1 plasma panel sensors for particle & beam detection (n31-7) peter s. friedman integrated...

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Plasma Panel Sensors for Particle& Beam Detection (N31-7)

Peter S. FriedmanIntegrated Sensors, LLC / Ottawa Hills, Ohio, USA / 419-536-3212

([email protected] / www.isensors.net)

R. Ball, J. W. Chapman, C. Ferretti, D. S. Levin, C. Weaverdyck, B. ZhouUniversity of Michigan / Dept of Physics / Ann Arbor, Michigan, USA

Y. Benhammou, E. Etzion, N. Guttman, M. Ben Moshe, Y. SilverTel Aviv University / School of Physics & Astronomy / Tel Aviv, ISRAEL

James R. Beene and Robert L. Varner Jr.Oak Ridge National Laboratory / Holifield Radioactive Ion Beam Facility / Oak Ridge, TN, USA

E. H. BentefourIon Beam Applications S.A. / Louvain La Neuve, BELGIUM

2012 IEEE Nuclear Science Symposium & Medical Imaging Conference, Anaheim, November 1, 2012

ntegrated ensors™ Transforming radiation detection

mailto:[email protected]

http://www.isensors.net/

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Plasma-TV / PDP (Plasma Display Panel)


• For detector mode, remove specific elements:

• No phosphors

• No MgO layer

• No dielectric layers (or ribs?)

• Add a quench resistor to pixels that terminates the discharge

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Plasma Panel Sensor (PPS) Concept


• The PPS was conceived as a high performance, low cost, radiation detector that could leverage off of a mature, plasma display panel (i.e. PDP-TV or plasma-TV) technology and manufacturing infrastructure.

• PDPs have a 45 year history and sell (with profit) for ~ $0.03 / cm2

including drive electronics. They are probably the lowest cost (per area), highly pixelated, highly integrated, digital device ever developed.

• PDPs are hermetically sealed devices with a demonstrated lifetime of hundreds-of-thousands of hours (i.e. decades of service life).

• PDPs are inherently digital, high gain (i.e. Geiger mode), radiation damage resistant, stable devices, operable over a wide range of environmental conditions and unaffected by external magnetic fields.

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Plasma Panel Detector

• 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

• High gain and inherently digital device with 2D readout

• Potential for:


• Low power consumption

• Large area with low cost

• Ultra-low mass structure

• < 1 ns response times

• High granularity

• Position resolution < 100 µm

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PPS Configurations

• Each pixel operates like an independent micro-Geiger counter and is activated either by direct ionization in the gas, or indirect ionization in a conversion layer. Our development focus has been on PPS device structures configured primarily for direct ionization.

• PPS ionization radiation detectors can have a variety of configurations, but we have focused on modified DC type columnar-discharge PDP structures.


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Commercial DC-PDP Structure


Concept drawing of columnar-discharge, 2-electrode panel structure. Orthogonal SnO2 or Ni electrodes are separated by a few hundred micron gas layer. Dark band around perimeter is a hermetic glass seal

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Modified-PDP Commercial Panel


Modified-PDP columnar-discharge (PPS) test panel with “refillable” gas capability. Each HV-cathode line (i.e. column electrode) has a current-limiting quench resistor.

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Columnar-Discharge PPS


dielectric

Cathodes

+ + + + + + +

- --Discharg

e Gap

glass

Anodes

glass

COMSOL Simulation of Single Cell E-field

No E-field E-field is localized

• Measurements of background signal and response to radioactive sources with different gases.

• Columnar-discharge PPS (pixels at intersections of orthogonal electrode array)

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PPS aims to inherit PDP features


Small cell size & fast response high spatial & temporal resolutionLow cost and scalable panel size from ~ 1 cm2 to 1 m2

Hermetically sealed volume & long lifetime no gas flow

Using modified plasma-TV technology for radiation detectors

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PPS Radiation Sources of Interest

• Sources demonstrated to date:

Cosmic-Ray Muons (relativistic energies ≥ GeV)

Beta Particles (max. electron energy): 137Cs (1.2 MeV), 90Sr (2.3 MeV), 106Ru (3.5 MeV)

Gamma-Rays: 57Co (122 keV), 99mTc (143 keV)

Proton Beam: 226 MeV (for proton beam cancer therapy)

• Sources planned for future demonstration

Muon Beams: GeV range (for high energy physics research)

Radioactive Ion Beams: 1-100 MeV/u (for nuclear physics research)

X-Ray Beams: 6-8 MeV (for X-ray cancer therapy & homeland security )

Electron Beams: 4 - 18 MeV (for electron beam radiation therapy)

Neutrons: Thermalized neutrons (for homeland security)


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PPS Technology & Projections

