Transcript GEatUM_v5x
PPS Overview & Experimental
Results
Daniel S Levin
UM/TAU/IS/ORNL meeting with GE
Sept 27, 2012
University of Michigan
D.S. Levin University of Michigan
9/27/2012
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Outline
1.
2.
3.
4.
Overview of desired PPS attributes
Basic physics of PPS
Proof-of-principle experiments & Establishing basic attributes
Laboratory setups and prototype testing
Hit rates with source and background
Signals, pixel capacitance, HV, Pashen potential etc
Cosmic Muons
Saturation measurement
Spatial measurements
Test Beam
D.S. Levin University of Michigan
9/27/2012
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Plasma Panel Detector Overview
Inherits many operational and fabrication principles common to PDPs:
• A dense micro-array of gas discharge cells or pixels
• Pixels bias for gas electrical discharge- Geiger mode operation
• Pixels are enclosed in hermetically-sealed glass panel
• Uses non-reactive, radiation-hard materials:
glass substrates, refractory metal electrodes, inert gas mixtures.
Anticipate eventual device fabrication as low-mass detectors
A high gain and inherently digital device
Potential for:
• < 1 ns response times
• low power consumption
• high granularity
• large area with low cost
• Position resolution < 100 um
• 2D readout
D.S. Levin University of Michigan
9/27/2012
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Plasma Television Display Panel (PDP)
As a detector
PPS remove or
replace specific
elements:
No phosphors
No MgO layer
No dielectric
layers
We add a
quench resistor
to the pixels
that
terminates the
discharge
D.S. Levin University of Michigan
9/27/2012
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Single pixel: Principles of operation
(-) High
Voltage
Muon
track
cathode
anode
50-100
D.S. Levin University of Michigan
9/27/2012
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Single pixel: Principles of operation
(-) High
Voltage
Muon
track
cathode
Ionizing particle creates ion pair clusters along
track
Cluster formation dictated by Poisson statistics
P ( ni )
n
e
n!
ni primary ion pairs clusters / cm bar
~ 30 for Ar
anode
50-100
D.S. Levin University of Michigan
9/27/2012
Cluster
statistics: ni=
>1 ion-pair.
avg is about 3,
with long
exponential
tail
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Single pixel: Principles of operation
(-) High
Voltage
Muon
track
+
++
++
++
++
+
cathode
Electron drift & acceleration in initiates
avalanche
High E –fields lead to streamers & gas
breakdown according to Paschen’s Law :
-----
P= pressure
d= gap size
V=voltage
a,b = gas
specific
parameters
anode
50-100
D.S. Levin University of Michigan
9/27/2012
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Paschen discharge potential
Wikipedia: Paschen entry.
Minimum voltage
occurs when
Small variations in Penning
gas mixtures can dramatically
affect breakdown voltage
A.K. Bhattacharya, GE
Company, Nela Park, OH
Phys. Rev. A, 13,3 (1975)
D.S. Levin University of Michigan
9/27/2012
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discharge cell: important gas processes
primary
ionization
ion ejected
electron
Metastable
ejection
photon
emission
metastable
generation
D.S. Levin University of Michigan
Penning
ionization
9/27/2012
Excitation
Image from: Flat Panel Displays and CRTs
(Chapter 10) L. Tannas, Jr,
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Electrical description
start with simplified schematic of single PPS discharge cell
Rquench
cathode -
+ anode
Cpixel
signal
Rterm
HV
Supply
During discharge cell becomes conductive
The E field drops, discharge self-terminates
The quench resistance on each pixel (or pixel chain) :
1) impedes E field rise until ions and meta-stables are neutralized
2) maintains HV on all other cells so that they are enabled for hits
D.S. Levin University of Michigan
9/27/2012
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More realistic cell model
include stray capacitances, line resistance, self inductance (More details in Robert
Varner’s presentation)
{ResNi}
Cpixel
D.S. Levin University of Michigan
9/27/2012
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Proof-of-principle & other tests with modified PDPs
1. Formation of discharge above Paschen potential
2. Self-termination
3. Response to a source
4. Gas hermetic envelope
5. Signal characteristics
6. Rate from radioactive source vs background
7. Discharge spreading
8. Response with various gases
9. Detection of CR Muons
10. Position sensitivity along a one coordinate axis
11. Proton beam tests
12. Response to multiple, simultaneous sources
D.S. Levin University of Michigan
9/27/2012
Yiftah Silver talk
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Lab setup
collimator
90Sr
22 cm
Panel A: Xe @ 650 torr
Filled: Aug 2003
106Ru
Panel B: Ar + CO2 (7%, 1%)
SnO2
Ni
Rout
High Voltage
Quench
50
Termination
Discriminat
or @ 2-4 V
Lecroy 574A
bandwidth 1 GHz
9/27/2012
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Demonstration using Commercial DC-PDPs
glass
SnO2 280 m cathodes
-
-
-
Discharge gap
220-340 m
dielectric
+ + + + + + +Ni anode
+ + 800 m
glass
E field at pixel (COMSOL
calculation)
D.S. Levin University of Michigan
9/27/2012
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proof-of-principle tests
At critical (Paschen) voltage (~700 V)
discharges appear in Xe.
