Reports until 01:23, Thursday 26 February 2015
H1 ISC
evan.hall@LIGO.ORG - posted 01:23, Thursday 26 February 2015 - last comment - 14:32, Thursday 26 February 2015(16931)
Closing common ETM alignment loops

Sheila, Alexa, Gabriele, Evan

Summary

In addition to the differential ETM loops, we now have closed the common ETM degrees of freedom using REFLA9I + REFLB9I. These loops are slow, with bandwidths of a few tens of millihertz.

Details

Previously (LHO#16883), we had closed loops around IM4 in order to reduce the amount of reflected light into REFL_A_LF. However, tonight we decided instead to close the common ETM DOF, so that the ETMs are nominally controlled in all four angular degrees of freedom. This (hopefully) leaves us free to pursue more loop-closing with the corner optics.

The common ETM loops are implemented in the CHARD filter modules. These modules are stuffed with the same filters as for their DHARD counterparts.

Comments related to this report
sheila.dwyer@LIGO.ORG - 01:40, Thursday 26 February 2015 (16933)
Link

This is a screen shot of QPDs durring a well aligned lock tonight.  

Images attached to this comment
sheila.dwyer@LIGO.ORG - 02:28, Thursday 26 February 2015 (16934)
Link

Since about 10:22 UTC Feb 26th, the IFO has been locked on DC readout with 4 ASC loops closed : DHARD PIT+YAW and CHARD PIT and YAW.  

We are leaving this locked with the intent bit undisturbed.  

lisa.barsotti@LIGO.ORG - 08:26, Thursday 26 February 2015 (16938)
Link 

For the records, ~3h lock
Images attached to this comment
evan.hall@LIGO.ORG - 14:32, Thursday 26 February 2015 (16954)
Link

For this lock stretch the ETM ASC loop settings were a bit different from what I said above:

  • All filter modules: FM3, FM4, FM7, FM8, FM9, FM10
  • Gains were 8 ct/ct diff pitch, 30 ct/ct diff yaw, -4 ct/ct comm pitch, -5 ct/ct comm yaw.