With Hirata-san.

See pictures in album PR3 Remedying Work.

The temperarture decreased after Miyoki-san and Yokozawa-san took action. When we went into the clean room it was already 23.6 °C. Becuase of this change we had to move the the BF and SF fishing rods down to set the keystones at suitable positions.

Then we measured the position of the SF keystone when the BF is at the setpoint and the mirror at the nominal height indicated by the laser level per the heigh mark on the chamber: it was -585 µm. This is about 705 µm above the value of the setpoint at the time. The setpoint must be changed to the new value.

We then checked the position of the SF fishing rod carriage. With the new temperature value it was far away from the upper limit, implying that we don't need to adjust the ballast mass from the top of the BF. Another element that helped in having the fishing rod in a suitable position, was that we corrected a systematic error in estimating the height of the mirror. The markings in the RM had to be compared with the bottom of the laser line, not with its centre as we did yesterday. The laser line has a thickness of roughly 2 mm as seen by bare eyes (the camera is more sensitive).

As an additional precaution, we moved the stop screws to the very top of the motor shaft as shown in this picture. Then we measured the fishing rod range with the LVDT:

• Upper limit per LVDT:  2,116 µm at -550,000 steps.  See this picture.
• Lower limit per LVDT:  -3,352 µm at 1,360,000 steps. See this picture.

Please note that I changed the stepper motor limits in the corresponding medm screen to the values above.

It's important to notice that the buoyancy effect is 585 µm (entry 16445) and we have plenty of fishing rod range to compensate for it.

At the end of the day I measured IM transfer functions. They looked fine. Then we locked the SF and covered it with a plastic sheet.