psd 7 september 2005
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PSD 7September 2005
Developments and Applications of Gas Based
Neutron Detectors
Introduction
Neutron Detector Characteristics Gaseous Detectors currently in use
Challenges for the future New developments Conclusion
N J Rhodes CCLRC ISIS Facility
Neutrons
Provide information on the structure and dynamic of materials on an atomic/molecular scale
Ideal probes for Condensed Matter Research
Zero charge – highly penetrating
Low KE – probe atomic / molecular dynamics(100 eV – sub meV)
Etc…
Non idealised particles for detection
Zero charge – generally weak interaction
Low KE – generally weak interaction
Require a nuclear converter
INTRODUCTION
Cross section at 1 Å
barnes
3He + 1n _______ 3H + 1p - 0.77 MeV 3 000
10B + 1n _______ 7Li + 4He - 2.3 MeV + 0.48MeV 2 100 (93%)
7Li + 4He - 2.7 MeV ( 7%)
6Li + 1n _______ 3H + 4He - 4.79 MeV 520
157Gd + 1n _______ s + Conversion electrons 74 000
natGd + 1n _______ s + Conversion electrons 17 000
Neutron Converters
Neutron ProductionThe ILL
ILL 60MW Reactor
Neutron ProductionISIS
SPALLATION NEUTRON SOURCE
Detector Properties
Detector characteristics for optimisation
Neutron detection efficiency 100 eV – sub meV
Gamma insensitivity 10-6 at 1 MeV
Intrinsic detector background 0.1 c-1 s-1 m-2
Spatial resolution 25 -1 mm2
Speed 1 MHz
Geometry 40 m2
Stability 0.1 % over days
Cost 0 -2 £M
Radiation Hardness gamma and fast n
3He Detector Efficiency
Neutron absorption efficiencyfor a 3He filled gastube, 1" diameter,
for various 3He pressures.
Wavelength (Å)
0 2 4 6 8 10Neu
tro
n a
bso
rpti
on
eff
icie
ncy
0.0
0.2
0.4
0.6
0.8
1.0
1 atm 2 atm 5 atm 10 atm
Detector TypesSingle element detectors
Chopper spectrometer MARI
900+ detectors - 300 mm long
Molecular spectroscopy TOSCA
Squashed detectors for accurate ΔT
MAPS 1 m long 8 pack detector array
18 channel ADC card
8 channel pre amp
card
Linear PSDsThe MAPS Spectrometer
The MAPS spectrometer
Data Quality truly exceptional
Even some of the simplest structures have revealed complex structures not seen before.
Linear PSDsThe MAPS Detector Array
Linear PSDsMERLIN
2.5m30o2.88m
Sample
3m
INSTRUMENT LAYOUT
DETECTOR ARRAY
3 m long detectors
Detector efficiency (1Å) 70%Gamma efficiency (60Co) 10-8
Intrinsic background 0.16 / pixel / hrSpatial resolution FWHM < 25 mmPulse pair resolution 4 µsArea 21m2
CHARACTERISTICS
No. Detectors No. Packs No. Pixels
280 35 70 000
Requirements
Linear PSDs MERLIN Characteristics
Developments ElsewhereMultitube IN5 ILL
2D PSD LOQ
Ordela 2661N
25% efficient at 1 Å
650 x 650 mm2 active area
5 x 5 mm2 resolution
3He CF4 at 1.5 Bar
2 x 105 rate (10% losses)
Brookhaven NLMWPCs
50% efficient at 1.5 Å
1500 x 200 mm2 active area
1.3 x 1.3 mm2 resolution
106 c / s
Brookhaven NLMWPCs
Cylindrical shape to eliminate parallax in one direction.
