development of plasma panel based neutron micropattern detectors
DESCRIPTION
Development of Plasma Panel Based Neutron Micropattern Detectors. Yan Benhammou Tel Aviv University for the PPS Collaboration. Oct 15, 2013. 1. 1. Collaborators. University of Michigan, Department of Physics Robert Ball, J. W. Chapman, Claudio Ferretti, Daniel Levin (PI) , - PowerPoint PPT PresentationTRANSCRIPT
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Development of Plasma Panel Based Neutron Micropattern
DetectorsYan Benhammou
Tel Aviv Universityfor the PPS Collaboration
Oct 15, 2013
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Collaborators• University of Michigan, Department of Physics
Robert Ball, J. W. Chapman, Claudio Ferretti, Daniel Levin (PI), Curtis Weaverdyck, Riley Wetzel, Bing Zhou
• Integrated Sensors, LLC Peter Friedman (PI)
• Oak Ridge National Laboratory, Physics Division Robert Varner (PI) , James Beene
• Tel Aviv University (Israel), School of Physics & AstronomyYan Benhammou, Meny Ben Moshe, Erez Etzion (PI), Yiftah Silver
• General Electric Company, Reuter-Stokes Division (Twinsburg, OH)Kevin McKinny (PI), Thomas Anderson
• Ion Beam Applications S.A. (IBA, Belgium)Hassan Bentefour (PI)
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Outline
• Motivation
• Plasma panel operational principles and description
• Neutrons detection
• Summary
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Motivations • Hermetically sealed
– no gas flow– no expensive and cumbersome gas system
• Over 40 years of plasma panel manufacturing & cost reductions ($0.03/cm2 for plasma panel TVs)
• Potential for scalable dimensions, low mass profile, long life– meter size with thin substrate capability
• Potential to achieve contemporary performance benchmarks– Timing resolution approx 1 ns– Granularity (cell pitch) 50-200 µm– Spatial resolution tens of µm
• Potential applications in– Nuclear and high energy physics, medical imaging, homeland security, etc
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TV Plasma Panel Structure
A Display panel is complicated structure with
– MgO layer– dielectrics/rib– phosphors– protective layer
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TV Plasma Panel Structure
• For detector, a simplified version with readout & quench resistor
– No MgO layer– No dielectric/rib– No phosphors– No protective layer
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Commercial Plasma Panel• Columnar Discharge (CD) – Pixels at intersections of orthogonal
electrode array• Electrodes sizes and pitch vary between different panels
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220 – 450 µm
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Principles of Operation• Accelerated electrons
begin avalanche • Large electric field
leads to streamers• Streamers lead to
breakdown - roughly follows Paschen’s law.
“A Theory of Spark Discharge”, J. M. Meek, Phys. Rev. 57, 1940
anode
cathode
Charged particle track HV(-)
50-100
10-1000 M
Gas volume in pixel
250
µm -1
mm
50 µm -1mm
• Gas gap becomes conductive• Voltage drops on quench
resistor • E-field inside the pixel drops• Discharge terminates
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Modified Commercial Panel (fill-factor 23.5%, cell pitch 2.5 mm)
“Refillable” gas shut-off valve
for R&D testing
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Signals from Panel
1. Signals amplitudes: volts2. Good signal to noise ratios. 3. Fast rise times O(ns) 4. Pulse shape uniform for a given
panel design
pulse from Xe fill 2003, tested 2010
panel sealed & tested in 2013, pulse from neutron source & 3He fill
30 V
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1 mm electrode pitch
2.5 mm electrode pitch
Neutron Detectionin collaboration with GE, Reuter-Stokes
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Objectives: high efficiency neutron detectors with high rejection develop alternate to 3He as neutron interaction medium
This test: explore PPS as a general detector structure for converting neutrons using thin gap 3He gas mixture
Gas fill: 80% 3He + 20% CF4 at 730 Torr
Panel: 2.5 mm pitch large panel used for CR muons Instrumented pixels = 600, Area: 6 in2
Method: irradiate panel with thermal neutrons from various sources
high activity (10 mrem/hr) gammas conduct count rates experiment with & w/o neutron mask plates.
