GEM Simulation & Test

Xinzhan Bai

China Institute of Atomic Energy

2012-07-18 KITPC, Beijing, China 1

Outline

1. Introduction

2. GEM Simulation

3. GEM foil

4. JLab GEM Test

5. Summary

2012-07-18 KITPC, Beijing, China 2

Introduction 1. Core Part: GEM Foil.

2. Typical GEM Foil has 3 layers, two 5-micron thick copper foils and one 50-micron thick kapton foil in the middle.

3. The foil is patterned with an array of holes.

4. Diameter of the hole is 70 microns, and the distance between them is 140 microns.

5. Apply electric voltages on the two copper layers.

6. Electric Field is very strong in the hole area, and weak outside the hole area.

2012-07-18 KITPC, Beijing, China 3

GEM Foil

GEM Field

Introduction

1. Avalanche happens in the hole area only. This improves the spatial resolution in a large extent.

2. For the triple-foil GEM detector, the total gain is the multiply of the gain of each gem foil.

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Triple-Foil GEM Detector

Introduction

1. Six layers of GEM detectors in all.

2. SIDIS (Semi-Inclusive Deep Inelastic Scattering) experiment is one kind of the experiments that will be conducted on this spectrometer.

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SoLID Spectrometer

Different (e,e’h) experimental configurations

Experiments Luminosity

(s·cm2)-1

Tracking Area

(cm2)

Resolution

Angular

(mrad)

Vertex

(mm)

Momentum

(%)

GMn - GEn

up to 7·1037 40x150

and 50x200 < 1 <2 0.5%

GEp(5)

up to 8·1038

40x120,

50x200 and

80x300

<0.7

~1.5 ~ 1 0.5%

SIDIS

up to 2·1037

40x120,

40x150 and

50x200 ~ 0.5 ~1 <1%

20

12

-07

18

K

ITP

C, B

eijin

g, C

hin

a 6

Maximum reusability: same trackers in different setups

High Rates Large Area Down to ~ 70 μm spatial resolution

Refer to GEM status by Evaristo

Outline

1. Introduction

2. GEM Simulation

3. GEM foil

4. JLab GEM Test

5. Summary

2012-07-18 KITPC, Beijing, China 7

GEM Simulation

1. Maxwell + neBEM for the electric field calculation.

2. Garfield + Magboltz + Heed for the Calculation of electron transportation in Gas.

3. We simulated the Spatial Resolution, Gain, Electron Transparency of gem foils, and the Counting Rate.

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Avalanche in a Single-Foil GEM Detector

Electric Field Distribution 1. Electric Field Distribution

along the line which is perpendicular to the GEM foil and crossing the center of a hole.

2. Electric field reaches its maximum value at the center of the hole.

3. During our simulation, avalanche won’t happen when E < 5 kV/cm, thus avalanche only happens in the hole area.

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Field Distribution on a line crossing the centre of a hole

Collection Area Drift Area

σ = 73.6 microns σ = 86.7 microns

Spatial Resolution

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Avalanche Cluster Distribution on the Readout Plane

Electron Transparency

20 50 80 100 200 300 400 500 600 700 800 900 1000 1100 1200 1300 1400 1500

0

5

10

15

20

25

30

35

40

45

50

Tran

spar

ency

%

Transparency Vs. V_Drift

Transparency is dependent to the voltages applied on the drift area, collection area and gem foil.

When two of them are fixed, how the transparency varies with the third one?

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V_Drift

V_Drift

V_Collect

V_Gem

Electron Transparency

200 300 400 500 600 700 800 900 1000 1100 1200 1300 1400 1500

0

5

10

15

20

25

30

35

40

45

50

V_GEM

Tran

spar

ency

%

Trans. Vs. V_Gem

2012-07-18 KITPC, Beijing, China 12

Electron Transparency

100 200 300 400 500 600 700 800 900 1000 1100 1200 1300 1400 1500 1600

0

5

10

15

20

25

30

35

40

45

50

V_Collect

Tran

spar

ency

%

Trans. Vs. V_Collect

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Gain

Distribution of Gain of Single-Layer GEM Detector

RMS Mean

= 0.6

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Energy Resolution of GEM detectors is dependent to its gain performance. Gain is not stable both from the experiment and from the simulation.

Gain

600 700 800

0

0.5

1

1.5

2

2.5

3

3.5

4

4.5

V_GEM

Log1

0 (

Gai

n )

Gain & Effective Gain vs. V_GEM

100 200 300 400 500 600 700 800-0.5

0

0.5

1

1.5

2

2.5

3

3.5

4

V_GEM lo

g10

(G

ain

) Gain vs. V_GEM

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How gain varies with the voltage applied on the GEM foil. Gain: Number of electrons from all of the avalanches. Effective Gain: Number of electrons that reach the readout board.

Counting Rate

1. Shut down the attachment process, there will be two ends for ions.

2. Trapped by GEM foils and Trapped by the Drift Electrode.

3. Most of the ions will be trapped by gem foils, where they are produced, which leads to a very short drifting time for ions.

