Log entry time 13:30:00 on March 27, 2014

Entry number 387800

This is the 1st of a series of several halog entries I want to make today explaining (belatedly) what's been happening with the target. There have been a plethora of issues, which I'll try to outline one at a time in separate halog entries.

The most recent was this morning's event with the fan. At 6 AM sharp (the attached plot is not on daylight savings time) the fan current jumped way up to around 4.6 A and the fan speed dropped simultaneously from 60 Hz to about 25 Hz. The counting room paged me (the correct response, thank you) and because the current was so close to the limit on the controller we just eased back the low alarm limit as already noted in the logbook, and limped along at 25 Hz for the time being. I emailed Chris and Dave about the problem.

They puzzled over this too and eventually this morning they (Chris, Dave, Josh) tried reversing the direction of the fan. This cleared up the problem! The fan is back to 60 Hz, drawing 1.5 A.

There are several possible explanations for this but the leading one is that there is some piece of junk in the loop that may have jammed the fan. This might even be the pid thermometer we lost yesterday, floating around, or part of it, maybe even part of its leads which are like angel hair. It might have broken loose and waited until 6 AM to jam in the fan. It could be fan bearing/retainer particulate- we know there are issues with the fan bearings which prevented us from cooling down for awhile.

Anyway this problem could return at any time, and we're all a little nervous about how soon that might be. For now it's working again though.

Figure 1