Micro Pixel Chamber 3 , , - - PowerPoint PPT Presentation

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Micro Pixel Chamber 3 , , - - PowerPoint PPT Presentation

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Micro Pixel Chamber 3 , , , , , , , Espoo-Vantaa O. Bouianov Institute of Technology CSC-Scientific Computing M.

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SLIDE 1

大面積Micro Pixel Chamberの開発 3

京都大学 永吉 勉 谷森達, 窪秀利, 身内賢太朗, 竹田敦, 折戸玲子, 植野優, 高田淳史,

Espoo-Vantaa Institute of Technology

  • O. Bouianov

CSC-Scientific Computing

  • M. Bouianov

2003年9月10日 日本物理学会2003年秋季大会 @宮崎ワールド コ ンベンショ ンセンタ ー・ サミ ッ ト

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SLIDE 2

Contents

  • 1. Micro Pixel Chamber (µ-PIC)
  • 2. Optimization of electrode structure
  • Simulation of electron drift
  • New manufacture technique
  • 3. Basis for MeV gamma-ray imaging
  • CF4 gas
  • Gas vessel
  • 4. Summary
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SLIDE 3

1.1 Micro Pixel Chamber (µ-PIC)

Printed Circuit Board (PCB) technology

polyimide substrate (prepreg)

10cm

Detection area = 100cm2

  • Large area
  • Low cost
  • 400µm pitch electrodes
  • 256 anodes and

256 cathodes

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SLIDE 4

1.2 Performances

X-ray imaging

103 104

gas gain

Gas: Ar/C2H6 (80/20) Source: 55Fe (5.9keV)

1mm slits

  • Gas: Xe/C2H6 (70/30)
  • Drift: 3mm (500V/cm)
  • Gas gain ~ 15,000 (max)
  • Stable operation (>1000h)

@ gas gain ~ 5000 Position resolution σ ~ 160 µm (knife edge test)

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SLIDE 5

2.1 Drift simulation ~ For the best electrode ~

Drift end points (simulation)

30% 65% 5%

260µm 314µm

collected near pin gap

3D simulation (Maxwell + Garfield)

Drift paths of electrons

RKF meth. MC meth. 20µm 100µm

Top of anode electrodes are below substrate.

Collection efficiency ~ 30%

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SLIDE 6

anode height [µm] substrate fraction

Collection efficiency ~ 97% Gas gain: ×3

Current µ-PIC ( -20µm) substrate thickness [µm] fraction Current µ-PIC Anode height = +10µm Anode diameter = 50µm Cathode width = 314µm Cathode diameter = 260µm

Thicker substrate Higher efficiency

collected near pin gap collected near pin gap

10 100 400

2.2 Drift simulation

Higher anode Higher efficiency Substrate > 200µm … difficult Anode = 10µm … possible!!

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SLIDE 7

Drift end points

Substrate = 5µm Substrate = 200µm

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SLIDE 8

2.3.1 New µ-PIC

  • Current type

… normal plating (“bottom-up”)

  • New type

… plating and etching (“top-down”)

  • 3. Surface etching

Coming soon!! Detection area 30cm × 30cm 100µm 3 4 µ m Electrode formation process

  • 1. Electroless plating

substrate

  • 2. Via-fill plating

anode

  • 4. Electrode etching

cathode

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SLIDE 9

2.3.2 New µ-PIC

30×30 cm2 detector

30cm Center region Edge region

some offset … Beautiful!

10×10 cm2 : Available for performance test

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SLIDE 10
  • 10×10cm2 detection area
  • Bad electrode < 0.1%
  • Leakage current

< 2nA @800V (in air)

  • uniform anodes
  • anode height

= cathode thickness

  • gas gain ~ 9000 @VA = 600V
  • gain uniformity (σ)

~ 7% Gain map Cathode Anode 103 Gas gain Former µ-PIC 104 New µ-PIC

VA = 560V

×3

2.3.3 New µ-PIC

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SLIDE 11

3.1 Gamma-ray imaging

µ-PIC NaI + PMTs

133Ba (356keV)

Reconstructed image Pre-amp

γ

α

γ’ e

φ ψ δ Compton scattering

  • Electron tracking Full reconstruction
  • Cross section σ ∝ number of electrons

Balloon experiment in 2006

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SLIDE 12

3.2.1 Gas study

~ Ar vs. CF4 ~

  • Number of electrons = 18
  • W value = 26 eV/pair
  • (dE/dx)min = 2.44 keV/cm
  • Number of electrons = 42
  • W value = 54 eV/pair
  • (dE/dx)min = 7 keV/cm
  • Fast drift (~9cm/µs), small diffusion

Ar

CF4 Standard gas

for gas detectors

Good properties for MIPs!

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SLIDE 13

3.2.2 Operation test

Operation test with CF4 gas

Gas vessel

Dependence on …

  • Mixture ratio (C2H6)
  • Pressure (1 – 2.5atm)

Source: 55Fe (5.9keV)

3×3cm2 µ-PIC

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SLIDE 14

3.2.3 Operation test

Anode voltage [V]

103 104

Gas gain

800 1200 1000

pure CF4

1atm 2atm 2.5atm

Anode voltage [V]

103 104

Gas gain

700 1000 1300

CF4 / C2H6 (80/20)

1atm 2atm 2.5atm

  • Maximum gas gain ~ 3500 (80/20 mixture)
  • Gas gain > 103 @ 2.5atm
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SLIDE 15

3.3 Gas vessel

Flexible boards for read-out

  • Available for

30×30 cm2 detector

  • Vacuum ~ 4atm (?)

µ-PIC in gas vessel

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SLIDE 16

4 Summary

  • 3D simulation of µ-PIC

– Higher anode high efficiency ( > 90%)

  • A new manufacture technology

– Anode height = cathode thickness – Gas gain ~ 9000 – Uniformity: σ ~ 7%

  • CF4 gas

– Stable operation @ gas gain > 1000

  • Gas vessel for 30×30cm2 detector

– Pressure-resistant test is in progress

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SLIDE 17

3.2.1 Drift and diffusion

~ Simulation by Magboltz ~

Drift velocity

E field [V/cm] 500 2000 4 10 Drift velocity [cm/µs]

Diffusion

E field [V/cm] 500 2000 Diffusion [µm for 1cm drift] 102 103 Pure CF4 CF4 / C2H6 (80 / 20) CF4 / C2H6 (60 / 40) Ar / C2H6 (80 / 20)

  • Drift: ×2 faster than Ar
  • Diffusion: 1/4 smaller than Ar