Density and velocity of H- in the extraction region of a negative ion source estimated from the change in H- beam current due to a pulse laser injection

A method to estimate H- density and velocity in the extraction region of a negative ion source plasma without a Langmuir probe is developed. It utilizes the laser photodetachment with a Faraday cup (PD-FC). The H- parameters estimated by PD-FC are compared to the results measured by laser-photodetachment with a Langmuir probe (PD-LP). The result shows that H- velocity estimated by PD-FC is in good agreement with the PD-LP result. Meanwhile, H- density estimated by PD-FC is twice larger than the PD-LP result. Though a more detailed research, including more effects that are ignored in this study, is needed for H- density measurement, PD-FC will be a very useful tool for H- measurements especially near an extraction hole in negative ion sources. (c) 2006 American Institute of Physics.