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neutron sources
252 Cf , 241Am-Be, 239Pu-Be
nested in stainless capsule, Pb cylinder, high density polyethylene (HDPE)
Gamma transparent, neutron blocking plates
(~ 0.1% transmission ) PPS panel
Setup
Signal from neutrons
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• Pulse “arrival” time (includes arbitrary trigger offset)
• = timing resolution (jitter) of the detector
~ 3ns
5 ns
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Results PPS panel
Neutron blocking plate
neutron source ( 252 Cf )
Background subtracted datais neutrons only
efficiency plateau
Background: from source
results
• GE Geant4 simulation of the neutron capture rate based on source activity: 0.70 ± 0.14 Hz
• PPS measured rate: 0.67 ± 0.02 Hz
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Approximately 100% of the captured neutrons were detected
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PPS panel
3x105 /sec at instrumented region
g source ( 137 Cs )
Reasonably good rejection before any optimizations offered by:
thin substrateslower gas pressurethinner metallizationImproving internal dielectrics around pixels
VPE HV (V)
detection rate Hz
efficiency
970 0.09 3.0e-07
1000 1.2 3.7e-06
1030 7.9 2.5e-05
Rejection
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Spatial Position
PPS panel
blocking plate with 5 mm slit
neutron source (239Pu-Be)
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SummaryWe have demonstrated functioning of modified plasma displays as
highly pixelated arrays of micro-discharge counters
– Sensitive neutrons [with appropriate conversion (3He ) ] & high rejection
– Timing resolution less than 3 ns
– Spatial response at level of pixel granularity
– New PPS devices start to be designed to replace the He-3 panel tested using B-10 and Gd-157 conversion layers. They should use much thinner substrates to improve gamma/neutron discrimination ratio. Should be ready next year.
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Microcavity-PPS
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Microcavity Concept
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E-field
glass
Equipotential lines
COMSOL simulation:
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radial discharge gaps cavity depth longer path lengthsindividually quenched cells isolation from neighbors
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Microcavity Prototype (Back Plate)
Via Plug
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Position Sensitivity
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Collimated Source Position Scan
Motorized X-Y table Test Panel
• Light-tight , RF shielded box
• 1 mm pitch panel
• 20 readout lines • 1.25 mm wide
graphite collimator
106Ru collimated source
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Source Moved in 0.1 mm Increments(1 mm pitch panel)
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PPS Position ScanMean fit for β-source moved in 0.1 mm increments
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*Electrode Pitch 1.0 mmCentroid measurement consistent with electrode pitch
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PPS Proton Test Beam
March 2012
IBA ProCure Facility - Chicago
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• Beam energy 226 MeV, Gaussian distributed with 0.5 cm width
• Proton rate was larger than 1 GHz on the entire spread of the beam
IBA Proton Beam Test
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Position Scan• Two position scans (panel filled with 1% CO2 in Ar at 600 Torr)
– 1 cm steps - using brass collimator with 1 cm hole, 2.5 cm from beam center– 1 mm steps with 1 mm hole directly in beam center
• Rate of protons thru 1 mm hole in center of beam was measured at 2 MHz
The Panel
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1 mm Scan
Number of hits per channel
Reconstructed centroid of hit map vs. PDP relative displacement with respect to the panel’s initial position
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PPS Cosmic-Ray Muon Results
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Cosmic Muon Measurement Setup
30 HV lines24 RO channels
Trigger is 3” x 4’’ scintillation pads
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Time Spectrum
• Pulse “arrival” time (includes arbitrary trigger offset)
• = timing resolution (jitter) of the detector
• We repeat this measurement with various gases and voltages
Ar / 1% CF4at 730 Torr
1100V
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= 40.1 0.9
Time Spectrum
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Ar / 1% CF4 at 730 Torr
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Timing Resolution using 65% He 35 % CF4 at 730 Torr
HV =1290 V
~ 10 ns
• trigger time subtracted;• arbitrary cable offset
PPS Muon Test Beam
November 2012
H8 at CERN
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Setup
180 GeV BEAM
2 scintillation pads 4 cm2 each
Ni-SnO2 PPSAr / 7% CO2
600 TorrHV = 1090 V
16 channels
8 HV lines 100 MΩ quenched
Panel active area is 2 cm x 4 cm
AND
OR
AND
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Time Resolution• Timing resolution with
Ar-CO2 better than 10 nsec
• Geometrical acceptance times efficiency ≈ 2% (pixel efficiency is much higher). Did not have beam time to optimize or even raise the voltage!
• Active area fill-factor for PPS detector is 23.5%
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