Experimental Observation of Radiation from Cherenkov Wakes in a Magnetized Plasma

A proof-of-principle experiment demonstrates the generation of radiation from the Cherenkov wake excited by an ultrashort- and ultrahigh-power pulse laser in a perpendicularly magnetized plasma. The frequency of the radiation is in the millimeter range (up to 200 GHz). The intensity of the radiation is proportional to the magnetic field intensity as expected by theory. Polarization of the emitted radiation is also detected. The difference in the frequency of the emitted radiation between these experiments and previous theory can be explained by the electrons’ oscillation in the electric field of a narrow column of ions in the focal region.

Figure 1

Experimental setup and measurement system for the observation of the emitted radiation from the Cherenkov wake. Temporal waveform of radiation and polarization of the radiation were directly measured without the grating.

Figure 2

Typical radiation waveform of Cherenkov radiation detected by the crystal detector.

Figure 3

Frequency spectrum of Cherenkov radiation measured by the grating spectrometer.

Figure 4

Relationship between the electric field of the emitted microwave and the angle of the horn antenna.

Figure 5

Output power of the radiation as a function of the applied dc magnetic field. Dashed line indicates the theoretical value.