Ametek Dycor Dymaxion Mass Spectrometer, Руководство пользователя

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5-2 | Dycor Dymaxion Mass Spectrometer
Sampling Under Vacuum
If the sample environment total pressure is less than 10
-4
Torr, the mass spectrom-
eter can be directly fitted into the sampling environment without an inlet with a
differential pumping system.
Sampling at Greater than 10
-4
Torr - High Conductance Inlet
If the sampling environment is greater than 10
-4
Torr, an inlet is required. For
these applications, a high conductance inlet (Figures 5-1 and 5-2) can be fitted
to the sample chamber. This inlet consists of a length of tubing installed between
the sample chamber port and the mass spectrometer. Connection of the high
conductance inlet makes it possible for the Dymaxion to sample from the sample
chamber without being directly fitted to the sample chamber.
When the pressure in the sampling chamber is greater than 10
-4
Torr (but be-
low atmospheric pressure), the high conductance valve is closed tightly and the
aperture inlet is opened. The aperture inlet consists of a small aperture within a
valve that connects the sampling system to the vacuum environment of the mass
spectrometer. The aperture inlet should be opened slowly to evacuate the bypass
arm. Once this volume has been evacuated, the pressure in the test chamber, the
diameter of the aperture, and the pumping speed determine the pressure of the
Dymaxion. Aperture diameters and their corresponding sample chamber pres-
sures are provided in Figure 5-3.
Figure 5-1 .
High conductance
inlet with manual
valves.