• Pixels/cells act as independent, parallel collectors (~ 103 − 104 cells/cm2)

• Inherently digital, highly linear, particle/photon counting devices

• Localized pulses minimal discharge spreading

• Low background noise no cooling

• Small drift regions & gas gaps minimally affected by magnetic fields

• Amorphous & non-reactive materials radiation damage resistant

• Wide detection range keV to TeV (i.e. X-rays to colliders)

• Avalanche response large signals (~ 107 gain for 1 mm cell)

• Targeted cell size ~ 100 - 200 µm spatial resolution ~ 50 µm

• Fast cell response rise time ≤ 1 ns

• Low energy consumption ~ 1 nJ per event discharge (200 µm cell)

• Low power consumption ~ 20 µW/cm2 at “hit” rate of 20 kHz/cm2


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PPS Measurements with Beta Sources


DAQ includes:4 channels 5 GHz digitizer

Simulated 90Sr β-spectrum in

panel

106Ru

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Two-fold coincidence hodoscope / trigger measurement with 106Ru beta-source in PPS (1% CO2 in 99% Ar at 600 torr. The same PPS has been successfully demonstrated with several other particle sources, including: 90Sr (beta source), medical proton beams (226 MeV), and cosmic ray muons (≥GeV). The PPS response appears about the same for all of the charged particle sources tested.

Rise Time: 1.2 ns (20-80%)

Pulse Duration: 1.9 ns (FWHM)

“Typical” Pulse Rise Time & Duration

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Rate Measurements Using β-Source


Ar CO2 (1%) 600 torr @ 815 VHV line=110, RO=3-6

Response to Source vs. 1/Rquench

Very high Rquench (high RC time constant) causes pixel to saturate at low Hz Moderate Rquench no rate dependence & rate is ~100 Hz, low bkgLow Rquench regeneration can occur resulting in inflated high Hz signals

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PPS Discharge Spreading Example


Triple-coincidence hodoscope measurement with 106Ru beta-source. The adjacent anode wires (i.e. channels 6, 7 & 8) appear as the black, red and green lines, and show no indication of any discharge spreading.

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Detection Setup of Cosmic-Ray Muons


PMT1PMT2

PMT-1

PMT-2

Ionizing Particle

Panel tested with CF4 or SF6 at 600 & 200 torr

Scaler & waveform digitizer

Events triggered with 3-fold coincidence

Signals collected with DRS-4 fast waveform digitizer

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Cosmic-Ray Muon Detection


About 8% of all muon triggers associated with signal from the panel

To further improve performance we are investigating panels with different structures and higher resolutions (i.e. smaller pixels with higher fill-factors and different discharge geometries)

• Pixel active area ~ 1.7 mm2

• Total 4x4 matrix (16 pixels) active area ~ 27 mm2

• Hodoscope triggering area ~ 250 mm2

• Geometric acceptance for muons ~ 11%

Our initial estimate of the PPS muon detection efficiency, when taking into account the geometric acceptance for the active cell area, is on the order of ~ 70%

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Arrival Time Measurement of Cosmic-Ray Muons


Time arrival distribution for 197 cosmic-ray muons detected in a PPS with SF6 at 500 torr & operating at 1530 V.

Both pure CF4 and SF6 gases show a signal with a very fast response time.

Arrival time is defined with respect to the hodoscope trigger (the offset reflects residual cable delays).

Timing jitter (σ) is 5 ns.

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Side Side viewview

Sr90 top

Ru106 bottom

Top Top viewview

HV=815VRO lines

Response to 2 Simultaneous Sources - Setup

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RO 24

RO 1

HV lines 1 20 100 110 128

Pickoff card 100X

attenuation

HV=815VR=400

MΩ

VPA 600 Torr 99%Ar/1%CO2

Filled Feb 15, 2012

Discriminator

-150 mVOR Scalar

106Ru

90Sr

RO lines 3-6

Expectation: rate with two sources = sum of the two rates in single mode until the sources starts (partially) overlapping

Response to 2 Simultaneous Sources - Setup

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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.

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Beta Scattering Simulation* with GEANT4


GraphiteCollimator

(1.2 mm slit)

106RuBeta

Source

PPS GlassSubstrates(2.25 mm)

Betas(orange)

GeneratedX-rays

(yellow)

Ar at 1 atm0.44 mm Gap

*106 tracks simulated(103 tracks shown)

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106Ru Example


GraphiteCollimator

(1.2 mm slit)

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PPS Position Resolution Experiment


Translation of “collimated” 106Ru beta-source through

a 1.25 mm wide graphite

slit (20 mm thick) in 0.5 mm

increments across the PPS

sense electrodes (anodes).

Plot shows the Gaussian

means vs. source position.

RMS position resolution

is ~ 0.7 mm, in panel with

a 2.5 mm electrode pitch.

