Test results for a sputter-ion pump with a new cell structure

Abstract

A test model of a sputter-ion pump using a new cell structure was fabricated, where the magnets reside within the Penning cell assembly. The magnetic field intensity in the cell, pressure (P) dependence of discharge current, and pumping speed are measured. An axial magnetic field larger than 700 G is created inside the cells using commercial magnets with a remanent magnetism of 12 kG. The discharge current (I) is proportional to P1.0–P1.6 in the measured pressure range from 7.5×10 −9 to 1×10−6 Torr. Pumping speed for nitrogen is proportional to P0.6 on the average in the pressure range from 2×10−8 to 1×10−6 Torr and can be written as 0.05 I/P for P≥1×10−7 Torr. The test model is almost less than a half, in both volume and weight, compared to conventional ion pumps with almost the same nominal pumping speeds. It was confirmed experimentally that the new cell structure has the possibility of becoming a compact and light ion pump. The problem remains to optimize the cell sizes to moderate the pressure dependence of the discharge current, i.e., the pumping speed.