Experimental observation of further frequency upshift from de to ac radiation converter with perpendicular dc magnetic field

A frequency upshift of a short microwave pulse is generated by the interact ion between a relativistic underdense ionization front and a periodic elect rostatic field with a perpendicular de magnetic field. When the de magnetic field is applied, further frequency upshift of 3 GHz is observed with resp ect to an unmagnetized case which has typically a GHz range. The radiation frequency depends on both the plasma density and the strength of the de mag netic field, i.e., the plasma frequency and the cyclotron frequency. The fr equency of the emitted radiation is in reasonable agreement with the theore tical values.