gem r&d for tpc readout - university of victoriakarlen/talks/tpc/bnl01.pdf14 november 2001 dean...

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GEM R&D for TPC Readout RHIC Detector Workshop BNL, November 14, 2001 Dean Karlen Carleton University Carleton GEM/TPC group: Bob Carnegie, Jacques Dubeau, Madhu Dixit, D.K., Hans Mes http://www.physics.carleton.ca/~karlen/gem

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Page 1: GEM R&D for TPC Readout - University of Victoriakarlen/talks/tpc/bnl01.pdf14 November 2001 Dean Karlen / Carleton University 2 Outline Brief summary of LC tracking issues TPC readout

GEM R&D for TPC Readout

RHIC Detector WorkshopBNL, November 14, 2001

Dean KarlenCarleton University

Carleton GEM/TPC group: Bob Carnegie, Jacques Dubeau, Madhu Dixit, D.K., Hans Mes

http://www.physics.carleton.ca/~karlen/gem

Page 2: GEM R&D for TPC Readout - University of Victoriakarlen/talks/tpc/bnl01.pdf14 November 2001 Dean Karlen / Carleton University 2 Outline Brief summary of LC tracking issues TPC readout

14 November 2001 Dean Karlen / Carleton University 2

Outline

Brief summary of LC tracking issuesTPC readout with GEMsGEM R&D studies at Carleton

space point resolution (x-rays)tracking resolution (cosmics)

Summary

Page 3: GEM R&D for TPC Readout - University of Victoriakarlen/talks/tpc/bnl01.pdf14 November 2001 Dean Karlen / Carleton University 2 Outline Brief summary of LC tracking issues TPC readout

14 November 2001 Dean Karlen / Carleton University 3

LC tracking systems

Tracking requirements:good momentum resolution for high energy isolated charged particles

recoil mass resolution for dileptons in HZend-point resolution for leptonic susy decays

reconstruction of hadron jetsgood two-track separationenergy flow requires good absolute position resolution with minimal mass

15 (GeV/c) 105)/1( −−×≈∆ tp

Page 4: GEM R&D for TPC Readout - University of Victoriakarlen/talks/tpc/bnl01.pdf14 November 2001 Dean Karlen / Carleton University 2 Outline Brief summary of LC tracking issues TPC readout

14 November 2001 Dean Karlen / Carleton University 4

LC tracking systems

To achieve these requirements:High magnetic fields (~ 4 T)Large tracking volume3D space point measurements

less sensitive to accelerator backgrounds

European and US baselineLC detector designs include alarge Time Projection Chamber

Page 5: GEM R&D for TPC Readout - University of Victoriakarlen/talks/tpc/bnl01.pdf14 November 2001 Dean Karlen / Carleton University 2 Outline Brief summary of LC tracking issues TPC readout

14 November 2001 Dean Karlen / Carleton University 5

TPC tracker for a future LC

European design:

Page 6: GEM R&D for TPC Readout - University of Victoriakarlen/talks/tpc/bnl01.pdf14 November 2001 Dean Karlen / Carleton University 2 Outline Brief summary of LC tracking issues TPC readout

14 November 2001 Dean Karlen / Carleton University 6

LC TPC R&D underway

International collaboration formed:Aachen, Carleton, CERN, DESY, Hamburg, Karlsruhe, Krakow, LBNL, Orsay, Saclay, MIT, NIKHEF, Novosibirsk, MPI Munich, RostockSeveral issues:

gas choicereadout technology (emphasis of R&D):

Gas Electron Multiplier (GEM)Micromesh Gaseous Structure (micromegas)conventional pads or siliconconventional wire chamber

pad geometryelectronics

goal: complete R&D and prototype: 2-3 years

see: DESY-PRC R&D 01/03October 4, 2001

Page 7: GEM R&D for TPC Readout - University of Victoriakarlen/talks/tpc/bnl01.pdf14 November 2001 Dean Karlen / Carleton University 2 Outline Brief summary of LC tracking issues TPC readout

