A spectroscopic investigation of the inter-electrode region in an open caesium plasma diode

Spectroscopic measurements were made of the population of the excited states in a low-voltage, low-temperature, open caesium plasma diode. Such a device is under certain conditions seen to run in a special mode that is essentially different from the ordinary plasma mode. This mode, which has been called the Rydberg current mode, exhibits many interesting features, such as a very strong electron emission from the cold to the hot electrode. The objective of the present study was to investigate and compare the plasma conditions of the two modes. The spectral line intensities and the excitation temperatures of the upper states were found to differ considerably although the current, the voltage and the electrode temperatures were comparable.