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ID Date Author Type Category Subjectup
  10059   Wed Jun 18 16:44:55 2014 ManasaUpdateElectronicsBBPD installed for BEATX detection

This BBPD is the spare that we pulled out and is installed for ALSX-PSL beat note detection.

  17152   Thu Sep 22 19:51:58 2022 AnchalUpdateBHDBH55 LSC Model Updates - part II

I updated follwoing in teh rtcds models and medm screens:

  • c1lsc
    • Added reading of ADC0_20 and ADC0_21 as demodulated BHD output at 55 MHz, I and Q channels.
    • Connected BH55_I and BH55_Q to phase rotation and creation of output channels.
    • Replaced POP55 with BH55 in the RFPD input matrix.
    • Send BH55_I and BH55_Q over IPC to c1hpc
    • Added BH55 RFPD model in LSC screen, in RFPD input matrix, whitening box. Some work is still remaining.
  • c1hpc
    • Added recieving BH55_I and BH55_Q.
    • Added BH55_I and BH55_Q to sensing matrix through filter modules. Now these can be used to control LO phase.
    • Added BH55 signals to the medm screen.
  • c1scy
    • Updated SUS model to new sus model that takes care of data acquisition rates and also adds BIASPOS, BIASPIT and BIASYAW filter modules at alignment sliders.

Current state:

  • All models built and installed without any issue or error.
  • On restarting all models, I first noticed 0x2000 error on c1lsc, c1scy and c1hpc. But these errors went away with doing daqd restart on fb1.
  • BH55 FM buttons are not connected to antialiasing analog filter. Need to do this and update medm screen accordingly.
  • The IPC from c1lsc to c1hpc is not working. One sender side, it does not show any signal which needs to be resolved.
  17157   Fri Sep 23 19:04:12 2022 AnchalUpdateBHDBH55 LSC Model Updates - part III

BH55

I further updated LSC model today with following changes:

  • BH55 whitening switch binary output signal is now routed to correct place.
    • Switching FM1 which carries dewhitening digital filter will always switch on corresponding analog whitening before ADC input.
  • The whitening can be triggered using LSC trigger matrix as well.
  • The ADC_0 input to LSC subsystem is now a single input and channels are separated inside the subsystem.

The model built and installed with no issues.

Further, the slow epics channels for BH55 anti-aliasing switch and whitening switch were added in /cvs/cds/caltech/target/c1iscaux/C1_ISC-AUX_LSCPDs.db


IPC issue resolved

The IPC issue that we were facing earlier is resolved now. The BH55_I and BH55_Q signal after phase rotation is successfully reaching c1hpc model where it can be used to lock LO phase. To resolve this issue, I had to restart all the models. I also power cycled the LSC I/O chassis during this restart as Tega suspected that such a power cycle is required while adding new dolphin channels. But there is no way to find out if that was required or not. Good news is that with the new cds upgrade, restarting rtcds models will be much easier and modular.


ETMY Watchdog Updated

[Anchal, Tega]

Since ETMY does not use HV coil driver anymore, the watchdog on ETMY needs to be similar to other new optics. We made these updated today. Now ETMY watchdog while slowly ramps down the alignment offsets when it is tripped.

  17150   Wed Sep 21 17:01:59 2022 PacoUpdateBHDBH55 RFPD installed - part I

[Radhika, Paco]

Optical path setup

We realized the DCPD - B beam path was already using a 95:5 beamsplitter to steer the beam, so we are repurposing the 5% pickoff for a 55 MHz RFPD. For the RFPD we are using a gold RFPD labeled "POP55 (POY55)" which was on the large optical table near the vertex. We have decided to test this in-situ because the PD test setup is currently offline.

Radhika used a Y1-1025-45S mirror to steer the B-beam path into the RFPD, but a lens should be added next in the path to focus the beam spot into the PD sensitive area. The current path is illustrated by Attachment #1.

We removed some unused OPLEV optics to make room for the RFPD box, and these were moved to the optics cabinet along Y-arm [Attachment #2].

