Energetic particles, such as protons, can be detected with a silicon detector. when a particle strikes a thin piece of silicon, it creates a large number of free electrons by ionizing silicon atoms. the electrons flow to an electrode on the surface of the detector, and this current is then amplified and detected. in one experiment, each incident proton creates, on average, 37,000 electrons; the electron current is amplified by a factor of 100; and the experimenters record an amplified current of 3.5 μa.