HAM6 being pumped by both turbo and ion pump for now

Preliminaries suggest some IPS could use some centering.  Currently unable to drive 0.7mm without maxing ADC (IPS side.)  More after tests complete.

I could not connect to nds1 this morning so I contacted Dave Barker.  He tried to log in but machine was locked up.  I looked at it with the attached terminal and no obvious reason for the machine to be non responsive, but it was.  I reset the machine and everything is back. The reboot took a little longer as a check disk was done automatically because it had been 238 days since the last one.

Current pump down much different that previous pump down of same volume (HAM6) -> Apparent gas load resulting in current HAM6 pump down curve can't be attributed to LVP Krytox grease added this last chamber entry -> Annulus volume in 10-6 torr range -> Adjacent blanked-off vent/purge and roughing pump port dead volumes were valved out after rough vacuum achieved and should still be at rough vacuum -> Need to leak test HAM6 particularly view ports and Turbo pump ballast port

SEI
Unlocking HAM6 HEPI
Clean up of blend filter work from yesterday

SUS
Checks on coil driver readbacks

VAC
Pumpdown curve for HAM6 is unexpected
Opening of GV5 and GV7 is contingent upon resolution of issues with installation of beam dump on top of HAM2

FAC
Stand to anchor in DCS building
Holes to drill for stand in LVEA
Landscaping removing trees tomorrow

CDS
Filiberto working on CPS timing

PCAL
Calibration work at end X

Evan and Rick reported that the Test1 and Test2 On/Off switches were always on, no matter
what the MEDM switch setting was.

The corresponding output of the AI filter checked out okay at the end of the lilac coloured
cables, for both Test1 and Test2.

The output was checked at the end of the DB37 cable going into the TTFSS.  Although a change
in voltage was observed when both switches were toggled, the change for Test2 was not high enough
to trigger the MAX333 switch inside the TTFSS.  This was traced to a problem with the HCPL2231
optocoupler on the TTFSS fieldbox (D1100367).

Since we do not currently have any HCPL2231s, part N1 and N2 were swapped since part B of N2
was not used.  This has fixed the problem for now.



Jeff B, Evan, Peter

Two tip-tilts have been assembled for 40m.  They are sitting on the optics bench in the Optics lab.

These have thinner wire (43 microns in diameter) to avoid the hysterises seen in the thicker 125 micron wire.  Therefore these have to be handled more carefully.  The wires are quite unforgiving of any kinks or handling errors.

As agreed, these do not contain BOSEMs.  Type-B (one stage before the production line)  bosems will eventually be used in these.

The tip-tilts are ready for shipment to 40m.  They have been wrapped in Al-foil.  For long term storage, these have to be stored in a dry atmosphere to avoid rusting of the "piano wire" fibers.  The mirror holders are locked into place for shipment using the eddy current dampers on either side of the mirror mounts. 

The Sl nos are 007 and 038 (Bottom Plate).  Images of the assembled tip-tilts and their various reference numbers are attached. 

The SUM counts on ETMX oplev laser were around 16000 counts.  I changed the Binary switch settings to increase the gain on the Whitening Chassis to bring the counts to 40k.

The new switch state of the binary switches is recorded here in the attached image.

[Dan, Koji]

Last week, the OMC cavity was scanned with the fully locked IFO at 5.22W. In addition to the usual cavity scan analysis (let's say "DC scan"),
the technique called "beacon scan" was tried in order to check the signal content in each carrier higher-order mode.
Here are some preliimnary results.

Motivation

- Dan took OMC scans in a full lock with and without the DARM offset a while ago (LHO ALOG 16747).
- When the DARM offset is zero, basically there is no (or almost no) carrier TEM00.
- No matter how the offset is, there are carrier higher-order modes.
- This means that we are actually not sure how much of the carrier higher-order mode is coming from the arm.
- Aren't we under-estimating the signal mode matching because of the carrier that has no signal?
- We want to characterize the signal mode matching.
- We can use the DARM signal to distinguish the signal carrier and the others

Measurement conditions

- The DRFPMI was locked at 5.22W MC input.
- DARM was locked with RF with an offset. (~10mA for TEM00)
- The OMC HV PZT (PZT2) was swept from 30V to 90V with the ramp speed of 0.6V/sec (i.e. 100s per ramp).
- During the scan, the whitening filters of the DCPDs were turned off in order to prevent from their saturation.

Signal processing (Attachment 1)

- DCPD_SUM and PZT2 Readback were sampled at 16k. All the signal processing have been done offline with MATLAB.
- DCPD_SUM was preconditioned for demodulation by a bandpass with the passband of fmod +/- 20Hz, where fmod is the demodulation frequency.
- The preconditioned signal and sin or cos signals at fmod were multipled.

