32″油拡散ボンプの性能 (II)

Abstract

In the previous paper, we reported many experimental data as to the various properties of the 32″ oil diffusion pump, which was to be used as a main pump of 63″ Cyclotron in the Institute of Nuclear Study, University of Tokyo. In this paper we tried to analyse some parts of those results and gave some discussions about pumping mechanism.According to Jakel, maximum pumping speed Sm is given bySm=v/4 1/1+1/4 v/u (1) per unit area, where, v is mean speed of thermal agitation of gases and u is velocity of oil jet stream. Using this formula, we obtained a constant value of about 120 m/sec as a value for u from our data which were obtained for air, hydrogen and helium gases respectively. It appears to show very good agreement of the theory with the experiment. However, in the formula (1) the terms including diffusion constant are neglected. In the original form Jackel givesS=v/4 1-ng (L) e-u/DL/1-1/4 v/u (1-e-u/DL) (2)=v/4 1-ng (L) /n nf (0) /nf (L) /1-1/4 v/u (1-e-u/DL) (3) We assured from our experiments that one could not neglect the concerning term in the expression (3), and taking this form, Sm resulted in negative value.Accordingly, we consider, that the replacement of (3) with (4) is not correct in general. But assuming that the diffusion constant D is negligibly small in the oil jet stream, we can obtain the formula (1) directly. and this assumption is more plausible.We calculated also the boiler pressure from electric power consumed in the heater and compared this value with the result of direct measurement. They show good agreement. And this gives one half of the value which is expected through the experience for the pumps of smaller type.