[email protected] eudet meeting, munich – october 18, 20061 ongoing activities at saclay david...
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[email protected] EUDET Meeting, Munich – October 18, 2006 1
Ongoing activitiesOngoing activitiesat Saclayat Saclay
David AttiéD. Burke; P. Colas; E. Delagnes; A. Giganon;
Y. Giomataris; M. Riallot; M. Was
EUDET Meeting – 18-20 October 2006
[email protected] EUDET Meeting, Munich – October 18, 2006 2
Introduction
•Micromegas using a pixellised readout works
• However the weak point is the system sensitivity to sparks
• At Saclay we work on:- finding a gas mixture for optimal stability- damping the sparks (specific supply circuit) complementary to the resistive layer study at NIKHEF and to the improvement of the chip robustness at CERN
[email protected] EUDET Meeting, Munich – October 18, 2006 3
Activities of the Saclay Team
• Gain measurements using a Micromegas chamber- find the breakdown limit for many gas mixtures to avoid sparking- look for “Penning mixtures” and a stable state
• Study of detector-to-detector gain homogeneity- using a microbulk
•Measurement of ions backflow using various InGrid geometries (with Max Chefdeville)
• Involvement of the Saclay design shop in progress
• We are ready to test TimePix in gas
• Future activities and development in Saclaydesign for a Mini-chamber using Medipix2 readout chip- SiTPC endplate for the Large Prototype
[email protected] EUDET Meeting, Munich – October 18, 2006 4
Description:
• Transparent plastic box of 23 cm x 23cm x 8 cm size
• “Standard” 50 m mesh of 10 cm x 10 cm size
• Sources: - Fe 55 (5.9 keV) - COOL-X (8.1 keV)
• Monitoring of: - pressure - H2O
• Gas mixing system with triple mixture available
Goals:
• find gas mixture comfortable gain margin to use into a Micromegas TPC• know as much as possible the maximum gain (to avoid spark)
Gain measurements : detector
[email protected] EUDET Meeting, Munich – October 18, 2006 5
Gain measurements : summary
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Mesh biais (kV/ cm/ atm)
Gai
n
Iso : 1%Iso : 2%Iso : 3%Iso : 4%Iso : 5%CF4 : 3%, Iso : 1%CF4 : 3%, Iso : 2%CF4 : 3%, Iso : 3%CH4 : 6.5%CH4 : 8%CH4 : 9%CH4 : 10%CH4 : 8%, CF4 : 3%CH4 : 8%, CF4 : 5%CH4 : 8%, CF4: 10%CH4 : 10%, CF4 : 3%CH4 : 5%, CO2 : 3%CH4 : 10%, CO2 : 10%CO2 : 10%CO2 : 20%CO2 : 30%CO2 : 10%, Iso 2%CO2 : 10%, Iso 5%CO2 : 10%, Iso 10%CF4 : 3%, CO2 : 1%CF4 : 3%, CO2 : 3%CF4 : 3%, CO2 : 5%Iso : 2%, CH4 : 10%Iso : 5%, CH4 : 10%Iso : 10%, CH4 : 10%Ethane 10%Ethane 5%Ethane 3.5%Ethane 2%Ethane 3.5% - CO2 10%Ethane 3.5% - CF4 3%Ethane 3.5% - CF4 10%Ethane 3.5% - Iso 2%
Mixtures of gases containing argon
iC4H10
Gaz froids: CO2, CH4
C2H6
Mesh : 50 m gap of 10x10 size
[email protected] EUDET Meeting, Munich – October 18, 2006 6
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Mesh Biais (V)
Gai
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Neon - Iso 5%
Neon - Iso 5% - Argon 1%
Gain measurements : Penning effect
Ne/Argon – Iso 5%
The Penning mixture is a mixture of inert gas with another gas, that has lower ionization voltage than either of its constituents
Penning effect : The other gas has to have lower ionization potential than the first excited state of the noble gas.The excitation of the noble gas atoms is tranfered to the quencher gas molecules via collisions
[email protected] EUDET Meeting, Munich – October 18, 2006 7
Gain measurements : Penning effect
Ne/Argon – Iso 5%
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Mesh Biais (V)
Gai
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Neon - Iso 5%
Neon - Iso 5% - Argon 1%
Neon - Iso 5% - Argon 1,9%
The Penning mixture is a mixture of inert gas with another gas, that has lower ionization voltage than either of its constituents
Penning effect : The other gas has to have lower ionization potential than the first excited state of the noble gas.The excitation of the noble gas atoms is tranfered to the quencher gas molecules via collisions
[email protected] EUDET Meeting, Munich – October 18, 2006 8
Gain measurements : Penning effect
Ne/Argon – Iso 5%
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Mesh Biais (V)
Gai
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Neon - Iso 5%
Neon - Iso 5% - Argon 1%
Neon - Iso 5% - Argon 1,9%
Neon - Iso 5% - Argon 10%
The Penning mixture is a mixture of inert gas with another gas, that has lower ionization voltage than either of its constituents
Penning effect : The other gas has to have lower ionization potential than the first excited state of the noble gas.The excitation of the noble gas atoms is tranfered to the quencher gas molecules via collisions
[email protected] EUDET Meeting, Munich – October 18, 2006 9
Resolution vs. gain
Argon/Isobutane
• Best RMS for a gain between 3.103 & 6.103
• Degradation increase in inverse proportion to the quencher
[email protected] EUDET Meeting, Munich – October 18, 2006 10
Simulation vs. measurements : Ar/CH4
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E/P (V/cm/atm)
Ga
in
ArCH4 10% : Sim
ArCH4 9% : Sim
ArCH4 7,5% : Sim
ArCH4 6% : Sim
ArCH4 10% : Mea.