14 November 2001 Dean Karlen / Carleton University 7

Outline

Brief summary of LC tracking issuesTPC readout with GEMsGEM R&D studies at Carleton

space point resolution (x-rays)tracking resolution (cosmics)

Summary

Page 8: GEM R&D for TPC Readout - University of Victoriakarlen/talks/tpc/bnl01.pdf14 November 2001 Dean Karlen / Carleton University 2 Outline Brief summary of LC tracking issues TPC readout

14 November 2001 Dean Karlen / Carleton University 8

Gas Electron Multiplier (GEM)

Edrift = 0.2 – 1.0 kV/cm

∆V ≅ 400 V

∆V ≅ 400 V

Etransfer ≅ 3 kV/cm

Einduction ≅ 3.5 kV/cm

Readout pads

Page 9: GEM R&D for TPC Readout - University of Victoriakarlen/talks/tpc/bnl01.pdf14 November 2001 Dean Karlen / Carleton University 2 Outline Brief summary of LC tracking issues TPC readout

14 November 2001 Dean Karlen / Carleton University 9

Using a GEM for TPC readout

Conventional TPCreadout

GEM TPCreadout

Induced signals (motion of positive ions) spread over large area.

Direct signals (electrons on pads) spread over smaller area. Induced signals (e- motion) also present.

Page 10: GEM R&D for TPC Readout - University of Victoriakarlen/talks/tpc/bnl01.pdf14 November 2001 Dean Karlen / Carleton University 2 Outline Brief summary of LC tracking issues TPC readout

14 November 2001 Dean Karlen / Carleton University 10

Potential advantages for GEM readout

Improved space point resolutionE×B and track angle systematics suppressed

Improved two particle separation powerr -φ : signals distributed over smaller areaz : faster pulses (ve > vion)

Natural ion feedback suppressionno gating required (non-triggered expt.)

Less mass in TPC endcapno wires held under tension

present focus

Page 11: GEM R&D for TPC Readout - University of Victoriakarlen/talks/tpc/bnl01.pdf14 November 2001 Dean Karlen / Carleton University 2 Outline Brief summary of LC tracking issues TPC readout

14 November 2001 Dean Karlen / Carleton University 11

Outline

Brief summary of LC tracking issuesTPC readout with GEMsGEM R&D studies at Carleton

space point resolution (x-rays)tracking resolution (cosmics)

Summary

Page 12: GEM R&D for TPC Readout - University of Victoriakarlen/talks/tpc/bnl01.pdf14 November 2001 Dean Karlen / Carleton University 2 Outline Brief summary of LC tracking issues TPC readout

14 November 2001 Dean Karlen / Carleton University 12

Point resolution studies at Carleton

x-ray tube

2D micrometerstage

pin holeGEM cell

Page 13: GEM R&D for TPC Readout - University of Victoriakarlen/talks/tpc/bnl01.pdf14 November 2001 Dean Karlen / Carleton University 2 Outline Brief summary of LC tracking issues TPC readout

14 November 2001 Dean Karlen / Carleton University 13

GEM foils and pads for this study

fabricated at the CERN PCB workshop

GEM foil

140 µm

50 µm

GEM pads

2.5 mm pitchhexagons

Page 14: GEM R&D for TPC Readout - University of Victoriakarlen/talks/tpc/bnl01.pdf14 November 2001 Dean Karlen / Carleton University 2 Outline Brief summary of LC tracking issues TPC readout

14 November 2001 Dean Karlen / Carleton University 14

Details

x-ray mean energy: 4.5 keVpinhole diameter: ~50 µmGas: Ar CO2 (~90:10) / P10 : Ar CH4 (90:10)pre-amps:

fast Lecroy HQV 810 with Ar CO2

slower ALEPH TPC pre-amp with P10

readout:two 4-channel digital scopes (9 bit ADC)