 


[Anchal, Yehonathan]

PD interfacing and connections

In parallel to setting up the optical path configuration in the ITMY table, we repurposed a DB15 cable from a PD interface board in the LSC rack to the RFPD in question. Then, an SMA cable was routed from the RFPD RF output to an "UNUSED" I&Q demod board on the LSC rack. Lucky us, we also found a terminated REFL55 LO port, so we can draw our demod LO from there. There are a couple (14,15,20,21) ADC free inputs after the WF2 and WF3 whitening filter interfaces.


Next steps

  • Finish alignment of BH55 beam to RFPD
  • Test RF output of RFPD once powered
  • Modify LSC model, rebuild and restart
  17155   Fri Sep 23 14:10:19 2022 RadhikaUpdateBHDBH55 RFPD installed - part I

[Radhika, Paco, Anchal]

I placed a lens in the B-beam path to focus the beam spot onto the RFPD [Attachment 1]. To align the beam spot onto the RFPD, Anchal misaligned both ETMs and ITMY so that the AS and LO beams would not interfere, and the PD output would remain at some DC level (not fringing). The RFPD response was then maximized by scanning over pitch and yaw of the final mirror in the beam path (attached to the RFPD).

Later Anchal noticed that there was no RFPD output (C1:LSC-BH55_I_ERR, C1:LSC-BH55_Q_ERR). I took out the RFPD and opened it up, and the RF OUT SMA to PCB connection wire was broken [Attachment 2]. I re-soldered the wire and closed up the box [Attachment 3]. After placing the RFPD back, we noticed spikes in C1:LSC-BH55_I_ERR and C1:LSC-BH55_Q_ERR channels on ndscope. We suspect there is still a loose connection, so I will revisit the RFPD circuit on Monday. 

  17156   Fri Sep 23 18:31:46 2022 ranaUpdateBHDBH55 RFPD installed - part I

A design flaw in these initial LIGO RFPDs is that the SMA connector is not strain releieved by mounting to the case. Since it is only mounted to the tin can, when we attach/remove cables, it bends the connector, causing stress on the joint.

To get around this, for this gold box RFPD, connect the SMA connector to the PCB using a S shaped squiggly wire. Don't use multi-strand: this is usually good, since its more flexible, but in this case it affects the TF too much. Really, it would be best to use a coax cable, but a few-turns cork-screw, or pig-tail of single-core wire should be fine to reduce the stress on the solder joint.

Quote:
 

Later Anchal noticed that there was no RFPD output (C1:LSC-BH55_I_ERR, C1:LSC-BH55_Q_ERR). I took out the RFPD and opened it up, and the RF OUT SMA to PCB connection wire was broken [Attachment 2]. I re-soldered the wire and closed up the box [Attachment 3]. After placing the RFPD back, we noticed spikes in C1:LSC-BH55_I_ERR and C1:LSC-BH55_Q_ERR channels on ndscope. We suspect there is still a loose connection, so I will revisit the RFPD circuit on Monday. 

 

  15524   Fri Aug 14 00:01:55 2020 gautamUpdateCDSBHD / OMC model channels now added to autoburt

I added the EPCIS channels for the c1omc model (gains, matrix elements etc) to the autoburt such that we have a record of these, since we expect these models to be running somewhat regularly now, and I also expect many CDS crashes.

  16954   Tue Jun 28 14:24:23 2022 yutaUpdateBHDBHD DC PD signals now also sent to c1lsc to circumvent IPC error

[JC, Yuta]

To circumvent IPC error sending BHD DC PD signals from c1sus2 to c1lsc, DB9 cable from BHD DC PD box sent to c1sus2 is now split and sent also to c1lsc.
They are now available in both

c1sus2 ADC1
C1:X07-MADC1_EPICS_CH16 (DC PD A) and CH17 (DC PD B)

c1lsc ADC1
C1:X04-MADC1_EPICS_CH4 (DC PD A) and CH5 (DC PD B)

Next:
 - Add battery powered SR560 to decouple c1sus2 and c1lsc to avoid the ground loop

  16932   Tue Jun 21 14:17:50 2022 yutaConfigurationBHDBHD DCPDs re-routed to c1sus2

After discussing with Anchal, we decided to route BHD related PD signals directly to ADC of c1sus2, which handles our new suspensions including LO1, LO2, AS1, AS4, so that we can control them directly.
BHD related PD signals will be sent to c1lsc for DARM control.

