Reduce water vapor in vacuum systems

It's a well-known and generally accepted fact that the residual gases durin g a pumpdown are dominated by water vapor when pumping down to a process di ctated by ultimate pressure in the high-vacuum region. it often seems as th ough this condition is merely accepted by vacuum practitioners as an irrita ting fact of nature that has to be tolerated. The irritation is traceable t o the amount of time it takes to achieve a low enough partial pressure of w ater vapor to meet process parameter requirements. The time delay is caused by the fact that the water vapor is clinging to the inner surfaces of the vacuum system with weak bonds.