development of plasma panel based neutron micropattern detectors
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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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