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Direct charge digital readout of dual phase Time Projection Chambers with GridPix. M. Alfonsi , N. van Bakel, A. P. Colijn, M. P. Decowski, H. van der Graaf, R. Schön, A. Tiseni, C. Tunnell. MPGD 2013 Conference,Zaragoza July 1-4, 2012. The GridPix detector. - PowerPoint PPT Presentation
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Direct charge digital readout of
dual phase Time Projection
Chambers with GridPix
M. Alfonsi, N. van Bakel, A. P. Colijn, M. P. Decowski, H. van der Graaf,
R. Schön, A. Tiseni, C. Tunnell
MPGD 2013 Conference,Zaragoza July 1-4, 2012
The GridPix detector
MPGD 2013, Zaragoza July 2nd, 2013 M. Alfonsi 2
• Micro-Pattern Gaseous Detector with pixel readout• Aluminum mesh supported by pillars (50 µm gap)• Wafer post-processing (MEMS)• Timepix readout (256x256 pixels, 55 µm pitch)• 4-8 µm resistive layer (spark protection)
The GridPix detector
MPGD 2013, Zaragoza July 2nd, 2013 M. Alfonsi 2
• Micro-Pattern Gaseous Detector with pixel readout• Aluminum mesh supported by pillars (50 µm gap)• Wafer post-processing (MEMS)• Timepix readout (256x256 pixels, 55 µm pitch)• 4-8 µm resistive layer (spark protection)
• Single electron detection efficiency > 98%
• < 20 µm spatial resolution• Time coordinate (µTPC)
• Low noise (no dark counts)
Dual phase noble gas TPC
MPGD 2013, Zaragoza July 2nd, 2013 M. Alfonsi 3
• Prompt light (S1) is collected by photodetectors arrays, electrons drift to liquid surface
• Charge is converted to light in the gas phase by proportional scintillation (S2)
• Time Projection Chamber: Z from S2 – S1 time delay
• S1/S2 ratio: large discrimination power between electronic and nuclear recoils
Direct charge readout
• Within the DARWIN Consortium [arXiv:1012.4767], we investigate GridPix as direct charge readout
• High spatial resolutiondigital readout
approach(high energy resolution at few e-)
• Low noise (no dark counts)
• Small device, mainly silicon, manufacturing processes:RadiopurityLow outgassing
MPGD 2013, Zaragoza July 2nd, 2013 M. Alfonsi 4
Digital readout approach
MPGD 2013, Zaragoza July 2nd, 2013 M. Alfonsi 5
Electroluminescence gain
• Energy deposits from nuclear recoils up to 40 keV (e.g. Dark Matter searches)
~ few to 200 ionization electrons (depending on setup) make the S2
MPGD 2013, Zaragoza July 2nd, 2013 M. Alfonsi 6
Electroluminescence gain
• Energy deposits from nuclear recoils up to 40 keV (e.g. Dark Matter searches)
~ few to 200 ionization electrons (depending on setup) make the S2
• Fluctuations to S2 due to:1.Electroluminescence gain (proportional)2.Light Collection Efficiency & PMT quantum
efficiency (5-20% typical)
MPGD 2013, Zaragoza July 2nd, 2013 M. Alfonsi 6
XenonGain 31.4sigma 7.5
Electroluminescence gain
• Energy deposits from nuclear recoils up to 40 keV (e.g. Dark Matter searches)
~ few to 200 ionization electrons (depending on setup) make the S2
• Fluctuations to S2 due to:1.Electroluminescence gain (proportional)2.Light Collection Efficiency & PMT quantum
efficiency (5-20% typical)
MPGD 2013, Zaragoza July 2nd, 2013 M. Alfonsi 6
XenonGain 31.4sigma 7.5
XenonGain 31.4sigma 7.5
Digital readout with pixels
• Counting the number of hit pixels
MPGD 2013, Zaragoza July 2nd, 2013 M. Alfonsi 7
Digital readout with pixels
• Counting the number of hit pixels
• Caveat:1. Every electron in a
different hole2. 100% single electron
detection efficiency
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• (1) depends on pixel pitch and diffusion along the
drift distance in the vapor phase.
• Toy MC for the case of xenon (diffusion coefficients
from Garfield/Magboltz)
Pixel pitch & diffusion in xenon
Pressure 1.0757 bar absolute• 10kV, 55µm pixel pitch,
1.0 cm path
MPGD 2013, Zaragoza July 2nd, 2013 M. Alfonsi 8
Pixel pitch & diffusion in xenon
Pressure 1.0757 bar absolute• 10kV, 55µm pixel pitch,
1.0 cm path• 10kV, 55µm pixel pitch,
3.0 cm path
MPGD 2013, Zaragoza July 2nd, 2013 M. Alfonsi 8
Pixel pitch & diffusion in xenon
Pressure 1.0757 bar absolute• 10kV, 55µm pixel pitch,
1.0 cm path• 10kV, 55µm pixel pitch,
3.0 cm path
• 2kV, 55µm pixel pitch, 1.0 cm path
MPGD 2013, Zaragoza July 2nd, 2013 M. Alfonsi 7
Pixel pitch & diffusion in xenon
Pressure 1.0757 bar absolute• 10kV, 55µm pixel pitch,
1.0 cm path• 10kV, 55µm pixel pitch,
3.0 cm path
• 2kV, 55µm pixel pitch, 1.0 cm path
• 2kV, 55µm pixel pitch, 1.0 cm path,95% efficiency
MPGD 2013, Zaragoza July 2nd, 2013 M. Alfonsi 7
Application to large areadual phase TPC ?
