Sorry, if this should have been in an homework section. Anyway, I was wondering what effects backstreaming has on the pumping speed of a diffusion-pumped system. I can see how you would not want backstreaming to maintain clean system, but would it also affect the net speed? Also, does anyone know how to calculate the volumetric flow rate at a point along the vacuum system. I know how to calculate it in theory, but how would one go about solving something of this sort in practice (with an actual vacuum system). Thanks for the help, me.