design and construction of a gem-tpc prototype for r&d

Design and Construction of a GEM-TPC Prototype for R&D Purposes

J. Kaminski , , B. Ledermann ,T. Müller , L. Ropelewski and F. Sauli

1) 1,2) 1)S. Kappler

1) 2) 2)

1) Institut für Experimentelle Kernphysik, Karlsruhe University (Germany)2) CERN, EP Division, Geneva (Switzerland)

2003 IEEE NSS - Satellite Workshop on Micro-Pattern Detectors for Time Projection Chambers

Portland, Oregon (USA)19-25 October, 2003

Outline

Steffen Kappler et al.IEKP, Karlsruhe University (Germany)

CERN, Geneva (Switzerland)

4 Introduction

4 Design of the COMPASS Triple-GEMs

4 Design & Construction of the GEM-TPC Prototype 4 Design Requirements 4 Overview 4 Choice of Materials 4 Field Cage and Drift Cylinder 4 Multi-GEM Endcap

4 Performance Tests

4 Summary & Outlook

The Gas Electron Multiplier (GEM)Principle of Operation



The GEM foil

+ Kapton foil of 50mm, two-side copper-clad (5mm each)

+ Perforated with a high density of holes (etched in a photolithographic process, typically p=140mm, D=70mm, d=60mm)

+ High voltage on electrodes (~0.4kV)

+ Fieldlines from the volume above the GEM are strongly compressed into the holes:

-> Proportional Gas Amplification

The Gas Electron Multiplier (GEM)Multi-GEM Detectors



ioniz

ing p

art

icle drift cathode

GEM

GEM

GEM

readout PCB

readoutelectronics

ele

ctr

ic fie

ld

3mm

2mm

2mm

2mm

Principle

+ Parallel plate detector with one or more GEMs inserted

Features

+ Amplification in several stages grants stable operation (low discharge prob.)

+ Separation of gas amplification and readout stage gives high flexibility in the design of the readout pads / strips

Example:

+ Triple-GEM detector as used in the

Small-Area-Tracker (SAT) of the

COMPASS experiment at CERN

The COMPASS Triple-GEMsSmall Area Tracking (SAT) with GEM Detectors



Overview2+ Active area 31x31cm

o+ Radiation length 7.19 / onlyoo

+ Ar-CO (70:30) 2

+ 2D microstrip readout

COMPASS SAT

+ 20 GEM Detectors installed

+ Since 2001 very successful

operation in the experiment

Performance

+ Fully 2D efficient at G=8000

+ s = 45mm, s = 15nsx t

2+ Aging test up to >7mC/mm

Common Muon Proton Apparatus for Structure and Spectroscopy

The COMPASS Triple-GEMsFinal Detector Design



+Triple-GEM detector

Standard Geometry GEM-foils, segmented

on one side into 12 sectors (plus central disk)

+ 3 GEMs powered by resistive voltage divider

and operated at asymmetric gain distribution

+ 2D Readout, 2x768 strips

400mm pitch, 70 & 350mm width

+ Rigid support with Nomex honeycomb

and Vetronite skin

+ Total thickness 15mm

2+ Active area 31x31cm

+

30

7mm

NIM A 490 (2002) 177-203

NIM A 479 (2002) 294-308=> minimize risk due to discharges!

Design

The TPC PrototypeDesign Requirements



Practical / Technical Requirements

+ Easy mounting / dismounting

+ Only well known, non-outgassing

materials facing the gas volume

+ Readout PCB and FEE on ground

potential

Study Prospects+ Electron drift properties in various gases+ Ion feedback suppression+ Performance in strong magnetic fields+ Tracking studies

??

R&D Aspects+ Easy replacement / modification of: a) Gas amplification stage b) Readout PCB c) Front-end electronics+ Robust design, but with moderate material budget+ Irradiation with X-rays and low-energy

b-rays must be possible

The TPC PrototypeDesign Overview



Drift cylinder

+ Inner diameter d = 20cm

+ Length

Field cage

Endcaps

+ Detector can be equipped

with different MPGD-types

or micro pad designs

l = 25cm

and l = 12.5cm

+ Irradiation windows

foreseen

+ Double-layer layout

+ Validated up to 12kV

Field Cage and Drift CylinderDesign



Field Cage

+ Double-layer technology

+ 3mm wide rings with 4mm pitch

+ Resistive voltage dividers outside

Drift cathode

+ 10mm Stesalite with round

holes (as irradiation windows)

+ 125mm Kapton + 18mm copper

the counting gas in order to avoid: - Distortions of the electric field - Heating of the counting gas - Possible outgassing of the resistors - Metallic tips due to soldering

Field Cage and Drift CylinderDesign



Field cage foil

+ 2x18mm copper rings on 125mm Kapton + 60 (59) rings with p = 4mm, w=3mm+ offset between the two layers 2mm+ Kapton guarantees gas tightness

Two resistive voltage divider chains

+ 10MW Resistors (BC Components, . -5 MBB0207, 1% tolerance, temp. coeff. 5 10 / K)

