平行平板間の狭い空間の自由分子流排気特性(流体工学,流体機械)  [in Japanese] Pumping Characteristics of a Narrow Gap Between Parallel Plates in Free-Molecular Regime  [in Japanese]

It takes very long time to exhaust gases from a narrow gap between parallel plates by a vacuum pump, especially in free molecular regime. Pumping characteristic of a narrow gap in free molecular regime is investigated by use of the DSMC method. An expression for the time constant, which governs the exponential decay of gas pressure, is proposed. Two kinds of gaps are considered; the gap between square plates, the gap between circular plates. The size of those plates is 10, 20, 50, 100, 200 or 500 mm. The gap δ is set 0.1 mm. The time constant is a function of only one factor L/δ or D/δ (L: size of square plate, D: diameter of circular plate), and increases exponentially with increase of L/δ or D/δ.