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

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 3 He + 1 n _______ 3 H + 1 p MeV B + 1 n _______ 7 Li + 4 He MeV MeV  (93%) 7 Li + 4 He MeV ( 7%) 6 Li + 1 n _______ 3 H + 4 He MeV Gd + 1 n _______  s + Conversion electrons nat Gd + 1 n _______  s + Conversion electrons Neutron Converters

Neutron Production The ILL ILL 60MW Reactor

Neutron Production ISIS SPALLATION NEUTRON SOURCE

Detector Properties Detector characteristics for optimisation Neutron detection efficiency 100 eV – sub meV Gamma insensitivity at 1 MeV Intrinsic detector background 0.1 c -1 s -1 m -2 Spatial resolution mm 2 Speed 1 MHz Geometry 40 m 2 Stability 0.1 % over days Cost 0 -2 £M Radiation Hardness gamma and fast n

3He Detector Efficiency

Detector Types Single element detectors Chopper spectrometer MARI 900+ detectors 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 PSDs The MAPS Spectrometer The MAPS spectrometer

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

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

Detector efficiency (1Å) 70% Gamma efficiency ( 60 Co) 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 Requirements Linear PSDs MERLIN Characteristics

Developments Elsewhere Multitube IN5 ILL

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)

Brookhaven NL MWPCs

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.

Developments Elsewhere MWPC D19 ILL

Developments Elsewhere MSGD 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 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

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

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.

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 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

Gadolinium Detector Efficiency

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

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

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

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

MWPCs

JRA2 –MILAND MSGDs

JRA2 -MILAND GSPCs

SNS Reflectometers 200 x 200 mm detector 1 mm pixel resolution 1.8 – 10.5 Å DesiredRequired Counts / pixel / s 1.3 x x 10 4 Total counts / s 1.2 x x 10 6 MagnetismLiquids

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