+ Total resistivity 294MW+ Dissipation 170mW @ 10kV

Schematic view of the layers

50mm copper150mm Ferrozell

3mm Honeycomb350mm Ferrozell

125mm Kapton foil

161mm field cage foil

All components glued with ARALDIT AY 103 + HD 991

outs

ide

insi

de

Multi-GEM EndcapDesign



HV

field platefield plate GEMs

Micropad Readout PCBgasinlet

HV

field platefield plateGEMs

micropad readout PCB

Gas amplification

+ Multi-GEM structure on PVC pillars2+ 10x10cm active area

+ Number of GEMs and gaps flexible

+ Field correction plate (copper on 2mm thick G10)

+ Possibility to add grids

Field correction plate avoids

distortions of the electric field outside

the (squared) GEM structure

HV

field platefield plate GEMs

Micropad Readout PCB



Readout PCB

+ Passivated copper on G10

+ HV feed-through for GEMs

Pitch adapter

+ 1:2 pitch adapter

+ FEE mounted

directly

to the

PCB

Micropad Readout PCBDesign

a) b) c)

1.27mm ->2.54mm

Micro pads

+ Rectangular shape2

+ 1.27x12.5mm pitch

The TPC PrototypeChoice of Materials



Drift Cylinder

Cathode Endcap

Multi-GEM Endcap Copper (passivated)Stainless steelKapton

StesaliteG10

PVC

CopperStainless steelKapton

CopperKaptonG10

ARALDIT AY 103 + HD 991O-ring

Assembly glue

Sealing

Materials facing the gas volume

+ Copper and passivated copper+ Stainless steel

+ Kapton+ pillars

+ Stesalite+ G10

+ Glue ARALDIT AY 103 + HD 991+ for sealing

PVC

O-ring

For parts in contact with or close to high voltage electrodes only HV proofed materialswere admitted.

All materials facing the gas volume were selected with respect to their outgassing properties.

NIM A 490 (2002) 177-203

NIM A 350 (1994) 464

The TPC PrototypeCurrent Setup



Gas amplification stage

+

Readout electronics

+ Modified version of the

STAR-TPC electronics

2Double-GEM, 10x10cm

+ No gating grid

Readout PCB2

+ 256 micro-pads, 1.27x12.5mm

+ Pitch adapter to 2.54mm

+ Pseudo-Gaussian pulse shape,

180ns peak time, 180ns fwhm

+ Signal sampling rate 19.7 MHz

(50.86ns per time slice)

Provided by LBNL, Berkeley (USA )

The TPC PrototypePerformance Tests



System checks

b) Energy resolution

Good energy resolution

with 5.9keV X-rays after

25cm drift distance, thus

no impurities in the gas

which could cause

electron-attachment

a) Drift velocity

Measurement of drift velocity excludes

distortions of the electric field and

impurities in the gas due to leaks




Ar-CH -CO (93:5:2)4 2 Ar-CO (70:30)2

Drift field

Drift velocity

0.31 kV/cm

0.70 cm/ms

0.24 V/cm

4.55 cm/ms

Beam Test

+ Operation in a hadronic beam at

the CERN PS in Summer 2003

Setup in T11+

+ 3Gev p beam, parallel to pads

+ Double-GEM, 2mm gaps

+ E =2.5kV/cm, E =3.5kV/cmT I

+ U = U + 10VGEM,1 GEM,2

without

magnetic field !

beam line




0 5 10 15 20 250.000

0.050

0.100

0.150

0.200

0.250

Ar-CO 2 (70:30, 0T)

TDR gas (0T)

resi

dual

ss

[mm

](w

ithou

ttrac

ker

ror)

drift distance [cm]

Fully efficient

. 3

@ G > 2.5 10down to s = 63mm

@ 1.27mm pitch

Efficiency scan Spatial Resolution in x ( p = 1.27mm )

0 2000 4000 600085

90

95

100

TESLA TDR gas, 6cm drift Ar-CO

2 (70:30), 13cm drift

effic

ienc

y[%

]

effective gain

0 2000 4000 600085

90

95

100

TESLA TDR gas, 6cm drift Ar-CO

2 (70:30), 13cm drift

effic

ienc

y[%

]

effective gain

0 5 10 15 20 250.000

0.050

0.100

0.150

0.200

0.250

Ar-CO 2 (70:30, 0T)

TDR gas (0T)

resi

dual

ss

[mm

](w

ithou

ttrac

ker

ror)

drift distance [cm]

Efficiency scan Spatial Resolution in x ( p = 1.27mm )




More results in session T17:

“A GEM-TPC Prototype with Low-Noise highly integrated Front-End Electronics for Linear Collider Studies”

Tuesday, 16:15, Timberline Room (JB)

Summary & Outlook



4

4 The design of and experience with the Triple-GEM detectors for the Small-Area-Tracker (SAT) of COMPASS offers a solid basis for the design of GEM-TPCs

4 Considering study prospects, R&D aspects and practical requirements, a prototype TPC has been designed and constructed: 4 Double-ring layout field cage 4 Currently equipped with Multi-GEM plus pads readout 4 Materials selected with respect to outgassing properties

4 Detector validated in performance tests and in hadronic particle beams (=> session T17)

GEM readout of TPCs is investigated for a number of future particle-physics experiments

design and construction of a gem-tpc prototype for r&d

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