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Leica S430 Scanning Electron Microscope (view source)
Revision as of 16:22, 2 May 2014
, 16:22, 2 May 2014→Final Vacuum
* Chamber and gun gaskets should be greased with a suitable high vacuum grease, e.g. Apiezon M.
* Chamber and gun gaskets should be greased with a suitable high vacuum grease, e.g. Apiezon M.
* Rotation speed on the turbomolecular pump can be checked, which correlates to chamber pressure.
* Rotation speed on the turbomolecular pump can be checked, which correlates to chamber pressure.
Cleaning the Penning gauge now results in a significantly more stable vacuum reading, with no wild fluctuations that defy the laws of physics. It had significant accumulated plating on the anode and cathodes, and loose black shiny grit in the gauge, which could cause erroneous readings. However, the gauge doesn't indicate below 1.09e-4 torr. Thoughts:
* Contamination in the Penning gauge often results in less current flow, which registers as a lower vacuum reading than is actually present.
* It is possible that we really have been running at 1e-4 torr all this time without realizing it. This is certainly not ideal, but a beam can pass through the column and image at this level.
* While the chamber air admit solenoid may be a possible culprit, this seems unlikely. Air leaks usually are larger than this. Still, plugging the solenoid is an easy way to check.
* The turbomolecular pump is now a likely suspect. 1e-4 torr is only marginally better than a roughing pump can achieve. Turbopumps should drop the pressure into the e-6 range. It is possible the pump is not running at full speed. This should be investigated via the pump controller.
=== Image Processor board loses communications ===
=== Image Processor board loses communications ===