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13513   Sun Jan 7 11:40:58 2018 KevinUpdatePonderSqueezeDisplacement requirements for short-term squeezing

Yes, this SRC detuning is very close to extreme signal recycling (0° in this convention), and the homodyne angle is close to the amplitude quadrature (90° in this convention).

For T(SRM) = 5% at the optimal angles (SRC detuning of -0.01° and homodyne angle of 89°), we can see 0.7 dBvac at 210 Hz.

13514   Sun Jan 7 17:27:13 2018 gautamUpdatePonderSqueezeDisplacement requirements for short-term squeezing

Maybe you've accounted for this already in the Optickle simulations - but in Finesse (software), the "tuning" corresponds to the microscopic (i.e. at the nm level) position of the optics, whereas the macroscopic lengths, which determine which fields are resonant inside the various cavities, are set separately. So it is possible to change the microscopic tuning of the SRC, which need not necessarily mean that the correct resonance conditions are satisfied. If you are using the Finesse model of the 40m I gave you as a basis for your Optickle model, then the macroscopic length of the SRC in that was ~5.38m. In this configuration, the f2 (i.e. 55MHz sideband) field is resonant inside the SRC while the f1 and carrier fields are not.

If we decide to change the macroscopic length of the SRC, there may also be a small change to the requirements on the RoCs of the RC folding mirrors. Actually, come to think of it, the difference in macroscopic cavity lengths explains the slight differences in mode-matching efficiencies I was seeing between the arms and RCs I was seeing before.

 Quote: Yes, this SRC detuning is very close to extreme signal recycling (0° in this convention), and the homodyne angle is close to the amplitude quadrature (90° in this convention). For T(SRM) = 5% at the optimal angles (SRC detuning of -0.01° and homodyne angle of 89°), we can see 0.7 dBvac at 210 Hz.

13515   Sun Jan 7 20:11:54 2018 KojiUpdatePonderSqueezeDisplacement requirements for short-term squeezing

In fact, that is my point. If we use signal recycling instead of resonant sideband extraction, the "tuning" of the SRC is opposite to the current setup. We need to change the macro length of the SRC to make 55MHz resonant with this tuning. And if we make the SRC macro length together with the PRC macro length for this reason, we need to thing again about the mode matching. Fortunately, we have the spare PRM (T=5%) which matches with this curvature. This was the motivation of my question. We may also choose to keep the current SRM because of its higher T and may want to evaluate the effect of expected mode mismatch.

13808   Thu May 3 00:42:38 2018 KevinUpdatePonderSqueezeCoil driver contribution to squeezing noise budget

In light of the discussion at today's meeting, Guantanamo and I looked at how the series resistance for the test mass coil drivers limits the amount of squeezing we could detect.

The parameters used for the following calculations are:

• 4.5 kΩ series resistance for the ETM's (this was 10 kΩ in the previous calculations, so these numbers are a bit worse); 15 kΩ for the ITM's
• 100 ppm transmissivity on the folding mirrors giving a PRC gain of 40
• PD quantum efficiency of 0.88

Since we need to operate very close to signal recycling, instead of the current signal extraction setup, we will need to change the macroscopic length of the SRC. This will change the mode matching requirements such that the current SRM does not have the correct radius of curvature. One solution is to use the spare PRM which has the correct radius of curvature but a transmissivity of 0.05 instead of 0.1. So using this spare PRM for the SRM and changing the length of the SRC to be the same as the PRC we can get

• 0.63 dBvac of squeezing at 205 Hz for 1 W incident on the back of PRM
• 1.12 dBvac of squeezing at 255 Hz for 5 W incident on the back of PRM

This lower transmissivity for the SRM also reduces the achievable squeezing from the current transmissivity of 0.1. For an SRM with a transmissivity of 0.15 (which is roughly the optimal) we can get

• 1 dBvac of squeezing at 205 Hz for 1 W incident on the back of PRM
• 1.7 dBvac of squeezing at 255 Hz for 5 W incident on the back of PRM

The minimum achievable squeezing moves up from around 205 Hz at 1 W to 255 Hz at 5 W because the extra power increases the radiation pressure at lower frequencies.

13841   Mon May 14 18:58:32 2018 KevinUpdatePonderSqueezeSqueezing with no SRM
 Quote: Note that for Signal Recycling, which is what Kevin tells us we need to do, there is a DARM pole at ~150 Hz.

To be quantitative, since we are looking at smaller squeezing levels and considering the possibility of using 5 W input power, it is possible to see a small amount of squeezing below vacuum with no SRM.

Attachment 1 shows the amount of squeezing below vacuum obtainable as a function of homodyne angle with no SRM and 5 W incident on the back of PRM. The optimum homodyne angle at 210 Hz is 89.2 deg which gives -0.38 dBvac of squeezing. Figure 2 is the displacement noise at this optimal homodyne angle and attachment 3 is the same noise budget shown as the ratio of the various noise sources to the unsqueezed vacuum.

The other parameters used for these calculations are:

• 4.5 kΩ series resistance for the ETM coils; 15 kΩ for the ITM coils
• 100 ppm transmissivity on the folding mirrors giving a PRC gain of 40
• PD quantum efficiency of 0.88

So maybe it's worth considering going for less squeezing with no SRM if that makes it technically more feasible.

Attachment 1: homodyne_heatmap.pdf
Attachment 2: displacement_noise.pdf
Attachment 3: noise_budget.pdf
14225   Tue Oct 2 23:57:16 2018 gautamUpdatePonderSqueezeSqueezing scenarios

[kevin, gautam]

We have been working on double checking the noise budget calculations. We wanted to evaluate the amount of squeezing for a few different scenarios that vary in cost and time. Here are the findings:

## Squeezing scenarios

Sqz [dBvac] fmin [Hz] PPRM [W] PBS [W] TPRM [%] TSRM [%]
-0.41 215 0.8 40 5.637 9.903
-0.58 230 1.7 80 5.637 9.903
-1.05 250 1.7 150 1 17
-2.26 340 10 900 1 17

All calculations done with

• 4.5kohm series resistance on ETMs, 15kohms on ITMs, 25kohm on slow path on all four TMs.
• Detuning of SRC = -0.01 deg.
• Homodyne angle = 89.5 deg.
• Homodyne QE = 0.9.
• Arm losses is 20ppm RT.
• LO beam assumed to be extracted from PR2 transmission, and is ~20ppm of circulating power in PRC.