500 MHz sampling for HQV 810125 MHz sampling for ALEPH preamps

Page 15: GEM R&D for TPC Readout - University of Victoriakarlen/talks/tpc/bnl01.pdf14 November 2001 Dean Karlen / Carleton University 2 Outline Brief summary of LC tracking issues TPC readout

14 November 2001 Dean Karlen / Carleton University 15

An event

1

2

3

4 6

7

8

-0.2

-0.15

-0.1

-0.05

0

0 0.02 0.04 0.06 0.08 0.1x 10 -5

-0.2

-0.1

0

0 0.02 0.04 0.06 0.08 0.1x 10 -5

-0.02

-0.01

0

0 0.02 0.04 0.06 0.08 0.1 x 10-5

-0.015

-0.01

-0.005

0

0 0.02 0.04 0.06 0.08 0.1x 10

-5 -0.015

-0.01

-0.005

0

0 0.02 0.04 0.06 0.08 0.1x 10 -5

-0.02

-0.01

0

0 0.02 0.04 0.06 0.08 0.1x 10 -5

-0.1

-0.075

-0.05

-0.025

0

0 0.02 0.04 0.06 0.08 0.1x 10 -5

Ar CO2 (90:10)HQV810 preamps

Page 16: GEM R&D for TPC Readout - University of Victoriakarlen/talks/tpc/bnl01.pdf14 November 2001 Dean Karlen / Carleton University 2 Outline Brief summary of LC tracking issues TPC readout

14 November 2001 Dean Karlen / Carleton University 16

Localization from charge sharing

1

2 8

-0.2

-0.15

-0.1

-0.05

0

0 0.02 0.04 0.06 0.08 0.1x 10

-5

-0.2

-0.1

0

0 0.02 0.04 0.06 0.08 0.1x 10-5

-0.1

-0.075

-0.05

-0.025

0

0 0.02 0.04 0.06 0.08 0.1x 10

-5

x

y

v

PAD 2 PAD 8

PAD 10.6

0.8

1

1.2

1.4

1.6

1.8

2

2.2

-0.8 -0.6 -0.4 -0.2 0 0.2 0.4 0.6 0.8

10

10

20

20

30

30

40

40

50

50

60

60

70

70

80

80

90

90Pad 1 fraction

Pad 8 fraction

x coordinate (mm)

y co

ordi

nate

(mm

)

2D Gaussian model

Page 17: GEM R&D for TPC Readout - University of Victoriakarlen/talks/tpc/bnl01.pdf14 November 2001 Dean Karlen / Carleton University 2 Outline Brief summary of LC tracking issues TPC readout

14 November 2001 Dean Karlen / Carleton University 17

Charge sharing result – P10

(x,y)col = (0.4,1.243) mm y = 1.265 mmσy = 0.064 mm

x = 0.408 mmσx = 0.066 mm

Page 18: GEM R&D for TPC Readout - University of Victoriakarlen/talks/tpc/bnl01.pdf14 November 2001 Dean Karlen / Carleton University 2 Outline Brief summary of LC tracking issues TPC readout

14 November 2001 Dean Karlen / Carleton University 18

Scan over entire pad

100 µm circles centred at pin hole locations during scan

With P10 gas:cloud size 550 µmx,y standard deviations: ~70 µm

Page 19: GEM R&D for TPC Readout - University of Victoriakarlen/talks/tpc/bnl01.pdf14 November 2001 Dean Karlen / Carleton University 2 Outline Brief summary of LC tracking issues TPC readout

14 November 2001 Dean Karlen / Carleton University 19

Localization from charge sharing

Method works only in regions where significant charge is deposited on 3 pads

P10Ar CO2

Chargesharingregions

Chargesharingregion

Page 20: GEM R&D for TPC Readout - University of Victoriakarlen/talks/tpc/bnl01.pdf14 November 2001 Dean Karlen / Carleton University 2 Outline Brief summary of LC tracking issues TPC readout