Re-cabling was done, and now they are online at C1:X07-MADC1_EPICS_CH16 (DC PD A) and CH17 (DC PD B) with 15ft DB9 cable.
Here, DC PD A is the transmission of BHD BS for AS beam, and DC PD B is the reflection of BHD BS for AS beam (see attached photo).

  17034   Mon Jul 25 18:09:41 2022 TegaConfigurationBHDBHD Homodyne Phase control MEDM screen

[Paco, Tega, Yuta]

Today, we made a custom MEDM screen for the BHD Homodyne Phase Control, which is basically an overview of the c1hpc model. See Attachments 1 & 2 for details.

  17024   Wed Jul 20 18:07:52 2022 PacoUpdateBHDBHD MICH test

[Paco, Yuta, JC]

We did some easy tests on the BHD readout in preparation for BHD MICH. With the arm cavities and LO beam misaligned, but the MICH aligned, we measured the transfer function from C1:LSC-DCPD_A_OUT to C1:LSC-DCPD_B_OUT to get a rough estimate of the gain balance: 1.8 * DCPD_A = DCPD_B. We then locked MICH using REFL55_Q and looked at

  • A=C1:LSC-DCPD_A_OUT
  • B=C1:LSC-DCPD_B_OUT
  • 1.8 * A - B (which we encoded using C1:LSC-PRCL_A_IN1)
  • 1.8 * A + B (which we encoded using C1:LSC-PRCL_B_IN1)

namely the DCPD BHD signals. After turning the MICH_OSC on (2000 gain @ 311.1 Hz), we took some power spectra under the following three configurations:

  1. LO misaligned, no MICH offset.
  2. LO overlap, no MICH offset.
  3. LO overlap and MICH offset.

For 1. the expectation was that since LO is misaligned and the AS port is dark, we would get no signal. In 2., however both A and B would might see some incoherent signal, but still no MICH. Finally in 3. all signals should be able to see MICH, including A-B. Attachment #1 shows the measurements 1, 2, and 3 (offset = -5.0). Then, with increasing offset values, the BHD MICH signals increased as well; discussion to follow.

  17037   Tue Jul 26 20:54:08 2022 PacoUpdateBHDBHD MICH test - LO phase control

[Yuta, Paco]


TL;DR Successfully controlled LO phase, and did BHD-MICH readout with various MICH offsets and LO phases.


Today we implemented a DCPD based LO phase control. First, we remeasured the balancing gain at 311.1 Hz (the MICH oscillator freq) and combined C1:HPC-DCPD_A_OUT with C1:HPC-DCPD_B_OUT to produce the balanced homodyne error signal (A-B). We feed this error signal to C1:HPC-LO_PHASE_IN1 and for the main loop filters we simply recycled the LSC-MICH loop filters FM2 through FM5 (we also copied FM8, but didn't end up using it much). Then, we verified the LO phase can be controlled by actuating either on LO1 or LO2. For LO2, we added an oscillator in the HPC LOCKINS at 318.75 Hz (we kept this on at 1000 counts for the measurements below).

