wir schaffen wissen – heute für morgen 10 th rd51 collaboration meeting, stony brook university,...
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![Page 1: Wir schaffen Wissen – heute für morgen 10 th RD51 Collaboration Meeting, Stony Brook University, USA Progress in Fast-Neutron THGEM Detector for Fan-Beam](https://reader030.vdocuments.net/reader030/viewer/2022032722/56649f485503460f94c69c2f/html5/thumbnails/1.jpg)
Wir schaffen Wissen – heute für morgen
10th RD51 Collaboration Meeting, Stony Brook University, USA
Progress in Fast-Neutron THGEM Detector for Fan-Beam Tomography
ApplicationsM. Cortesi1,2, R. Zboray1, R. Adams1,2, V. Dangendorf3, A. Breskin4 and H-M Prasser1,2
1. Paul Scherrer Institute (PSI), Villigen PSI, CH-5232 Switzerland2. Eidgenössische Technische Hochschule Zürich (ETHZ), CH-8092 Switzerland3. Physikalisch-Technische Bundesanstalt (PTB), D-38116 Braunschweig,
Germany 4. Weizmann Institute of Science (WIS), Rehovot 76100, Israel
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10th RD51 Collaboration Meeting, Stony Brook University, USA
Fluid dynamic studies in BWR Fuel Rod Bundles
Motivation
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10th RD51 Collaboration Meeting, Stony Brook University, USA
ICON beam line, SINQ at PSI, Switzerland:
Example: Imaging using cold neutrons
Double subchannel + spacer inside:
neutron guide tube
multiphase outlet
scintillator screen
air-water inlets, turn table
FOV 6.5*6.5cm
double subchannel
(Zboray et al. Nucl. Eng. Des. 241 pp.3201)
More penetration depth Fast Neutron
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10th RD51 Collaboration Meeting, Stony Brook University, USA
Goal: Fast-Neutron TomographyDetector Requirements:
• Good time resolution (ns range)• High Counting rate (MHz/cm2
range)• Good spatial resolution (mm
scale)• High Detection Efficiency (few
%)• Large area (m2)
1D High-Efficiency Fast-Neutron Imaging Detector
TwoFast Project:• Multiple fast-n point sources (e.g. D-D fusion, 2.5 MeV)• Ring-shaped Fast-Neutron
detector
detector ring
phantom
(G)APD matrices
Plastic converter +(THGEM) as 2D fast neutron detector
Plastic scintillator +(G)APD matrix
In this presentation
D-D pulsed neutron generator
RF-driven Plasma ion source
Multiple point source sequentially pulse
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10th RD51 Collaboration Meeting, Stony Brook University, USA
2D Imaging with neutrons
Fast/Cold Neutron 2D radiography
2 mm pitch, 1.35ns/mm
• 2x 10x10cm2 THGEM• 2-sided pad-string anode • Delay-line readout (SMD)
Ionization electrons are multiplied & localized in cascaded-THGEMs imaging detector.
-) Detection efficiency: < 0.1%(fast-n) ~ 5% (cold-n) -) Spatial Resolution ~ 1 mm -) Counting Rate ~ 1 kcps/cm2
7Li/4He
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10th RD51 Collaboration Meeting, Stony Brook University, USA
High Efficiency Detector
…….+ + +Neutron Neutron Neutron
resistive layer on insulatorRead-out
2D radiography: for efficiency need to cascade many detectors!
100 detector elements for efficiency ≈ 6%
1D radiography 2D cross-sectional tomography
1 detector for efficiency ≈ 10%
Neutron source
Projectional image 1D distribution of neutron attenuation inside the object,
integrated over projection chords
5-1
0 m
m
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10th RD51 Collaboration Meeting, Stony Brook University, USA
Multi-layer converter + THGEM detector
n’
np
2D Readout Board
Antistatic HDPE layer (no charging up)
THGEM1
THGEM2
ΔV
E
Detector Concept:• n scatter on H in HDPE-radiator foils, p escape the foil. • p induce e- in gaseous conversion gap.• e- are multiplied and localized in THGEM-detector.• Combine several 1D radiographs 2D cross sectional tomography.
