S. Biscans, H. Radkins, J. Warner, J. Kissel

[[Belated entry from last night]]

In order to investigate the recently found oscillations and/or frequency combs in ISI ITMX that has been troubling the Green Team (see LHO aLOG 9494), we explored a few different configurations of the corner station BSC-ISIs. This aLOG covers the first three configurations we tested. Since these initial tests, Seb, Jim and Hugh have explored more configurations (see LHO aLOG 9537). This serves as the record for the temporary temporary solution which got the performance needed to satisfy the Green Team (see LHO aLOG 9518) -- the addition of a high-Q notch in the ISI-ITMX displacement sensor blend filters on both both stages.

With the 0.5 [Hz] notch on both stages, we're able to reduce the RMS optic pitch motion from 160 [nrad] to 80 [nrad].

Attachment 1: performance of ST2, as measured by the ST2 GS13s (stage 2 inertial censors) in three different configurations:
(1) Initial measurement in the current best configuration,  Level 1 isolation filters, with "T100mHz_N0.44" blends on ST1 XY and "750mHz" on ST1 ZRXRYRX and all of ST2.
(2) Exact same configuration of ISI-ITMX, but with the ISI-ITMY CPS turned off at the racks in the high-back (via the independent rocker switches on the back panel).
(3) With ISI-ITMY's CPS still off, similar control loop and blend filter configuration of ISI-ITMX except with a 0.5 [Hz] notch filter  in the X and Y degrees of freedom of both stages.

Attachment 2: A comparison between blend filters used in the current best configuration, with and without the 0.5 [Hz] notch filter. Note that this an export from the filters *actually installed* in foton, so the blend filters include the sensor response inversion, so they're not just the complementary blend shape (which is why the 750 mHz filters look screwy upon first glance). 

Remember, this notch is a temporary temporary solution. We're continuing to investigate the source of the problem, and we look forward to both the temporary (see LLO aLOG 10584) and permanent hardware / analog electronics solution (still under development) to the CPS oscillators beating against each other. However, while it's obvious the beating oscillators cured *some* of the frequency comb (comparing Initial Measurement against ISI-ITMY CPS OFF) we're not convinced the beating oscillators is the source of the exactly-0.5[Hz]-line.

For the record, 
- The foton design is notch(0.5,20,20) for a frequency of 0.5 [Hz] a Q of 20 and a depth of 20 dB. It also has a ramp time of 10 sec on the output.
- The notch lives in a separate filter module (FM5, called "notch_narrow") in the CPS blend filter banks (e.g. ITMX_ST1_BLND_X_CPS_CUR)
- You cannot access/turn ON/OFF from the main blend filter screen -- you have to open the "CURR" CPS sub-screen

The PSL shut down because the chiller had a flow sensor 1 error.  Reseting the status then restarting the chiller cleared the error.  The PSL is back on now. 

Travis/Betsy

This morning, we staged to put the ETMy QUAD monolithic structure back together.  We vacuumed as much of the structures as we could.  I re-first-contact-cleaned the ERM-front surface since it had been exposed to the elements since the last vent and showed much particulate dispite blowing it with N2.  The FC cleaning worked and the surface looked improved.  We then removed the ETMy test mass HR First contact (which has been on since it left CIT) and attached the 2 lower structures.  Using the Genie, w transfered the completed lower structure to the silver pallet jack + 5-axis lift table.  We then maneuvered the LS into place and attached it to the upper structure already on the ISI table.  We removed all of the lifting EQ from the QUAD and stowed everything in the unused welding cleanroom.  All went well.  We did not suspend the QUAD - we'll start that on Monday.

Apollo – In LVEA working on nitrogen piping.

Jim B. - 2 DAC restarts
Apollo & Justin – On top of HAM2 installing the parking beam beam dump
Betsy & Travis - At End-Y working on monolithic 
Corey & Filiberto – At End-Y working on TMS cable problem
Doug – Moving survey equipment into LVEA
Justin - Transition LVEA to Laser Safe
Soil & Ground Water on site checking wells
Betsy & Travis At End-Y working on monolithic
Corey – At End-X TMS lab looking for parts
Jeff K. - Running long TFs on PRM – needs Mode Cleaner
PSL laser down 

Opsws0. Should complete sometime early Saturday.

(Corey, Filiberto)

Went out during an open window for access at the Test Stand to perform an in-situ Hi-Pot cable test of our Seismically-Responsible TMS Beam Diverter Cable (D1000223 s/n S1104078); it was observed to have an electrical short in it.  Unfortunately, the Hi-Pot tester was not able to run a measurement on the cable with it clamped on the ISI. 

