Reports until 18:25, Thursday 08 July 2010
X1 SEI
hugh.radkins@LIGO.ORG - posted 18:25, Thursday 08 July 2010 - last comment - 09:25, Friday 09 July 2010(66)
Assembly H3 GS-13 failure
As Fabrice and Corey eluded to in the LSU SEI logs 1762,63, & 65, the H3 GS-13 was not right.  There was some statements that it was OK one week and then not the next.  I believe this initial observation was only in the Table-was-locked state.  Corey and Vincent may have mined some further data in that regard.  Regardless, the observation that it looked OK when the table was locked but not when unlocked made me think of the internal pod clamping hardware.  Never liked it and sure glad the BSC is different.  Anyway, I thought maybe the sensor had shifted a little bit in the Pod and the Mass was just seated and would see the un-damped world when locked.  But, when the table was unlocked, the stuck mass would have no 'power' in the low frequencies.  I'm sure it doesn't matter why I thought anything but...

So, we tilted the table such that the sensor would tilt down even lower, by adding a couple pounds, and observed no difference in the GS-13.  Then we shifted the weight to the other side so that the GS-13 would tilt up--same weight shift.  This time the time series looked good!  I think Corey took a spectrum to confirm.  We then swapped out that unit for the one spare Celine sent (thank you!) and it worked--without the tilting weight added of course.  I believe Fabrice is suggesting we do a similar tilt test to confirm we are in the center of the likely small 'level' range of the sensor.

JoeH has asked I send this unit back where he'll autopsy; so I can't offer any more info than that.
Comments related to this report
hugh.radkins@LIGO.ORG - 09:25, Friday 09 July 2010 (67)
Assembly as in Assembly #1.  Doesn't really matter as it is the GS-13 with the issue.