MPGD 2013, Zaragoza July 2nd, 2013 M. Alfonsi 9
Large Area dual phase TPC?
MPGD 2013, Zaragoza July 2nd, 2013 M. Alfonsi 10
Large Area dual phase TPC?
• Maybe!• Recent production on
8” wafers prospects industrialization and large volume at reduced cost.
MPGD 2013, Zaragoza July 2nd, 2013 M. Alfonsi 10
A small-sizehigh-impact application
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Light & charge yield in xenon
• The response of the medium, i.e. the scintillation light (Ly) and the ionisation charge (Qy) yield, must be measured for electronic and nuclear recoils
MPGD 2013, Zaragoza July 2nd, 2013 M. Alfonsi 12
Scheme from Manzur et al., Phys.Rev.C81 (2010) 025808
Light & charge yield in xenon
• The response of the medium, i.e. the scintillation light (Ly) and the ionisation charge (Qy) yield, must be measured for electronic and nuclear recoils
MPGD 2013, Zaragoza July 2nd, 2013 M. Alfonsi 12
Adapted from Manzur et al., Phys.Rev.C81 (2010) 025808
From G. Plante et al., arXiv:1104.2587
Ly & Qy measurements
Dedicated measurements:• neutron elastic scattering for nuclear recoils• Compton scattering for electronic recoils• small size noble liquid target
MPGD 2013, Zaragoza July 2nd, 2013 M. Alfonsi 13
θ
Neutron / Gamma generator
detector
Ly & Qy measurements
Dedicated measurements:• neutron elastic scattering for nuclear recoils• Compton scattering for electronic recoils• small size noble liquid target
Systematic uncertainty from the unknown position within target or double scatters.GridPix adds high
resolution position reconstruction and digital charge readout!
MPGD 2013, Zaragoza July 2nd, 2013 M. Alfonsi 13
θ
Neutron / Gamma generator
detector
Xe TPC @ Nikhef
MPGD 2013, Zaragoza July 2nd, 2013 M. Alfonsi 14
Measurements
with GridPix
MPGD 2013, Zaragoza July 2nd, 2013 M. Alfonsi 15
Cryogenic robustness
MPGD 2013, Zaragoza July 2nd, 2013 M. Alfonsi 16
New geometries under test
New geometries for the dykes (the “perimeter support” for the mesh).
Pillars with additional extended structures.(NIM A718 (2013) 446-449)
Dummy wafers (full anode instead of Timepix) under test.
MPGD 2013, Zaragoza July 2nd, 2013 M. Alfonsi 17
Pure nobles gasses
• Measurements at CERN in 2011 in a gaseous and dual phase argon TPC
• Measurements at Nikhef in a gaseous argon or xenon TPC
MPGD 2013, Zaragoza July 2nd, 2013 M. Alfonsi 18
CERN 2011 Nikhef
Pure noble gasses
• Stable operation with a reasonable charge amplification only with non ultra-pure gas (e.g. industrial standard argon 99.997%).
MPGD 2013, Zaragoza July 2nd, 2013 M. Alfonsi 19
• With argon 99.9999% or xenon 99.999% we observe a sharp transition between a too small gas amplification region and the discharge regime
Future plans
MPGD 2013, Zaragoza July 2nd, 2013 M. Alfonsi 20
Towards full ceramics
• Full ceramics devices under study:–SiO2 as insulator
–Si-rich Si3N4 as the resistive material
• Matching thermal expansion properties
• Low Outgassing and high radiopurity
MPGD 2013, Zaragoza July 2nd, 2013 M. Alfonsi 21
Towards full ceramics
• Full ceramics devices under study:–SiO2 as insulator
–SiRN is the resistive material• Matching thermal expansion
properties • Low Outgassing and high
radiopurity • A resistive grid can limit the charge available for a spark to only one cell.
• An embedded conductive network can distribute voltage uniformly
MPGD 2013, Zaragoza July 2nd, 2013 M. Alfonsi 21
In the meanwhile…
• A more sensitive pixel electronics would be helpful
• Recent literature keeps emphasizing that closed structure and confined amplification region are the key of success
• Producing and testing GridPix with any GEM-like or other specific amplification structure can be time / money consuming
• “Test the water” placing the amplification structure very close to a bare TimePix
• Investigate some specific quencher that does not spoil the scintillation signal
MPGD 2013, Zaragoza July 2nd, 2013 M. Alfonsi 22
Thanks for your attention!
MPGD 2013, Zaragoza July 2nd, 2013 M. Alfonsi 23
Spare slides
MPGD 2013, Zaragoza July 2nd, 2013 M. Alfonsi 35
M. Alfonsi 36
CERN 2011
MPGD 2013, Zaragoza July 2nd, 2013
In collaboration with the ETH Zurich:- gaseous warm / cold argon TPC.- dual phase argon TPC.
IEEE NSS-MIC Conf. Rec. 2011, 92-98
M. Alfonsi 37
CERN 2011: cold argon gas
The amplification of the GridPix can be verified with the light detected by PMT.
MPGD 2013, Zaragoza July 2nd, 2013
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M. Alfonsi 38
CERN 2011: cold argon gas
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MPGD 2013, Zaragoza July 2nd, 2013 M. Alfonsi 39