aLIGO LHO Logbook

H2 SUS

betsy.weaver@LIGO.ORG - posted 14:06, Friday 03 February 2012 - last comment - 12:36, Monday 06 February 2012(2146)

ETMy-to-ISI Alignment

This afternoon, after a quick consult between IAS/SUS (Dennis, Calum, Hugh, Gerardo, Travis, Doug, Jason, me), it was decided that we would proceed with translating the QUAD to bring the longitudinal measurement back into tolerance.  So, we will mobilize to push the suspension ~4mm towards the corner station.  Doug has confirmed that on Monday (and probably Tuesday) IAS/SUS together will:

- fix pitch R0
- translate QUAD longitudinally, monitoring yaw, x, y

 --Need to insert possible "fix" to R0 roll/side shift if indeed we need to.  Norna is checking on tolerances of these DOFs.

- make IAS gap measurement
- Adjust R0 to fix gap and yaw if needed.

OSEM general health has been checked, and all open light voltages have been measured and set.

Comments related to this report

betsy.weaver@LIGO.ORG - 12:32, Monday 06 February 2012 (2156)

Link

Shortly after my prompt alog, Dennis emailed the following:
>
Betsy et. al.,
I have discussed the 4mm longitudinal position error with Peter Fritschel. Peter and I both recall that the tolerance for the arm cavity length is more like centimeters. (The +/- 3 mm position may apply to the recycling cavity lengths.) Given this fact plus a possible change in longitudinal position related to the move into the WBSC6 chamber, we do not think it is worthwhile to correct this 4 mm positional error on the test stand.
Once the cartridge is installed into WBSC6, a new IAS measurement of the longitudinal positional error will be made. It is likely that this error will be within the static correction range for HEPI, or at the very least well within the true allowable arm cavity length tolerance.

Dennis Coyne
>
The longitudinal position tolerance can be relaxed for all arms, not just the H2 Y-arm for the ALS test.

Dennis Coyne

betsy.weaver@LIGO.ORG - 12:34, Monday 06 February 2012 (2157)

Link

Further, we solicited for roll and side-shift tolerances which need to be fixted, and received the following email from Ken Strain:

Hi,

a roll error mixes the coordinates, a transverse error of a few mm 
has little effect on the force (as the pattern still faces the TM), 
but the resulting torque changes a little.
Due to the large ratio between the radius of the mirror an the ESD 
gap, and the relatively benign nature of the changes in torque, the 
effects are very small compared to the permitted variation in 
force/torque among the 4 quadrants due to relative pitch and yaw 
wedge angles (between TM and RM).
With errors described, of order 2mm, I can't see any consequences 
worse than (or even comparable to) those that have already been 
permitted.
Ken

betsy.weaver@LIGO.ORG - 12:36, Monday 06 February 2012 (2158)

Link

While the emails above appear to clear the plate of many adjustments, we are currently working on the suspension to fix the yaw of both chains and height of the reaction chain.