The LO phase control was achieved with a loop gain in the range of 10-30 (we used 20), no offset, and FM4, and FM5 engaged. FM2 can be added to boost, but we usually skipped FM3. Then, we went through a set of measurements similar to the ones described in a previous elog. A key difference with respect to the measurements from before is that we locked MICH using AS55Q (as opposed to REFL55Q). This allowed us to reach higher MICH offsets without losing lock. After turning on the MICH oscillator at 3000 counts, we looked at:

  1. LO misaligned + MICH at dark fringe (offset = -21).
    • Here, we don't expect to see any MICH signal and indeed we don't, except for a small residual peak from perhaps a MICH offset or slightly imbalanced PDs.
  2. LO aligned, but uncontrolled + MICH at dark fringe (offset = -21).
    • Here we would naively expect MICH to show up in A-B, but because of the uncontrolled LO phase, we mostly see the noise baseline (mostly from LO RIN? ...see measurement 3) under which this signal is probably buried. Indeed, the LO fringe increased noise in A, B, and A-B but not in A+B. This is nice. yes
  3. LO aligned, but uncontrolled + MICH with dc readout (offset = +50).
    • Here we expected the MICH signal to show up due to the large offset, and we can indeed see it in A, B, and A+B, but not in A-B. Nevertheless we see almost exactly the same noise level even though we allow some AS light into the BHD readout, so maybe the noise observed in the A-B channel from measurements 2 and 3 is mostly from LO RIN. This needs further investigation...
  4. LO aligned, controlled at no offset + MICH with dc readout (offset = +50).
    • In general here we expected to see a noise reduction in the A-B channel since the LO fringe is stable, and a MICH signal should appear. Furthermore, since LO phase is under control, we expect the LO2 Oscillator to appear which it does for this and the following measurements. Because of the relative freedom, we tried this measurement in two cases:
      1. When feeding back to LO1
        • We actually see MICH in the A-B channel, as expected, after the noise level dropped by ~ 5. We also observed small sidebands +- 1 Hz away from the MICH peak, probably due to local damping in either LO or AS paths.
      2. When feeding back to LO2
        • We also see MICH here, with a slightly better drop in noise (relative to feeding back to LO1). Sidebands persisted here, but around at +- 2 Hz.
  5. LO aligned, controlled (offset = 10) + MICH with dc readout (offset = +50). *
    • Here, we expected the A-B MICH content to increase dramatically, and indeed it does after a little tuning of the LO phase heart. The noise level decreased slightly because LO phase noise is decreased around the optimal point.
  6. LO aligned, controlled (offset = 20) + MICH with dc readout (offset = +30). *
    • Here, we naively expected A+B MICH content to decrease, but A-B remain constant. In order to see this we tried to keep the balance between the offsets, but this was hard. We don't really see much of this effect, so this also needs further investigation. As long as we keep controlling the LO phase using the DCPDs because the offsets tend to reduce the error signal we will have a harder time.

* For these measurements we actuated on LO2 to keep the LO phase under control.

Note that the color code above corresponds to the traces shown in Attachment #1.


What's next?

  • Alignment of LO and AS might be far from optimized, so it should be tried more seriously.
  • What's the actual LO power? How does it compare with AS power at whatever MICH offsets?
  • Try audio dither LO phase control.
    • With MICH offset.
    • Without MICH offset, double demod (after dolphin fix crying)
  15357   Tue May 26 19:19:30 2020 HangUpdateBHDBHD MM-- effects of astigmatism

Please see the attached doc. 

I think the conclusion is that if the AS1 RoC error is not significantly more than 1%, then with some adjustment of the AS1-AS3 distance (~ 1 cm), we could find a solution that simultaneously makes the AS path mode-matching better than 99% for the t- and s-planes. 

The requirement of the LO path is less strict and the current plan using LO1-LO2 actuation should work. 

  15684   Mon Nov 23 12:25:14 2020 gautamUpdateBHDBHD MMT Optics delivered

Optics --> Cabinet at south end (Attachment #1)

Scanned datasheets--> wiki. It would be good if someone can check the specs against what was ordered.

  15685   Mon Nov 23 14:52:10 2020 KojiUpdateBHDBHD MMT Optics delivered

Basically, they repeated our specs and showed the coating performances for HR/AR for 10deg P and PR/AR for 45deg P. There is no RoC measurement by the vendor.
Nevertheless, their RoC (paper) specs should be compared with our request.

  16198   Fri Jun 11 20:19:50 2021 KojiSummaryBHDBHD OMC invacuum wiring

Stephen and I discussed the in-vacuum OMC wiring.

