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.

[Michael R., Cheryl V., Volker Q.]

The H1 modulator has been installed on the PSL table, the temporary H2 modulator
got swapped out.  The H2 modulator will be re-tuned and become the H1 spare.

The beam after the modulator was not parallel to the grid on the optics table
because IO_MB_M2 was not movable far enough to allow for the about 5 degrees
of beam deviation going into the EOM.

At LLO this problem was solved by using a New Focus Pedestal Base with
Clamping Forks and moving mirror to an off-grid position.

Here we decided to use a mirror mount with three adjustment screws and
a modified blue base to mount IO_MB_M2.  This provided a stable mounting
the mirror mount and the needed flexibility to steer into the EOM.
All IO PSL optics were realigned using pinhole 4 inch beam height apertures
to keep the beam on the grid of the optical table.

We also found that the reflections from the AR surfaces of the mode
matching lenses IO_MB_L1 and IO_MB_L2 were surprisingly strong.
(We followed various stray beams with 10W into the EOM)

The immediate reflection from IO_AB_L1 hits the brushed aluminum
surface of the modulator housing - the lens is turned slightly to
not reflect the beam back into the modulator.
This creates a wide horizontal "spray" of scattered light because of
the brushed surface.  We worked around this problem by placing a dog
clamp beside the EOM aperture. See picture (dog_clamp_and_beam_dump.jpg),
this works, but is certainly not a permanent solution.

The next beam we blocked was a reflection from IO_MB_L2 partially hitting
the rim of IO_MB_L1 and partially going trough hitting the dog clamp
area.  See the razor blade dump roughly in the center of the dog clamp
picture.

Another beam we blocked was going towards IO_MB_L2, see (L2_dump.jpg).
(At the time of writing this we are not sure anymore if this beam was
already blocked by the dump in front of IO_MB_L1, this needs
verification).

Finally we placed a razor blade dump close to IO_MB_M3 to catch the
wrong polarization in the separated beam coming from the modulator
crystal.  See picture (wrong_pol_bd.jpg)

Sideband strength and RFAM will be reported in a separate log entries.

35W beam

We briefly transitioned to high power yesteday for IO work. While transitioning I forgot to turn off the FE watchdog, so when I closed the FE shutter the laser tripped, which is the discontinuity you see.

- HAM 2 alignment - Jason
- HAM ISI transfer functions - Hugo
- Reclean Optics table lab - Terry
- Connecting H2 ITMY Ring Heater Cables - Fil
- HAM 3 : Doug & Jason
- HAM 6 leak checking - Kyle & 2:45 to 2:55
- RFAM measurements - Michael & Volker

Pulled H2 Ring Heater Cable from BSC8 along Y-Arm to H2 PEM/TCS Rack. Ring Heater Chassis power is connected, but unit was left off. IO Chassis still needs work, missing ADC card. Work was done around 10-11 am. Bram/Hugo/Control room was notified prior to start of work.

Bubba and I went walk-about in the LVEA. There is a chamber cleanroom in place over HAM 5/6. There is an iLIGO garbing room on the south side of the chambers and an aLIGO garbing/staging cleanroom on the north side. As far as cleanroom positioning goes, we are in good shape for a HAM install next week. (I forgot to check the sock situation but I'll follow-up tomorrow.) 

Cheryl and I went down to Xend and removed the ETM from the SUS Cage and put it in a cake tin. Cheryl returned the cake tin to the corner station Optics Lab.

The Apollo crew removed the passive SEI stack from the chamber, then shimmed it and wrapped it for short-term storage. It is sitting on the near-side termination slab with CAUTION tape around it.

Apollo will continue to stage for ICC.

At EY, I checked the voltages on  the laser controller diagnostic cable (H2:ISC_WSCBSC_81), which runs from the Laser controller to the Backhoff interface chassis. They seem to be possible so I connected it up to the Beckhoff chassis. Now we have more meaningfull values on the ALS_CUST_LASER.adl screen.

The attached is the latest transfer function measurements taken on H1 SUS PR2 SAGM1 stage.  The data was taken 07-29-2012 and is plotted with the predicted model and a previous measurement from the metal build in the Staging Building.  The pdfs are committed to the SUS SVN under:
'~/sus/trunk/HSTS/Common/Data/allhstss_2012-07-29_*'

Data committed in:
'~/sus/trunk/HSTS/H1/PR2/SAGM1/Data/2012-07-29_H1SUSPR2_M1_WhiteNoise_*DoF*_0p1to50Hz.txt'

DTT templates used had the same name but with an "xml" extension.

[Elli, Bram, Alberto]

Yesterday we intentially unlocked the ALS PLL to do some work with the reference cavity in the optics lab. Later on, when we locked it again, the beat note ampltide was much smaller than before. At the common mode board monitor output it was -60 dBm vs ~-30 dBm that we had before. (The board monitor output is about 20 dB smaller than the actual RF beat amplitude).

We managed to bring it back to -25 dBm by realigning the fiber output. We also lightly reduced the power of the local oscillator's beam to suppress higher harmonics in the signal.

Alberto, Bram

The arm has been locked since 20:00 local time.

Due to the RFM not working iwrote a littel Perl script which reads the  H2:ISC-ALS_EY_ETM_LONG_OUTPUT and writes it in H2:HPI-ETMY_ISCPF_LONG_OFFSET to get the communication between the ISC modle and the ETMY HEPI model going. It runs in a terminal window.

We ran a sine response function at 10 mHz, which pushed ETMY HEPI at _ISO_Y_EXC and recorded the _BLEND_IPS_Y_IN1 and in the ISC model the _ETM_LONG_OUT. The ETM_LONG_OUT ratio was 0.44 at -180 degrees. We wanted the UGF at 1 mHz, so we set it to +0.2 (~6dB less). The filter is an intergrator (pole at 0) in _EY_ARM_LONG FM1 and there is a cutoff with two complex poles at 100 mHz in EY_ETM_LONG in FM1. There is a 1x1 matrix between the ARM_LONG and ETM_LONG. In the EY_ARM_LONG the limiter is engaged at 200k.

We locked tha cavity and enganged the offloading to HEPI .... it ramped quite nicely as seen in the first striptool plot. In between I changed the gain down to 0.15 as I thought I saw the beat frequency breathing with a period of ~5min (~3 mHz), but returned it to 0.2 after ~30 min.

In the attached spectrum the peak at 2.75 Hz is down quite a bit, but then there is an increase in noise at the higher frequencies. At other moment, the 2.75 Hz peak is as previous but the higerh frequencies are much lower.

Due to the power fluctuations, I adjusted the _REFL_PWR_MON offset to keep th eoutput below 9000 (although it did shoot above that, but the cavity was still locked!).

We will leave the cavity locked over night ..