| Kind of radiation. |
Substance |
Origin |
Property |
| Big classification | Small classification |
Particle beam
(Flow of particles) |
Alpha ray
(α-ray) |
A lump of two protons and two neutrons. they are discharged by an atomic nucleus. A helium atomic nucleus. Mass number 4. |
It is discharged by an atomic nucleus. Alpha decay. |
Even paper does not go through. Because we can interrupt it with skin from outside, there is not the danger.
However, when it entered the body, we have vast numerical ionization and excitation locally, and influence of the big biology appears.
|
Beta ray
(β-ray) |
Electron of high speed. |
When the neutron of atomic nucleuses changes to a proton, it occurs. Beta decay.
|
Transmission power and the ionization action are middle of alpha rays and gamma ray. It is irradiate from the outside and arrive only to the several mm bottom of the skin. |
| Neutron radiation. |
Particle beam of neutron. The mass is more slightly heavier than a proton. It electric charge is zero. |
It is discharged at the time of nuclear fission. |
Because the neutron is the particle which does not have an electric charge,
it interact with atomic nucleus of materials by the nuclear force. when we hit the material with a neutron radiation,
the neutron loses energy by repeat collision with atomic nucleus in the material.
Ratio of average energy to lose by one collision of neutron, it is 1/(A+1), when the atomic nucleus mass number is A.
Water and paraffin are effective for the interception of the neutron, because water and paraffin include a lot of hydrogen.
Because the hydrogen is A=1, neutron lose half energy by one collision. But when neutron hit the uranium of A=238, neutron lose energy of only 1/239.
|
Electromagnetic radiation
(Electromagnetic wave of high energy. Because it do not have an electric charge, it is not changed direction by electromagnetic force.)
|
Gamma ray
(γ-ray) |
It is the electromagnetic wave which wavelength has shorter than about 10pm. |
It is discharged by the atomic nucleus of the high energy state. |
Lead, iron, concrete are used for the shielding of the gamma ray.
Lead is the highest about ability for shielding. The more massive elements are effective for preventive ability of permeability.
Because the lead has high density of the atom per the unit volume, it is superior in the interception power of radioactive rays. |
| X-ray |
Wavelength 1mm - 10mm radiation. |
Electron in high-energy orbit was outside of the atom, and electromagnetic wave occurs when electron falls in inner low energy orbit. |