ArCH4 9% : Mea.
ArCH4 7,5% : Mea.
ArCH4 6% : Mea.
G < 104
Good agreement:measurements are consistent
with simulations, but…
[email protected] EUDET Meeting, Munich – October 18, 2006 11
Simulation vs. measurements : Ar/CO2
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E/P (V/cm/atm)
Ga
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ArCO2 10% : Mea.
ArCO2 20% : Mea.
ArCO2 30% : Mea.
ArCO2 10% : Sim.
ArCO2 20% : Sim.
ArCO2 30% : Sim.
G ~ 103
Agreement with the slope but not with the absolute gain
[email protected] EUDET Meeting, Munich – October 18, 2006 12
Simulation vs. measurements : Ar/C2H6
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E/P (V/cm/atm)
Ga
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ArEth 2% : Mea.
ArEth 3,5% : Mea.
ArEth 5% : Mea.
ArEth 10% : Mea.
ArEth 2% : Sim
ArEth 3,5% : Sim
ArEth 5% : Sim
ArEth 10% : Sim
Penning effect
G < 105
UV photons
Agreement with the slope at low fields but not with the absolute gain and the photons effects
[email protected] EUDET Meeting, Munich – October 18, 2006 13
Simulation vs. measurements : Ar/iC4H10
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E/P (V/cm/atm)
Ga
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ArIso 1% : Mea.
ArIso 2% : Mea.
ArIso 3% : Mea.
ArIso 4% : Mea.
ArIso 5% : Mea.
ArIso 1% : Sim
ArIso 4% : Sim
ArIso 2% : Sim
ArIso 3% : Sim
ArIso 5% : Sim
G ~ 105
Agreement with the slope at low fields but not with the absolute gain and the photons effects
[email protected] EUDET Meeting, Munich – October 18, 2006 14
The Medipix2 chip
MUROS2
USB Interface
Ready to test TimePix !
[email protected] EUDET Meeting, Munich – October 18, 2006 15
Future development in Saclay
MEDIPIX2 MICROMEGAS+
Mini-chamber
SiTPC endplate+
Large Prototype
• 55 m pixels• Direct X-ray conversion• selection of window in energy• 13-bit counter per pixel
• no ExB effect• good for 2-track separation• high gain• very fast electron signal on the anode plane• very small ion feedback in the space cheap• robust and easy to implement
[email protected] EUDET Meeting, Munich – October 18, 2006 16
Mini-chamber for the Medipix2 chip
Field cage
Box
Micromegasmesh
Medipix2 readout chip
M. RIALLOT (DAPNIA/SEDI)
Windows for X-rays source
Windows for source
6 cm
2.5 cm
Design plan:
[email protected] EUDET Meeting, Munich – October 18, 2006 17
Next steps
• Gain measurements with He, Ne mixtures (double or triple) using the same Micormegas detector
• These should help us to choose a gas mixture with a voltage providing a stable state to operate with the Medipix2 chip
• Build a small box of 20 cm x 8 cm x 4 cm to put a Medipix2 + Micromegas in the gas
• Measurements with sources…
[email protected] EUDET Meeting, Munich – October 18, 2006 18
Conclusion
• Continue on the understanding of the gas properties using Micromegas detector
• Observations with the Mini-chamber with Micromegas and Medipix2 readout chip
• Mini-chamber -> Large Prototype…