There has been some concern that there might be excess cps noise in some of the channels. So i looked at 20 minutes of data at 1am sunday night/monday morning.

Looking only above 30Hz where the sensors have hit the noise floor, all of the coarse channels are similar and between 3.5-4.5E-10m/rrtHz about what we expect.

The stage 2 channels show two outliers, ITMX H2 and ITMX V1, maybe BS H2 also but that is close enough so that it could just be at a large offset (we expect the noise floor to go as the gap squared) I'll check that.

  The first thing to do is for me to look at another time, and to check the cables and connections for those sensors

I looked at a second data set calling it "B" (24 hours later)  ST2 ITMX H2 and ST2 ITMX V1 still show excess noise BS H2 is down to 4.5-5E-10m/rtHz which is a little bit noisy, but probably within what we are calling acceptable. I attached the data because Jeff asked to see the ADC noise on the plot

When I say large offset I mean > 10000 counts, so 1200 counts is centered for this discussion 

Nic, Sheila, Alexa

We pulled the CM summing junction from R4 (in the ISC racks by the PSL, the one closest to HAM1).  The OK light was not on and the measured transfer function was -80 when it should have been 0dB.  The TF from the excitation to the output was also garbage.

To have maximum power transmitted by the IMC, I had to move the beam on WFS_A a bit out fo the center (WFS_A_DC_PIT = 0.1, WFS_A_DC_YAW = 0.23).  I was not able to recover the same power with centered WFS and an offset on DOF1/2. But maybe just because I didn't have much time to try. Right now, I'm leaving the IMC angular control runnng without any offset. Intensity noise should be good enough.

In a previous report I showed that the beam can wander on the IMC WFS by something like 0.1 in QPD normalized units. To understand how much this can affect the optimality of the IMC alignment, I moved the beam on WFS using the picomotors, and tracked the change of jitter to RIN coupling.

I injected a 11 Hz pitch line on the PZT (amplitude 0.5) and a 17 Hz yaw line on the PZT (amplitude 2) and looked at the amplitude of induced RIN, both in the second loop signals and in IM4_TRANS. All signals gave consistent result, so here I'm quoting only one value.

Here are the raw results. The first four columns give the deviation of the beam position with respect to the initial one (which was not centered)

The effect is not so small, in particular a pitch miscentering of the beam can increase by as much as a factor 3 the coupling of jitter to RIN.

So it seems that the normal wandering of the beam on the long period can give some IMC misalignment that will cause a significant worsening of intensity noise. One solution would be to implement the beam size modification already done at Livingston.

re 15131, attached are pdfs of spectra for the ITMY HEPI L4Cs around 1am Tuesday and Wednesday before and after I made these changes Tuesday morning.  The first two pages are the individual runs and the third crowds things up and puts them on the same plot to maybe improve the comparison.

Bottom line--some places better some not as good even considering the differing ground motion.  I think these controller could be more aggressive if we want.

• SEI BSC2 and HAM3 HEPI still need attention
• Jim working on sensor correction at ETMX and ETMY
• SR3 OpLev recentering today
• 3IFO baffle suspension builds ongoing in LVEA West Bay
• EY PEM power cabling ongoing
• 3IFO storage can craning scheduled for tomorrow morning
• VPW cleanup for DCS build ongoing

model restarts logged for Tue 18/Nov/2014
2014_11_18 01:41 h1fw0
2014_11_18 10:51 h1isiham4
2014_11_18 10:51 h1isiham5
2014_11_18 10:56 h1sussr2
2014_11_18 10:58 h1sussr3
2014_11_18 10:58 h1sussrm
2014_11_18 11:01 h1hpiitmy
2014_11_18 11:27 h1broadcast0
2014_11_18 11:27 h1dc0
2014_11_18 11:27 h1fw1
2014_11_18 11:27 h1nds0
2014_11_18 11:27 h1nds1
2014_11_18 11:29 h1fw0
2014_11_18 11:54 h1psliss
2014_11_18 11:57 h1broadcast0
2014_11_18 11:57 h1dc0
2014_11_18 11:57 h1fw0
2014_11_18 11:57 h1fw1
2014_11_18 11:57 h1nds0
2014_11_18 11:57 h1nds1
2014_11_18 11:58 h1nds1

one unexpected restart. Maintenance day. Ham4,5 ISI and SUS work, with associated DAQ restart. PSL ISS work with associated DAQ restart. Double restart of h1nds1?