Panel has 1% CO2 in 99%

Ar, at 600 torr, and 890V.

slope = 0.39 ± 0.01 per mm

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PPS Proton Beam Accelerator Test


PPS Panel

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Proton Beam Position Scan


Position scan of 226 MeV proton beam (1 mm diameter). Plot of position centroid of “hit” map for 16 runs in which PPS was shifted by increments of ~ 1 mm relative to the proton beam from an IBA-C235 medical accelerator.

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Modeling and Simulations


• COMSOL:– Electric field and charge motion– Estimate capacitance of cells

• SPICE:– Electrical characteristics of PPS cell signals– Role of stray capacitance & inductances

• GEANT4:– Passage of particles through matter

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Modeling with SPICE and COMSOL


Capacitive coupling to neighboring cells is critical !

Stray capacitance, self-inductance & line resistance included

Cell parameters generated from COMSOL

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Particle Scattering Simulations


Principal tool is GEANT4• CERN developed tool, similar to MCNPx• Simulates particle scattering in materials

• Particle production mechanisms• Coulomb scattering• Nuclear scattering• Very general geometry and materials

• Widely used in nuclear physics• Gives event-by-event or summary output for later analysis• Open source, easily available for researchers

Cases• 106Ru and 90Sr production and propagation

• PPS• Collimators• Trigger detectors

• Neutron capture in Gd• Photosensor in a Compton Telescope

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106Ru Example


106Ru β-energy spectrum

Glass

PPS Gas

Hodoscope detectors

Source

31106Ru Example

1.30 MeV Beta

2.83 MeV Beta(90Sr) 3.54 MeV Beta

1.30

2.83 3.54

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Summary

Modified, off-the-shelf, commercial plasma panels have demonstrated:

1) Low-cost PDP-based technology can be modified to detect ionizing radiation

2) Sensitivity to charged particles – betas, protons and muons

3) Devices produce fast, self-terminating, self-contained, high-gain pulses

4) Inherently digital, particle counting, non-proportional Geiger-mode operation

5) Can be hermetically sealed & fabricated with inherently rad-hard materials – e.g. panels sealed with gas 9 years ago (2003) work similar to new panels

6) Panel “sealed” with shut-off valve & vac fittings still operating after 8 months


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Summary

7) Good timing jitter using triggered muons (~ 5 ns)

8) Fast cell response (≤ 1 ns)

9) Sensitivity to independent, separate sources

10) Position sensitivity to high intensity sources (~ 1 MHz of protons / mm)

11) Spatial resolution commensurate with high granularity of electrode pitch – can detect a stream of particles with sub-millimeter separation.

12) Low background noise

13) New generation of PPS devices being fabricated with projected higher performance capability


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Backup


35Single pixel: Principles of operation

Muon track

(-) High Voltage

cathode

anode

50-100

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Single pixel: Principles of operation

Muon track

(-) High Voltage

cathode

Charged particle creates ion-pairs clusters Cluster formation dictated by Poisson

Arfor

barcmclusterspairsionprimaryn

en

nP

i

n

i

30~

/!

)(

Cluster statistics: ni >1 ion-pair. Avg = 3, with long exponential tail

anode

50-100

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Single pixel: Principles of operation

Muon track

(-) High Voltage

cathode

---------

++++++++++

Electron drift & acceleration initiates avalanche.High E–fields lead to streamers.Gas breakdown (discharge potential) according to Paschen’s Law: P= pressure

d= gap sizeV=voltagea,b = gas specific parametersanode

50-100

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Minimum voltage occurs when

Wikipedia: Paschen entry.

A.K. Bhattacharya, GE Company, Nela Park, OH Phys. Rev. A, 13,3 (1975)

Small variations in Penning gas mixtures can dramatically affect breakdown voltage

Paschen discharge potential

39Discharge cell: Important gas processes

primary ionization

metastable generation

Excitation Penning ionization Image from: Flat Panel Displays and CRTs

(Chapter 10), L. Tannas, Jr,

photon emission

Metastable ejection

ion ejected electron

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Rquench

Rterm

Cpixel

Electrical description

During discharge cell becomes conductiveThe E field drops, discharge self-terminates

HV Supply

cathode - + anode

The quench resistance on each pixel (or pixel chain): 1) Impedes E-field rise until ions and meta-stables are neutralized2) Maintains HV on all other cells so that they are enabled for hits3) Signal amplitude set by cell capacitance: Cpixel

signal

start with simplified schematic of single PPS discharge cell

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{ResNi}

More realistic cell model

Cpixel

Include stray capacitances, line resistance, self inductance

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Full Schematic

1 plasma panel sensors for particle & beam detection (n31-7) peter s. friedman integrated...

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