Detector design:-) Foils thickness (2.5 MeV neutron)-) Gas gap thickness (Deposited Energy)-) Converter height (Axial resolution)-) Number of converter foils (Detector Length)
Detector Performances:-) Spatial Resolution -) Efficiency of transport e- in small gap-) Detector Efficiency
Cortesi et al. 20012 JINST 7 C02056
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10th RD51 Collaboration Meeting, Stony Brook University, USA
Simulation Converter Thickness
Impinging neutron
(En)
θ
Scattered neutron
Target
Recoiled nucleus
(ER) θcos
A)(1
4A
E
E 22
n
R
Escaped protons (GEANT4)
For 2.45 MeV Neutron impinging on HDPE layer:
-) Max. Efficiency ≈ 0.06%-) Effective Conversion length = 100 μm-) Broad Spectrum (0 2.5 MeV)
Target Max. Ener. Tran. σ(2.45 MeV)
1H 100% 2.5 MeV ~2.55 b12C 28.4% 0.7 MeV ~1.6 b
HDPE (C2H4 – Mass Density = 0.93 g/cm3)
0 40 80 120 160 2000.000
0.025
0.050
0.075
0.100
Recoil Protons Efficiency
Det
ectio
n ef
ficie
ncy
(%)
HDPE thickness (m)
Neutron 2.5 MeV
HDPE density = 0.93 g/cm3
MCNPX calculation
Effi
cien
cy (
%)
MCNP calculated energy spectrum of escape protons
HDPE
Range of 2.5 MeV protons
Escape protons
Fraction of interaction neutrons
Energy (MeV)
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10th RD51 Collaboration Meeting, Stony Brook University, USA
Simulation Deposited Energy in the Gas
Geant4 Simulation snapshot
n n’
p
δe-
t d
HDPENe/5%CH4 (1 atm)
1 mm
MPV~ 2.7 keV (~ 75 e-)
Gas Gap = 0.6 mm
0 500 1000 1500 2000 250010-1
101
103
105
107
X-Rays Limit
Ar/CH4(5%)
X-Rays Limit Ne/CH4(23%)
Ne/CH4(5%)
Effec
tive-
Gain
VTHGEM
(Volt)
Ne
1 atm gas Flow modeCsI + UV Light
X-Rays Limit
X-Rays Limit
single THGEM (t = 0.8, d = 0.5, a=1mm, rim = 0.1 mm)
Gain
Cortesi et al. 2009 JINST 4 P08001
Broad Spectrum of Energy deposited by
recoil proton
Larger dynamic range in Ne-Mixtures
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10th RD51 Collaboration Meeting, Stony Brook University, USA
-50 -25 0 25 50
10-4
10-3
10-2
10-1
100
101
Position (mm)N
orm
aliz
ed
PS
F
Simulations Efficiency & Resolution
10-1
100
101
102
103
0
400
800
Energy (keV)
Co
un
ts
100 Conv.
200 Conv.
300 Conv.
Deposited Energy Spectrum Distribution of the deposited charge
Signal
Scattering
Cost effective solution: 300 HDPE layer
Conversion Efficiency ~8%
HD
PE f
oils
Neutrons (2.45 MeV)
Dete
ctor
Vess
el
SSR = Signal-to-Scattering ratio
LayersLayers
Layers LayersLayers
Layers
Parameters-) HDPE Thickness = 0.4 mm-) Gas Gap = 0.6 mm
0 100 200 300 400 500 6000
5
10
15
20
# of Converters
De
t. E
ffici
en
cy (
%)
0 100 200 300 400 500 6000
2
4
6
8
10
SN
RS
SR
Cortesi et al. 20012 JINST 7 C02056
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10th RD51 Collaboration Meeting, Stony Brook University, USA
Converter Prototypes
Produced using 3D printing technologiesFoils thickness = Gas gap = 0.6 mm
Height = 6 mm, 10 mmMaterial Antistatic ABS
• 2x 10x10cm2 THGEM• 2-sided pad-string anode • Delay-line readout (SMD)
Cortesi et al. 2007 JINST 2 P09002 6 mm height converter
10 mm height converter
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10th RD51 Collaboration Meeting, Stony Brook University, USA
e- Collection Efficiency Vs Electric Field
Full Collection efficiency above 0.4 kV/cm in the Converter Gas
Gap
Gas Ne/CF4 (1 atm)Detector Gain ~ 103
X-Rays
Side-Irradiation with soft (5.9 keV)
X-Rays
MCNP Snapshot
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10th RD51 Collaboration Meeting, Stony Brook University, USA
Electric Fields (Converter-Drift) Tuning
Field Ratio = Drift / Converter
Focusing of the ionization electron transferred from the converter Gas Gap to the Drift Gap (THGEM hole pitch ≠ Converter Foils
pitch Drift Gap)
Full transfer efficiency for field ratio > 2:1Ideal values: (1kV/cm Drift Field, 0.5 kV/cm Converter Field)
1.2 mm
1 mm
THGEM
Converter
New THGEM Configuration hole pitch
= Foils pitch(No drift Gap)
NEXT
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10th RD51 Collaboration Meeting, Stony Brook University, USA
Electron Transport through the (0.6 mm) gas gap
6-10 mm
3.2 mm
