Came in to find the SEM unable to pump down and a low LN2 indicator despite the fact that the EDS detector dewar was filled with LN2 yesterday.
On a hunch I checked the EDS detector window. The picture shows the end of the EDS detector with the electron trap removed. Clearly the window is damaged. It's curious that it appears to be blown into the SEM chamber. This is consistent with a catastrophic and sudden loss of vacuum in the EDS detector-- which would also explain the dry LN2 dewar less than 12 hours after its last fill.