Princeton 4300 User Manual
Appendix C
Repumping the Vacuum
99
99
Pumping Down
1. Do not bake during pumping. Maintain ambient temperature (≈25°C).
2. Continue pumping for 48 hr. The final vacuum must be below 10 mTorr. At the
2. Continue pumping for 48 hr. The final vacuum must be below 10 mTorr. At the
factory, a much higher initial vacuum level is generated using a turbo pump.
Although this is desirable, it is not necessary and may be cost prohibitive for the
user to purchase similar equipment; 10 mTorr is sufficient to assure normal
operation of the unit.
Although this is desirable, it is not necessary and may be cost prohibitive for the
user to purchase similar equipment; 10 mTorr is sufficient to assure normal
operation of the unit.
3. When the required vacuum level has been achieved, tighten down the Indium-
tipped Vacuum Seal with the 5/16
torque wrench to crush the Indium tip and
reseal the vacuum. A sealing torque of 28 in. lb. or 3.2 Nm is required.
4. Shut down the pump and remove the vacuum hose from the Vacuum Pumping
fitting. Although it shouldn’t be required, a 7/16
nut driver may prove helpful in
removing the fitting.
5. Replace the vacuum port cap.
Installing a New Vacuum Seal
Preventing atmospheric contamination of the vacuum chamber is imperative to the
operation and longevity of the camera.
Placing the camera inside a plastic bag filled with dry nitrogen gas prior to removing
the Vacuum Seal will backfill the camera when the Vacuum Seal is removed and
help prevent contamination. Consult the factory.
Alternatively, a dry nitrogen pressure may be applied to the vacuum pumping fitting
before removing the vacuum valve. Pressure should be 3 psig or less. Maintain a flow
of nitrogen until the valve is replaced in Step 3. Consult the factory.
1. Using the 5/16" hex torque wrench, rotate the Indium-tipped Vacuum Seal
1. Using the 5/16" hex torque wrench, rotate the Indium-tipped Vacuum Seal
counterclockwise to where the threads completely disengage and then remove it
from the vacuum block.
2. Lightly grease the Viton O-ring on the new Indium-tipped Vacuum Seal. Use a
high-quality grade of vacuum grease such as Apiezon M.
3. Carefully insert the new Indium-tipped Vacuum Seal into the corresponding
opening on the camera vacuum block to where the threads can be engaged – a
turn or two is sufficient. Do not rotate the plunger to where it bottoms out. The
Indium tip should not be disturbed until the new vacuum has been established.
Indium tip should not be disturbed until the new vacuum has been established.
4. Turn on the pump and follow the "Pumping Down" instructions.
Caution