1. Alpha and Beta Interactions
Rad Pro III
NUCP 2331

2. Interactions How radiation interacts with matter depends on
Energy
Mass
Charge
Charged particles interact differently than uncharged

3. Attenuation
Attenuation- process by which the intensity of a radiation beam is reduced as it passes through matter
Can be either
Particulate
Electromagnetic
Direct
indirect

4. Absorption of Radiation By Matter
Alpha and beta particles interact with matter differently, hence producing different patterns of absorption g b

5. Alpha Particles
Charged particle emitted from the nucleus as a component of decay
2 protons and 2 neutrons
Emitted with a discrete amount of energy
Emitted from large nucleii
Daughter product has Z-2 and A-4 of parent
Can predict what your daughter will be if one knows the decay method

6. Alpha characteristics
+2 charge
Atomic mass of 4
Travel in straight lines
Highly ionizing
Deposits a lot of energy short distance
Easily shielded
Internal hazard
Can interact directly or indirectly
Does it interact more or less as energy increases?

7. Alpha interactions Direct collisions with other particles
Electric fields of charged particles will interact as well
If particle has high velocity the time it will interact with other particle is very small
As it slows down the time it interacts with other particle increases , increasing the probability of ionization

8. Alpha interactions
The, now free, electrons that were ionized by the alpha particle can now go and ionize other atoms
These ionized particle that are generated by these interactions are called delta rays
Delta rays can cause secondary ionization in matter

9. SPECIFIC IONIZATION 
Specific ionization for a 4.8 MeV alpha particle in air is 40,000 ion pairs /cm

10. SHIELDING Alpha Radiation
Alpha radiation will be stopped by very thin absorbing materials, dead layer of skin, paper
Range in air in cm: (about .7 cm/MeV)
R = (E3/2)
The ratio of the density of air to the density of any material times the range of the alpha particle in air will give you the range of the alpha particle in that material

11. Alpha range
Compare formula with chart for
2 MeV
5MeV
7 MeV

12. CHANGE IN LET WITH INCREASING PATH LENGTH
For Heavy Charged Particles
Bragg Peak
Relative
LET
Distance of Penetration

13. Beta Particle
Charged particle emitted from the nucleus that has mass of an electron and can be either – or + 1
Beta – is emitted from nucleus that has too many neutrons
Neutrons decays into a proton and beta -
Beta+ is emitted form nucleus that has too many protons
Proton sucks up a close electron and turns into a neutron

14. Beta Characteristics -1 charge (or +1) 1/1860 mass of proton
Travel in very curvy path
Atomic number after Beta - decay increases by 1
Atomic number after Beta + decay decreases by 1
Less ionizing than alpha more than gamma
Still easily shielded (not as easily as alpha)

15. Beta Range = 0.526E - 0.094 E> 0.8 MeV Shielded by tin, Al, plastic
g/cm2
Divided by density of material will give range
About 3 m in air/Mev
Shielded by tin, Al, plastic
Internal hazard,
semi-infinite cloud
Compare to chart

16. SPECIFIC IONIZATION 
Specific ionization for a 4.8 MeV beta particle in air is 37 ion pairs/cm

17. SHIELDING Beta Radiation
The beta particle (electron) produces much less ionization in a given path than the alpha
The beta range curve will work for all materials if one corrects for density
The thickness and choice of shield material depends upon energy and Bremsstrahlung

18. SHIELDING Bremsstrahlung
Secondary photon radiation produced by the acceleration of charged particles passing through matter
Bremsstrahlung losses (radiative losses) increases with increasing atomic number (Z) and beta energy

19. Electromagnetic wave
Beta Particle
Bremsstrahlung

20. Bremsstrahlung Calculation
Fraction of Beta energy that is converted to gamma ray energy
F= K Z Emax
K= 3.5 E-4 (low Z shields) 5 E-4 (high Z shields)
Z= Atomic number of shield material
Emaz= Max energy of the beta particle

21. Bremsstrahlung Calculation
Have P-32
1.7 MeV beta
Compare the amount of energy released as Bremsstrahlung from shielding materials of Al Pb

22. Questions