2012-07-18 KITPC, Beijing, China 16

Ion Drifting Time Distribution

Trapped by GEM foils

Trapped by Drift Electrode

μs

Outline

1. Introduction

2. GEM Simulation

3. GEM foil

4. JLab GEM Test

5. Summary

2012-07-18 KITPC, Beijing, China 17

The Construction of Clean Room at CIAE for GEM Foil R&D

Mask plate from CIAE

50um diameter

Mask plate from CERN

60um diameter

After half year negotiation, CIAE has signed officially the LICENSE AGREEMENT FOR MANUFACTURING AND COMMERCIALISATION OF GEM FOILS AND GEM-BASED PRODUCTS with CERN, and will get full technology support from CERN.

8/16/2012 18 China Institute of Atomic Energy

1. We can reach a minimum thickness of 12 microns of the copper foil coated on the Kapton layer.

2. Exposure and developer have some problems. We will try the recipe of the etchant provided by CERN.

3. Copper etching. Etching success rate < 70% with the hole diameter of 70 microns.

4. Kapton etching. CIAE has over 20 years nuclear pore foil production and kapton etching experience.

5. Clean room and GEM test lab is ready at CIAE.

The Study of GEM foil at CIAE

8/16/2012 19 China Institute of Atomic Energy

Process flow diagram of GEM foil

8/16/2012 20 China Institute of Atomic Energy

1. Particles which are accelerated by HI-13 pass through the kapton foil.

2. kapton etching，20um. 3. control the hole size by etching

time .

CIAE Nuclear Pore Foil

HI-13 tandem accelerator

Building Collaboration with a PCB Factory

Laminator Photoetching machine

Etching machine

The PCB factory is located in the south of Beijing. They would like to make the GEM foils for us if we provide the technology support.

8/16/2012 21 China Institute of Atomic Energy

Outline

1. Introduction

2. GEM Simulation

3. GEM foil

4. JLab GEM Test

5. Summary

2012-07-18 KITPC, Beijing, China 22

Chamber Structure

1. Three-Foil GEM Detector.

2. Work Gas Argon/CO2 = 70%/30%.

3. The whole Detector Setup consists of three chambers.

4. We used two scintilators to construct the coincidence signal.

2012-07-18 KITPC, Beijing, China 23

Top Cover

Drift

GEM 1

Read Out

Bottom Cover

GEM 2

GEM 3

Frame

Composition of a chamber

Gas in

Gas out

Detector System

Chamber Construction

Stretch

System

Re

ado

ut B

oard

Ch

amb

er in

bu

ildin

g

Ch

amb

er b

uilt

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Detector Prototype

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Readout Chip

Gassiplex Readout (not optimized for negative charge), 700 ns shaping time.

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Gassiplex Functional Module

Trigger System

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Electronic System

1. Mod V551b controls the time sequence.

2. Mod V550 as the ADC Module.

2012-07-18 KITPC, Beijing, China 28

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Gassiplex Board

Pre-Amplifier Electronics System

Electronic System

ADC Distribution

adc x1 Entries 15962

Mean 785.5

RMS 565.6

0 200 400 600 800 1000120014001600180020000

100

200

300

400

500

adc x1 Entries 15962

Mean 785.5

RMS 565.6

X1 ADC

adc y1

Entries 7620

Mean 900.9

RMS 583.1

0 200 400 600 800 1000 1200 1400 1600 1800 20000

20

40

60

80

100

120

adc y1

Entries 7620

Mean 900.9

RMS 583.1

Y1 ADC

adc x2 Entries 6189

Mean 669.4

RMS 542.7

0 200 400 600 800 1000120014001600180020000

50

100

150

200

250

300

350

adc x2 Entries 6189

Mean 669.4

RMS 542.7

X2 ADC

adc y2

Entries 5454

Mean 710.8

RMS 537.4

0 200 400 600 800 1000 1200 1400 1600 1800 20000

20

40

60

80

100

120

140

160

180

adc y2

Entries 5454

Mean 710.8

RMS 537.4

Y2 ADC

adc x3 Entries 2945

Mean 386.3

RMS 414.4

0 200 400 600 800 1000 1200 1400 1600 1800 20000

50

100

150

200

250

300

350

adc x3 Entries 2945

Mean 386.3

RMS 414.4

X3 ADC

adc y3

Entries 2616Mean 546.9

RMS 421.7

0 200 400 600 800 1000 1200 1400 1600 1800 20000

20

40

60

80

100

120

adc y3

Entries 2616Mean 546.9

RMS 421.7

Y3 ADC

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ADC Distribution from Simulation

1. We can produce two peaks of the three.

2. The third peak is difficult to get due to the unstable gain.

2012-07-18 KITPC, Beijing, China 31

Simulation Setup

Simulation Results

Radiation source results

2012-07-18 KITPC, Beijing, China 32

Outline

1. Introduction

2. GEM Simulation

3. GEM foil

4. JLab GEM Test

5. Summary

2012-07-18 KITPC, Beijing, China 33

Summary

1. We got some preliminary simulation results.

2. Further study of GEM foil

3. We will compare results from simulation and experiments in details.

2012-07-18 KITPC, Beijing, China 34

Gain Spatial Resolution Counting Rate Transparency

Thank you!

2012-07-18 KITPC, Beijing, China 35