Developments ElsewhereMWPC D19 ILL
Developments ElsewhereMSGD D20 ILL
Compare characteristics with
the ISIS instrument suite
THE ISIS SECOND TARGET STATION
Schedule
First neutrons 2007
User run starts end 2008
Other sources
ANSTO Australia
SNS USA
FRM-11 Germany
JSNS Japan
Low Energy Transfer Chopper Spectrometer
Detector array
4m high array at 3.5 m radius
-35 to +135 degrees horizontal coverage
Area 40 m2
Position resolution 15 mm FWHM
Energy range 0 – 80 meV
Resistive wire technology
4 m long detectors
Position resolution limited by pre amp
WISH A high resolution magnetic diffractometer
Detector array
~ 1m high array at 2.2 m radius
± 10 to ± 170 degrees horizontal coverage
Position resolution 8 x 8 mm pixels
Wavelength range 1.5 – 15 Å
Large area powder / single crystal diffractometer for the study of magnetic materials
Resistive wire technology
~1500 detectors
1 mm3 crystal 100 kHz per detector
5 mm3 crystal 12 MHz per detector
Resistive Wire TechnologyThe MAPS Detector Array
SANS 2dMWPC
19 m19 m
Active area : 1m x 1m
Position resolution : 5 x 5 mm2
Count rate: 2 x 10 5 n/s at 10% . deadtime
Neutron efficiency: 50% at 2 Å
Commercial solution
Ordela Inc.
Neutron Detector Development in FP6
Under the EU Framework Programme 6
An Integrated Infrastructure Initiative has been set up for
Neutron Scattering and Muon Spectroscopy
NMI3
includes 8 Joint Research Activities
JRA1 - (DETNI) Detectors for Neutron Instrumentation - Burckhard Gebauer
JRA2 - (MILAND) Millimetre Resolution Large Area Neutron Detector - Bruno Guerard
JRA1 -DETNI
DETNI: Detectors for Neutron Instrumentation
Within DETNI there are three types of detector under development
• Double-sided Si MSD with 157Gd converter
•50 m FWHM, >100 MHz global count rate
• Low pressure MSGD with composite 157Gd/CsI converter
•100 m FWHM, >100 MHz global count rate
• Cascade, a GEM based detector with multiple 10B layers
•1 mm FWHM, >10 MHz global count rate, large areas
Coordinator B. Gebauer HMI-Berlin
GadoliniumDetector Efficiency
Neutron absorption efficiency of5m natGd and 2.5m 157Gd foils.
Wavelength (Å)
0 2 4 6 8 10Neu
tro
n a
bso
rpti
on
eff
icie
ncy
0.0
0.2
0.4
0.6
0.8
1.0
Nat 157
JRA1 -DETNI HYBRID MSGD
B Gebauer et al., HMI Berlin TECHNI and DETNI
JRA1 -DETNI HYBRID MSGD Characteristics
Segmented Delay line readout
Efficiency 1-3 m 157Gd
Position Resolution 0.3 mm FWHM
Rate 2 x 106 c/s/segment
With ASIC for single strip readout
development under DETNI
Efficiency 1-3 m 157Gd
Position Resolution 0.1 mm FWHM
Rate 108 c/s/segment
JRA1 -DETNI CASCADEMartin Klein et al., Heidelberg
Neutron Detector Efficiency 40 – 50 % at 1.8 Å (10 GEMs)
Count Rate 107 n cm-2 s-1
Position Resolution 1 – 5 mm
Size 200 x 200 mm2
29% at 1.8 Å, 17% at 1.0 Å
Ar / CO2
JRA2 -MILAND
MILAND: Millimetre resolution Large Area Neutron Detector
Within MILAND there are three types of detector under development
● MWPC ● MSGD ● Gas Scintillation Detector
Coordinator B. Guerard ILL-France
Detection Efficiency: 50% for thermal neutrons aiming for 80%
Area: 320 mm x 320mm aiming for 400 mm x 400 mm
Spatial Resolution: 1 mm x 1 mm
Count rate: 1 MHz global rate at 10% dead time
JRA2 -MILAND
JRA2 -MILAND MWPCs
JRA2 –MILANDMSGDs
JRA2 -MILAND GSPCs
SNSReflectometers
200 x 200 mm detector
1 mm pixel resolution
1.8 – 10.5 Å
Desired Required
Counts / pixel / s 1.3 x 10 6 1.3 x 10 4
Total counts / s 1.2 x 10 8 1.2 x 10 6
Magnetism LiquidsLiquids
MWPCs and MSGDs
Conclusions
Gas detectors have played a vital role in Neutron Detector applications to date.
This will continue in the foreseeable future
Future Requirements
Improvements in position resolution and count rate.
Parallax an issue for some instruments with high resolution and short sample to detector distances.
User friendly, reliable detector electronics is essential
Existing qualities of detectors need to be maintained.
High neutron detection efficiency
low gamma sensitivity
low quiet count
Possibilities for further exploiting these detectors is high
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