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PSD 7 September 2005

PSD 7 September 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.

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PSD 7 September 2005

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  1. PSD 7 September 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

  2. INTRODUCTION • 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

  3. Neutron Converters Cross section at 1 Å barnes 3He + 1n _______ 3H + 1p - 0.77 MeV 3 000 10B + 1n _______ 7Li + 4He - 2.3 MeV +0.48MeV g2 100 (93%) 7Li + 4He - 2.7 MeV ( 7%) 6Li + 1n _______ 3H + 4He - 4.79 MeV 520 157Gd + 1n _______ gs + Conversion electrons 74 000 natGd + 1n _______ gs + Conversion electrons 17 000

  4. Neutron Production The ILL ILL 60MW Reactor

  5. Neutron Production ISIS SPALLATION NEUTRON SOURCE

  6. 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 Hardnessgamma and fast n

  7. 3He Detector Efficiency

  8. Detector Types Single element detectors Molecular spectroscopy TOSCA Chopper spectrometer MARI Squashed detectors for accurate ΔT 900+ detectors - 300 mm long

  9. Linear PSDs The MAPS Spectrometer The MAPS spectrometer 8 channel pre amp card 18 channel ADC card MAPS 1 m long 8 pack detector array

  10. Linear PSDs The MAPS Detector Array Data Quality truly exceptional Even some of the simplest structures have revealed complex structures not seen before.

  11. Linear PSDs MERLIN DETECTOR ARRAY 3m 2.88m 30o INSTRUMENT LAYOUT 2.5m Sample 3 m long detectors

  12. Linear PSDs MERLIN Characteristics CHARACTERISTICS Detector efficiency (1Å) 70% Gamma efficiency (60Co) 10-8 Intrinsic background 0.16 / pixel / hr Spatial resolution FWHM < 25 mm Pulse pair resolution 4 µs Area 21m2 Requirements No. Detectors No. Packs No. Pixels 280 35 70 000

  13. Developments Elsewhere Multitube IN5 ILL

  14. 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)

  15. Brookhaven NL MWPCs

  16. Brookhaven NL MWPCs • 50% efficient at 1.5 Å • 1500 x 200 mm2 active area • 1.3 x 1.3 mm2 resolution 106 c / s Cylindrical shape to eliminate parallax in one direction.

  17. Developments Elsewhere MWPC D19 ILL

  18. Developments Elsewhere MSGD D20 ILL

  19. Compare characteristics with the ISIS instrument suite THE ISIS SECOND TARGET STATION Schedule First neutrons 2007 User run starts end 2008

  20. Other sources ANSTO Australia FRM-11 Germany JSNS Japan SNS USA

  21. 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

  22. 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 Resistive wire technology ~1500 detectors 1 mm3 crystal 100 kHz per detector 5 mm3 crystal12 MHz per detector Large area powder / single crystal diffractometer for the study of magnetic materials

  23. Resistive Wire Technology The MAPS Detector Array SANS 2d MWPC 19 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.

  24. 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

  25. JRA1 -DETNI  DETNI: Detectors for Neutron Instrumentation Coordinator B. Gebauer HMI-Berlin • Within DETNI there are three types of detector under development • Double-sided Si MSD with 157Gd converter • 50 mm FWHM, >100 MHz global count rate • Low pressure MSGD with composite 157Gd/CsI converter • 100 mm 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

  26. Gadolinium DetectorEfficiency

  27. JRA1 -DETNI HYBRID MSGD B Gebauer et al., HMI Berlin TECHNI and DETNI

  28. JRA1 -DETNI HYBRID MSGDCharacteristics • Segmented Delay line readout • Efficiency 1-3 mm 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 mm 157Gd • Position Resolution 0.1 mm FWHM • Rate 108 c/s/segment

  29. JRA1 -DETNI CASCADE Martin Klein et al., Heidelberg 29% at 1.8 Å, 17% at 1.0 Å Ar / CO2 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

  30. JRA2 -MILAND JRA2 -MILAND  MILAND: Millimetre resolution Large Area Neutron Detector Coordinator B. Guerard ILL-France • Within MILAND there are three types of detector under development • ● MWPC ●MSGD ●Gas Scintillation Detector 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

  31. JRA2 -MILAND MWPCs

  32. JRA2 –MILAND MSGDs

  33. JRA2 -MILAND GSPCs

  34. SNS Reflectometers Magnetism Liquids 200 x 200 mm detector 1 mm pixel resolution 1.8 – 10.5 Å

  35. MWPCs and MSGDs

  36. 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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