kHz/tube)

    • total charge 1C/cm in 10 years

  • Choice of gas

    • low diffusion, fast, linear, stand 1C/cm

    • Ar/N2/CH4 91/4/5: fast, linear, cannot stand 1C/cm

    • Ar/CO2 93/7: slow, nonlinear, however the only gas known to survive 1C/cm

      Therefore Ar/CO2 the ATLAS baseline gas !

W. Riegler/CERN

precision tracking


Single tube performance l.jpg
Single Tube Performance Drift Tubes

for Ar/N2/CH4

NIMA 443(2000) 156-63

  • ‘typical’ signal shape

    • for tp=5 and tp=15ns

    • many ‘spikes’ due to clustering

    • tp=15ns makes the signals more ‘smooth’

  • Simulated and measured resolution

    • simulation and measurement match very well

    • close to the wire: primary ionization effects

    • far from the wire: diffusion

W. Riegler/CERN

precision tracking


Single tube performance19 l.jpg
Single Tube Performance Drift Tubes

for Ar/N2/CH4

NIMA 443(2000) 156-63

  • Effect of diffusion

    • increases with distance for the wire

  • Effect of charge deposit fluctuation

    • decreases the primary cluster and time slewing effects

W. Riegler/CERN

precision tracking


Single tube performance20 l.jpg
Single Tube Performance Drift Tubes

for Ar/N2/CH4

NIMA 443(2000) 156-63

  • Higher gas gain

    • improves resolution (less slewing effects) but no possible due to:

    • aging

    • space charge effects (gain drop)

  • Amplifier bandwidth

    • tp=5ns to tp=15ns:

    • only 10um difference

    • tp=15ns is nicer to handle

W. Riegler/CERN

precision tracking


Rate capability gain drop l.jpg
Rate Capability, Gain Drop Drift Tubes

NIMA 446(2000) 435-43

W. Riegler/CERN

precision tracking


Space charge effects l.jpg
Space Charge Effects Drift Tubes

for Ar/CO2

  • In addition to gain drop: space charge changes the electric field

    • shift of the rt-relation

  • Variations of the drift field

    • constant space charge wouldn’t give a problem

    • the drift field for the electrons of one event are influenced only by neighboring ion clouds (slice of 1cm)

    • only a few background events influence the drift field (~6 at 1500Hz/cm)

    • this number of preceding events of importance is Poisson distributed

    • each event has a different drift field and hence a different rt-relation

    •  resolution deterioration

  • Strong gas dependence

    • linear gases: small effect

    • non-linear gases: dominating effect

W. Riegler/CERN

precision tracking


Single tube performance23 l.jpg
Single Tube Performance Drift Tubes

for Ar/CO2

NIMA 446(2000) 435-43

NIMA 446(2000) 435-43

  • Resolution for low rate and 1.4kHz/cm

    • space charge effect deteriorates the resolution

    • the fluctuation of the space charge is responsible

    • calculation matches data very well

  • Effect of gas gain

    • at low rate higher gas gain improves the reoslution

    • at high rate the resolution decreases

W. Riegler/CERN

precision tracking


Atlas mdt front end electronics l.jpg
ATLAS MDT Front-End Electronics Drift Tubes

3.18 x 3.72 mm

Single Channel Block Diagram

  • 0.5m CMOS technology

    • 8 channel ASD + Wilkinson ADC

    • fully differential

    • 15ns peaking time

    • 32mW/channel

    • JATAG programmable

Harvard University, Boston University

W. Riegler/CERN

precision tracking


Precision timing lhcb muon system l.jpg
Precision Timing: Drift Tubes LHCb Muon System

  • A muon trigger is given by a coincidence of all 5 muon stations within 25ns

  • >99% efficiency/station in 20ns time window

  • Time resolution <3ns

  • Up to 1MHz/cm2

  • 50% Wire Chambers(MWPCs)

  • 50% RPCs (<1kHz/cm2)

W. Riegler/CERN

precision timing


Segmentation l.jpg
Segmentation Drift Tubes

quadrant of a single station

  • Segmentation in station 2

    • R4: 5 x 25 cm2

    • R3: 2.5 x 12.5 cm2

    • R2: 1.25 x 3.15 cm2

    • R1: 0.63 x 3.1 cm2

  • Segmentation achieved by

    • connecting wires  Wire Pad

    • segmenting cathode  Cathode Pad

    • limit to segmentation of cathode pads comes from crosstalk due to direct induction (1-2cm in this case)

s=1.5mm, 2h=5mm, developed by PNPI

W. Riegler/CERN

precision timing


Single station l.jpg
Single Station Drift Tubes

  • One station consists of 4 gaps forming a single chamber element

  • Two independent front end channels per station

LHCb, CERN

W. Riegler/CERN

precision timing


Cathode pad readout structure l.jpg
Cathode Pad Readout Structure Drift Tubes

  • Cathode signals are guided to the chamber side with traces on the bottom of the PCBs.

