Diamond Monochromator
pump down & venting procedure
This document is a step-by-step description of the procedure to vent and pump down the Diamond Monochromator vacuum chamber:
Numbers in parenthesis refer to parts labeled in the picture.
See http://8id.xor.aps.anl.gov/elog/8-ID/7 for directions on how to use the monochromator ion pump controller.
Venting
- Close gate valves immediately upstream and downstream of the monochromator
(if you don't know how to do this, it is most likely because you should
NOT attempt to do it!)
- Connect a venting supply of Nitrogen.
Best would be to get the Vacuum/Mechanical engineering group to perform this procedure as they have considerable experience in doing this properly. They will typically vent chambers with boil off from liquid N2.
As a distant second alternative, hook up a nitrogen cylinder to the venting port (1) and set the regulator
to 5 psi. Also, please include a relief valve in the venting assembly.
(In Jan. 2006 there was a a serious accident at 3-ID wherein a Be window was exploded because a relief valve was not used during the bleed up)
- Turn off the ion gauge
- Turn off the ion pumps
- Close the small manual valve for the diaphragm pump (3)
- Put the handle back on the large manual valve (2) and open it slowly
to vent the vacuum chamber (make sure to avoid any pressure build-up inside the chamber)
Pumping
- Hook up a dry pump to the venting port (1) and start pumping
Start the diaphragm pump.
- Open the large manual venting valve (2)
- Open the venting valve for the small ion pump (4) using the torque wrench stored in the monochromator toolbox
- Pump down until the pressure reaches into the 10-6 Torr
- Start the large ion pump (#1)
- Leave the turbo pumping on the chamber until the pressure displayed by the ion pump starts to decrease
- Close the large manual venting valve (2)
- At this point, the turbo is still pumping on the small ion pump
- Start the small ion pump (#2)
- When the pressure displayed by the ion pump starts to decrease, close the
venting valve for the small ion pump using the torque wrench adjusted to 30 lbs/in
(The valve is rated to 2.5 lbs/ft and the wrench (which is calibrated in lbs/in) should be set to 30 lbs/in)
- Make sure Protection Mode is engaged for both pumps
- Turn on the ion gauge
- Stop and then disconnect the turbo pump
- Put a blank on the venting/pumping port (1)
- Remove the handle from the large manual venting valve (2) but leave it in this hutch!....
- Typical pressure is: 5 x 10-7 Torr (it used to considerably better (10-9) before the monochromator
was vacuum-integrated with the 8-ID-E shuuter; now there appears to be insufficient
pumping speed for the whole assembly)
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