The temporal evolution of electrons in EUV-induced plasmas

We studied the temporal evolution of the electron density in a low pressure pulsed plasma induced by high energy photons (92 eV) by means of microwave cavity resonance spectroscopy (MCRS). Although MCRS generates space averaged information about the electron density, we demonstrate here the possibility to obtain spatial information by combining different resonant modes. The results show that the plasma expands to the wall of the cavity on a time scale of tens of microseconds. The speed of this expansion depends on the gas pressure; the higher the gas pressure, the slower the expansion. This effect is explained by ambipolar diffusion, which is inversely proportional to the gas pressure