Transcript Input Protection for Gas Detector Electronic Readout

Input Protection for
Gas Detector Electronic
Readout
• Streamer theory
• Protection schemes
• Some ideas
Frédéric Druillole
Thanks to :Alain Le Coguie, Xavier De La Broïse, Estelle Monmarthe
CEA DSM Dapnia Sédi
GEMs and µMegas
• Discharge probability :
• Performance degradation due to discharge
• High Gain
• Energy resolution ~18%FWHM
• Spatial resolution <~60µm
• High rate
• Large scale
~3.10-12 (104)
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CEA DSM IRFU Sédi
• Discharge probability : ~10-3 to 10-9 (104)
• No Performance degradation due to discharge
• High Gain
• Detection efficiency ~100%
•Energy resolution ~20%FWHM
• Spatial resolution <~100µm
• High rate, weak radiation length
• Large scale
- Frédéric Druillole - [ Worshop ACTAR CENBG]
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Electric Field in GEM
S1/S2 ~ Eamp/Edrift
S1
mesh pitch l
2 σ
S2
Total
transparency of
the grid
derive
multiplication
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CEA DSM IRFU Sédi
- Frédéric Druillole - [ Worshop ACTAR CENBG]
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Streamer Theory
Streamer : If the number of electron produced during
the avalanche reach 107 ~108  Divergence of the
avalanche goes to a streamer phenomenum.
Impurities in the amplication zone could also
amplify the Electric field and increase the number of
electrons.
QUENCHER
Photon
Impurity: dielectric
E increases,
electrons increase
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CEA DSM IRFU Sédi
Secondary avalanche
- Frédéric Druillole - [ Worshop ACTAR CENBG]
Primary avalanche
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Streamer consequences
------
++++
+ ++++
+
++
++
++
++
+ ++
++
+
+
+
+
+++
++
+++
++
++
+
+
+
+
+ + ++++ + +
+ + ++++ + +
+
+ ++++++++ ++ +
++ ++ ++++++++ ++ ++
+ + ++++++ ++ ++
++ ++ ++++++ + +
++++
Négative Streamer
• Avalanche with a critical size
• Creation of secondary electrons in the head of the
streamer
• Creation of a conducting channel
• Could weld the grid on the pad (Permanent short
circuit)
16-06-2008
CEA DSM IRFU Sédi
- Frédéric Druillole - [ Worshop ACTAR CENBG]
5
Protection schemes
1.
2.
3.
4.
Sparks protection
No additional noise
Unsupplied diode
No current injection risk
1. Sparks protection
2. Permanent short circuit protection
3. High Voltage Components
4. supplied diodes (additional noise)
5. current injection risk
(diode symetry)
16-06-2008
CEA DSM IRFU Sédi
- Frédéric Druillole - [ Worshop ACTAR CENBG]
6
AC Coupling
• Cac-coupling changes the charge sharing between
detector and preamp :
Qpreamp = Qdet* Cac-coupling/(Cac-coupling + Cdet)
• Cac-coupling increases crosstalk channel to channel
(Cc/Cac-coupling)
•Variation of Cac-coupling changes gain uniformity
• Cac-coupling controls the dead time due to sparks
Test must be perform if we need High Voltage components
in the case of the second scheme.
 Purpose: Try to reduce the size of the protection circuit
16-06-2008
CEA DSM IRFU Sédi
- Frédéric Druillole - [ Worshop ACTAR CENBG]
7
How to connect (preliminary ideas)
« Fakir » Board : Needles in a hole to pack and
to connect pads to the electronic in horizontal plane
Insertion force
Mechanic tool
• High density pad
• new technology to test
16-06-2008
CEA DSM IRFU Sédi
- Frédéric Druillole - [ Worshop ACTAR CENBG]
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How to connect (preliminary ideas)
y
z
x
•To choose to put different protection
depending of the detector type
• Reduce electronic place in z
• Good for large pad size
16-06-2008
CEA DSM IRFU Sédi
- Frédéric Druillole - [ Worshop ACTAR CENBG]
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How to connect (preliminary ideas)
• Add components into the plane.
• Maintenance and repairs
• Unsupplied diodes
16-06-2008
CEA DSM IRFU Sédi
- Frédéric Druillole - [ Worshop ACTAR CENBG]
10
Connectors
• To look for high density connectors : (connectics, samtec,HRS,ERNI)
• Depend on the mechanical structure of the TPC, the available space
for the electronic.
• Need more detector specification
• Higher Density  Very expensive (2 euros / pads)
16-06-2008
CEA DSM IRFU Sédi
- Frédéric Druillole - [ Worshop ACTAR CENBG]
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Conclusion
• Protection is mandatory for GEMs and µMegas, necessary
for wired chamber.
• Need to test more compact solution to reduce the taken
place by protection components
• Mandatory to produce very clean detector components in
term of impurities and also in term of radioactive matter.
• Protection schemes depends on how we want to handle the
Electric field uniformity and the current production for short
circuit.
• Need to study the influence of AC coupling with high
density pads and the foreseen performances.
• Large choice of connectors depending the mechanical
architecture, the budget and the maintenance of the system.
16-06-2008
CEA DSM IRFU Sédi
- Frédéric Druillole - [ Worshop ACTAR CENBG]
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