Measurements of collected ion energy by time-of-flight method in static electric field ion-collection

Gadolinium ions were produced between parallel electrodes by resonance photoionization and were collected on a negative electrode by static electric field. Kinetic energy of ions collected on the electrode was measured by the time-of-flight method. When electric potential Vo(V) was applied between the parallel electrodes, the followings were confirmed : 1. At high ion density, the kinetic energy of ions collected on electrode was equal to Vo(eV) because the ions constituted a plasma and the potential of the plasma was equal to that of higher potential electrode. 2. At low ion density, the kinetic energy of the ions collected on the electrode was equal to 1/2Vo(eV) because the potential between the electrodes does not change due to ion production. The kinetic energy of ions increased continuously from 1/2Vo(eV) to Vo(V) with increasing the ion density. The transition ion density can be estimated by a simple one-dimensional model. (author)