PUMPING CHARACTERISTICS OF SPUTTER ION PUMPS WITH HIGH-MAGNETIC-FLUX DENSITIES IN AN ULTRAHIGH-VACUUM RANGE

Pumping characteristics of sputter ion pumps with anode cells of 17, 24, and 29 mm diameters, respectively, were measured for N2 at three magnetic fields (i.e., approximately 0.15, approximately 0.2, and approximately 0.3 T) in an ultrahigh-vacuum range between 1 X 10(-8) and 1 X 10(-6) Pa. The pumping speed of the pump with 17-mm-diam cells increased significantly with increasing magnetic fields. However, the pump with 17-mm-diam cells and a magnetic field of 0.3 T evidenced negligible pumping speed at pressures < 1. 5 X 10(-8) Pa. The pump with 24-mm-diam cells and a magnetic field of 0.3 T showed a fairly high pumping speed in the range between 1 X 10(-8) and 1 X 10(-6) Pa. The pump with 29-mm-diam cells and 0.3 T showed the highest pumping speed among all the test pumps at pressures < 2 X 10(-8) Pa, though its speed in the 10(-7) Pa range was comparatively low.