- The DC and demodulated signals were decimated to 512Hz (the decimation ratio=32).
- The decimation filter is the MATLAB default one. (i.e. fc=0.8*fsample, 0.05dB ripple 8th Cheby LPF)
- The decimated demodulation signals were further LPFed for noise reduction. (f_LPF = 5Hz)
- The RMS of the demodulated signals are calculated to obtain the beacon amplitude.
- The noise reduction filter imposes the phase delay in the pass band. This was approximated as a time delay.
  i.e. Negative time delay (or sample shift) of 60 samples were applied. (Dan suggested me to use "filtfilt" function
  in order to suppress this kind of phase delay. I'll use it in the future scan.)

Result (Attachment 2)

- The demodulation frequency of 1009.4Hz was used for the beacon scan.
  There was a big peak in DARM spectrum due to undamped ITM violin mode.

- As seen in the figure, a big response found at the carrier TEM00 mode. (Success!)
  (In fact, the response was too weak at the demod frequency of the calibration lines. That's the reason why the violin peak is used.)

- Not all the carrier amplitudes in the DC scan were explained by the beacon scan result.
  This indicates that each higher order modes consists of a signal carrier from the arm and a non-signal carrier.
  Note that the peaks in the DC scan and beacon scan are matched up by multiplying the factor of 5800 to the beacon result.

- As the background data, the demod frequency of 700Hz was used. There was no visible peak in the DARM spectrum at 700Hz.
  Most of the carrier peaks are above the background level. So this is not an artifact of the noise power in a peak.

Discussion

- The table below is showing the peak heights that were read from the plot. (Note this is not a peak fit result.)
  The ratios were estimated from the sum up to 8th order.

Mode       DC_scan         Beacon_scan
  #      [mA]   [ratio]      [ratio]
---------------------------------------
  0    9.18      0.589        0.928
  1    0.539     0.035        0.010
  2    0.675     0.043        0.020
  3    1.327     0.085        0.024
  4    0.564     0.036        0.004
  5    0.821     0.053        0.005
  6    1.355     0.087        0.006
  7    0.568     0.036        0.001
  8    0.559     0.036        0.001
---------------------------------------

- The table indicates that the signal mode matching was 92.8% and was way better than the DC matching.
- The 3rd and 6th order modes (both in DC and beacon) are larger than the others. Is there any reason?

How can we improve?

For better result:

- Slower scan: The cut off of the noise reduction filter is determined by the scan speed. Slower scan will improve the SNR of the measurement.
- Beacon at ETMs: The current beacon isone of the ITM violin mode. I suspect that is the reason why some of the sidebands shows some signal
above the background level. We should use pure DARM signal.
- Better alignment: The alignment of the beam to the OMC was not perfect. We can definitely improve it.

For better understanding of the result:

- Mode healing/harming: What does the SRC do for the peak heights? Are any particular modes enhanced/suppressed by the SRC?

SRM & SR2 Phase 3b Acceptance TFs were presented in LHO aLOG entries 17633 and 17634, however, there was an issue affecting the scaling of the plots of the lower suspension stages.

The discrepancy in the scaling was as a consequence of the recent modifications to the Triple Coil Driver actuation strength carried out only at H1 (ECR E1400369) not being taken account of in the Matlab calibration script. Therefore, I've updated the Matlab (calib_hsts.m) script to support different calibrations factors for suspensions at both sites.

The aforementioned TFs have been re-processed using the updated Matlab scripts. Measurements for each stage have been compared with similar L1 and H1 Suspensions at Phase 3b (in-vacuum), as follows:-

- SRM & SR2 M1-M1 undamped & damped results (allhstss_2015-04-09_Phase3b_H1HSTSs_M1_D*_ALL_ZOOMED_TFs.pdf)
- SRM & SR2 M2-M2 undamped & damped results (allhstss_2015-04-09_Phase3b_H1HSTSs_M2_D*_ALL_ZOOMED_TFs.pdf)
- SRM & SR2 M3-M3 undamped & damped results (allhstss_2015-04-09_Phase3b_H1HSTSs_M3_D*_ALL_ZOOMED_TFs.pdf)

Summary:

M1-M1, undamped TFs are consistent with model and similar suspensions. Very minor shift of H1 SRM pitch modes above 3 Hz. Damped TFs demonstrate variation in damping between sites. However, just to note that H1 SRM vertical DOF peaks still remain relatively high Q.

M2-M2, both undamped and damped TFs taken are consistent with model and simialr suspensions. However, H1 SR2 can be seen to be weaker due to failed UL actuator (Integration Issue #930).

