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. 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

3. Cross section at 1 Å barnes 3 He + 1 n _______ 3 H + 1 p - 0.77 MeV 3 000 10 B + 1 n _______ 7 Li + 4 He - 2.3 MeV + 0.48MeV  2 100 (93%) 7 Li + 4 He - 2.7 MeV ( 7%) 6 Li + 1 n _______ 3 H + 4 He - 4.79 MeV 520 157 Gd + 1 n _______  s + Conversion electrons 74 000 nat Gd + 1 n _______  s + Conversion electrons 17 000 Neutron Converters

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 mm 2 Speed 1 MHz Geometry 40 m 2 Stability 0.1 % over days Cost 0 -2 £M Radiation Hardness gamma and fast n

7. 3He Detector Efficiency

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

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

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

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

12. Detector efficiency (1Å) 70% Gamma efficiency ( 60 Co) 10 -8 Intrinsic background 0.16 / pixel / hr Spatial resolution FWHM < 25 mm Pulse pair resolution 4 µs Area 21m 2 CHARACTERISTICS No. Detectors No. Packs No. Pixels 280 35 70 000 Requirements Linear PSDs MERLIN Characteristics

13. Developments Elsewhere Multitube IN5 ILL

14. 2D PSD LOQ Ordela 2661N 25% efficient at 1 Å 650 x 650 mm 2 active area 5 x 5 mm 2 resolution 3 He CF 4 at 1.5 Bar 2 x 10 5 rate (10% losses)

15. Brookhaven NL MWPCs

16. 50% efficient at 1.5 Å 1500 x 200 mm 2 active area 1.3 x 1.3 mm 2 resolution 10 6 c / s Brookhaven NL MWPCs 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 SNS USA FRM-11 Germany JSNS Japan

21. Low Energy Transfer Chopper Spectrometer Detector array 4m high array at 3.5 m radius -35 to +135 degrees horizontal coverage Area 40 m 2 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 Large area powder / single crystal diffractometer for the study of magnetic materials Resistive wire technology ~1500 detectors 1 mm 3 crystal 100 kHz per detector 5 mm 3 crystal 12 MHz per detector

23. Resistive Wire Technology The MAPS Detector Array SANS 2d MWPC 19 m Active area : 1m x 1m Position resolution : 5 x 5 mm 2 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 Within DETNI there are three types of detector under development Double-sided Si MSD with 157 Gd converter 50  m FWHM, >100 MHz global count rate Low pressure MSGD with composite 157 Gd/CsI converter 100  m FWHM, >100 MHz global count rate Cascade, a GEM based detector with multiple 10 B layers 1 mm FWHM, >10 MHz global count rate, large areas Coordinator B. Gebauer HMI-Berlin

26. Gadolinium Detector Efficiency

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

28. JRA1 -DETNI HYBRID MSGD Characteristics Segmented Delay line readout Efficiency1-3  m 157 Gd Position Resolution0.3 mm FWHM Rate2 x 10 6 c/s/segment With ASIC for single strip readout development under DETNI Efficiency1-3  m 157 Gd Position Resolution0.1 mm FWHM Rate10 8 c/s/segment

29. JRA1 -DETNI CASCADE Martin Klein et al., Heidelberg Neutron Detector Efficiency 40 – 50 % at 1.8 Å (10 GEMs) Count Rate 10 7 n cm -2 s -1 Position Resolution 1 – 5 mm Size 200 x 200 mm 2 29% at 1.8 Å, 17% at 1.0 Å Ar / CO 2

30. 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

31. MWPCs

32. JRA2 –MILAND MSGDs

33. JRA2 -MILAND GSPCs

34. SNS Reflectometers 200 x 200 mm detector 1 mm pixel resolution 1.8 – 10.5 Å DesiredRequired 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 MagnetismLiquids

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