[Elli and Bram]

After the OAT RefCav work, we relocked the PLL in EY. We had to tune the laser crystal temperature up to 42.27 degC (from 42.08 degC). We also teaked the waveplate, setting the beatnote power to -31dB.

I had a look at the refernce cavity today to see where we losing our gain. Initially I tweaked the alignment increasing it by approximately 10%, the 01-mode is now much dimmer on the monitor (I didn't do a scanning alignment, and tried to kept the cavity locked).

Also, I rotated the QWP just infront of the cavity to maximise the power on the RF LSC diode. In the beam just after the PBS, which taps the beam for the RF LSC diode, is a ~90/10 beam splitter (unlabelled), directing 90% of the beam to a CCD camera! Due to a lack of looking for a smaller splitting ratio beam splitter I left it inplace, so we now geting ~4 mW onto the RF LSC diode (of the 34.4 mW available in the return beam).

I dropped lock, so I could measure the power. Into the cavity is 46 mW, reflected is (out of the PBS) 34 mW. I measured the power incident on the transmitted diode but forgot to measure the total power transmitted! There is 4 mW on the RF LSC diode (reading 169 mV at the DC output). Once locked the power drops to 40 mV out of the DC output.

The UGF is 287 kHz, with the folowing Interface Settings

It runs with Common at 850 and Fast at 700 (UGF 315 kHz), but it becomes more sensitive to bumping and floor motion and starts to oscillate.

You can recover from the oscillation by reducing the Common gain to below 160, and bring it back up.

The relock of the RefCav is at a slightly different mode, asI tweaked the coarse tuning down wards to find the 00-mode. There is 210 micro Watts on the transmitted diode, reading ~828 mV (it has a gain setting of 20 dB).

Attached are plots of dust counts > .5 microns in particles per cubic foot. The dust monitor at location 8 in the LVEA (H0:PEM-LVEA_DST8_5) was put in the assembly prep area near HAM2 and HAM3.

Vincent finished installing the HEPI system. Because the ISC signals are now added into the HEPI feedback just after the compensation filters, the gain and sign have changed.

Now we have a gain of -2 (from +0.2). Also the units are not in nm anymore .... not a drama but makes thinking about limits a bit harder ...

I engaged the ISI isolation on ITM, but the ETM kept tripping so I left it in damping only (didn't further investigate).

Left the cavity locked for the night.

Kyle 

With the leak detector configuration as left yesterday, i.e. backing the Vertex MTP (100% of the turbo exhaust) the helium background had decreased from 1.3 x 10-8 torr*L/sec (as left yesterday) to 6.2 x 10-9 torr*L/sec today -> I vented the HAM5 and HAM6 annulus volume and decoupled the HAM5 aux. pump components leaving the pump port connection open to the room.  Then I let the HAM6 aux. cart diaphram backing pump pump air through the annulus, i.e. room air enters HAM5 pump port and routes through annulus volume and exits HAM6 pump port.  This was another attempt to expedite removal of any helium permeated in the annulus O-rings -> No help, too slow.  Next I calibrated our 2nd leak detector and swapped it in place of the initial leak detector -> No change.  It measured and behaved within 10% of the first.  This was done to rule out any instrument-specific inability the initial leak detector might have had in resolving helium ions from non-helium ions in the spec. tube (as the leak detector inlet pressure is relatively "high" baking the MTP).  This concludes my attempt to get the helium background to the nominal <2 x 10-9 torr*L/sec value.  

Moving on, I reconnected the initial leak detector and began testing CF joints on the output MC tube with a background of 6.2 x 10-9 torr*L/sec.  Two of the first three flanges I tested were 10-6 range leakers!! Ouch!!  Will have to continue tomorrow after this pumps away.  

Day's Activities:

Since there was not OAT activities during the day, this allowed for noisy activities in the LVEA/EY.

• HAM3 Survey work started off the morning
• Chris/Karen given ok for LVEA vacuuming
• Apollo crew were craning around ISC tables
• Vincent reconfiguring HEPI model for filter name changes
• Betsy turned on PR2 Damping
• Szymon did some ETMy SUS measurements earlier in the day
• Robert/Richard addressed a "noisy" transformer at EY
• SEI crew removed mass from HAM3 via forklift
• SUS crew staging to mount Installation Arm on HAM3
• Apollo busy down at EX (removing doors from BSC9, and staging for In-Chamber cleaning)
• YMCA Tour in the afternoon

This morning, the HEPI master model was updated, corrected and committed. The two HEPI models (BSC6 and BSC8) were recompiled, re-installed, restarted and restored. The safe burt snapshots were updated. Bram was able to lock the cavity with the new configuration.
Note that the Yaw offset is now introduced in the DC_BIAS and the ISCMON filter output signals are not going through the isolation filters.
Now, ISC signals can be read by the HEPI models using the reflective memory.

