position-sensitive detectors of thermal neutrons: types, characteristics, applications. a.v....

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

A.V. Churakov

IX International school-seminar: Actual problems of microworld physicsIX International school-seminar: Actual problems of microworld physics

Belarus, Gomel, July 23- August 3, 2007Belarus, 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

Neutronsource

n nn

n

n

CollimatorDetectors

Sampleenvironment

and positioningsystems

Sample

Schematic view of the neutron scattering facility

Spectrum of the magneticSpectrum of the magnetic multilayer sample multilayer sample

measured at the refletometer REFLEXmeasured at the refletometer REFLEX


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 experimentBecomes possible real-time measurements

and research dynamic of the processesand many other benefits


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


Registration of thermal neutrons

Neutron capture reactions, commonly used in neutron

detectors

n+3He → 3H+p+0,77 MeVn+6Li → 3H+α+4,79 MeVn+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 KeVn+235U → fission fragmentsn+239Pu → fission fragments

0,001 0,01 0,1 1

102

103

104

105

106

3He

10B

6Li

natGd

Energy (eV)C

ross

-sec

tion

(bar

n)

From P.Convert, J.Bruce Forsyth “Position sensitive detectors of thermal neutrons”


Scintillation PSDs

Scintillator

n

CCDcamera

Electronics

Reflector

PM1 PM2

Decoder

Discretescintillationelements

n

Optic fibres

Photomultipliers

Discrete elements PSD

Scintillator with CCD-camera

Photomultipliers

nReflector

PM1 PM2 PM3

Scintillator

Lightdisperser

The Anger cameraFrom P.Convert, J.Bruce Forsyth “Position sensitive detectors of thermal neutrons”


Gaseous PSD

e

From F. Sauli “Survey of the GEM technology and applications”

e

Microstrip detectors GEM-based detectors

Multi-wire proportional chambersArray of counters

e

+Hv+Hv


Types of PSD

Spatial resolution

Efficiency Linearity StabilityCount Rate

γ-sensitivity Note

Counter Array 5 mm 90% Good* Excelent High Very Low

MWPC 1 mm 80% 5% Good High* Very Low

Microstrip 1 мм 80% No data Good Good Very Low

Small active area

GEM-based 0,1 мм 80%* Good Good Low

Discrete element scintillator 3 mm 90% 3%

Quiet good Good High

The Anger camera 3 mm 85% 7%

Quiet good Good High

Scint. with CCD-camera 0,5 мм 60% 3% No data

No data High

Films 0,05 мм * 7% GoodNo data Low

Not suited for TOF


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


Experimental results

Diffraction spectraDiffraction spectra of theof the (La(La0.10.1PrPr0.90.9))0.70.7CaCa0.30.3MnMn0.30.3 sample, measured at the sample, measured at the

channel channel №5№5. of the IBR-2 reactor. . of the IBR-2 reactor.

T=10T=10˚K˚KT=290T=290˚K˚K

Profile of the channelProfile of the channel №10 №10 of the IBR-2 of the IBR-2 Profile of the channel Profile of the channel №6№6b of the IBR-2b of the IBR-2


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.


Thank your for attention!


position-sensitive detectors of thermal neutrons: types, characteristics, applications. a.v....

Documents

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neutron detectorsn

light elements

magnetic multilayer

pu fission fragmentsfrom

development of psd

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