Scenarios:

1. Existing setup, new RC folding mirrors for PRG of ~45.
2. Existing setup, send Innolight (Edwin) for repair (= diode replacement?) and hope we get 1.7 W on back of PRM.
3. Repair Innolight, new PRM and SRM, former for higher PRG, latter for higher DARM pole.
4. Same as #3, but with 10 W input power on back of PRM (i.e. assuming we get a fiber amp).

Remarks:

• The errors on the small dB numbers is large - 1% change in model parameters (e.g. arm losses, PRG, coil driver noise etc) can mean no observable squeezing.
• Actually, this entire discussion is moot unless we can get the RIN of the light incident on the PRM lower than the current level (estimated from MC2 transmission, filtered by CARM pole and ARM zero) by a factor of 60dB.
• This is because even if we have 1mW contrast defect light leaking through the OMC, the beating of this field (in the amplitude quadrature) with the 20mW LO RIN (also almost entirely in the amplitude quad) yields significant noise contribution at 100 Hz (see Attachment #1).
• Actually, we could have much more contrast defect leakage, as we have not accounted for asymmetries like arm loss imbalance.
• So we need an ISS that has 60dB of gain at 100 Hz.
• The requirement on LO RIN is consistent with Eq 12 of this paper.
• There is probably room to optimize SRC detuning and homodyne angle for each of these scenarios - for now, we just took the optimized combo for scenario #1 for evaluating all four scenarios.
• OMC displacement noise seems to only be at the level of 1e-22 m/rtHz, assuming that the detuning for s-pol and p-pol is ~30 kHz if we were to lock at the middle of the two resonances
• This assumes 0.02 deg difference in amplitude reflectivity b/w polarizations per optic, other parameters taken from aLIGO OMC design numbers.
• We took OMC displacement noise from here.

Main unbudgeted noises:

• Scattered light.
• Angular control noise reinjection (not sure about the RP angular dynamics for the higher power yet).
• Shot noise due to vacuum leaking from sym port (= DC contrast defect), but we expect this to not be significant at the level of the other noises in Atm #1.
• Osc amp / phase.
• AUX DoF cross coupling into DARM readout.
• Laser frequency noise (although we should be immune to this because of our homodyne angle choice).

Threat matrix has been updated.

Attachment 1: PonderSqueeze_NB_LORIN.pdf
15688   Tue Nov 24 16:51:29 2020 gautamUpdatePonderSqueezePonderomotive squeezing in aLIGO

Summary:

On the call last week, I claimed that there isn't much hope of directly measuring Ponderomotive Squeezing in aLIGO without some significant configurational changes. Here, I attempt to quantify this statement a bit, and explicitly state what I mean by "significant configurational changes".

Optomechanical coupling:

The I/O relations will generally look something like:

$\begin{bmatrix} b_1\\ b_2 \end{bmatrix} = \begin{bmatrix} C_{11} & C_{12}\\ C_{21} & C_{22} \end{bmatrix} \begin{bmatrix} a_{1}\\ a_2 \end{bmatrix} + \begin{bmatrix} D_1\\ D_2 \end{bmatrix} \frac{h}{h_{\mathrm{SQL}}}$.

The. magnitudes of the matrix elements C_12 and C_21 (i.e. phase to amplitude and amplitude to phase coupling coefficients) will encode the strength of the Ponderomotive squeezing.

For the inital study, let's assume DC readout (since there isn't a homodyne readout yet even in Advanced LIGO). This amounts to setting $\zeta = \phi$ in the I/O relations, where the former angle is the "homodyne phase" and the latter is the "SRC detuning". For DC readout, the LO quadrature is fixed relative to the signal - for example, in the usual RSE operation, $\zeta = \phi = \frac{\pi}{2}$. So the quadrature we will read out will be purely $b_1$ (or nearly so, for small detunings around RSE operation). The displacement noises will couple in via the $D_1$ matrix element. Attachment #1 and Attachment #2 show the off-diagonal elements of the "C" matrix for detunings of the SRC near RSE and SR operation respectively. You can see that the optomechanical coupling decays pretty rapidly above ~40 Hz.

SRC detuning:

In this particular case, there is no benefit to detuning the SRC, because we are assuming the homodyne angle is fixed, which is not an unreasonable assumption as the quadrature of the LO light is fixed relative to the signal in DC readout (not sure what the residual fluctuation in this quantity is). But presumably it is at the mrad level, so the pollution due to the orthogonal anti-squeezed quadrture can be ignored for a first pass I think. I also assume ~10 degrees of detuning is possible with the Finesse ~15 SRC, as the linewidth is ~12 degrees.

Noise budget:

To see how this would look in an actual measurement, I took the data from Lee's ponderomotive squeezing paper, as an estimate for the classical noises, and plotted the quantum noise models for a few representative SRC detunings near RSE operation - see Attachment #3. The curves labelled for various phis are the quantum noise models for those SRC detunings, assuming DC readout. I fudged the power into the IFO to make my modelled quantum noise curve at RSE line up with the high frequency part of the "Measured DARM" curve. To measure Ponderomotive Squeezing unambiguously, we need the quantum noise curve to "dip" as is seen around 40 Hz for an SRC tuning of 80 degrees, and that to be the dominant noise source. Evidently, this is not the case.

The case for balanced homodyne readout:

I haven't analyzed it in detail yet - but it may be possible that if we can access other quadratures, we might benefit from rotating away from the DARM quadrature - the strength of the optomechanical coupling would decrease, as demonstrated in Attachments #1 and #2, but the coupling of classical noise would be reduced as well, so we may be able to win overall. I'll briefly investigate whether a robust measurement can be made at the site once the BHD is implemented.

