I'm currently working in a REU project. I need to get a pressure profile on the ion accelerator that I'm working with. Basically, I need to find out: conductance for all the tubes and pipes pump speed for the diffusion pumps conductance for the pumps outgassing rates for various stuffs. I need help on the following: 1. I know how to calculate conductance for a pipe, but what about a chamber like thing? Basically, the pipes are horizontal cylinders, and the chambers are vertically placed cylinders (like a standing up soda cans), would the conductance be any different? 2. what about branching? there is a magnet chamber that has 6 branches sticking out, two of them goes to other pipes, the others are dead-ends, how can the equivalent conductance be calculated? or how can I take the branching out into account? 3. I'm using a program coded by some physicist called vaktrak.... I've tried my best to understand it (there aren't much documentations...) if you guys are familiar with it, perhaps you can tell me a little more about the program. I apologize if it sounds like I'm too lazy to go search these things myself... The fact is, I've went to the library and searched online many times, and couldn't find much information. Two days ago, I didn't even know what conductance and outgassing is... I'm basically trying to learn everything from scratch. I've asked my advisor and the grad student who is also working on the project... but they are more like experimentalists and they told me to get some rough approximations... However, I would like to get some more accurate calculations. I would appreciate it if you guys can help me out.