14 November 2001 Dean Karlen / Carleton University 20

Localization from induced signals

3

4 6

7

-0.02

-0.01

0

0 0.02 0.04 0.06 0.08 0.1 x 10-5

-0.015

-0.01

-0.005

0

0 0.02 0.04 0.06 0.08 0.1x 10

-5

-0.015

-0.01

-0.005

0

0 0.02 0.04 0.06 0.08 0.1x 10

-5

-0.02

-0.01

0

0 0.02 0.04 0.06 0.08 0.1x 10 -5

1.75

2

2.25

2.5

2.75

3

3.25

3.5

3.75

4

0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.08 0.09 0.1 0.11dist

ance

fro

m p

ad c

entr

e (m

m)

-3

-2

-1

0

1

2

3

-3 -2 -1 0 1 2 3

-5

-

-

rel. signal amplitude

Page 21: GEM R&D for TPC Readout - University of Victoriakarlen/talks/tpc/bnl01.pdf14 November 2001 Dean Karlen / Carleton University 2 Outline Brief summary of LC tracking issues TPC readout

14 November 2001 Dean Karlen / Carleton University 21

Scan over entire pad

With P10 gas:x,y standard deviations: ~80 µmnote: systematics in x clearly seen

Page 22: GEM R&D for TPC Readout - University of Victoriakarlen/talks/tpc/bnl01.pdf14 November 2001 Dean Karlen / Carleton University 2 Outline Brief summary of LC tracking issues TPC readout

14 November 2001 Dean Karlen / Carleton University 22

Strip geometry – charge sharing

strip 1

frac

tion

of c

harg

e co

llect

ed b

y st

rip 1

With P10 gas:x standard deviation: ~70 µm

strip 1 strip 2

Gaussian model

Linear model

x

strip 2

Page 23: GEM R&D for TPC Readout - University of Victoriakarlen/talks/tpc/bnl01.pdf14 November 2001 Dean Karlen / Carleton University 2 Outline Brief summary of LC tracking issues TPC readout

14 November 2001 Dean Karlen / Carleton University 23

Strip geometry – induced signals

2

2.5

3

3.5

4

4.5

5

5.5

6

0.02 0.04 0.06 0.08 0.1 0.12 0.14 0.16 0.18 0.2

dist

ance

fro

m s

trip

cen

tre

Strip geometry has larger induced signals by factor of 2 – 3

x standard deviation: ~70 µm

strips

pads

rel. signal amplitude

Page 24: GEM R&D for TPC Readout - University of Victoriakarlen/talks/tpc/bnl01.pdf14 November 2001 Dean Karlen / Carleton University 2 Outline Brief summary of LC tracking issues TPC readout

14 November 2001 Dean Karlen / Carleton University 24

Outline

Brief summary of LC tracking issuesTPC readout with GEMsGEM R&D studies at Carleton

space point resolution (x-rays)tracking resolution (cosmics)

Summary

Page 25: GEM R&D for TPC Readout - University of Victoriakarlen/talks/tpc/bnl01.pdf14 November 2001 Dean Karlen / Carleton University 2 Outline Brief summary of LC tracking issues TPC readout

14 November 2001 Dean Karlen / Carleton University 25

Tracking studies

Mini-TPC constructed

15 c

m

Page 26: GEM R&D for TPC Readout - University of Victoriakarlen/talks/tpc/bnl01.pdf14 November 2001 Dean Karlen / Carleton University 2 Outline Brief summary of LC tracking issues TPC readout

14 November 2001 Dean Karlen / Carleton University 26

Tracking studies

Cosmic ray telescope Readout pad layout

5 m

m

2.5 mm

Page 27: GEM R&D for TPC Readout - University of Victoriakarlen/talks/tpc/bnl01.pdf14 November 2001 Dean Karlen / Carleton University 2 Outline Brief summary of LC tracking issues TPC readout