Alexa, Dan, Nic, Sheila, Evan

Tonight we made some improvements to our automation, and we reduced the CARM offset with DRMI locked on 3F.

• We measured some open loop gains with DRMI 1F + arms off resonance (by 1000 Hz at 532).  They seem to have about the same UGF as wihout the arms, for PRCL we change the gain from 22 to 11 when adding arms, and for MICH we changed it from 5 to 4, SRCL we did not change.
• We turn on the DRMI ASC, it brings AS 90 positive, then if we leave it on we start mode hopping.  For now we are just turning the ASC off once we get a decent build up in AS 90.
• We have not changed the ratio between the 3F and 1F signals in the input matrix.  Evan got a measurement of the sensing matrix.
• Then we decreased the CARM offset without any problems. 

J. Kissel

Interested to see how the projected ISI channels compared with Kiwamu's assessment of PR3 (see LHO aLOG 15048), I've plotted 
(a) The input noise budget for the Suspension Point Longitudinal Motion, and
(b) The Transfer function between suspension point and L, P and Y of the optic using whatever local sensor was available.
for SRM, SR2, and SR3. Remember that the damping loops for these suspensions is still the "hand-tuned" dumb velocity damping. Also note that SR3, Oplev to M2 Pitch damping is ON for this measurement.

A couple of conclusions:
From the Susp. Point L budget --
(1) For all three SUS, with the current HAM ISI blend design, we're limited by the HAM4 / HAM5 Y motion at just about all frequencies. Where there has been effort to carve out performance at 1-2 [Hz] in Y in the ISI, RX of the ISI limits the performance.
(2) Some how, even though RZ appears WELL below the limiting noise source for L, it's still somehow ~70 to 80% coherent between 0.1 and 0.6 [Hz]. Huh??

From the Susp. Point L to Optic TFs --
(4) Susp. Point Longitudinal is the dominant contributor to Pitch at the optic, by a long shot.
(5) The OSEMs, which are relative motion sensors between the cage and suspension, fall off in response below the SUS's first resonance as 1/f^2 as expected. 
(6) Perhaps unexpectedly, the OSEMs are still *coherent* below the first SUS resonance, down to quite low frequencies.
(7) Susp. Point L, some how contributes a great deal of motion to Yaw as well as Pitch between 0.7 [Hz] and 1.5 [Hz], amplifying input motion as much as a factor of ~100. 
(8) The difference in damping between SRM and SR2 seems to have significant affect on the Susp. L to Optic L TF at the first and second resonances (0.7 [Hz] and 1.53 [Hz] for the HSTS).

Recall that for angle, SR3 contributes the most to *cavity* angular fluctuations.

K. Venkateswara

After the problems with BRS last week (15005), it was left off for the last ~five days. I tested the damper controller and it looked like the issue with vibration driving the BRS had cropped up again (14596). It wasn't clear why this problem had reappeared but since the foam sheet had worked previously, I went back to that configuration. With the foam sheet under it, the damper appears to be working fine. However another issue with it is that the zero position of the turn-table appears to change, seemingly randomly. It is possible that the stepper motor is occasionally getting stuck. As it's not servo'd this may explain the drift in the zero position. For the moment, I think it requires periodic checking to ensure its zero hasn't changed too much. If it changes by 90 degrees, it can drive the BRS in a positive feedback loop like last week. A servo loop is a better long term solution.

I have also modified the following filters:

1. BRS transfer function inversion filter to correctly account for the imaginary zero at 7.3 mHz (due to the finite d). I was using pairQ(7.3e-3,3) before whereas pair(7.3e-3,0) should be the right choice.

