direct charge digital readout of dual phase time projection chambers with gridpix
DESCRIPTION
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 PresentationTRANSCRIPT
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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
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The GridPix detector
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• 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)
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The GridPix detector
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• 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)
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Dual phase noble gas TPC
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• 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
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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
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Digital readout approach
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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
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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)
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XenonGain 31.4sigma 7.5
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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)
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XenonGain 31.4sigma 7.5
XenonGain 31.4sigma 7.5
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Digital readout with pixels
• Counting the number of hit pixels
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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)
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Pixel pitch & diffusion in xenon
Pressure 1.0757 bar absolute• 10kV, 55µm pixel pitch,
1.0 cm path
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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
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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
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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
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Application to large areadual phase TPC ?
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Large Area dual phase TPC?
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Large Area dual phase TPC?
• Maybe!• Recent production on
8” wafers prospects industrialization and large volume at reduced cost.
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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
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Scheme from Manzur et al., Phys.Rev.C81 (2010) 025808
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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
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Adapted from Manzur et al., Phys.Rev.C81 (2010) 025808
From G. Plante et al., arXiv:1104.2587
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Ly & Qy measurements
Dedicated measurements:• neutron elastic scattering for nuclear recoils• Compton scattering for electronic recoils• small size noble liquid target
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θ
Neutron / Gamma generator
detector
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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!
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θ
Neutron / Gamma generator
detector
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Xe TPC @ Nikhef
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Measurements
with GridPix
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Cryogenic robustness
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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.
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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
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CERN 2011 Nikhef
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Pure noble gasses
• Stable operation with a reasonable charge amplification only with non ultra-pure gas (e.g. industrial standard argon 99.997%).
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• With argon 99.9999% or xenon 99.999% we observe a sharp transition between a too small gas amplification region and the discharge regime
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Future plans
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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
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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
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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
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Thanks for your attention!
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Spare slides
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CERN 2011
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In collaboration with the ETH Zurich:- gaseous warm / cold argon TPC.- dual phase argon TPC.
IEEE NSS-MIC Conf. Rec. 2011, 92-98
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CERN 2011: cold argon gas
The amplification of the GridPix can be verified with the light detected by PMT.
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CERN 2011: cold argon gas
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