Attachment 1: QN_heatmap_RSE.pdf
Attachment 2: QN_heatmap_SR.pdf
Attachment 3: noiseBudget.pdf
4503   Fri Apr 8 01:05:45 2011 SureshUpdateRF SystemRF Source Harmonics

The measured power levels of the RF source harmonics are given below:

We are considering inclusion of bandpass filters centered on 11 and 55 MHz  to suppress the harmonics and meet the requirements specified in Alberto's thesis (page 88).

Attachment 1: RF_Source_Harmonics_Sheet1.pdf
4511   Mon Apr 11 19:09:59 2011 SureshUpdateRF SystemInstalled low pass filters in the demod boards

As part of the RF system upgrade some of the demod boards in the lab were modfied.  The filter U5 (see the circuit schematic) was replaced. These changes are tabulated below.

 Serial number Old name of the card New name of the card Filter installed Remarks 107 POY33 REFL33 SCLF-33+ R14=50Ohm 118 AP133, ASDD133 REFL55 SCLF-65 114 PO199 REFL165 SCLF-190 R14=50Ohm 120 PO133 POP110 SCLF-135 123 SP133 POP55 SCLF-65+ AT1 removed, R14=50Ohm 122 SP199, REFLDD199 AS165 SCLF-190 121 SP166, REFL16 POP11 SCLF-10.7 116 AP199 199 MHz POP165 SCLF-190 126 AS166 33.3 MHz POX11 SCLF-10.7 119 POX 33.3 MHz POY11 SCLF-10.7 021 24.5 MHz (LLO) REFL11 SCLF-10.7 020 24.5 MHz SCLF-45 POP22 SCLF-21.4 022 24.5 MHz SCLF-45 AS11 with amp SCLF-10.7 029 24.5          SCLF-f5 AS55 with amp SCLF-65

Next, I and Q phase has to be checked for orthogonality. And noise levels of the cards have to measured.

4514   Mon Apr 11 23:35:02 2011 ranaUpdateRF SystemInstalled low pass filters in the demod boards

I am a little concerned about using these low pass filters so close to the band edge. Recall that there is no on-board preamp for the RF input to the mixer.

So, if the input impedance of the filters is not 50 Ohms, we will get some unwanted reflections and sensitivity to cable length.

I think its worth while to check the impedance or S-parameters of these things with the LO activated to find out if we need to remove them or not.

4547   Wed Apr 20 21:53:01 2011 SureshConfigurationRF SystemRF system: Stray heliax cable

We found a stray unused heliax cable running from the LSC rack 1Y2 to a point between the cabinets 1X3 and 1X4. This cable will need to be redirected to the AS table in the new scheme.   It is labled C1LSC-PD5  The current situation has been updated as seen in the layout below

Attachment 1: rogue_cable_1.png
4548   Wed Apr 20 22:29:07 2011 sureshUpdateRF SystemPlan for LSC rack

The suggested layout of the 1Y2 Rack is shown below.

To simplify the wiring, I have largely kept demod boards with the same same LO frequency close to each other.

The Heliax cables land on the top and bottom of the of subracks.  These are currently flexible plastic sheets.  Steve has agreed to replace them with something more rigid.  It would be good to have eight N-type connectors on the top and eight  at the bottom.  As  demod boards occur in sets of eight per subrack.  So it would be convenient if the 11 and 55 Mhz Heliax cables land on the top and the rest at the bottom.  In the layout I have shown the current situation.

The LO signals to the boards come from the RF Distribution box and this is kept in the middle so that cables to both the subracks can be kept short.

The outputs of the AA filter boards from both subracks  have to be connected to the SCSI Interface board with a twisted pair ribbon cable.

4551   Thu Apr 21 14:39:43 2011 steveUpdateRF Systemnew strain relieved N connectors at AP

New right angle PVC, 2 x 2 x  1/4" installed at the AP table to strain relief the 1/4" spiral corrugated RF coaxes.

Attachment 1: P1070562.JPG
Attachment 2: P1070564.JPG
4557   Fri Apr 22 09:05:53 2011 SureshUpdateRF SystemRF Source Harmonics
As seen in the previous measurement the first harmonic of both the 11 MHz and 55 MHz outputs are about 30dB
higher than desired.  In an attempt to attenuate these and higher harmonics I introduced SBP-10.7 filters into
the 11MHz outputs and SLP-50 filters into the 55 MHz outputs.
Then I measured the height of the harmonics again and found that they were suppressed as expected.  Now harmonic
at 22 MHz is 58dB lower than the 11 MHz fundamental.  And the 110 MHz is lower by 55 dB compared to the 55 MHz
fundamental.  None of the higher harmonics are seen => they are below 70dB

SLP-50 has an insertion loss(IL) of 4.65 dB and Return Loss(RL) of 3dB.  It would be better to use SBP-60
(IL=1.4 dB and RL=23dB)

The filter on the 11 MHz lines is okay. The SBP-10.7 has IL=0.6 dB and RL=23 dB.
4558   Fri Apr 22 09:25:43 2011 SureshUpdateRF SystemRF Source: Temperature sensor relocated

RF Amp operating temperature

Earlier measurement reported by Alberto in LIGO-T10004-61-v1 based on the LM34 temperature sensor were lower than that shown by placing a calibrated thermocouple sensor directly on the heat sink by about 5deg C. The difference probably arose because the LM34 was located on a separate free-hanging copper sheet attached to the RF Amp by a single screw, resulting in a gradient across the copper strip.   I tried to move the LM34 which was glued down, but broke the leads in the process.  I then replaced it with another one mounted much closer to the heat sink and held it down with a copper-strip clamp.  There is no glue involved and there is heatsink compound between the flat surface of the LM34 and the heatsink.  Picture attached.

The picture also shows the new filters which have been put in place to reduce the harmonics.  Note that the SBP-10.7 which was to go on the 11 MHz Demod output is located much farther upsteam due to space constraints.

4559   Fri Apr 22 10:28:22 2011 ranaUpdateRF SystemRF Source Harmonics
You should be able to resolve the other harmonics by decreasing the IF BW or RBW on the analyzer. Even though
they're OK, its useful to have the final measurement of all of them in some kinds of physical units (like dBm, but
not dBm/Hz or dB or dBcubits).
4578   Thu Apr 28 06:46:30 2011 SureshUpdateRF SystemRF Source installed

RF Source box has been mounted in the 1X2 rack.