2. The tilt-subtraction filter has also been changed - the high-pass filter (2-pole) has been changed from 2.5 mhz to 4.3 mHz to correctly compensate for the T240 resonance.

The attached pdfs show the ASD for the BRS and the ground T240 in angle and displacement.

J. Warner, J. Kissel, K. Venkateswara

After improved modelling of sensor correction (SC), thanks to Rich M. (615, 623), we re-attempted SC along X (and along Z). X sensor correction was to stage 1 ISI, while Z was on HEPI. Unlike our previous attempt (14896), we used Rich's SC_filter described previously in 14570.

The first pdf shows the ASD from before SC for X and Z. Stage 1 T240, CPS and ground motion is shown and the coherence between them. The second shows the platform motions after SC. The third pdf shows a comparison between the configurations as measured by the T240 showing the expected 2-5 factor improvement between 0.1 to 0.5 Hz. It also shows an improvement below that which is more surprising (maybe from Z SC?). There is no visible re-injection of noise (factor of ~2 is epxected between 20-40 mHz), because we are probably dominated by pre-existing noise which is larger. More testing will be done tomorrow. The OpLevs are currently mis-aligned so I can't see the effect of SC on them.

Note that the we did not use tilt-subtraction at the moment because wind-speeds were practically zero. We will test the tilt-subtraction when winds pick up a bit.

Once again, if this appears to be adding noise instead of helping, the comissioners can turn it off from the ETMX ISI medm screen as before.

Patrick, Dave

The conlog reporting of frequently changing EPICS channels has discovered several code issues in the past week. Conlog reports hourly those channels which have logged 500 or more changes in the previous hour. I have written a python script to concatinate 24 hourly reports into a daily report, which I'll post in the alog. 

Below is the log from yesterday (Monday 11/17). We discovered a guardian node which was setting the end station SUS L1_LOCK_L filters RSET (clearing history) at 16Hz. This was fixed between 1pm and 2pm.

The per-second number is calculated as total/(hours-active * 3600). Numbers in the 16 range are most probably front end or guardian related, higher than 16 most probably Beckhoff or scripts.

11/17/2014                                         hs    total per-sec

                        H1:SUS-ETMX_L1_LOCK_L_RSET 14   751286 14.9

                        H1:SUS-ETMY_L1_LOCK_L_RSET 14   751286 14.9

                         H1:ALS-C_COMM_VCO_TUNEOFS 02    90021 12.5

         H1:ALS-Y_FIBR_LOCK_TEMPERATURECONTROLS_ON 06    62062 2.9

                          H1:ALS-Y_CAM_ITM_PIT_POS 24    58548 0.7

                          H1:ALS-Y_CAM_ITM_YAW_POS 24    58548 0.7

                              H1:ALS-Y_CAM_ITM_SUM 24    58539 0.7

                           H1:GRD-ALS_YARM_USERMSG 05    16658 0.9

                         H1:ALS-X_REFL_SERVO_IN1EN 05    11208 0.6

                 H1:SUS-IM4_M1_OPTICALIGN_Y_OFFSET 03     6052 0.6

                 H1:SUS-IM4_M1_OPTICALIGN_P_OFFSET 02     3136 0.4

                            H1:GRD-ALS_XARM_STATUS 02     3082 0.4

                           H1:GRD-ALS_COMM_USERMSG 03     1781 0.2

              H1:SYS-MOTION_C_PICO_A_CURRENT_DRIVE 02     1516 0.2

                          H1:GRD-ALS_XARM_TARGET_S 01      632 0.2

                           H1:GRD-ALS_XARM_STATE_S 01      550 0.2

                 H1:SUS-PRM_M1_OPTICALIGN_P_OFFSET 01      504 0.1

Here is a collection of suspicious CPS trips on ITMX.  This is a problem only on this chamber, which has just cropped up in the last few weeks.  It needs to be investigated.