14 November 2001 Dean Karlen / Carleton University 27

Details – cosmic data taking

Gas: Ar CH4 (90:10)Drift field: 135 V/cmpre-amps: ALEPH TPC pre-ampreadout: 32 channel custom FADC

200 MHz sampling8 bit

trigger rates:cosmic telescope: 0.4 Hzrequire at least one pad hit: 0.04 Hz

Data:6 days of running (end of October, 2001)

Page 28: GEM R&D for TPC Readout - University of Victoriakarlen/talks/tpc/bnl01.pdf14 November 2001 Dean Karlen / Carleton University 2 Outline Brief summary of LC tracking issues TPC readout

14 November 2001 Dean Karlen / Carleton University 28

First event

BOTTOMTOP

Page 29: GEM R&D for TPC Readout - University of Victoriakarlen/talks/tpc/bnl01.pdf14 November 2001 Dean Karlen / Carleton University 2 Outline Brief summary of LC tracking issues TPC readout

14 November 2001 Dean Karlen / Carleton University 29

Gain stability

Charge per row Charge vs time

Stable within 5%

Page 30: GEM R&D for TPC Readout - University of Victoriakarlen/talks/tpc/bnl01.pdf14 November 2001 Dean Karlen / Carleton University 2 Outline Brief summary of LC tracking issues TPC readout

14 November 2001 Dean Karlen / Carleton University 30

Tracking studies

Fit x-y and y-z separately

y-z fit:for each row form weighted average of pulse arrival timeperform unweighted linear fit of the 5 rowy-coordinates vs row timespulse arrival time (50% rise) dependant on pulse amplitude

needs further study

Page 31: GEM R&D for TPC Readout - University of Victoriakarlen/talks/tpc/bnl01.pdf14 November 2001 Dean Karlen / Carleton University 2 Outline Brief summary of LC tracking issues TPC readout

14 November 2001 Dean Karlen / Carleton University 31

y-z fit results

Not diffusion limitedpulse arrival time definition needs improving

800 micron resolution independent of drift length

Page 32: GEM R&D for TPC Readout - University of Victoriakarlen/talks/tpc/bnl01.pdf14 November 2001 Dean Karlen / Carleton University 2 Outline Brief summary of LC tracking issues TPC readout

14 November 2001 Dean Karlen / Carleton University 32

x-y fit

use model of uniform line of charge, with Gaussian transverse spread, σ

charge fractions given by integral over pad

fit uses observed charge fractions within each row

min χ2 with x0, φ and σ free

ionization fluctuationsnot included in modelunimportant for φ = 0leads to track angle effect on resolution

Page 33: GEM R&D for TPC Readout - University of Victoriakarlen/talks/tpc/bnl01.pdf14 November 2001 Dean Karlen / Carleton University 2 Outline Brief summary of LC tracking issues TPC readout

14 November 2001 Dean Karlen / Carleton University 33

Transverse width of line charge

Results from fit of data: diffusion apparent

σ(m

m)

σ2(m

m2 )

drift time (ns) drift time (ns)

Page 34: GEM R&D for TPC Readout - University of Victoriakarlen/talks/tpc/bnl01.pdf14 November 2001 Dean Karlen / Carleton University 2 Outline Brief summary of LC tracking issues TPC readout

14 November 2001 Dean Karlen / Carleton University 34

Track x0 resolution

x0 resolution from single row:

do fit excluding the row: x0, φ, σfreedo fit for single row: only x0freecompare 1 row x0 to 4 row x0

σx = 220 ± 20 µm σx = 320 ± 10 µm

σx = 420 ± 8 µm σx = 560 ± 8 µm

Page 35: GEM R&D for TPC Readout - University of Victoriakarlen/talks/tpc/bnl01.pdf14 November 2001 Dean Karlen / Carleton University 2 Outline Brief summary of LC tracking issues TPC readout