I removed the cable off the ISI and then Filiberto ran a Hi-Pot test, and it was confirmed that Pin#1 (Shield) is shorted to Pin#23. 

We will either fix this cable or replace it with a D1000225 (different guage wire cable).

(Alexa, Sheila)

We wanted to compare our senstitivty to angular motion between HIFOX and Y. I used Seigman (Lasers, Chap 19) equation for the beam displacement from the optical axis as a function of mirror displacements. In my calculation, I used the following values

• L = cavity length = 3994.472 (alog 9402)
• IMTX_ROC = 1939.52m     ETMX_ROC = 2241.54m
• TTMY_ROC = 2307m         ETMY_ROC = 2313m (from LIGO-T1300158)
• Assumed all mirror motion was .1urad.

I found the ratio of HIFO X to HIFOY for...

• motion of ETM resulting in displacement on ETM = 2.86
• motion of ETM resulting in displacement on ITM = 2.29
• motion of ITM resulting in displacement on ETM =1.97
• motion of ITM resulting in displacement on ITM = 2.46

11:50 - Bubba & Justin install parking beam beam dump cover on top of HAM2. Done 12:00 

11:09 - Justin on top of HAM2 checking parking beam beam dump mount. Done 11:16

10:00 - Betsy and Travis at End-Y working on monolithic install. 

09:25 - Mitch in LVEA West Bay working on ACB assembly. Done 12:10.
1:25 - Mitch in LVEA West Bay working on ACB assembly. Done 3:30. 

Sebastien, Hugh

We investigated a little more on BSC-ITMX comb issue that we noticed yesterday (see Jeff's log).

Our guess what that the position sensors are cross talking with each other between the chambers at the corner station. To verify that, we turned off the CPSs of BSC-BS, to see if it makes the comb disappear.

In the plots attached, the red curves are the reference curve (BSC-BS ON). We can see a comb on the rotational DOFs, starting at 0.45Hz. When the CPSs of the BS are OFF (blue curves), the comb goes away. At this point, I think we can clearly assest that we have a CPS issue.

PS: the huge spike at 0.5Hz on X and Y seems unrelated with the CPS effect. We're still investigating to understand where it comes from. For now, we just installed a narrow notch at this frequency in our blend filters as a temporary solution.

Hugh gave me instructions for recovering from a HEPI and ISI trip on ETMx, which should work for the ITM:

1) turn off any large inputs from lsc to hepi, set a large ramp time for reengaging it later. 

2) untrip watch dogs

3)isolate level 1

4) check RX +Ry (or all) current set points (in the bias screen) to see if they are the same as the target setpoints, if not set them to be the same. (this should only be a problem for the ETM)

ISI:

1)in watchdog screen set T240 limit to something large (only needed for ETM)

2) reset watch dogs if they are tripped

3) commands undamp (may not be necessary, especially if drives are small)

4) for ETM, make sure stage1 blends are all 750mHz

5) Isolate level 1

6) after that is done make sure that St 1 blend_x and blend_Y are T100mHz_N0.44 for the ETM.  For the ITM make sure that Sebastians Notch_narrow (for the 0.5Hz noise) is engaged. 

I think that is all!

The Apollo working on parking beam beam dump cover installation on HAM2 from 09:07 to 09:15.
 

h1dc0 data concentrator restarted to clear .ini mismatch on h1isiham5.

Both frame writers are now writing longer frames.  Testing is ongoing.

GPIB01-wifi IP: 10.22.10.20/20

GPIB01 IP: 10.22.10.30/20

...are at EX hooked up to the SR785

Green team-

The arm cavity is finally locking stably, thanks to the work of Sebastian, Hugh, Jeff and company to reduce our pitch fluctuations.  Now we have about 5% fluctuations in the transmitted power that comes from pitch fluctuations, much better than the 50% we had this morning, and the cavity has been locked at least for 10s of minutes.  The slow feedback is now on, controlled by the autolocker. 

We get a max transmission of about 740 counts on ALS-C_COMM_LF, while the single shot beam stayed at 45 counts, which means that the on resonance/single shot resonance is 16.1, so we are getting 74% of the power that we would expect and probably have 26% of our power in higher order modes ( improved from 45% this morning).  This may have been due to Alexa and I moving the EOM in our effort to reduce the RF AM.  Maybe it is worth tweaking the EOM alingment when the cavity is locked to see if this is the sourcce of our mode mismatch. 

I will leave the cavity locking with the autolocker on, until the red team wants to misaling it.