Investigation of discharge characteristics and optimized insulator of a miniature penning ion source

In the paper, the influence of covered gas and oxidization of molybdenum electrode surface on the field emission current at the initiation of high voltage vacuum breakdown is presented. Since enhanced field emission (EFE) is often observed there, we have investigated the influence of covered gas and oxides on the EFE of Mo by means of a field emission vacuum system (FEVS) and the field emission current was measured. The Mo samples were prepared and the experimental platforms were built up. The measured results show that the oxidation of Mo electrode surface will lead to the increase of field emission current and the covered gas from Mo electrode surface will induce the decrease of field emission current. At the same time, the experiments also have been completed under the different pressure of helium gas. Comparison with the emission current of 10
^-6
Pa vacuum pressure, the results indicate the current will raise when gas pressure is 10
^-3
Pa, while the current will keep invariability at 10
^-2
Pa and 10
^-4
Pa pressure. The experimental results are significant to evaluate the influence of oxidization, covered gas and rarified gas atmosphere on the vacuum breakdown voltage of electrode gaps which have been stored for a long time.