After the false start with damping measurements earlier, I went in and center the M2/M3 lower stage AOSEMs.  Unfortunately, we broke a magnet off of the temporary lowest mass during transport/rehanging, so LR AOSEM is not "seeing" anything.  We'll skip repairing it since we are about to move on to installing the real glass mass shortly.  I just turned damping on again now.

I would not normally put this here, but the stochastic log was unavailable.

To build our confidence in our understanding of instrumental H1-H2 correlations, we are attempting to identify the features in the H1-H2 coherence. I did this for part of the S5 data back during S5 (here), when I was able to trace many of the features to particular sets of fans, or to low frequency (0-15 Hz) BSC and HAM resonances in the bilinear coupling regions around 60 Hz peaks; the summary from 2006 is repeated here as Figure 1.

Here we check these earlier results with full-S5 data, making sure that the rest of the run is consistent with the earlier partial results by comparing the full-run and partial-run features in coherence and by comparing the full-run PEM spectra to the full-run coherence.

A comparison of Figure 1 and Figure 2 indicates that the clusters of peaks from certain fans and the bilinear coupling features are present in both the partial run and the full run, suggesting that the specific partial-run identifications could be extended to the full run.

We expect that peaks in the H1-H2 coherence are associated with peaks in important PEM channels (sensors at coupling sites or half way between H1 and H2 coupling sites). The full-run PEM spectra of important channels show peaks that correspond with the coherence features, except for the peak at 114 Hz. The 114 Hz peak in Figure 1 is the only peak labeled “uncertain” – there were fans in this frequency band, but the shape of the peak did not quite match the shape in the partial-run spectra. This is again true for the full-run spectra, so I am not confident that we understand the source of the 114 Hz peak in coherence.

We are currently looking into the possibility that a sudden change in coupling when I floated ISCT4 to reduce H1 H2 coupling might be responsible for the inconsistency in coherence and ASDs. 

I've turned the damping on for PR2 (chamberside, all metal HSTS) at 18:34 UTC / 11:32 PT, in order to take some damped spectra.  Motion on the optic looks steady as per the speed dials.

(not Bram)

Attached is a plot of the response of the laser crystal TEC when stepping 13mK up and then down at the slow input (assume -1K/V sensitivity). The response shows a spike by about +9mK and then -9mK (not clear how good either calibration is). The response time is roughly 5 sec which would indicate a ~30 mHz pole in the slow input of the laser.

B. Bland, J. Kissel

[[ These results are extremely belated, but I want to post them for posterity. ]]

After making adjustments to the static Roll of the optic, we've remeasured (as much as we remembered to of) H1 SUS MC2. Attached are the results.

Several things that these results indicate:

- The alleviation of the DC/static roll in the optic appears to have restored normalcy on the lowest L and T mode, i.e. they're no longer split in frequency. Huh!
- Now all degrees of freedom match well with the model, and other degrees of freedom.
- Spectra compared against in-chamber LLO suspensions indicate that excess noise seen at high-frequency is indeed most likely due to the noisy external environment on the optical tables. However, you'll notice that the noise has significantly reduced from when the SUS was in LHO staging building, so this confirms that the LHO assembly area is simply the noisiest environment where testing takes place, and it's not a problem fundamental to the suspension itself.


As of these results, H1 SUS MC2 has passed Phase 2b testing and is ready for install into HAM3.

I re-locked the arm, after I had unlocked it earlier to take some measuremens with the ALS table PZTs.

I'm leaving it locked overnight.

I replaced the old ALS QPD output matrices (measured empirically by Elli and Thomas several weeks ago) with new ones based on Cartesian coordinates. I obtained these by ray-tracing on the ALS table. Then I measured the input matrices with a Matlab script (/svn/cdsutils/trunk/ALS).

Now the inputs of the IP_POS and IP_ANG filter modules should be calibrated in meters and radians.

