[Kiwamu, Stefan, Joe, Paul]

Last Thursday, measurements of several IMC FSR resonances were taken using the sideband sweep method [see e.g. LLO alog entry 4849].

In short, this method involves phase modulating the light into the IMC with a swept sine signal from a network analyzer and observing the signal in transmission of the IMC with an RF photodiode to observe various optical resonances within the cavity.

In this case, the RF photodiode was the broadband REFL AIR photodiode on ISCT1. The network analyzer output was split with a power splitter, with one output going to the REF input, and the other fed to a mini-circuits RF amp with a gain of 18.8dB. The network analyzer source Voltage was tuned to give around 10Vpkpk output from the RF amplifier. The RF amplifier output was then passed to the 45.5MHz input of the EOM on the PSL table. The RF output of the REFL AIR photodiode was connected to the A input of the network analyzer.

When the sideband frequency gets close a multiple of the FSR, a broad peak in the the N.A -->REFL AIR PD transfer function is observed, as reported in [1] and subsequent errata [2]. According to these references as well as Araya et al. [3] this broad peak is only present if there is an offset in the length/frequency lock of the cavity (more on that in a forthcoming post). There is a narrow dip in this peak however, when the sideband frequency approaches the exact FSR multiple frequency. The frequency at which this dip hits a minimum is an integer multiple of the cavity FSR.

The first attached plot shows 5 FSR peaks measured in this way. Since we apply the signal to the 45.5MHz input of the EOM, the modulation depth, and thus the SNR of the measurement, is low at frequencies far from 45.5MHz (e.g. the 18.2MHz FSR, the 27.3MHz FSR and the 54.5MHz FSR). The 36.4MHz peak and the 45.5MHz peak measurements came out the best, so I fitted the central dip using a simple Lorentzian function to estimate the frequency of the minima (see second attached plot).

The results from these two fits are summarised and compared to the design values in the following table:

The calculated lengths from each peak fit agree to within 100um, and are within 0.5mm of the design length.

If higher precision on this measurement is required later on, we could try syncing the network analyzer with a rubidium standard, and also try implementing the measurement technique described in [3]. Also, separately using the 9.1MHz input of the EOM to measure a greater sample of FSRs could be helpful.

[1] K. Skeldon and K. Strain, Applied Optics Vol 36, Number 27 (1997): http://www.opticsinfobase.org/ao/abstract.cfm?uri=ao-36-27-6802

[2] K. Skeldon and K. Strain, Applied Optics Vol 37, Number 21 (1998): http://www.opticsinfobase.org/ao/abstract.cfm?uri=ao-37-21-4936

[3] A. Araya et al, Applied Optics Vol 38, Number 13 (1999): http://www.opticsinfobase.org/ao/abstract.cfm?uri=ao-38-13-2848

An NPRO was setup for aligning and testing the outer loop power stabilisation photodetector array in the H2 PSL Laser Area Enclosure.  The power incident on the array was measured to be 250-260 mW, the beam diameter close to the location of the 8 individual photodiodes was about 800 microns.

Attached are plots of dust counts requested from 4 PM October 9 to 4 PM October 10.

Jason and I set 2new monuments and a new elevation target in preparations for tomorrow baffle alignment. I will setup the total station in the AM and be ready in the first hr.

Thanks to the matlab script Stuart A. wrote, I processed the DTT transfer functions of PR3 M2-M2 undamped TF and compared them with the ones from Livingston.

The TF were taken with a white noise excitation, while PR3 was under vacuum in July 2013, with the ISI damped.

The results of the three degrees of freedom are presented in the attached pdf

(1) First attachement compares the measured LHO PR3 M2-M2 transfer function against the model.

(2) Second attachement compares LHO PR3 M2-M2 against last measured PR3 M2-M2 TF from LLO (today) which was under vacuum.

Data are noisy at DC and above 5Hz but the measurements are matching very well the model and LLO's transfer functions.

