Beta decay is a type of radioactive decay that involves the emission of either an electron (β− decay) or a positron (β+ decay). To stop beta decay, you need a material that can effectively absorb or deflect these emitted particles.
Materials that can stop beta decay:
- Dense materials: Materials with high atomic numbers, like lead, steel, and concrete, are effective at absorbing beta particles. These materials have a large number of atoms packed closely together, which increases the probability of the beta particles interacting with the atoms and losing energy.
- Water: Water is also a good absorber of beta particles due to its high density and the presence of hydrogen atoms.
- Plastic: Some plastics, like polyethylene, can be used to stop beta particles. However, they are not as effective as denser materials.
How these materials work:
- Absorption: Beta particles lose energy as they interact with the atoms of the material. This interaction can involve ionization, where the beta particle knocks electrons out of the atoms, or excitation, where the beta particle causes the atoms to jump to a higher energy state.
- Deflection: Beta particles can also be deflected by the electric fields of the atoms in the material. This deflection can cause the beta particle to change direction and lose energy.
The thickness of the material required to stop beta decay depends on the energy of the beta particles. Higher energy beta particles require thicker materials to stop them.
Practical Insights:
- Lead is commonly used in shielding for radioactive sources that emit beta particles.
- Water is often used as a shielding material in nuclear reactors and other applications where beta decay is a concern.
- Plastic is used in some applications where the weight of heavier materials is a concern.
Example:
- A typical thickness of lead needed to stop beta particles from a common medical isotope like Iodine-131 is about 1 cm.
