Time dependent field and particle density measurements in the acceleration gap of a high power ion diode

Using a newly developed two-wavelength dispersion interferometer system of exceptionally high sensitivity we have been able to measure for the first time the electron density distribution inside a high power ion diode. The assumption of a flat electron density distribution across the gap-often made in theoretical models-is compatible with the present observations up to peak diode power. Afterwards a rapid increase of the electron density is seen. Combining these results with spectroscopic measurements in the anode plasma we conclude that the diamagnetic field penetration into the anode plasma can lead to its fast acceleration after peak power, affect the electron density increase in the gap, and the diode impedance collapse associated with it