Pumping speed and position of the cryopanels

Considering the position of the cryopanels In the cryopump, the conductance from the vacuum flange to this surface and also the subtractive pumping sequence (what has already condensed at the baffle can not arrive at the second stage and consume capacity there), the situation arises as shown In Fig. 2.69. 

The gas molecules entering the pump produce the area related theoretical pumping speed according the equation 2.29a with T = 293 K. The different pumping speeds have been combined for three representative gases H2, N2 and H2O taken from each of the aforementioned groups. Since water vapor is pumped on the entire entry area of the cryopump, the pumping speed 

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