Consideration of fluctuation in secondary beam intensity of heavy ion beam probe measurements

Heavy ion beam probes have the capability to detect the local fluctuation of density in the interior of plasmas through the fluctuation of the intensity of the detected beam. However, this intensity fluctuation may suffer from a certain degree of distortion from fluctuations of electron density and temperature along the beam trajectory; as a result, the fluctuation signal may be quite different from the local density fluctuation. This article presents the conditions where the intensity fluctuation can be regarded as being local fluctuation of electron density, where it cannot, and discusses the contamination of the fluctuations by fluctuations along the trajectory, particularly in the case of magnetohydrodynamics fluctuations.