Superconducting cavities accelerate particles using radiofrequency (RF) power. But where does the power to accelerate a beam by millions of electronvolts come from? The ILC’s power source can provide only about 100 watts, but to push that power up to the required level you need a device called a klystron.
The klystron is a power amplifier. It can expand a few tens of watts into millions, or megawatts. Each ILC klystron will supply amplified power to 39 superconducting cavities for the baseline design.