- One of the OMCs has already been completed. (Blue)
- The other OMC is still being built. It means that these cables need to be built. (Pink)
- However, the cables for the former OMC should also be replaced because the cable harness needs to be replaced from the metal one to the PEEK one.
- The replacement of the harness can be done by releasing the Glenair Mighty Mouse connectors from the harness. (This probably requires a special tool)
- The link to the harness photo is here: https://photos.app.goo.gl/3XsUKaDePbxbmWdY7

- We want to combine the signals for the two OMCs into three DB25s. (Green)
- These cables are custom and need to be designed.

- The three standard aLIGO-style cables are going to be used. (Yellow)

- The cable stand here should be the aLIGO style.

  16318   Thu Sep 9 09:54:41 2021 StephenSummaryBHDBHD OMC invacuum wiring - cable lengths

[Koji, Stephen - updated 30 September]

Cable lengths task - in vacuum cabling for the green section (new, custom for 40m) and yellow section (per aLIGO, except likely with cheaper FEP ribbon cable material) from 40m/16198. These arethe myriad of cables extending from the in vacuum flange to the aLIGO-style on-table Cable Stand (think, for example, D1001347), then from the cable stand to the OMCs.

a) select a position for the cable stand.

 - Koji and I discussed and elected to place in the (-X, -Y) corner of the table (Northwest in the typical diagram) and near the table edge. This is adjacent to the intended exit flange for the last cable.

b) measure distances and cable routing approximations for cable bracket junctions

- Near OMC bracket to the cable stand, point to point = 17.2, routing estimate = 24.4.
- Far OMC bracket to the cable stand, point to point = 20.5, routing estimate = 32.2.

  - Recommendation = 48" for all green section cables (using one length for each OMC, with extra slack to account for routing variation).

c) (outdated - see item (b) and attachment 3) measure distances (point to point) and cable routing approximations for all items.

 +X OMC (long edge aligned with +Y beam axis) (overview image in Attachment 1)

- QPDs to the cable stand, point to point = 12, routing estimate = 20.
- DCPDs to the cable stand, point to point = 25, routing estimate = 32.
- PZTs to the cable stand, point to point = 21, routing estimate = 32.

+Y OMC (long edge aligned with +Y beam axis) (overview image in Attachment 1)

- QPDs to the cable stand, point to point = 16, routing estimate = 23.
- DCPDs to the cable stand, point to point = 26, routing estimate = 38.
- PZTs to the cable stand, point to point = 24, routing estimate = 33.

Cable stand to flange (Attachment 2) (specific image in Attachment 2)

- point to point = 35, routing estimate = 42

  - Recommendation = 120" for all yellow section cables, per Koji's preferences for zigzag cable routing on stack and coiling of slack.

  16839   Mon May 9 22:19:06 2022 KojiUpdateBHDBHD Platform Progress status

[Don, Koji]

Don is working on finalizing the BHD Platform design. All the components on the BHD platform are almost populated and aligned.

Don is still working on the table legs so that we can detach the legs when we need to float the table in the future.
The BHD BS mount will have a third picomotor so that we can steer 3 dof with the mount while the remaining dof needs to be provided by the OMC.
The BHD BS position is going to be adjusted so that the incident and trans beams have sufficient clearance.
The OMC legs (kinematic mounts) need more work so that we can adjust their positions for initial setup while they can be the reference for the reproducible placement of the OMCs.
The OMCs are rigidly held with the legs. For the damping of the 1-kHz body bode, which has a relatively high Q, there will be a dissipative element touching the glass breadboard.

  16840   Mon May 9 23:18:44 2022 KojiUpdateBHDBHD Platform Progress status

I quickly ran the FEA model to check the resonant freqs of the BHD platform.
The boundary conditions were:

  • The platform was not loaded
  • FIxed constraints were given to the five legs

Don has optimized the cut-out size for the OMCs to increase the rigidity of the plate. Also, the ribbed grid is made at the bottom side.

