H1−Production by Hydrogen Positive Ion Bombardment of a Tungsten Surface

Abstract

A study of the energy distribution of the negative ions is described. One-kilovolt ions are used. The double mass spectrograph used allows analysis of both the incoming positive- and outgoing negative-ion beams. Two peaks are studied: a low-energy peak of negative hydrogen ions created by the bombardment of a dirty surface by an assortment of positive ions, and a high-energy peak of negative hydrogen ions created only under bombardment of a surface by ${\mathrm{H}}_2^{+}$ and ${\mathrm{H}}_1^{+}$. The height of the low-energy peak is found to be proportional to the amount of hydrogen on the surface. The curve has a peak three volts wide at its half-maximum, and a tail 25 volts long on the high self-energy side. The high-energy peak ranges from zero self-energy to a value resulting from a head-on collision between a proton in the incoming ion beam and one of the atoms in the surface. This curve is flat over its whole-energy range, dropping to zero at the low self-energy end independent of incident ion energy. On a clean surface the shape of this curve is independent of target temperature.