09:19 Hugh to BSC3, electronics checkout
10:10 Betsy going to end X
10:32 Dale taking camera into LVEA
10:34 Filiberto working on cabling at end Y
10:45 Delivery for Richard
11:06 Justin turning off optical lever lasers in LVEA
11:30 Arnaud bypassing BS SUS IOP watchdog
12:32 Ops computer froze, restarted
13:51 Thomas heading into BSC2
14:30 I restarted h1conlog
15:50 Jonathan going into LVEA to test GC wireless network

MCL C02219: EX Table PZT 2, NB85-AR10 (to be replaced)

MCL C02218: EX Table PZT1, ND2-AR10-ISS

MCL C02718: EY Table PZT 2

MACL C02722: EY Table PZT 1 (test previously and seen similar results to MCL C02718)

The three PZT's (two on EY, one on EX) have a range from 0 to 10V. Another 0 to 10 V will be placed on EX. Important note: the controller must be hooked up to it's respective PZT in order to be properly tested.

It's been a few days since either activity has been mentioned, therefore:

ITMx cartridge cleanroom has been cleared for access and the suspension is clamped, shielded, and bagged in prep for the flight likely to happen ~Monday.  We still wait for elliptical baffle work to conclude before parking the ITMx cartridge in the baffle's alignment line-of-sight.

ETMx in-chamber alignment is still on hold after a stack up of longitudinal errors was found late last week.  Two possible paths forward of where to take up the residual error (14mm) are under consideration.

In preperation for trying out some HEPI to ISI tilt decoupling I've modified Hugo's controller in the X direction to be more like what we have decided will be the "standard" HEPI-PS controller

It now has a close to 5Hz UUG and some what less gain peaking

Black and Pink are the old Open loop and Suppression

Red and Blue are the current Open Loop and Suppression

  Hopefully the rest of the DOFs will get upgraded soon.

Looking at the counts since the dust monitor software change (alog 8055), I noticed that some of these channels have started picking up 'noise'.

It appears on the .3 micron counts in the first attached plot for the following channels:

Ch 1: H0:PEM-CS_DUST_DR1_300NM_PCF
Ch 3: H0:PEM-CS_DUST_LAB2_300NM_PCF
Ch 5: H0:PEM-CS_DUST_LVEA4_300NM_PCF
Ch 8: H0:PEM-CS_DUST_LVEA16_300NM_PCF
Ch 9: H0:PEM-EX_DUST_VEA1_300NM_PCF

It appears on both the .3 micron and .5 micron counts in the other three attached plots.

While the install work is taking place along the X-manifold I have de-energized the optical lever power supplies for HAM2, HAM3, Beamsplitter and ITMY (okayed by Thomas Vo).

(Daniel, Alexa)

We have installed all the RF cables on the field and remote racks at EX for ISC. We still need to intall the RF cables that go from the field rack onto the table. There are also some short cables missing:

1 x DB37 - 6 ft (for RF Amp concentrator)

2 x BD25 - 5 ft (for RF Amp concentrator to RF oscillators)

1 x DB15 - 3 ft (to phase frequency discrimantor from port 1 of demod concentrator)

1 x DB14 - 5 ft (to demod from port 2 of demod concentrator)

1 x DB37 - 3 ft (for timing concentrator; to replace a 5ft cable)

There is also a long cable missing from the RF Pre Amplifier (D1201294) to the concentrator.

We also noticed that the 71 MHz RF Oscillator did not seem to be properly tuned.

Roof work is progressing well.

The first 3 photos show a mid station ready for sheet metal trim installation. All four out buildings are at this stage.

Other photos show the upper level of the LVEA about 1/2 covered with membrane and the lower part (OSB) staged with materials.

cdsfs1 locked up again Wed morning, with the same symptoms it has had in the past when the RAID controller hangs.  I reviewed the logs, but they did not provide any additional clues (other than what we know from previous cases).  I've verified that we are running the current tools versions for the card in the OS.

I've upgraded the firmware to the latest release, 4.10.00.027, as the installed version was rather old.  We will see if this improves things; it may be that we picked up an upstream kernel driver update when upgrading the OS that required the firmware to be upgraded, and we've missed this fact.  That may explain why cdsfs1 has historically been 'more unreliable', because we've updated the OS on cdsfs1 much earlier, and more often.  But this is largely speculation.  We will just have to wait to see if this improves things.

