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MALAVIYA NATIONAL INSTITUE OF TECHNOLOGY,

JAIPUR

SEMINAR ON-

BETA RAY SPECTROMETER

SUPERVISED BY: SUBMITTED BY:

Deptt. of physics Megha Gupta

2009PPH118IIIrd Sem.

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Introduction & Properties of beta-rays

Beta ray are positively and negatively charge particle. it

also consists electron and positron.

Beta ray has ionizing nature.

Energy spectrum of beta rays is continuous

They have typically energies in the range of a few

hundred keV to several MeV.

Beta ray are also corpuscular in nature.

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BEAT-DECAY

Beta-decay is types of radio active decay, in which betaparticle (electron, positron) is emitted.

The emitted beta particles have a continuous energyspectrum range in (0 to maximum).

It has definate energy limit at point E0, is the max. energy ,it

is also called End-point energy.

Energy continuous spectrum has definate height. it dependson nucleus emitting -particle.

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Continuous Energy spectrum ofbeta rays

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TYPES OF -DECAY

1. decay (electron emission)-neutron transformed in protonwith emission of eand antineutrino .

n p + e + e

A remains same Z increase by 1

2.+ decay (positron emission)-proton transformed in neutronwith emission of e+ and neutrino.

p n + e+

+ e

A remains same Z decrease by -1

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decay and + decay

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decay

On a fundamental level, an up quark is convertedinto a down quark, emitting W boson that thendecays into e- andantineutrino.

http://en.wikipedia.org/wiki/File:Beta_Negative_Decay.svg

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-ray spectrometer

Electron and positron emitted during beta-decay internalconversion electron emitted during the de-excitation ofnuclear levels.

This instrument carry out the energy analysis of electron iscalled ray spectrometer .

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Types of -ray spectrometer

1.Magnetic spectrometer

2.Electrostatic spectrometer

3.Scintillation spectrometer

4. Semiconductor spectrometer

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Magnetic spectrometer

Momentumof e- detected in spectrometer. it will be exhibit fullwidth at half the height of line.

Ratio of R=(B)/(B)(%) is called resolution(resolving

power)of spectrometer. It denoted as percentage.

It is constant for spectrometer ,if electron follow a fixedgeometry.

Fraction of e- detected & counted by a detector ,this fraction iscalled transmission(t).

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Electron conversion spectra in amagnetic spectrometer

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Resolution-Resolution of a spectrometer is measure of itsability to resolve two peaks that are close together inenergy.

Resolution=(FHWM)x100/peak channel no. =(E)x100/E

Where,E-full width of peak at half of maximum.

E-based line voltage at the centroid of photo-peak.

Calibration-energy of photo peak of Cs137

corrosponding channel no .

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Transverse spectrometer

Velocity of e- perpendicular direction to magnetic field.

Two types-

(1)Semicircular spectrometer(2)Double focusing spectrometer

Semicircular spectrometer produces lower resolution andtransmission.

Double focusing spectrometer produces best resolution .01%to .01%.

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Longitudinal spectrometer Velocity of e- parallel direction to magnetic field.

In which Magnetic field obtained by solenoid coils.it is alsocalled long-lens spectrometer. it has R=1%,t=4%.

Disadvantage- Use coil to obtained magnetic field.

Source &detector placed in magnetic field.

To overcome these difficulties, a short lens spectrometer was

developed

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Electrostatic spectrometer

Electrostatic spectrometer is modify form of magneticspectrometer.

electrostatic spectrometer mostly used at lower

energies(energy limit 1.5Mev)

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Scintillation spectrometer

Electron from an external source normally pass through protective

covering and light reflector.

Detector does not opaque secondary bremsstrahulung photon.

Full energy peak corresponding to energy absorption of incidentof electron energy.

scintillator with low atomic are generally prefer for electron

spectroscopy.

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split crystal-spectrometer in which -ray source wassandwiched between a pair of anthracene phosphors.

Scintillator for detection of beta ray spectra Beta source

Collimator

anthrance Scintillator

Photomultiplier

tube

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Scintillation spectrometer

Scintillation spectrometer ,in high efficiency causes cannotdistinguish between two coincide pulses.

one proper beta pulse.

Other due to electron conversion.

Advantage-

high deflection efficiency.

Simple structure

Disadvantageit have poor resolution & non linear responsecompared to magnetic or electro magnetic spectrometer.

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Electron conversion spectra forplastic scintillator & Cs(TI)

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Semiconductor spectrometer Semi-conductor radiation detector used for study of beta ray

and measured electron conversion spectra.

These spectrometer are commonly used at low energy and highenergy detection.

Magnetic -ray spectrometer are preferable to semiconductordetector high energy resolution.

Advantage (i)cheaper

(ii)Si(Li) detector used to measure internal conversioncoefficient for.

(iii)used for large angle geometry & total spectrum can berecorded.

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Semiconductor spectrometer

Disadvantage two problem arise for detection of electron.back scattering of e- from the surface of the crystal give to

low energy with conversion lines.

window counter used to so that loss of energy in detector

window kept to minimum.

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Electron conversion spectra withSi(Li) detector

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Comparison

Ideal spectrometer produces higher transmission and lowerresolution.

Electrostatic spectrometer is modify form of magneticspectrometer. it is also used at lower energies.

Semiconductor spectrometer used to both low energy and highenergy electron detection.

Magnetic beta ray spectrometer are preferable to semiconductordetector for high energy resolution.

scintillation spectrometer have poor resolution compared tomagnetic and electrostatic spectrometer, so it is the best

spectrometer for beta rays is mostly used in practical lab.

O i

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ObservationS.No. Channel number Count rate per 10

seconds1 1.0 1514

2 1.1 10903 1.2 8734 1.3 767

5 1.4 9286 1.5 4824

7 1.6 198828 1.7 283529 1.8 13586

10 1.9 186611 2.0 112

12 2.1 5113 2.2 42

14 2.3 3915 2.4 39

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Complete spectra of Sr-90

Channel number

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Reference

Google

R.M.Singru

Glenn.F.Knoll

Jadish verma

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THANKS