(in Russian, vakuumfaktor). (1) The suction coefficient. The ratio of the actual rate of evacuation of a vacuum pump to its theoretical maximum value. (The suction coefficient is often called the Ho coefficient after the Japanese scientist who introduced the concept.)
(2) A rarely used term indicating the ratio of the ion current of a multielectrode electron tube to its electron current, which serves to measure the residual gas pressure in the tube.