Reports until 18:20, Wednesday 17 September 2014
H1 SEI (SEI)
sebastien.biscans@LIGO.ORG - posted 18:20, Wednesday 17 September 2014 - last comment - 21:37, Wednesday 17 September 2014(13989)
LHO configuration vs LLO configuration

On the BSC-ISIs, things have been running differently at LHO and LLO for quite a while.

I took a look at a random chamber (ITMY) for both sites to see how we can make the best out of both configurations.

LLO ITMY Status:

Stage 1

- X, Y: 45mHz blend, FeedForward from HEPI, Sensor Correction

- Z: 90mHz blend, FeedForward from HEPI, Sensor Correction

- RX, RY: 250 mHz blend

- RZ: 200mHz blend

Stage 2

- X, Y: 250mHz Blend

- Z, RX, RY, RZ: Damping only

 

LHO ITMY Status:

Stage 1

- X, Y, Z: 45mHz blend

- Z: 90mHz blend

- RX, RY, RZ: 250 mHz blend

Stage 2

- All DOFs: 750mHz Blend

 

As we can see, the main difference is on Stage 2: most of the DOFs are turned off (damping only) at LLO. On the other hand, they have more features (FeedForward, Sensor Correction) installed on ST1 then at LHO.

By looking at the results, we see pretty similar results in X and Y.  LLO seems to do a little better at 0.5Hz (better blend design, sensor correction). But, by looking at the rotational degrees of freedom, we can see that having a high blend on ST2 at LHO doesn't affect the low frequencies and help a little around 1Hz (we see that also in the optical lever).

In conclusion, turning on the sensor correction at LHO seems to be the next step. At LLO, it seems that turning ON the stage 2 loops with high blend filters wouldn't hurt.

Non-image files attached to this report
Comments related to this report
peter.fritschel@LIGO.ORG - 19:40, Wednesday 17 September 2014 (13994)

Sebastien - it's great to see this kind of comparison and combining of the benefits of both sites - thank you!

The y-axis units on the optical lever plot - it's in radians, I assume?

sebastien.biscans@LIGO.ORG - 21:37, Wednesday 17 September 2014 (13999)

Peter- Yes! Sorry about the confusion, I did all those plots with the same template without seeing my mistake (same thing goes for the rotational degrees of freedom on the other plots)