Oil Diffusion Vacuum Pumps for Demanding High Vacuum Applications. Agilent VHS and HS diffusion pumps have pumping speeds from 65 L/s to 28,000 L/s, in an operating range of 1 x 10-3 Torr to 5 x 10-9 Torr. The patented bulge body diffusion pump design maximizes pump throughput while delivering pressure stability and reducing back-streaming to a minimum. Our broad range of pump sizes with multiple flange options, as well as input voltages (from 90 V to 575 V) so you can find the right pump fit for your application, with accessories including robust heaters, baffles, cold caps, and thermal protection switches.