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

There is an exictation running on ITMX L2 Y, I would like to start locking the green arm, so I would like to stop this. 

With the reduced pitch motion in the green arm, I tried again to use the pure PZT dither scheme in pitch too. (I used it for yaw from the start).

That seemed to work just fine. So I disabled XPIT DOF1 and enabled XPIT DOF2.

I disabled the arm locking for the night to finish taking Y2Y transfer functions for L2 for ITMX and ETMX.

Another PtoP measurement on the M2 stage of PRM was launched at around 1:15 AM. It is running on opsws8 (which is Kissel's favorite workstation).

The diag file is in the official place:

/ligo/svncommon/SusSVN/sus/trunk/HSTS/H1/PRM/Common/Data/2014-01-25-H1SUSPRM_M2_PtoP_SweptSince_0p2to5Hz.xml

Kiwamu, Stefan

We increased the input power to 10Watt.

- We removed the lock from the rotational stage interlock.
- We rotated the Laser Power rotation stage from 56.1 to 30deg, raising the power by a factor of 10.
- The power levels IMC REFL and IMC WFSs were kept thge same by adjusting the lambda/2 rotation stage on IOT2L. We had and have 12mWatt on IMC REFL.
- We reduced the analog electronic gain on MC TRANS by a factor of 10.
- We verified that we now have 29.7mWatt on LSC-REFLAIR_A, and 30mWatt on on LSC-REFLAIR_B on ISCT1.


- We confirmed that the IMC UGF is still 54kHz.
- We updated the IMC Guardian to switch on all 3 stages, and increased the in-lock gain to 13dB. This left the phase margin at 26deg.

[Keita, Koji, Yuta] (written by Yuta, poted by Koji)

ETMY green transmissivity and reflectivity were measured to be T=31.6 +/- 0.2(stat.) % and R=67.8 +/- 0.3(stat.) %
at the incident angle of 0.4 +/- 0.1(sys.) deg.

From the incident angle dependence measurement, the trasmissivity at 0 deg was estimated to be T=31.4 +/- 0.4(stat.) %.

[Motivation]
We wanted to check the transmissivity and reflectivity of ETMY at 532nm since ETMX has lower transmissivity than designed.

[Method]
1. Injected the green beam of the Prometheus laser from the HR side of ETMY at the quad stand.
Measured the incident, reflected, and transmitted power levels with the OHIR power meter configured for the wavelength of 532nm.
Performed three sets of the measurements at the spots at the top part of the mirror horizontally separated by 1 inch
around the horizontal center of the mirror. The horizontal shift of the spots were

The incident angle was assessed by measuring the beam separation at reflection.
The beam separation was 0.5 +/- 0.1 inch at 36 +/- 1 inch away from the HR surface. The incident power was ~50 mW.

2. Rotate ETMY and measured the transmitted power and the beam separation at reflection. Repeat the measurement with different incident angle.

During the measurement, ETMY was kept inside the clean booth at the end Y station. The beam spot on ETMY was ~2 inch blow the top edge of the mirror.

[Result]
1. At the incident angle of 0.4 +/- 0.1(sys.) deg;

T = 31.6 +/- 0.2(stat.) %
R = 67.8 +/- 0.3(stat.) %

2. ETMYtrans.png shows the transmissivity dependence on the incident angle. By fitting the measured data with a quadratic curve, we get

T = 31.4 +/- 0.4(stat.) %

at the incident angle of 0 deg. The incident angle dependence was

k = -0.25 +/- 0.09(stat.) %/deg^2


[Wavelength dependence]
We can estimate the wavelength dependence of the transmissivity from the incident angle dependence.
The wavelength dependence can be expressed by

T = T0 + dT/dlambda * dlambda

When the incident beam has some incident angle, the effective thickness of the coating changes. Thus,

dlambda = lambda/cos(theta) - lambda = theta^2/2*lambda

where theta is the refraction angle incide the coating and

theta = theta_{in}/n_eff

when theta << 1. n_eff is the effective refractive index of the coating.

So,

T = T0 + dT/dlambda (theta_{in}/n_eff)^2/2*lambda
  = T0 + k*theta_{in}^2

From the measurement of k,

dT/dlambda = 2*k*n_eff^2/lambda = -9 +/- 3(stat.) %/nm

Here, we assumed n_eff=1.7.

I will be working on the IMC characterization as a part of the 10 W prep. During the period, the IMC probably will drop its lock several times.

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.