The lowest mode is at 168Hz. Because there is no leg around, it seems reasonable to have this kind of mode as the fundamental mode.
The other mode lined up at 291Hz, 394Hz, 402Hz, ...
The mode freqs will be lower once the platform is loaded. But as the unloaded platform mode, these mode freqs sound pretty good numbers.

  15901   Thu Mar 11 02:10:06 2021 KojiSummaryBHDBHD Platform vertical dimentions

Stephen and I discussed the nominal heights of the BHD platform components.

  • The beam height from the stack is 5.5"
  • The platform height is 1.5" and the thickness of 0.4", according to the VOPO suspension, which we want to be compatible with.
  • Thus the beam height on the BHD platform is 4".
  • The VOPO platform has a minimum 0.1" gap from the installation surface when it is suspended.
  • When the BHD platform is fixed on the table, we'll use positioners that are fixed on the stack table. Then the BHD platform is fixed on the positioner rather than fixing the entire platform on the stack. This leaves us the option to suspend the platform in the future. The number of the positioners is TBD.
  • Looking at the head size for 1/4-20 socket head screws, It'd be nice to have the thickness of 0.5" for the positioners. This makes the thin part of the stiffener to be 0.6" in thickness.
     
  • The numbers are nominal for the initial design and subject to the change along with FEA simulations to determine the resonant frequency of the body modes.
  16785   Mon Apr 18 16:09:07 2022 YehonathanUpdateBHDBHD Readout simulation

I'm planning on simulating the BHD readout noise in a manner very similar to the ALS noise model using Simulink. I've made a sketch of the model for the longitudinal DOFs (attached). A model for ASC will be similar but with more measurement devices (OpLevs, QPDs, WFSs).

I'm not pretending to simulate everything in this diagram on the first go, it is just a sketch of the big picture.

  16828   Tue May 3 21:07:17 2022 YehonathanUpdateBHDBHD Readout simulation

I feel like there is an instability in my thought process on this. Before my tendency to try to scale and generalize this problem brings me to a full stop I will make small but quick progress.

First thing is to calculate the noise budget for a simple Michelson. The involved optics are:

  • ITMX
  • ITMY
  • BS
  • LO1
  • LO2
  • AS1
  • AS4

all sensed with OSEMs and OpLevs only.

Things to fetch:

1. OSEM sensing noise. Where do I get the null stream (AKA butterfly mode)?

2. Oplev noise, look at the SUM channel (or this elog)

3. Actuation TF. Latest elog.

4. Coil driver noise. Going to take the HP supply curve from this elog.

5. Seismic noise + Seismic stack TF. Or maybe just take displacement noise from gwinc.

6. Laser noise. Still need to search.

7. DAC noise. Still need to search.

 

 

Quote:

I'm planning on simulating the BHD readout noise in a manner very similar to the ALS noise model using Simulink. I've made a sketch of the model for the longitudinal DOFs (attached). A model for ASC will be similar but with more measurement devices (OpLevs, QPDs, WFSs).

I'm not pretending to simulate everything in this diagram on the first go, it is just a sketch of the big picture.

 

  16834   Thu May 5 17:50:48 2022 YehonathanUpdateBHDBHD Readout simulation

I have made a Simulink diagram to use in the MICH modeling (attachment) for the homodyne angle detection scheme. The model will be used for each optic separately and the noises will be combined in quadrature.

I gathered some more bits of info to fill the Simulink boxes. This is what I have so far:

Noise sources

# Displacement noises from gwinc
# OSEM sensing noise from the null stream
# OpLev noise from SUM channel + Seismic motion

freq = np.logspace(1, 4, 100)
coil_driver_noise = 1*freq/freq # pA/sqrt(Hz), elog 15846 
RIN = 1e-2*freq/freq #1/sqrt(Hz), elog 16082  
freq_noise = (1e6/freq**2) #Hz/sqrt(Hz), elog 15431
dark_noise = 1e-8 #V/sqrt(Hz) https://wiki-40m.ligo.caltech.edu/Electronics/RFPD/AS55
ADC_noise = 1e-6 #V/sqrt(Hz)
DAC_noise = 1e-6 #V/sqrt(Hz), elog 13003
 