2-cascade THGEM Detector:-) Effective area 10x10 cmConverter Prototypes geometry:-) Foils Thickness = 0.6 mm-) Gas Gap = 0.6 mm-) Converter Height = 6mm / 10 mm-) number of foils = 83
Transport efficiency - Methodology: -) “Top” irradiation with soft (5.9 keV X-rays)-) Comparison between the spectra of Deposited Energy (MCNP) and measured Pulse-Height Spectra using the THGEM detector
MCNP calculated spectra of deposited energy
6 mm height Converter
Measured Spectra
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10th RD51 Collaboration Meeting, Stony Brook University, USA
Electron Transport through the (0.6 mm) gas gap
6-10 mm
3.2 mm
2-cascade THGEM Detector:-) Effective area 10x10 cmConverter Prototypes geometry:-) Foils Thickness = 0.6 mm-) Gas Gap = 0.6 mm-) Converter Height = 6mm / 10 mm-) number of foils = 83
Transport efficiency - Methodology: -) “Top” irradiation with soft (5.9 keV X-rays)-) Comparison between the spectra of Deposited Energy (MCNP) and measured Pulse-Height Spectra using the THGEM detector
6 mm height Converter
Measured Spectra
Electron Transport Efficiency Converter-to-Drift Counts Rate ratios = MCNP/Measured (full efficiency
= 1)MCNP calculated spectra of deposited energy
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10th RD51 Collaboration Meeting, Stony Brook University, USA
Efficiency ≈ 92%
Deposited Energy (MCNP) Measured Spectra
Efficiency ≈ 30%
6 mm height Converter
10 mm height Converter
Significant loss of Efficiency due to
charging up of the foils &/or secondary
effects(Distorted converter field)
Electron Transport through the (0.6 mm) gas gap
Small Efficiency loss due to electron
diffusion
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10th RD51 Collaboration Meeting, Stony Brook University, USA
Transport Efficiency (Garfield simulation)
2D Readout Board
100 electron per event simulated in the gas gap
at various height (2-8 mm)
THGEM1
THGEM2
E
Converter
Detected Event at least one electron focused in the THGEM hole
for 6 mm height Aver. Transport efficiency = 95% (≈ measured efficiency soft X-rays)------------------------------------------
for 10 mm height Aver. Transport efficiency = 70% (> measured efficiency soft X-rays) Charging up!
Charge lost due to electron diffusion!
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10th RD51 Collaboration Meeting, Stony Brook University, USA
Detection Efficiency (fast neutron)
2.5 MeV neutron induced recoil proton in 0.6 mm Gas Gap MVP = 2.7 KeV
Detected Event at least one electron focused in the THGEM hole
6 mm height converter: Aver. Transport efficiency = 97%
-) Conversions efficiency ≈ 8% for ~300 foils-) Transport Efficiency ≈ 97% for 6 mm height, 0.6 mm gas gap-) Discrimination threshold (front-end electronics) ≈ 90%
Estimated Fast-n Detection Efficiency ≈ 7%
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10th RD51 Collaboration Meeting, Stony Brook University, USA
Summary & Future Plan
Goal TWO-FAST: Fast neutron tomographic 2D cross-sectional images
Main Application: non-destructive testing for the nuclear energy industry: multi-phase flow, spent nuclear fuel bundles inspection, safeguards …
Others: detection of SNM, explosive (border control), material science …
Two Detector technologies Feasibility study Gaseous Detector (THGEM)
New Idea many n-to-p converters, single 2D Detector readout
* Expected detection efficiency ~7% (300 foils) * 1D Radiography, spatial resolution ~ 1 mm * Low sensitivity to gamma background
* 10x10 cm2 imaging detector prototype ready for neutron with antistatic HDPE multi-layers converter produced using 3D printing Converter thickness = Gas gap ≈ 0.6 mm (83 layers) * Improvement of charge-readout electronics * Implementation with TWO-FAST compact D-D generator
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10th RD51 Collaboration Meeting, Stony Brook University, USA
1. Emitting spot size: Ø2mm
Burning plasma in the RF-driven ion source with external antenna
Compact, pulsed neutron generator
2.45 MeV
TWOFAST: Fast imaging with fast neutrons, feasibility study
Cooperation: Prof. Ka-Ngo Leung, Berkeley
3. Nominal yield: 108 neutrons/s
2. Pulsed operation: 1kHz; D.F.:1-10%
High fraction (>90%) mono-atomic plasma