These are the matrices:

INPIT =
  -0.001934944012837   0.000295830132597
  -0.000025683755141  -0.000141436038465
INYAW =
   0.001338191005451  -0.000236296533156
  -0.000010597031521   0.000352368394300

OUTPIT =OUTYAW=
   1.0e+07 *
  -0.746993867828206   2.240981603484618
   0.048486940975147  -0.800820822925440

The loops have UGF of about 10 Hz with these gains:

IP_POS_PIT= -8; IP_ANG_PIT=-8; IP_POS_YAW=-8; IP_ANF_YAW=-4

Attached are some spectra measured with the loops either open or closed.

The TMS table relative lateral stability seems to comply with the requirements (=100urad RMS). On the other hand the angular stability seems to be a bit worse than desired (=1urad RMS).

Long term stability (12+ hrs) still has to be evaluated.

Attached are plots of dust counts > .5 microns in particles per cubic foot.

[Michael R., Volker Q.]

After installing the new EOM and measuring the PM sidebands, see previous entry, we measured the RFAM on the core modulation frequencies 9.1MHz, 45.5MHz and 24.1MHz. All frequencies were driven with 10Vpp. The measurement was performed using a LZH aLIGO PSL locking PD (D1002163) mounted at the position of IO_AB_PD1.

The AC path of this diode has a 4x amplification with respect to the DC path and 50 ohm output impedance.  The DC path also has 50 ohm output impedance.

The DC value was measured with a TDS 2024 into high impedance, the AC output was measured with an Agilent 4395a into 50 ohm. (Note, this gives another factor of 2 for the DC value.)

The RFAM was calculated using this formula RFAM = (V_AC/4) / (V_DC/2) accounting for AC amplification and DC path impedance.  V_AC denotes the Vrms as measured with the spectrum analyzer and V_DC the voltage read from the oscilloscope. The PM value below is the modulation index as measured previously.  As a sanity check the V_AC measurements were done with the dBv, dBm and Volt settings of the spectrum analyzer to confirm that Vrms is displayed. The following table shows the measurements:

The Agilent 4395a was set to BW = 3kHz.

Kyle, Gerardo

7/31/2012 

With the leak detector backing a 50l/sec turbo which was pumping the HAM5 HAM6 annulus and the Vertex Volume being pumped by the Vertex MTP (@ 3.4 x 10-7 torr), we sprayed (~5sec bursts of audible flow) at each of the test ports of the HAM6 side of the HAM5/HAM6 septum.  No response.  Next, we moved the leak detector over to back the Vertex MTP such that 100% of the exhaust was being sampled and, at some point, noticed that the helium background had risen (from the ~ 2 x 10-9 torr*l/sec when backing annulus turbo) to 6.5 x 10-9 torr*L/sec


8/1/2012

The indicated helium background of the leak detector was 6.5 x 10-9 torr*L/sec when we left yesterday.  It remained unchanged today.  This value falls off rapidly as the 10" gate valve at the MTP inlet is closed and is behaving as if it is a real signal sourced on the VE side of the 10" gate valve.  Any helium introduced via cross talk to a leaking metal joint yesterday would not remain unchanged for this many hours of 2000 l/sec MTP pumping.  It is much more likely to be a reservoir permeated through the annulus viton from the previous days spraying  -> Today we vented, then pumped, then vented, then pumped, then vented then pumped the HAM6 and HAM5 annulus space over the course of the afternoon in hopes that this might expedite the removal of helium permeated into the annulus viton.  We observed during the initial annulus vent that the helium signal increased slightly while the annulus was vented.  

With the helium background too high for acceptance testing of new conflat or feed-through joints we decided to eliminated any gross leaks existing on HAM5 and HAM6.  All conflat joints and electrical feed-throughs were sprayed with 10 second blasts of audible flow.  The helium background rose slowly and steadily from 6.5 x 10-9 torr*l/sec to 1.3 x 10-8 torr*l/sec over the 1 hour period we were testing

[Michael R., Volker Q.]

Following the measurements at LLO we measured the frequency dependent sideband generation around the resonant frequencies. See here for the LLO measurements.

The table below shows the sideband height as measured with a OSA on the PSL table.  The frequency is the modulation frequency in MHz.  All three modulator inputs were driven with 10Vpp (in 50ohm).

The sideband strength is well centered around the target frequencies of 9.1MHz and 45.5MHz.  The 24.1MHz modulation is slightly off by 100kHz, but I did not want to risk to change the other two frequencies while trying to change the not so important 24.1MHz frequency.