The GV7 annulus has been vented in preparation for spool removal. PT134(beam tube side of valve) held steady at 3e-9 torr while venting.

For future reference I took a spectrum of the 5 HSTS (MC1 MC2 MC3 PR2 PRM) from monday morning before the corner station was vented.

The isolation and damping on HAM2 and HAM3 ISIs were ON, and feedforward was OFF. The suspensions damping loops were closed. The chambers were under vacuum.

The attached pdf shows a comparison between the 5 HSTS, for every "mass" levels (M1 M2 and M3) and every degree of freedom.

Few things to notice on the plot :

- The performances are really consistent from one chamber to an other

- Signal is really close to sensor noise, especially at the bottom mass

- There is an interesting feature between ~0.1Hz and ~1Hz seen for longitudinal transverse and vertical dofs. This is something I would need to double check, but I'm pretty sure it is transmitted ground motion.

(Kiwamu, Stefan)

Triggered by Anamaria (https://alog.ligo-la.caltech.edu/aLOG/index.php?callRep=8984) 
we looked into whether we see the same excess noise when the demodulators are driven by 135MHz.

Short answer: yes - it seems to be a characteristic intrinsic to the demod board design.

Long answer:

1) We switched the LO of the 135MHz and 27MHz. The noise stayed with the 135MHz (i.e. both demod boxes act identical).
2) We verified the demodulation gain on the 135MHz board: 6.0mVpkk of RF into the PD input produced 33mVpkk at the monitoring point. That's 14.8dB gain, or a factor of 5.5.
3) The digital gain after this is x2 (single to differential on the demod board) x 10^(45/20) (whitening gain) x 2^16cts/V = 583kcts/V. We measured about 560kcts/V. We put its inverse - 1.8e-6V/ct - as calibration factor into the input filter modules.
4) Plot 1 shows the terminated demod noise, referred to the demod mon point, for the 135MHz and the 27MHz demodulators. To compare to Anamaria's numbers, divide by 5.5 to refer to the demod input.
5) Plot 2 shows the same thing, but taken in analog at the demod monitoring point. The noise agrees. We also verified that there are no outrageous high frequency signals - the largest signal is not surprisingly at 135MHz, with -63dBm at the monitoring point. There is also a 410MHz signal with -73dBm.
6) We also verified that the LO signals look clean - there were no competing peaks. We also took a hi-res spectrum around the carrier - at 100Hz offset from the carrier we have 95dBc/Hz for the 135MHz (-99dBc/Hz for the 27MHz), plots 3-6.

In summary , we cant find anything wrong with the LO signal or the sensing chain - the problem is most likely intrinsic to the design.

- 8:40 Fred escorting visitors out on LVEA (laser safe)
- Praxair inspecting cryo-tubes
- Rick and ¿Peter K.? inside H2 PSL since early morning
- Apollo working at BSC3
- "Roofers" after yesterday's shower, works continue
- 11:30 EX clean toilet
- Micheal L. escorting an "IEEE interviewer" (if I understand correctly)
- 12:00 Cheryl in OSB Optics Lab
- 12:40 Dave reconfigured h1nds0 (read only science framed) so Hugo can perform some tests. (check entry 8064)
- Nchole W., Scott S., and Thomas V. going into BSC2 through BSC3 and do "baffle's" work
 

Nice day, wasn't it?

pablo

The dome and east door of the BSC 3 chamber was removed and walking plates were placed on the work platform. These have not been installed because we have not located the C channel pieces that bolt to the walking plates so the C 3 cover can be secured to the walking plates. We also installed the permanent flooring in BSC 3 chamber. We installed the soft roof that was on the BSC 3 clean room onto the clean room over the cryo pump spool. The SEI soft roof "sock" is on the clean room over BSC 3.

HughR, HugoP, 

Here is the current status of the aLIGO SEI work at Hanford. Everything in red is a change from last status. Everything in green is available.