On waveform distortion in observing density fluctuations by microwave scattering method

Theoretical and experimental examinations are given for the apparent waveform distortions occurring when ion wave packets propagating in plasma are measured by a microwave scattering method. Since the measurement of scattered waves is done through a scattering region extending to a finite distance, there are changes in the apparent width, amplitude and total shape of the wave packet even when the spread of the wave packet in propagation is negligible. The theoretical analysis adopts a model in which an ion-acoustic wave of sinusoidal pulse propagates without spreading in a one-dimensional Vlasov plasma. In the experiment an ion-acoustic wave packet propagating in the axial direction is excited by means of a grid in a mercury glow column of diameter 5 cm and length 45 cm.