Heliax cables have been directly attached to the box and anchored on the side of the 1X2 rack.  Here is a list of Helix cables which have been connected so far.

 Cables old name New name From -> To 1 133 MHz 11 Mhz Demod 1X2 to 1Y2 rack 2 199 MHz 55 MHz Demod 1X2 to 1Y2 rack 3 166 EOM 11 MHz EOM 1X2 to PSL table 4 33 EOM 55 MHz EOM 1X2 to PSL table 5 REFL 33 AS11 AS table to 1Y2

4579   Thu Apr 28 07:14:34 2011 SureshUpdateRF SystemRF Distribution box installed

RF Distribution box has been mounted in the 1Y2 rack and is ready for use.

The box receives 11 and 55 MHz Demod Signals from the RF source located in the 1X2 rack.

4591   Fri Apr 29 18:24:05 2011 SureshUpdateRF SystemRF system: 1X2 Rack cabling

[Joe, Jamie, Suresh]

We have installed the IDE to SCSI adaptor module into the 1X2 rack and have connected the AA filter outputs to it.

We have removed the following cables running between the 1X2 and 1X3 racks.

The long twisted pair ribbon cable which previously carried the ADC signals.

1X2-ASC 6, 1X2-ASC 47, 1X2-ASC 9, 1X2-ASC 8, 1X2-ASC 10, 1X2-ASC 7,

CAB-1X2-LSC 42, CAB 1X2-LSC 56,  CAB 1X2-LSC 41, CAB 1X2-LSC 43

1X3-2 ASC 47

We have also removed the following by mistake.  We will put them back them on Monday

1X2-LSC 21, 1X2-LSC-20.

We have also removed the ASC QPD cables and moved the QPD cards which were present in the middle Eurocate (#2) to the unused Eurocrate at the bottom position (#3).

The binary input cables at the back of the cards require to be supported so that their weight does not pull them out of the sockets at the back of the crates.

Some of the slots where we plan to plug in Demod boards (the 165 MHz boards)  are not currently connected to any binary output on the C1:LSC computer.  We need these binary controls for the fitlter modules on the cards.

When we eventually begin to use the 15PDs as planned, then we will occupy 30 ADC channels (I & Q outputs).  Currently we have just one ADC card installed on the C1:LSC providing 32 ADC channels.  Joe found another 16bit 32 channel ADC card in his stash but we need to get a timing+adaptor board for it. In general we are going to need the third Eurocrate.

A platform for the power supply of the RF Distribution box needs to be built and the power supply needs to be moved into the 1X2 rack rather than sit on top of 1X2 rack.

4622   Wed May 4 12:07:48 2011 SureshUpdateRF SystemREFL55 installed on the AP table

REFL55 has been installed on the AP table.  REFL11 has been moved to make space for a 50% beam splitter. The reflected beam from this splitter is about 30% of the transmitted beam power.  The reflected beam goes to REFL11 in the current configuration.  The DC levels are 1.2V on REFL 11 and 3.5V on the REFL55.

I redid some of the cabling on the table because the we need to choose the heliax cables such that they end up close to the demod board location.  As per the 1Y2 (LSC) rack layout given here, some of the PD signals have to arrive at the top and others at the bottom of the LSC rack.

Currently the PDs are connected as follows:

REFL11 PD --> Heliax (ASDD133) (arriving at the top of LSC rack) --> REFL11 Demod Board

REFL55 PD --> Heliax (REFL166) (arriving at the top of LSC rack) --> AS55 Demod Board

AS55 PD --> Heliax (AS166) (arriving at the top of the LSC rack) --> not connected.

We are waiting for the Minicircuits parts to modify the rest of the demod boards.

The heliax cables arriving at the LSC rack are not yet fixed properly.  I hope to get this done with Steve's help today.

4628   Wed May 4 15:39:32 2011 SureshUpdateRF SystemRF Source Harmonics

I have measured the RF source harmonics in dBm using the HP 8591E spectrum analyser. There is a small discrepancy (< 1 dBm) in the value of RF power shown by the power meter and the HP8591E. This is probably due to the loss of calibration over time.

Initial problem I faced was that when we try to measure the weak harmonics, many below -50dBm we have to choose a small band as advised by Rana. However due to the large amplitide of the fundamental typically around 15dBm or so, the preamp on the spectrum analyser becomes saturated and nonlinear. This gives rise spurious harmonics not present in the source but are rather an aritifact of measurement. The power in harmonics to avoid this I used filters to selectively attenuate the fundamental component (11 or 55 MHz) and then measure the weak harmonics.

However the filters proved difficult to use, because over their stop-band they do not have an input impedance of 50 Ohm. As a result they produce unreliable power measurements for those frequency components which are within the stop band.

To get around this problem I used a suitable attenuator so that even when the internal attenuation is decreased the preamp does not saturate

All the measurements are recorded in the attached document. Pages 4 and 5 give the reliable measurements with the attenuator.

Notes:
1) At times we can see the 29.5 MHz component reflected back from the triple resonant EOM driver.
2) In the 29.5 MHz source output there is a forest of peaks around 100 MHz, which disappear after passing through the AM stabiliser. This suggests that they are associated with AM modulation and have been removed by the stabilizer. But I did not check this further.

 Quote: You should be able tosd resolve the other harmonics by decreasing the IF BW or RBW on the analyzer. Even though they're OK, its useful to have the final measurement of all of them in some kinds of physical units (like dBm, but not dBm/Hz or dB or dBcubits).
Attachment 1: RF_Harmonics_Sheet1.pdf
4644   Thu May 5 15:33:37 2011 steveConfigurationRF SystemLSC rack

New right angle PVC front panel with SMA bulkhead connectors are in place. The connections are still lose. It is ready for Suresh to finalise his vision on it.

Attachment 1: P1070641.JPG
Attachment 2: P1070639.JPG
4650   Fri May 6 06:36:18 2011 SureshUpdateRF SystemPD DC signals at each port connected

We now have the DC signal from three PDs available in the ADC channels 14,15 and 16.  The signals are from  REFL55, AS55 and POY photodiodes respectively.  As the DC signals on all the other PDs of the same port (REFL, AS and PO)  have the same information we do not need to monitor more than one DC PD at each port.

