Density measurements of negative hydrogen ions using mass spectrometer

Abstract

Measurement of negative ion density in a source plasma is necessary for optimizing the extraction of negative ion current. Bacal and co-workers proposed a method to measure the negative ion density by detaching the electron current due to the photodetachment of negative ions using a pulse laser. This paper describes a method to determine the negative ion density in a plasma by a coupled mass analysis and Langmuir probe diagnosis of the plasma. The H^- ion density was estimated from the relation equating the ratio of the negative ion and electron currents to the ratio of the ion and electron densities; I_-/I_e = n_-/n_e.The proposed estimates consider the collection factor of n_-/n_e.