  • Danger of capacitive crosstalk due to high amplifier bandwidth (tp=10ns).

  • Input resistance must be lower than 50

  • Traces were carefully designed in order to minimize crosstalk (MAXWELL).

LHCb, CERN

W. Riegler/CERN

precision timing


Slide29 l.jpg

Full size prototype of inner region (close to beam-pipe) Drift Tubes

LHCb, CERN

W. Riegler/CERN


Detector parameters l.jpg
Detector Parameters Drift Tubes

  • Parameters

    • 5mm gas gap

    • 30 m wire

    • 1.5mm wire pitch

    • Readout pads on 1.6mm G10

  • Operating point

    • Ar/CO2/CF4 40/50/10

    • 3150V on wire

    • Gain 105

    • 8kV/cm on cathode, 260kV/cm on wire

  • Gas parameters

    • 21.4 clusters in 5mm for 10 GeV muon (Heed)

    • v  90m/ns (8kV/cm, Magboltz)

    • Proportional mode

    • Average total charge induced on cathode = 0.37pC (gain=105)

    • total avalanche charge=0.74pC

W. Riegler/CERN

precision timing


Performance of a single gap l.jpg
Performance of a Single Gap Drift Tubes

LHCb, CERN

  • Intrinsic time resolution 3ns

  • optimum amplifier peaking time 10ns

W. Riegler/CERN

precision timing


Efficiency and time resolution l.jpg
Efficiency and Time Resolution Drift Tubes

Double Gap

Efficiency and time resolution vs. HV

Efficiency and time resolution vs. threshold

LHCb, CERN

W. Riegler/CERN

precision timing


Comparison with garfield l.jpg
Comparison with GARFIELD Drift Tubes

  • Full Simulation

    • primary ionization (HEED)

    • drift, diffusion (MAGBOLTZ)

    • induced signals (GARFIELD)

  • no parameters to tune

  • we understand our detector

W. Riegler/CERN

precision timing


Measurement of edge effects l.jpg
Measurement of Edge Effects Drift Tubes

LHCb, CERN

‘chamber ends’ 1 gap size from first obstacle

‘chamber ends’ last wire

W. Riegler/CERN

precision timing


Front end electronics carioca l.jpg
Front End Electronics ‘CARIOCA’ Drift Tubes

3x4mm prototype, (2.5x3mm final)

  • 0.25m CMOS technology

    • chip is under development

    • 8 channel ASD

    • fully differential

    • 10ns peaking time

    • 30mW/channel

UFRJ Rio, CERN

W. Riegler/CERN

precision timing


Pulse shaping l.jpg
Pulse Shaping Drift Tubes

results from 3 prototype chips on a chamber

LHCb, CERN

  • detector signal has 1/(t+1.5ns) tail

  • dead time leads to inefficiency

  • shaping circuit for tail cancellation

  • prototype shows <50ns average dead time at the working point

W. Riegler/CERN

precision timing


Conclusions l.jpg
Conclusions Drift Tubes

  • Wire chambers will be widely used at LHC experiments for tracking and triggering.

  • Ar/CO2/CF4 gas mixtures are used because of their good aging properties.

  • Position resolutions of 80 m per single tube and 5ns per single MWPC layer are expected even for large systems.

  • The basic detector elements haven’t changed much, but the front-end electronics integration is progressing fast.

  • The long experience with wire chambers and the fact that one can calculate and predict their behavior very accurately makes this detector a competitive candidate also for future experiments.

W. Riegler/CERN


Detector simulation l.jpg
Detector Simulation Drift Tubes

  • Garfield (Rob Veenhof)

    • electric fields, particle drift, induced signals, electronics ….

  • Magboltz (Steve Biagi)

    • transport properties of gas mixtures

  • Heed (Igor Smirnov)

    • charge deposit of fast particles in gas mixtures

  • Very reliable simulation of all the chamber and signal processes

W. Riegler/CERN