The LSC PD Interface Card, D990543 - Rev B, can take 4 PDs and provides the DC signals of the PDs on the connector P2 (the lower of the two) on the back plane of the chassis. An adaptor card, D010005-00, plugs into the back plane from the rear of the Eurorack and provides the four DC signals on two-pin lemo sockets.

I have connected the three DC signals from the relevant RF PDs (above) to a DC whitening filter, D990694-B-1 which is associated with the channels 9 to 16 of the ADC card.

The cables are in a bit of a mess right now as some of the PD power supply lines are too short to reach up the the Interface card in the top Eurocart. Steve and I plan to redo some of the cabling later today

4657   Sat May 7 10:59:11 2011 SureshUpdateRF SystemRF Source filters changed

The SLP-50 filters which were on the 55 MHz lines have been replaced with the SBP-60.  Their respective characteristics are given below:

 at 55MHz Insertion loss (dB) Return Loss (dB) SLP-50 4.65 1.5 SBP-60 1.36 23

SBP-60 has lower insertion loss and higher return loss.

This may however change the phase of I and Q in the demod boards and they will therefore need to be readjusted.  Currently the output power level of 55 MHz demod is at 2dBm, whereas it ought to be at 6dBm.   I have not yet corrected that.  Once that is completed Kiwamu will adjust the phases.

I shifted the temperature sensor to a new location.  See the photograph below.  I noticed that the higher temperature is reached on the side where there are two RF Amps.  So it would be better to check the temperature of that  area and make sure that it remains well below 65 deg.  The operating maxium is 65deg C

Here is a picture of the new RF source layout.

And here is a photograph of it

4670   Mon May 9 17:23:25 2011 SureshUpdateRF SystemRF Cables near LSC Rack

[Steve, Suresh]

We started to clean up the RF cables (heliax and PD interface cables)  at the LSC rack.

We have pulled out all the RF cables from the small hole on the side-board close to floor.  Passing the cables through this hole makes some of the cables much too short for good strain relief.  So we removed the side panel on the vacuum tube side and are going to pass the cables into the rack from there at about waist height.  We now have plenty of cable lengths to tie them off to the rack at several points.

We have traced all the available Heliax cables and have attached blank tags to them.  We have allocated some cables to REFL11, REFL55 and AS55.  These are therefore back in working order.  We have also taken stock of the available PD interface cables.  They do not have consistent names on both ends of the cable and we will identify and label the ends tomorrow.

MC is locked.  The auto-locker works fine.

Handing over the system for night time interferometer work now.  Will continue with the cabling tomorrow.

4675   Tue May 10 01:39:41 2011 SureshUpdateRF SystemRF source troubles

Today after Steve and I finished the RF cabling work for the day, Kiwamu noticed that there were no RF signals to be seen.  The problem was traced to disconnected 11 and 55 MHz Demod lines from the RF source.  But reconnecting them did not restore the signals.  It turned out that one of the Heliax cables had a loose N-type connector at its end and it finally came off while we were tightening it into place.

We replaced the damaged heliax with another (we have two spare running from 1X2 IOO rack to the 1Y2 LSC rack.  The new cable is used to be the LO 33.  It seems to have a 1.5dB loss.  Have to check this again tomorrow.

In the mean time I noticed that the power output of the 55MHz Demod port of the source was less than about -12dB. So I opened the source to take a look and found that all the voltage stabilisers were supplying 15V.  Even those which were supposed to be supplying 24V.  This was traced to a mistake in wiring the external power supply.  The wires had been labeled wrongly and as a result the 18V input line was connected to 28V source and vice versa.

After fixing this problem I reassembled the source checked the power output on all the ports and found everything was functioning as expected.  However after installation once again the unit failed.  The blue light on the power supply was not lighting up when switched on.  Suspecting a power supply problem I opened the unit again and found that a weak solder joint on one of the RF amplifiers had come loose and had overloaded one of the 24V stabilisers.   We, found a spare and replaced it.  The unit has been reassembled and is functioning fine.  The output power levels are

11MHz Demod -- 6dBm

55MHz Demod -- 5.5 dBm

11MHz EOM --   24dBm

55MHz EOM -- 28dBm

The Marconi is serving as the 11MHz source.  The Wenzel 11MHz source is giving 13.3 dBm and is okay.  But it needs to be checked for its performance as it may have been exposed to higher than rated power supply levels.

The 29.5MHz source is giving 7dBm.  It is supposed to be giving 13dBm.

The Laboratory DC power supplies currently used for both the RF source and Distribution boxes need to be replaced with rack mounted Sorensen power supplies available in the lab.

4698   Thu May 12 02:31:07 2011 SureshUpdateRF Systeminstallation of RF splitters in Demod boards

[Jamie, Koji, Suresh]

We replaced splitters in several demod boards as per the table given below:

 Demod Board S. No. Power Splitter Frequency range of splitter (MHz) Phase unbalance from datasheet (deg) Amplitude Unbalance from datasheet (dB) REFL55 118 PQW-2-90 30 to 90 90.14 0.92 AS11 021 PSCQ-2-51W 5 to 50 87.49 0.1 POY11 119 PSCQ-2-32 3.2 to 32 87.58 0.05 POY22 020 PSCQ-2-32 3.2 to 32 90.26 0.02 POY110 120 PSCQ--120 80 to 120 90.88 0.58

While doing a rough check of the boards I noticed that the REFL11 demod board had no signal on the Q output.

Rana also advised that we must use the boards which have the piggy-back amplifiers on those signals which are most useful.  We referred to Alberto's thesis and chose POY55 (MICH and SRCL), REFL11(PRCL)  and AS55 (DARM) as the most useful signals.  We currently have these amps on AS11, REFL11 and AS55.  We need to convert either AS11 or REFL11 into a POY55.  Since we need to troubleshoot REFL11, I thought we might as well modify that and in the process also fix its Q output.  So I renamed AS11 as REFL11 and will convert the old REFL11 into POY55 tomorrow.

Power splitter of different types have different pin-outs.  The way we mount a splitter depends on which type we are using.   I will detail the mounting scheme in a separate elog tomorrow.