TFs and gains

#POS->BHD from Finesse
#RIN->BHD from Finesse
#Frequency noise->BHD from finesse
#Control filters from MEDM
#Whitening filters from https://wiki-40m.ligo.caltech.edu/Electronics/WhiteningFilters
#Dewhitening filters from elog 12983  

DAC_gain = 6.285e-4 #V/cts, elog 16161

coil_driver_gain = 31 # elog 15534

coil_driver_TF = 0.016 #N/A per coil, elog 15846 
coil_R = 20e3 #Ohm,, elog 15846 
SUS_TF = 1/(0.25*freq**2) #m/N, single pendulum
OSEM_TF = 2*16384*1e3 #cts/m, https://wiki-40m.ligo.caltech.edu/Calibration
ADC_TF = 1638.4 #cts/V 
DCPD_responsivity = 0.8 #A/W
DCPD_transimpedance = 1e3 #V/A

  16815   Wed Apr 27 16:28:57 2022 AnchalSummaryBHDBHD Upgrade - Retreiving arm cavity alignment

[Anchal, Paco, JC]

We had to open ITMY, ETMY chamber doors to get the cavity aligned again. Once we did that, we regained cavity flashing and were able to align the input injection and cavity alignment to get transmission flashing to 1.0 (C1:LSC-TRY_OUT_DQ). JC later centered both ITMY and ETMY oplevs. The ITMY oplev had become completely out of range.

We also opened ITMX, ETMX chamber doors to get Xarm alignment. Again, it seems that ITMX had moved a lot due to cable post installation.

To be continued

  15540   Wed Aug 26 00:52:55 2020 gautamUpdateBHDBHD activities

Listing some talking points from the last week of activity here.

