Interaction of Nuclear radiation with Matter

Radioactive elements/ materials emit alpha, beta and gamma radiations. Neutrons are released in fission as well as in other nuclear reactions. " The interaction of these nuclear radiations with matter depends upon the charge mass and energy of the radiated particles. " The interaction of different radiations with matter is different.

A) Interaction of Alpha Particles with matter:

1--Alpha particle is a helium nucleus which has 4amu mass 2e positive charge.

2-- Because of greater mass and high charge, the interaction of Alpha=Particles with matter is very strong as compared to beta-Particles of the same speed.

3--When Alpha-Particles are passing through a medium, they knock out electrons from its atoms and the medium is ionized.

4-- The ionization power of Alpha -particles is very high.

5--On average, 35eV energy is used to produce one ion pair.

6--The range of 7.7 MeV Alpha-Particles in the air is about 7cm and about 0.04cm in Aluminum foil.

B) Interaction of Beta-particles with matter:

1--A beta-Particle is relatively light and negatively charged, bearing a charge (-e).

2--When Beta-Particle are passing through a medium, the can knock out electrons from its atoms due to Coulomb's repulsion. So the medium is ionized.

3--Their ionization power is smaller than Alpha-particles.

4--They lose most of their energy is a single collision with atoms.

5--They are deflected by electric and magnetic field.

6--Their penetrating power is greater than Alpha-Particles. Its range in the air is about 100 times times greater than Alpha-particles of the same energy.

7--They produce fluorescence in some substances such as Beta Platinocyanido and calcium tungstate.

C) Interaction of Gamma rays with matter:

1--Gamma rays are electromagnetic radiations based on photons which have no charge and no rest mass.

2--Gamma rays interact with matter by three main process and lose energy.

(a) Photoelectric Effect:

In this type of process the Gamma rays is completely absorbed and photo electrons is emitted. It takes place when Gamma-Ray photon has energy less than 0.1 MeV.

(b) Compton Effect:

In Compton effect, the Gamma-rays photon collides with an electron in the atom, transfer some of its energy to the electron and is deflected. This process takes place when Gamma-Rays has energy in the range of 0.1 MeV to 1.0 MeV.

(c) Pair Production:

In pair production, the Gamma-Rays photon is converted into a pair of electron and positron in the vicinity of a nucleus. This process occur when the energy of Gamma-Rays (Photon) exceeds 1.02 MeV.

3--Gamma radiations has no specific range in a medium. Its range is estimated from the decreases in the intensity of the Gamma-rays beam when passes through a matter.

4--Those materials which have large number of electrons per unit volume absorb more Gamma-Radiations. That is why, lead Pb is generally used to shield Gamma-rays.

D) Interaction of Neutrons with matter:

1--being uncharged, neutrons are highly penetrating particles.

2--They are slowed down by direct collision with protons or some other particles whose mass is comparable to neutrons.

3--Neutron can enter into the nucleus and can induce nuclear disintegration, i.e

(a) Capture of neutron by a nucleus results the formation of radio-isotopes.

(b) In case of heavy nucleus, the capture of neutron causes fission reaction.

4--Neutron can cause some ionization in substances which have large fraction of hydrogen , i.e Body tissues.