4702   Thu May 12 10:27:02 2011 ranaUpdateRF Systeminstallation of RF splitters in Demod boards

 Quote: Rana also advised that we must use the boards which have the piggy-back amplifiers on those signals which are most useful.  We referred to Alberto's thesis and chose POY55 (MICH and SRCL), REFL11(PRCL)  and AS55 (DARM) as the most useful signals.  We currently have these amps on AS11, REFL11 and AS55.  We need to convert either AS11 or REFL11 into a POY55.  Since we need to troubleshoot REFL11, I thought we might as well modify that and in the process also fix its Q output.  So I renamed AS11 as REFL11 and will convert the old REFL11 into POY55 tomorrow.

I think we should leave them as is; the AS11 was made by taking into account the SB levels at the AS port and should not become REFL11. We should instead convert one of the old 25 or 33 MHz diodes into a POY55.

4703   Thu May 12 16:50:22 2011 SureshUpdateRF Systeminstallation of RF splitters in Demod boards

We have no plan to change the AS11 PD. I was referring to the AS11 Demod board which currently has the "Demodulator Preamp" circuit installed as a piggy back. In future I will append "_Demod" when I am referring to a demod board, to avoid confusion.

Quote:

 Quote: Rana also advised that we must use the boards which have the piggy-back amplifiers on those signals which are most useful.  We referred to Alberto's thesis and chose POY55 (MICH and SRCL), REFL11(PRCL)  and AS55 (DARM) as the most useful signals.  We currently have these amps on AS11, REFL11 and AS55.  We need to convert either AS11 or REFL11 into a POY55.  Since we need to troubleshoot REFL11, I thought we might as well modify that and in the process also fix its Q output.  So I renamed AS11 as REFL11 and will convert the old REFL11 into POY55 tomorrow.

I think we should leave them as is; the AS11 was made by taking into account the SB levels at the AS port and should not become REFL11. We should instead convert one of the old 25 or 33 MHz diodes into a POY55.

4708   Thu May 12 23:50:10 2011 SureshUpdateRF SystemPOY55_Demod board Hardware change completed

The Demod board with S. No. 022 (being used earlier as REFL11) has been modified.  It now has SCLF-65 as its input LP filter on the PD input line and a PQW-2-90 power splitter.  The unit functioning okay (I and Q signals are 90 deg apart.

The loss of Q output was traced to a possible loose solder joint and we now have both the I and Q signals after resoldering all components in the vicinity of U7 (Ref Schematic of D990511)

There is a strong oscillation around 350Hz present on I and Q signals of both REFL55_Demod and POY55_Demod.  Don't know the source.

We have run out of power splitters to continue with the Demod board modification. We do not currently have an AS11_Demod board.  All the others are in place and ready for the I<->Q phase angle measurement.

In summary we now have the following Demod boards in place:

[ REFL11, POY11, REFL55, AS55, POY55, POY22, POY110]_Demod

4711   Fri May 13 01:51:56 2011 SureshUpdateRF SystemRF Status update

I have posted the attached RF status update and 1Y2 rack layout to the svn.

Attachment 1: 1Y2_Rack_Layout.pdf
Attachment 2: RF_Work_Status.pdf
4714   Fri May 13 22:45:37 2011 SureshUpdateRF SystemThe full set of 8 Demod boards is ready for testing

We have Completed the hardware changes to the full set of 8 demod boards.  The last one completed today is AS11.  I have collected the info on all the demod boards available so far in the table below.  As we measure the actual phase and amplitude unbalance we will expand this table to include new info.

 Demod Board S. No. Power Splitter Frequency range of splitter (MHz) Phase unbalance from datasheet (deg) Amplitude Unbalance from datasheet (dB) AS11 121 PSCQ-2-51W 5 to 50 87.49 0.1 REFL11 021 PSCQ-2-51W 5 to 50 87.49 0.1 POY11 119 PSCQ-2-32 3.2 to 32 87.58 0.05 AS55 029 PSCQ-2-51W 5 to 50 no info no info REFL55 118 PQW-2-90 30 to 90 90.14 0.92 POY11 119 PSCQ-2-32 3.2 to 32 87.58 0.05 POY22 020 PSCQ-2-32 3.2 to 32 90.26 0.02 POY110 120 PSCQ--120 80 to 120 90.88 0.58

4715   Fri May 13 23:04:58 2011 SureshUpdateRF SystemDC power supply on RF distribution box has been replaced.

[Steve, Koji, Suresh]

We shifted two Sorensen power supplies from the Auxiliary rack next to 1X2 to 1Y2.  And have installed them there (pic below).  The local ground reference was picked up from the racks ground reference.  A shielded cable with two twisted pairs was used to make a new power cable for the RF rack.  Since we are using three of the four conductors (+18,+28 and ground), one of them is not connected to anything.  This situation can be improved in a future iteration when, for example, we might wish to relocate the Sorensens to a different rack.

We are still working on changing the power supply to the RF source.  Will complete this early next week

4716   Sat May 14 14:12:16 2011 KojiUpdateRF SystemDC power supply on RF distribution box has been replaced.

### Key points of the power supply installation

• We followed the grounding configuration for KEPCO except for the signal ground connection
• AC power supply has been obtained from the local power strip. This also provides chassis earthing (for safety)
• The chassis is connected to the shieldin of the DC supply cable. The other end should be isolated.
• The low voltage side of Sorensen's DC outputs are connected in order to share the same reference  level.
• The ground level is provided from the cross connect. The cable is connected between the cross connect ground to the sorencen.
Unlike the KEPCO case, this cable does not have the current return, but just is to define the voltage level of those Sorensens.
• New AC&DC cables have been nicely strain-relieved.

