Cyclotron Produced Radionuclides

7/31/2019 Cyclotron Produced Radionuclides

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CyclotronProduced

Radionuclides


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The majority of radionuclide are artificially

produced in Cyclotron and Reactor.

Some short lived radionuclide are available

from radionuclide generators in which long

lived parents are loaded and decay to short

lived daughters.


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Cyclotron

Cyclotron is known as particle accelerator to

accelerate charged particle to a very high

speed.

It uses crossed magnetic and electric fields

at right angles.


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Construction of cyclotron


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It consists of two hollowsemicircular Dees sonamed because of theirD-shape.

The plane of Dees is theplane of revolution ofcharged particle,preferably a planemidway in the Dees.

The Dees are constructedof conducting materiallike copper -> in order

1. to function as electrodes

for applying alternatingelectrical potential usingelectrical source knownas electrical oscillator

2. to shield moving

charged particle fromelectric field within theDees.


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The Dees are kept face to face diametricallyopposite at a small distance known as thegap.

Electric field operates only in the gap tochange speed of the charged particle.

The electric field does not accelerate charged

particle when it is moving along semicircularpath within the Dees as it is shielded fromelectrical field.


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There is an exit channel at the perimeter ofone of Dees which finally guides theaccelerated charged particle towards a target.

The whole set up of Dees is placed betweentwo poles of a powerful magnetic such that itsfield is perpendicular to the plane of Dees andhence perpendicular to the plane of motion.

This system of Dees is placed in evacuatedconfinement.


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Working


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Working principle

The charged particle (say a positively charged

proton) is released near mid point of the face

of one of the Dees.

Being in the electric field from one Dee to

another, it is accelerated by the electric force

in the direction of electric field.


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Working principle

As the particle enters the adjoining Dee, themagnetic force, being perpendicular to it,renders the charged particle to move along a

semicircular path within the Dee. By the time, it emerges again in the narrow

gap separating the two Dees, the electricalpolarity of Dees changes so that the particle isagain accelerated again with an increase inspeed


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Frequency of alternating voltage

supply

Numbers of changes in

directions are equal to

numbers of revolutions.

This means thatfrequency of electric

oscillator should be

equal to frequency of

revolutions.


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CyclotronProduced Radionuclides

These acceleratedparticles can posses afew keV to BeV ofkinetic energydepending on thedesign of cyclotron.

The charged particle aredeflected by a deflectorthrough window (w)outside the cyclotron toform an external beam.

In a cyclotron chargedparticles (S) such asprotons, deuterons,alpha particles ,He-particles are used


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Contd

When the targets of

stable elements are

irradiated by placing

them in the external

beam of the accelerated

particles .

The accelerated particles

interact with the targetnuclei and nuclear

reactions take place.

In nuclear reaction, the

incident particle may

leave the nucleus after

interaction with a

nucleon (i.e , protons and

neutrons) , leaving some

energy in it , or it may be

completely absorbed by

the nucleus depending on

the energy of the

incident particle.


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Contd

In either case , a nucleuswith excitation energy isformed and the excitationenergy is disposed of byemission of nucleons.

Depending on the energydeposited by the incidentparticle several nucleonare emitted randomly

from the irradiated targetnucleus leading to theformation of differentnuclides.

As the energy of theirradiated particle isincreased , more nucleonsare emitted and muchwider variety of nuclidesis produced.


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Medical cyclotrons


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Cyclotron produced radionuclides are

usually neutron deficient and therefore decay

by emission or electron capture.

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Cyclotron Produced Radionuclides