Last week I latched on to a Danielson Vacuum dry pump, consisting of an Alcatel 5010 molecular drag/turbo pump backed with a diaphragm pump. The whole assembly fits in a case the size of a small satchel, with the turbo pump flange (NW63) poking out the top. The thing has an on/off switch and 3 idiot lights, and is the epitome of a dummy's dry vacuum system. I decided to try the thing out, and blanked off the pump with a hodge-podge of flange adapters crowned by a 100 micron (full scale) capacitance manometer, the goal being to zero out the gauge. On the first try, I bottomed out at about 0.5 micron after an hour of pumping, disappointing for a turbo pump. In order to do some diagnostics, I took the system apart, and placed a gate valve between the pump and chamber/gauge, in order to be able to separate the pump from the gauge and check the leak rate with the pump isolated from the chamber. On the second try, the pump zeroed out the capacitance gauge within minutes (the scale actually read negative, meaning the gauge/readout combo had not been properly zeroed yet). I figure that my up-to air valve might have been a bit flaky. Tightening and re-tightening it appeared to improve the seal. For the next pass, I want to try using a cold cathode gauge along with the capacitance manometer to see whether the manometer is really and truly at a pressure that would be a legitimate zero for it (<10^-5 torr). This is one of the old Varian Penning-type gauges with an analog power supply and readout. Does anyone have any pointers on starting one of these things up?
Created on Thursday, April 12, 2001 9:35 PM EDT by Richard L. Hester Last Modified on Friday, April 13, 2001 2:15 AM EDT by Richard L. Hester