Transcript TAU_13.10.14_CERN-Neutron-Talk_RD51_v2.1x

Development of Plasma Panel
Based Neutron Micropattern
Detectors
Yan Benhammou
Tel Aviv University
for the PPS Collaboration
Oct 15, 2013
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Collaborators
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University of Michigan, Department of Physics
•
Integrated Sensors, LLC
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Oak Ridge National Laboratory, Physics Division
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Tel Aviv University (Israel), School of Physics & Astronomy
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General Electric Company, Reuter-Stokes Division (Twinsburg, OH)
Robert Ball, J. W. Chapman, Claudio Ferretti, Daniel Levin (PI),
Curtis Weaverdyck, Riley Wetzel, Bing Zhou
Peter Friedman (PI)
Robert Varner (PI) , James Beene
Yan Benhammou, Meny Ben Moshe, Erez Etzion (PI), Yiftah Silver
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
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–
–
–
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MgO layer
dielectrics/rib
phosphors
protective layer
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TV Plasma Panel Structure
• For detector, a
simplified version
with readout &
quench resistor
–
–
–
–
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No MgO layer
No dielectric/rib
No phosphors
No protective layer
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Commercial Plasma Panel
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•
Columnar Discharge (CD) – Pixels at intersections of orthogonal
electrode array
Electrodes sizes and pitch vary between different panels
220 – 450 µm
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Principles of Operation
10-1000 M
• Accelerated electrons
begin avalanche
• Large electric field
leads to streamers
• Streamers lead to
breakdown - roughly
follows Paschen’s law.
HV(-)
Charged particle track
250 µm -1mm
50 µm -1mm
cathode
Gas volume in pixel
anode
50-100 
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“A Theory of Spark Discharge”,
J. M. Meek, Phys. Rev. 57,
1940
• 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
 pulse from Xe fill 2003, tested 2010
1 mm electrode
pitch
 panel sealed & tested in 2013,
pulse from neutron source & 3He fill
30 V
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2.5 mm
electrode pitch
1.
2.
3.
4.
Signals amplitudes: volts
Good signal to noise ratios.
Fast rise times O(ns)
Pulse shape uniform for a given
panel design
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Neutron Detection
in collaboration with GE, Reuter-Stokes
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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Setup
Gamma transparent, neutron
blocking plates
 PPS panel
(~ 0.1% transmission )
neutron sources
252 Cf
,
241Am-Be, 239Pu-Be
nested in stainless capsule, Pb
cylinder, high density polyethylene
(HDPE)
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Signal from neutrons
• Pulse “arrival” time (includes
arbitrary trigger offset)
•  = timing resolution
(jitter) of the detector
5 ns
~ 3ns
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Results
PPS
panel
neutron
source
( 252 Cf )
Neutron
blocking
plate
Background
subtracted data
is neutrons only
efficiency
plateau
Background:
 from source
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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
Approximately 100% of the captured neutrons were detected
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 Rejection
 source
PPS
panel
( 137 Cs )
3x105 /sec at instrumented region
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
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Reasonably good  rejection
before any optimizations offered by:
thin substrates
lower gas pressure
thinner metallization
Improving internal dielectrics around pixels
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Spatial
Position
neutron
source
PPS
panel
(239Pu-Be)
blocking plate with 5
mm slit
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Summary
We 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
radial discharge gaps
cavity depth  longer path lengths
individually quenched cells
isolation from neighbors
COMSOL simulation:
E-field
Equipotential lines
glass
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Microcavity Prototype (Back Plate)
Via
Plug
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Position Sensitivity
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Collimated Source Position Scan
106Ru
collimated source
• Light-tight , RF
shielded box
• 1 mm pitch panel
• 20 readout lines
• 1.25 mm wide
graphite collimator
Motorized X-Y table
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Test Panel
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Source Moved in 0.1 mm Increments
(1 mm pitch panel)
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PPS Position Scan
Mean fit for β-source moved in 0.1 mm increments
*
*Electrode Pitch 1.0 mm
Centroid measurement consistent
with electrode pitch
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PPS Proton Test Beam
March 2012
IBA ProCure Facility - Chicago
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IBA Proton Beam Test
• 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
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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
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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
Trigger is 3” x 4’’
scintillation pads
24 RO channels
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30 HV lines
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Time Spectrum
• Pulse “arrival” time
(includes arbitrary trigger
offset)
 = 40.1  0.9
•  = timing resolution
(jitter) of the
detector
Ar / 1% CF4
at 730 Torr
1100V
• We repeat this
measurement with
various gases and
voltages
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Time Spectrum
Ar / 1% CF4 at 730 Torr
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Timing Resolution
using 65% He 35 % CF4 at 730 Torr
 ~ 10 ns
HV =1290 V
•
•
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trigger time subtracted;
arbitrary cable offset
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PPS Muon Test Beam
November 2012
H8 at CERN
Setup
8 HV lines 100 MΩ quenched
Ni-SnO2 PPS
Ar / 7% CO2
600 Torr
HV = 1090 V
16 channels
OR
180 GeV BEAM
AND
2 scintillation pads
4 cm2 each
AND
Panel active area is 2 cm x 4 cm
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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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