14 November 2001 Dean Karlen / Carleton University 35

Centroid finding

Linear weighted x0 coordinate less accurate

linear weightingGaussian modelσx = 220 ± 20 µm σx = 290 ± 20 µm

Page 36: GEM R&D for TPC Readout - University of Victoriakarlen/talks/tpc/bnl01.pdf14 November 2001 Dean Karlen / Carleton University 2 Outline Brief summary of LC tracking issues TPC readout

14 November 2001 Dean Karlen / Carleton University 36

Track angle effect

Appears to be significant, but small statistics

σx = 110 ± 15 µm σx = 280 ± 50 µm

05.0<φ 15.005.0 <φ<mm 10<z mm 10<z

Page 37: GEM R&D for TPC Readout - University of Victoriakarlen/talks/tpc/bnl01.pdf14 November 2001 Dean Karlen / Carleton University 2 Outline Brief summary of LC tracking issues TPC readout

14 November 2001 Dean Karlen / Carleton University 37

Sample events (z < 10 mm, |φ| < 0.05)

Page 38: GEM R&D for TPC Readout - University of Victoriakarlen/talks/tpc/bnl01.pdf14 November 2001 Dean Karlen / Carleton University 2 Outline Brief summary of LC tracking issues TPC readout

14 November 2001 Dean Karlen / Carleton University 38

Sample events (z < 10 mm, |φ| < 0.05)

Page 39: GEM R&D for TPC Readout - University of Victoriakarlen/talks/tpc/bnl01.pdf14 November 2001 Dean Karlen / Carleton University 2 Outline Brief summary of LC tracking issues TPC readout

14 November 2001 Dean Karlen / Carleton University 39

Sample events (z < 10 mm, |φ| < 0.05)

Page 40: GEM R&D for TPC Readout - University of Victoriakarlen/talks/tpc/bnl01.pdf14 November 2001 Dean Karlen / Carleton University 2 Outline Brief summary of LC tracking issues TPC readout

14 November 2001 Dean Karlen / Carleton University 40

Sample events (z < 10 mm, |φ| < 0.05)

Page 41: GEM R&D for TPC Readout - University of Victoriakarlen/talks/tpc/bnl01.pdf14 November 2001 Dean Karlen / Carleton University 2 Outline Brief summary of LC tracking issues TPC readout

14 November 2001 Dean Karlen / Carleton University 41

Sample events (z < 10 mm, |φ| < 0.05)

Page 42: GEM R&D for TPC Readout - University of Victoriakarlen/talks/tpc/bnl01.pdf14 November 2001 Dean Karlen / Carleton University 2 Outline Brief summary of LC tracking issues TPC readout

14 November 2001 Dean Karlen / Carleton University 42

Sample events (z < 10 mm, |φ| < 0.05)

Page 43: GEM R&D for TPC Readout - University of Victoriakarlen/talks/tpc/bnl01.pdf14 November 2001 Dean Karlen / Carleton University 2 Outline Brief summary of LC tracking issues TPC readout

14 November 2001 Dean Karlen / Carleton University 43

Future plans for Carleton studies

Continue cosmic tracking studiesalternative gases (lower diffusion)include calibration constants (none so far!)alternative readout pad geometriesQ: can direct charge signals alone provide optimal resolution and two particle separation?Q: are the small induced signals helpful?

Try new ideas for spreading signal over more pads

resistive layer above pads that absorbs charge and leave only induced signals

Page 44: GEM R&D for TPC Readout - University of Victoriakarlen/talks/tpc/bnl01.pdf14 November 2001 Dean Karlen / Carleton University 2 Outline Brief summary of LC tracking issues TPC readout

14 November 2001 Dean Karlen / Carleton University 44

Summary

TPC is the leading candidate for a future linear collider

Coordinated international effort for R&D for a LC TPCemphasis is on new readout methods involving micro-pattern gas detectors

Findings from Carleton GEM/TPC R&D:Good space point resolution and tracking resolution achieved with relatively large pads

pad diameter ~ 4 x transverse diffusion is ok

GEM readout for TPCs looks promising