Position-sensitive detectors of thermal neutrons: types, characteristics, applications. A.V. Churakov IX International school-seminar: Actual problems of microworld physics Belarus, Gomel, July 23- August 3, 2007 FLNP JINR 2007

Neutron scattering methods  It is possible to study light elements and elements with close atomic numbers  Deep penetration into the sample – allow to explore in volume  Magnetic moment of neutron allow studies magnetic structure of the sample Spectrum of the magnetic multilayer sample measured at the refletometer REFLEX IX International school-seminar: Actual problems of microworld physics

Why PSD? Position-sensitive detectors allows to observe not only the fact of the particles transit throughout the detector volume, but exact coordinate of the particle.  All spectrum can be measured in one experiment  Decrease the time of the experiment  Becomes possible real-time measurements and research dynamic of the processes  and many other benefits IX International school-seminar: Actual problems of microworld physics

Main characteristic of the PSD  Spatial resolution  Efficiency  Count rate  Active area (in some cases – angle range)  Integral and differential nonlinearity  Stability, reliability  Sensitivity to γ-rays  Capability to work in TOF mode  Size and mass IX International school-seminar: Actual problems of microworld physics

Registration of thermal neutrons Neutron capture reactions, commonly used in neutron detectors n+ 3 He → 3 H+p+0,77 MeV n+ 6 Li → 3 H+α+4,79 MeV n+ 10 B → 7 Li+α+γ(0,48 MeV)+2,3 MeV (93%) → 7 Li + α + 2,79 MeV (7%) n+ 157 Gd → Gd* → γ-ray → conv. electron up to 182 KeV n+ 235 U → fission fragments n+ 239 Pu → fission fragments From P.Convert, J.Bruce Forsyth “Position sensitive detectors of thermal neutrons” IX International school-seminar: Actual problems of microworld physics

Scintillation PSDs Discrete elements PSD Scintillator with CCD-camera The Anger camera From P.Convert, J.Bruce Forsyth “Position sensitive detectors of thermal neutrons” IX International school-seminar: Actual problems of microworld physics

Gaseous PSD From F. Sauli “Survey of the GEM technology and applications” Microstrip detectors GEM-based detectors Multi-wire proportional chambers Array of counters e +Hv IX International school-seminar: Actual problems of microworld physics

Types of PSD Spatial resolution EfficiencyLinearityStability Count Rate γ-sensitivityNote Counter Array5 mm90%Good*ExcelentHighVery Low MWPC1 mm80%5%GoodHigh*Very Low Microstrip1 мм80%No data Good Very Low Small active area GEM-based0,1 мм80%* Good Low Discrete element scintillator3 mm90%90%3% Quiet goodGoodHigh The Anger camera3 mm85%85%7% Quiet goodGoodHigh Scint. with CCD- camera0,5 мм60%3%No data High Films0,05 мм*7%Good No dataLow Not suited for TOF IX International school-seminar: Actual problems of microworld physics

Developments of FLNP JINR  2D monitor for thermal neutrons Active area 100x100 mm 2 Spatial resolution 4x4 mm 2 Direct beam weakening <5% Intended for direct beam observation  1D multi-purpose PSD Active area 200x800 mm 2 Spatial resolution 1,8 mm Multi-purpose detector for neutron diffraction and reflectometry  2D multi-purpose PSD Active area 225x225 mm 2 Spatial resolution 2x2 mm 2 Multi-purpose detector for various neutron scattering measurements IX International school-seminar: Actual problems of microworld physics

Experimental results Diffraction spectra of the (La 0.1 Pr 0.9 ) 0.7 Ca 0.3 Mn 0.3 sample, measured at the channel №5. of the IBR-2 reactor. T=10˚K T=290˚K Profile of the channel №10 of the IBR-2 Profile of the channel №6b of the IBR-2 IX International school-seminar: Actual problems of microworld physics

Results  A great progress in development of PSD`s for detection of thermal neutrons have been achieved. But on the present moment there is no type of detectors, that completely satisfied all demands of the physicists.  Leading world centers of neutron research continues work for further improvements of their detector complexes. IX International school-seminar: Actual problems of microworld physics

Thank your for attention! IX International school-seminar: Actual problems of microworld physics