As seen in the attached 10-day pressure trend, we had some sort of pressure transient around 2100 hrs. local time on Tuesday. This doesn't appear to correspond with any of the normal suspects, i.e., a loss of pump speed due to an ion pump HV switching event or from an ambient temperature increase (corresponding VEA temperture compared separately). Note that the amount of gas needed to cause this trivial increase is of no concern. Rather, it is the "unexplained" nature of this that is of concern. These circumstances are similar to past events in which we theorized that ice may have fallen off of the cryopump's inner vessel, evaporated and then re-condensed.
Attached is more recent data. This is troubling to me. Upon further consideration the "ice" theory isn't applicable because of the time duration of the pressure anomaly. Chandra R. has had a long standing request to connect the RGA at the MY into the network but, for now, we can't "see" the partial pressures.
After looking at trend data in seconds, we see the pressure rose at corner station first.
Here is a seven day pressure and temperature trend in mid-Y VEA. No surprise that as temperature decreases, so does pressure. However, doesn't explain the initial abnormal rise in pressure we saw on Tuesday evening. Let's keep an eye on this, and I will work with CDS team to connect RGA for remote access.
