Negative deuterium ion thermal energy measurements in a volume ion source

A diagnostic technique has been developed to determine the negative hydrogen ion (H-/D-) thermal energy in a variety of conditions in a volume production ion source. The method is based on Nd:YAG laser photodetachment of the negative ions. The photodetachment produces local changes in the ion and electron densities, whose space and time evolution are traced by the use of a probe and a time-delayed second Nd:YAG laser pulse. The results of measurements using this technique for deuterium ions are describe. Information was collected from the center of the source to near the plasma electrode. The effects of the presence of electric and magnetic fields near the probe during measurements are addressed. The paper demonstrates that the extracted ion current is equal to the thermal flux through the extraction aperture