Superconducting RF (radio frequency) cavities are used in particle accelerators to accelerate charged particles to high energies. These cavities are typically made of niobium, which is a superconductive material at low temperatures. However, there are two different types of superconducting cavities: bulk niobium cavities and thin-film cavities.
Thin-film superconducting cavities are made by depositing a thin layer of niobium onto a copper substrate. Bulk niobium cavities, on the other hand, are made by shaping a large piece of niobium into the desired cavity shape.
There are several benefits to using thin-film superconducting cavities over bulk niobium cavities:
- Higher achievable acceleration gradients: Thin-film cavities have been shown to achieve higher acceleration gradients than bulk niobium cavities. This means that particles can be accelerated to higher energies in a shorter distance, which can reduce the size and cost of accelerators.
- Lower surface resistance: Thin-film cavities have a lower surface resistance than bulk niobium cavities, which reduces the amount of power that is lost as the particles are accelerated. This can also reduce the size and cost of accelerators.
- Better performance at higher frequencies: Thin-film cavities can perform better at higher frequencies than bulk niobium cavities. This is important for future accelerators that may operate at higher frequencies than current accelerators.
- Easier manufacturing: Thin-film cavities are easier to manufacture than bulk niobium cavities. The process of depositing the niobium layer onto the substrate is simpler and more reliable than shaping a large piece of niobium.