Signal from Xe
filled panel
O(ns) rise time (for ~ 1 mm dimensions)
Large amplitude indicates discharge of
5-10 pf effective capacitance
Increase voltage amplitude increase
& hit rate increase (next slide)
Signal (attenuated) from
Ar-CO2 filled panel
Observed signals are single pulses
quenching works
Panel filled and sealed in 2003- gas
containment works
Clear response to
90Sr
(beta) source
Low discharge spreading: 2% to a single
neighbor pixel in open structure
D.S. Levin University of Michigan
9/27/2012
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Rate Measurements using source
Response to Source vs HV
Rate increases as expected with HV
Response to source is ~100 Hz with very low background
D.S. Levin University of Michigan
9/27/2012
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Rate Measurements using source
Response to Source vs Rquench
1/Rquench
Rquench
Rate increases as expected with HV and depends on Quench resistance
High Rquench (high RC time constant) causes pixel to saturate
Response to source is ~100 Hz with very low background
D.S. Levin University of Michigan
9/27/2012
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Detection Setup of Cosmic Ray Muons
Panel tested with CF4
or SF6 at 600, 200 torr
PMT1
PMT2
Scaler & waveform
digitizer
Events triggered with
3-fold coincidence
Signals collected with
DRS-4 fast waveform
digitizer
D.S. Levin University of Michigan
9/27/2012
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Arrival Time Measurement of Cosmic Ray Muons
Both pure CF4 and
SF6 gases shows a
signal with a very fast
response time.
Arrival time is defined
with respect to the
hodoscope trigger
Timing jitter is 5 ns
D.S. Levin University of Michigan
9/27/2012
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Detection of Cosmic Ray Muons & Efficiency
About 8% of triggers were associated with signal from the panel
This factor represents a convolution of several factors:
Geometric acceptance ion-pair probability intrinsic efficiency
net = Ag AE P(l,p,r) (r) = 8 %
Ag = geometric acceptance of pixel (wrt to trigger area*solid angle)
AE = Pixel area enhancement from fringe E field
P(l) = Probability to produce at least one ion-pair at distance R from
anode
(r) = efficiency: probability to generate a discharge for ion-pair
created at distance R from anode.
D.S. Levin University of Michigan
9/27/2012
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Response to two simultaneous sources (setup)
Side view
Sr90 top
Ru106 bottom
RO lines
HV=815V
Top view
D.S. Levin University of Michigan
9/27/2012
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Response to two simultaneous sources (setup)
HV lines 1
RO
20
Pickoff
24 card
100x
attenuatio
n
100 110
128
VPA 600 Torr Ar 99%CO21%
Filled Feb 15, 2012
RO 1
HV=815V
R=400 MΩ
RO lines 3-6
Discriminator
-150 mV
OR
Sr90
Ru106
Scalar
Expectation: rate with two sources = sum of the two rates in
single mode until the sources starts (partially) overlapping
D.S. Levin University of Michigan
9/27/2012
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Response to 2 simultaneous sources (Results)
Result: Panel responds independently to
each source until they nearly overlap and saturate a line
D.S. Levin University of Michigan
9/27/2012
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Summary
Using off-the-shelf commercial Plasma Panels we have
demonstrated
Producing fast, self-terminating, high gain pulse
Sensitivity to charged particles betas (also muon, protons)
Good timing jitter using triggered muons
Sensitivity to independent sources
Spatial resolution commensurate with the high granularity of the
electrode pitch (Yiftah’s talk)
Panels sealed with gas in 2003 produce signals 9 years later
D.S. Levin University of Michigan
9/27/2012
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