 Quote: [Steve, Koji, Suresh]    We shifted two Sorensen power supplies from the Auxiliary rack next to 1X2 to 1Y2.  And have installed them there (pic below).  The local ground reference was picked up from the racks ground reference.  A shielded cable with two twisted pairs was used to make a new power cable for the RF rack.  Since we are using three of the four conductors (+18,+28 and ground), one of them is not connected to anything.  This situation can be improved in a future iteration when, for example, we might wish to relocate the Sorensens to a different rack.    We are still working on changing the power supply to the RF source.  Will complete this early next week

Attachment 1: sorensen.png
4736   Wed May 18 07:13:00 2011 SureshUpdateRF SystemDemod board measurements

I measured the amplitude and phase imbalances of the demod boards which have been modified.  This is just a basic health check.  We hope to use the script that Kiwamu is developing for a more accurate test.  The script can also use these measurements as a sanity check.  POP110  requires some further attention.

The RF distribution box outputs corresponding to the demod board (eg. AS55_LO --> AS55_demod) were used as LO sources.  The RF signal was generated with a Marconi and held a kHz away from the LO frequency.  The amplitude and phase unbalance were measured with SR785.  The RF Power meter was used to check the LO power in each case.

Attachment 1: Demod_Board_measurements.png
4737   Wed May 18 07:18:15 2011 SureshUpdateRF SystemPOY55_Demod board Hardware change completed

The ~350 Hz noted in the elog below was traced to an RF modulation of the 11 MHz sideband.  This modulation was set up in the Marconi which is currently supplying the 11 MHz local oscillator signal to the RF source.  lt was used during the MC length study completed last week by Valera and Ryan.  The frequency measured was 322 Hz.

As we do not require this any longer, I have switched off this modulation.

 Quote: The Demod board with S. No. 022 (being used earlier as REFL11) has been modified.  It now has SCLF-65 as its input LP filter on the PD input line and a PQW-2-90 power splitter.  The unit functioning okay (I and Q signals are 90 deg apart. The loss of Q output was traced to a possible loose solder joint and we now have both the I and Q signals after resoldering all components in the vicinity of U7 (Ref Schematic of D990511) There is a strong oscillation around 350Hz present on I and Q signals of both REFL55_Demod and POY55_Demod.  Don't know the source.  We have run out of power splitters to continue with the Demod board modification. We do not currently have an AS11_Demod board.  All the others are in place and ready for the I<->Q phase angle measurement. In summary we now have the following Demod boards in place: [ REFL11, POY11, REFL55, AS55, POY55, POY22, POY110]_Demod

4738   Wed May 18 15:54:50 2011 KojiUpdateRF SystemDC power supplies for the RF generation box in place

[Koji, Steve]

DC power supplies for the RF generation box are now in place. They are the top two of the 6 Sorensens in the OMC short rack next to 1X2.

We made the connections as we did for the RF distribution box, the power supplies labele, and the cables strain-relieved.

The power supply is not yet connected to the actual RF generation box. This should be done by Suresh or someone with the supervision of him.

Note:
We have two +18V supply on the short OMC rack, in total. One is for the RF source, the other is for the OMC PZTs, whitening, etc.
This is to avoid unnecessary ground loop
although the grounding situation of the OMC side is not known to me.

4739   Wed May 18 16:52:23 2011 SureshUpdateRF SystemCables for AS11 PD are in place

[Larisa, Suresh]

All the cables needed for the AS11 PD are in place... the heliax cable runs from the AS table to the PSL rack.  The LO and RF cables to demod board as well as the I and Q cables into the LSC Whitening board are connected.

The cables get rather densely packed when the LSC Whitening filter sits between the PD Interface Board and the LSC AA filter board.  This makes it difficult to access the SMA connectors on the LSC whitening filter.  So we shifted the LSC Whitening and AA Filter boards one slot to the right.  The LSC rack looks like this just now.  We have also shifted the binary cables at the back of the Eurocart by one slot so the same cables are associated with the cards.

4740   Wed May 18 17:06:39 2011 SureshUpdateRF SystemDC power supplies for the RF generation box in place

I have checked the voltages on the connector.  They are okay and I have plugged in the Sorensen power into the RF Source.  The ground reference for the Sorensens comes from the 1X2 Rack ground reference lines on the south side of the rack.

I looked for the OMC ground reference. Could not find one on either of the the OMC half racks.

 Quote: [Koji, Steve] DC power supplies for the RF generation box are now in place. They are the top two of the 6 Sorensens in the OMC short rack next to 1X2. We made the connections as we did for the RF distribution box, the power supplies labele, and the cables strain-relieved. The power supply is not yet connected to the actual RF generation box. This should be done by Suresh or someone with the supervision of him. Note: We have two +18V supply on the short OMC rack, in total. One is for the RF source, the other is for the OMC PZTs, whitening, etc. This is to avoid unnecessary ground loop although the grounding situation of the OMC side is not known to me.

4751   Thu May 19 19:41:17 2011 SureshUpdateRF SystemDAQ channel Assignments for RF PDs

[Kiwamu, Suresh]

In trying to keep the wiring of the LSC rack as neat as possible, we came up with the following channel assignments of the RF PD signals.

PDI = PD Interface, The PD Interface D-type connectors (#1 to #12) are numbered:  Top -> Bottom and Left -> Right in ascending order.

The Analog channels on the LSC Whitening Filter boards are numbered similarly, 1 to 32 in four sets.

4755   Fri May 20 05:41:22 2011 SureshUpdateRF SystemDemod board measurements

The POP110 board which had the large Amplitude and Phase unbalances was examined today.  It turned out that there was some stray solder which had connected the Sum port of the PSCQ-2-120 splitter to its body (ground).  After I removed that the amplitude unbalance was 0.3dB however the phase was 105deg.  The phase reduced to 90 deg only if the power on the splitter is around 19 dBm.  So removed the AT1 (10dB attenuator) and the phase unbalance dropped to 91 deg.  However this is not a sustainable solution as the ERA-5 max output is about 19.5 dBm.

As this is a side band power monitor (and not a length sensing RFPD), we can make do with a poorer phase.  I will therefore replace the AT1 and adjust the residual phase with cable delay lines.

 Quote: I measured the amplitude and phase imbalances of the demod boards which have been modified.  This is just a basic health check.  We hope to use the script that Kiwamu is developing for a more accurate test.  The script can also use these measurements as a sanity check.  POP110  requires some further attention.    The RF distribution box outputs corresponding to the demod board (eg. AS55_LO --> AS55_demod) were used as LO sources.  The RF signal was generated with a Marconi and held a kHz away from the LO frequency.  The amplitude and phase unbalance were measured with SR785.  The RF Power meter was used to check the LO power in each case.

