11.10.PROJECTS 349 6.This problem sucks! Have you ever wondered how one can make a vacuum? One can make a good vacuum,comparable to the molecular/atomic density in deep space by employing a multi-stage process.In the first stage would we would take,say, a cylinder with a piston in it (much like a combustion chamber in a car)and a pipe attached to a closed canister that you want to evacuate.With a valve in the canister (to the cylinder)open and a valve in the cylinder (to the outside)closed,withdraw the piston.The pressure in the canister and the pipe is reduced.Now,close the valve to the canister and open the valve to the outside,allow the piston to descend and repeat.One can only go so far with this method.Soon there are too few molecules in the canister and enough molecules in the mechanism of the outside valve that one gets very little or no gain on each stage of the pump cycle. The second stage (the one that this problem is concerned about)is to introduce a cold trap.A separate chamber (attached to the canister)has a cold surface in it to which molecules adhere.This further reduces the number of molecules.A third stage might involve causing the molecules to become ionized and then they may be "swept out"with an electric field.Making a vacuum is an interesting combination of a lot of different technologies-mechanical,electrical,chemical...Let's focus on the second stage.With MATLAB,first construct two chambers of identical dimensions,connected 2 20 0.5 10 15 20 25 30 Figure 11.9:Two chambers and a pipe (evacuated,value =0)surrounded by walls (solid, value =-1). together with a pipe.The ones I made were made up of 2D arrays and look like those depicted in first figure.In my example I used chambers that were 30 units high and 10 units wide.The pipe was 16 units high and 10 units wide.(A "unit"is the width of11.10. PROJECTS 349 6. This problem sucks! Have you ever wondered how one can make a vacuum? One can make a good vacuum, comparable to the molecular/atomic density in deep space by employing a multi-stage process. In the first stage wouldwe wouldtake, say, a cylinder with a piston in it (much like a combustion chamber in a car) and a pipe attachedto a closedcanister that you want to evacuate. With a valve in the canister (to the cylinder) open and a valve in the cylinder (to the outside) closed, withdraw the piston. The pressure in the canister and the pipe is reduced. Now, close the valve to the canister and open the valve to the outside, allow the piston to descend and repeat. One can only go so far with this method. Soon there are too few molecules in the canister andenough molecules in the mechanism of the outside valve that one gets very little or no gain on each stage of the pump cycle. The secondstage (the one that this problem is concernedabout) is to introduce a cold trap. A separate chamber (attachedto the canister) has a coldsurface in it to which molecules adhere. This further reduces the number of molecules. A third stage might involve causing the molecules to become ionizedandthen they may be “swept out” with an electric field. Making a vacuum is an interesting combination of a lot of different technologies—mechanical, electrical, chemical... Let’s focus on the second stage. With MATLAB, first construct two chambers of identical dimensions, connected −1 −0.5 0 0.5 1 1.5 2 2.5 3 3.5 4 5 10 15 20 25 30 5 10 15 20 25 30 Figure 11.9: Two chambers and a pipe (evacuated, value = 0) surrounded by walls (solid, value = -1). together with a pipe. The ones I made were made up of 2D arrays and look like those depictedin first figure. In my example I usedchambers that were 30 units high and10 units wide. The pipe was 16 units high and 10 units wide. (A “unit” is the width of