M3-M3, despite suffering poor coherence below 0.5 Hz, both undamped and damped TFs taken are very consistent with model and similar suspensions.

Therefore, these TFs raise no concerns for SRM & SR2 suspensions, other than the failed SR2 M2 stage actuator noted above.

All data, scripts and plots have been committed to the sus svn as of this entry.

I've been working on trying to improve BSC performance by adding elliptical filters to the CPS part of different blend filters, see logs 17702 and 17488. At ETMX I was getting good improvements in Z (first plot, black(sts) and grey (gs13) is 2 nights ago with the "old" blends, green(sts) and red(gs13) are for my new blends) so I was trying to clean up the extra filters I had (which prevent the seismic blend switching scripts from working nicely) and start exporting what I had to other chambers. This involved cutting some elements out of some existing blends and a lot of copy/paste. For example, on St1, the 90 mhz Z blend, I cut out a couple of pole and zero pairs that were very close to each other (almost cancelling each other out) and adding my ellipse. The result is shown in the second plot, blue is the stock, red is the modded version. There's a third, barely visible green trace, which is what I cut the original blend down to before adding my elliptical. I also modified a version of the 01_28 blend  from the HAMs, (third plot, blue is stock, red modded) to use in Z but ETMY keeps ringing up with this blend, so maybe I've compromised the complementarity too much. I've tried my modified blends on ETMX and ITMY and it works there. I'll get all of the chambers in a consistent configuration by tomorrow afternoon, but as of now ETMX and ITMY are in slightly different configurations from ETMY and ITMX.

We wanted to install the proper parking beam dump on HAM2 before we go high power, and the arm gate valves are closed right now so it seemed like a perfect opportunity. We tried, and failed.

1. Assy in question

https://dcc.ligo.org/LIGO-d1201430

It doesn't show the viewport, so it's not clear how it is supposed to be mounted, except that three hooks grab the outer edge of the flange.

2. The problem

The beam comes out of HAM2 at a steep angle (this picture was taken when we installed the non-final version back in Jan. 2014).

The new beam dump assy seems to be mounted on top of the viewport protector assy. The problem is that the protector is too high, which is kind of obvious from the above picture. For the non-final version, we had to cut the protector ring so the beam comes out of the ring, and a beam dump outside received the beam. We cannot do that with the final beam dump, and as far as the dump sits on top of the protector assy, the beam will hit the protector assy.

As of now, there is a large space between the bottom of the lexan plate and the viewport. There seems to be two versions of the protector assy, one higher than the other, and we're using the higher version. However, even if we use the lower version, it seems likely to me that the beam still does not come to the steering mirror inside the beam dump assy. It should be possible to modify the viewport protector assy such that the lexan plate sits almost flush to the viewport while the beam dump optic table sits almost fluch to the top of the lexan plate. It seems as if this works, but I'm not 100% sure without CAD.

Or maybe it is designed to be used without viewport protector assy. I couldn't find drawing that shows how it's mounted, so I'm asking around.

I told Kyle to hold off to open the gate valve in a hope that somebody offers me an easy solution by tomorrow morning.

I found damped TFs which Kissel took last Dec when he imported the LLO HLTS filters and applied them to the LHO HLTSes 15730.  Today, I ran the undamped set.  Attached are results and comparisons with other HLTSes.  I think this closes the PR3 acceptance measurement dedt.

Rick, Evan

Summary

This evening we went into the PSL and examined OLTF of the FSS.

Since we want to increase the FSS gain, but cannot turn the common gain slider up any further, we looked for other ways to squeeze more gain out of the loop.

Rick had the idea to try to increase the error signal slope by adjusting the demod phase using the delay line. Indeed, we were able to increase the loop gain uniformly by 3 dB. The phase remained more or less unchanged below 700 kHz.

We now have a UGF of about 350 kHz with 50° of phase. The gain margin is about 3 dB.

Details

Delay line switch positions (up/down) are as follows:

So the phase change at 21.5 MHz is 56°. That seems like quite a lot, so perhaps we should take a closer look at the error signal with the FSS unlocked to make sure it's reasonable.

Also, on the manual FSS MEDM screen, we found that the TEST2 enable/disable button didn't really work; we seemed to get a sensible transfer function no matter what.

Attached are the Phase 3b damped and undamped TFs of SR2 taken over the last few months.

Note, there is only the damped M2 stage TF due to the fact that there is a broken coil o magne at that stage and I was leary of driving too hard or too much.

Attached are the Phase 3b damped and undamped TFs of SRM taken over the last few months.