4804   Fri Jun 10 12:04:57 2011 JenneUpdateRF SystemBad RF connections!!

I am in the process of calibrating AS55's shot noise, and I noticed that the AS55 PD input to the demod board was only finger-tight.  I then checked all of the other SMA connections in the set of RF PD demod boards, and found several more that were loose, including all of the REFL55 connections.  This is no good!!!! RF connections need to be tightened!  I went through and tightened all of the offending connections with my personal Snap-on SMA wrench.

4957   Fri Jul 8 19:50:19 2011 SureshUpdateRF SystemLSC rack channel assignment

[Jamie, Suresh]

We looked at the ADC channel assignments in the LSC model and wanted to make sure that the LSC rack wiring and the LSC model are in agreement with each other.  So the plan is to wire the rack as shown below.  I will also post this file on svn so that we can keep it updated in case there are changes.

5249   Tue Aug 16 16:59:20 2011 AnamariaUpdateRF SystemAM in the PM

Kiwamu, Keiko, Anamaria

Looking at the I and Q signals coming from REFL11 and REFL55 we saw large offsets, which would mean we have amplitude modulation, especially at 11MHz. We checked the PD themselves with RF spectrum analyzer, and at their frequencies we see stationary peaks (even if we look only at direct reflection from PRM). We changed the attenuation of the PSL EOM, and saw the peak go down. So first check is beam out of PSL EOM, to make sure the input beam is aligned to the crystal axis and is not giving AM modulation in adition to PM.

5251   Wed Aug 17 02:48:56 2011 kiwamuUpdateRF SystemRe: AM in the PM

[Keiko / Suresh / Anamaria / Kiwamu]

The AM components do exist also on the beam after the EOM.

The peaks were found at 11, 29 and 55 MHz, where the PM are supposed to be imposed.

Suresh and Keiko minimized them by rotating the HWP, which is in front of the EOM.

Also Anamaria and I tried minimizing them by adjusting the EOM crystal alignment.

However everytime after we minimized the AM peaks, they grew back in a time scale of ~ 1 min.

Potentially it could be a problem of the HWP and/or EOM alignment.

Since we wanted to proceed the in-vac work anyways, we stopped investigating it and decided to postpone it for tomorrow.

We again adjusted the incident power to 20 mW.

-- P.S.

The incident power going to MC went down to 7 mW for some reasons. This was found after ~ 6 hours from our works on the PSL table.

We haven't touched anything on the PSL table since the daytime work.

Possibly the angle of the HWP is drifting (why?) and changed the amount of the P-polarizing beam power.

Suresh locked the angles of two HWPs, which are the one just after the EOM and the one after the attenuation PBS.

 Quote from #5249 So first check is beam out of PSL EOM, to make sure the input beam is aligned to the crystal axis and is not giving AM modulation in adition to PM.

5278   Mon Aug 22 20:37:43 2011 AnamariaConfigurationRF SystemPlan for install of 3f PDs

I made a quick sketch of how to include two more RF PDs on the REFL beam, given the space we have on the table. We want to install REFL33 and REFL165, 3f signals for the the two modulation frequencies we are using. The point is to make the distance from first beam splitter the same to all PDs so that we can use only one lens before this BS to make the beam the right size. Currently there are 2 PDs on the refl beam, REFL11 and REFL55, predictably. So the drawing shows 4 PDs. Drawing is to scale but is a bit coarse. Hopefully we'll take pictures once we're done.

Reference from current BS splitting beam to the existing PDs.

Attachment 1: 40m3fReflPdLayout.pdf
5921   Thu Nov 17 11:04:02 2011 JenneUpdateRF SystemStochmon?

Is there an update on Stochmon?  Are the signals acquired somewhere already?  What's the current deal-io?  The new EOM mount should be here later today, and I'm jazzed to start checking how my EOM box helps (hopefully) the amount of RFAM we see.

I'll start making the adapter plate while I wait...

5923   Thu Nov 17 11:35:27 2011 KojiUpdateRF SystemStochmon?

The  Stochmon channels for 11&55MHz have been reasonably working since last night.

The output is not yet calibrated as the RF power detector has a strange scaling.
I am analyzing the calibration data.

5926   Thu Nov 17 14:38:16 2011 ZachUpdateRF SystemStochmon?

It turns out that we don't have all the parts I would need to do a full prototype of the precision temperature controller. I am guessing that we won't want to sit around and wait for the parts given the upcoming TAC meeting, so I'll do the next best thing:

• More-or-less complete heater driver

Does anyone have a suggestion for how this thing will be packaged? I.e., should it be in a box or should it be mounted in a rack, etc. In the end, a real board will be printed and stuffed, so this need not be a really professional job in the short term.

 Quote: Is there an update on Stochmon?  Are the signals acquired somewhere already?  What's the current deal-io?  The new EOM mount should be here later today, and I'm jazzed to start checking how my EOM box helps (hopefully) the amount of RFAM we see.  I'll start making the adapter plate while I wait...

5951   Fri Nov 18 19:07:07 2011 JenneUpdateRF SystemFoam house on EOM

[Jenne, Zach, Frank]

Frank helped Zach and I cable up at PT-100 RTD, and make sure it worked with the Newport Model 6000 Laser Diode Controller.  We're using this rather than the Newport 3040 Temperature Controller because Dmass says the output of that isn't working.  So we're using just the temp control part of the Laser Diode controller.

The back of the controller has a 15-pin D-sub, with the following useful connections.  All others were left Not Connected.

1 & 2 (same) - Pin 2 is one side of TEC output (we have it connected to one side of a resistive heater)

3 & 4 (same) - Pin 4 is the other side of the TEC output (connected to the other side of the resistive heater)

7 - connected to one side of PT-100 temp sensor

8 - connected to other side of PT-100 temp sensor

I used aluminum tape to attach the sensor and heater to the 40m's EOM, and we plugged in the controller.  It seems to be kind of working.  Zach figured out the GPIB output stuff, so we can talk to it remotely.

ELOG V3.1.3-