Position-sensitive detectors of thermal neutrons: types, characteristics, applications.

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

2. 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 magneticmultilayer sample measured at the refletometer REFLEX IX International school-seminar: Actual problems of microworld physics

3. 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

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

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

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

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

8. Types of PSD IX International school-seminar: Actual problems of microworld physics

9. Developments of FLNP JINR • 2D monitor for thermal neutrons • Active area 100x100 mm2 • Spatial resolution 4x4 mm2 • Direct beam weakening<5% • Intended for direct beam observation • 1D multi-purpose PSD • Active area 200x800 mm2 • Spatial resolution 1,8 mm • Multi-purpose detector for neutron diffraction and reflectometry • 2D multi-purpose PSD • Active area 225x225 mm2 • Spatial resolution 2x2 mm2 • Multi-purpose detector for various neutron scattering measurements IX International school-seminar: Actual problems of microworld physics

10. Experimental results T=10˚K T=290˚K Diffraction spectraof the(La0.1Pr0.9)0.7Ca0.3Mn0.3sample, measured at the channel №5. of the IBR-2 reactor. Profile of the channel №6b of the IBR-2 Profile of the channel №10 of the IBR-2 IX International school-seminar: Actual problems of microworld physics

11. 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

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