  1. LO delivery fiber cable may be damaged.
    • The throughput itself doesn't suggest any problems, I get almost all the light I put in out the other end.
    • However, even when I slightly move the fiber, I see huge amplitude fluctuations in the DCPD readouts. This shouldn't be the case, particularly if the light is well matched to one of the special axes of the PM fiber. I checked with a PBS at the output that this is indeed the case, so something else must be funky?
    • In any case, I don't think it's a great idea to use this 70m long fiber for bringing the light from the PSL table to the adjacent AP table. Chub has ordered a 10m patch cable.
    • I was a bit too hasty this morning, thinking we had a patch cable in hand, and so I removed the fiber from the AP table. So right now, the LO beam doesn't make it to the BHD setup. Depending on the lead time for the new patch cable, I may or may not resurrect this old setup.
    • I have also located some foam and rigid plastic tubing which I think will help in isolating the fiber from environmental length(phase) modulation due to acoustic pickup.
  2. BHD commissioning activities
    • Basically, I've been trying to use the Single Bounce ITM reflection/ Michelson / PRMI with carrier locked to get some intuition about the BHD setup. These states are easily prepared, and much easier to understand than the full IFO for these first attempts.
    • One concern I have is the angular stability (or lack thereof). When the PRMI is locked, the DC light level on each DCPD fluctuates between ~0 (which is what it should be), up to ~30 cts (~85uW).
    • Using the empirically determined attenuation factor between the DCPDs and the dark port of the beamsplitter, I estimate the power can be as high as 20mW. This is a huge number, considering the input to the interferometer is ~800mW. I assume that all the light is at the carrier frequency, since the PRC should reject all the sideband light in this configuration. In any case, the total amount of sideband light is ~20mW, and the carrier stays resonant in the PRC even when there are these large ASDC excursions, so I think it's a reasonable assumption that the light is at the carrier frequency. Moreover, looking at the camera, one can see a clear TEM10/01 profile, indicative of imperfect destructive interference at the beamsplitter due to beam axis misalignment.
    • The effect of such excursions on the BHD readout hasn't yet been quantified (by me at least), but I think it may be hampering my attempts to dither the homodyne phase to estimate the LO phase noise.
  3. High voltage coil driver project - see thread for updates.
  4. Trek HV driver has arrived.
    • I haven't opened the box yet, but basically, what this means is that I can dither the mirror intended for homodyne phase control in a reasonable way.
    • Previously, I was using the OMC HV driver to drive the PZTs - but this dither signal path has a 2kHz high pass filter (since the OMC length dither is a kHz dither). I didn't want to futz around with the electronics, particularly since the unit was verified to be working.
    • So the plan now would be to drive the input of the Trek with a DAC output (an appropriate AI chassis has been prepared to interface with the CDS system).
    • Hopefully, there's enough DAC dynamic range to dither the PZT and also do the homodyne phase locking using a single channel. Else, we'd need to use two channels and install a summing amplifier.
    • We definitely need more high-voltage amplifiers/supplies in the lab:
      • Any Thorlabs HV drivers we can recover? 
      • Eventually, we will need HV for coil drivers, OMC PZTs, steering PZTs, homodyne phase control PZT. 
  5. PMC bases have arrived.
    • Joe Benson from the machine shop informed me today afternoon that the bases were ready for pickup.
    • We have 3 bases in hand now. The finish isn't the greatest in the world, but I think it'll work. You can see some photos here.
    • I will hold off on putting this together while I work on the basic airBHD commissioning tests. We can install the PMCs later.
  6. AS port WFS project
    • We now have in hand almost all the components for stuffing the ISC whitening and LSC demod boards.
    • Rich, Chub, Luis and I had a call on Monday. The advise from Rich/Luis was:
      • Choose an inductance that has Z~100 ohms at the frequency of interest, for the resonant transimpedance part.
      • Choose a capacitance that gives the appropriate resonant frequency.
      • Don't stuff more notches than you need - start with just a 2f notch (so 110 MHz for us), and make sure to place the highest frequency notch closest to the photodiode.
      • Rich also suggested looking at the optical signal with a non-optimized head, get an idea of what the field content is, and then tune the circuit as necessary. There are obviously going to be many issues that only become apparent once we do such a test.
    • The aLIGO modulation frequencies are only 20% different from the 40m modulation frequencies. So I thought it is best if for our first pass, we stick to the inductance values used in the aLIGO circuits (same footprint, known part etc etc). Then, we will change the capacitance so that we have a tuning range that is centered our modulation frequencies.
    • The parts have been ordered.
  7. ISS project
    • Half of the LO light on the BHD breadboard is diverted for the purpose of sensing the LO intensity noise, for eventual stabilization. Right now, it is just getting dumped.
    • A PD head has been located. It has a minimalist 1kohm transimpedance amplifier circuit integrated into the head.
    • Our AOM driver has an input range of 0-1V DC. We want to map the servo output of +/-10V DC (or +/-4V DC if we use an SR560 based servo for a first pass) to this range.
    • I wanted to do this for once in a non-hacky way so I drew up a circuit that I think will serve the purpose. It has been fabricated and will be tested on the bench in a couple of days.
    • Once I get a feel for what the signal content is, I will also draw up a interface board to the PD head that (i) supplies the reverse bias voltage and +/-15 V DC to the PD head and (ii) applies some appropriate HPF action and provides a DC monitor as well.
  8. Summary pages are dead.
  9. General lab cleanup
    • I moved all the PPE from the foyer area into the designated cabinets along the east arm.
    • Did some basic cleanup of the lab in preparation for crane inspection. Walkways are clear.
    • I de-cluttered the office area a bit, but today I received ~10 packages from Digikey/FrontPanelExpress etc. So, in fact, it got even more cluttered. Entropy will go down once we ship these off to screaming circuits for stuffing the PCBs.
  16880   Fri May 27 17:45:53 2022 yutaConfigurationBHDBHD camera installed, GRY aligned

[JC, Paco, Yuta]

After the IFO recovery (elog 40m/16881), we installed an analog camera for BHD fringe using a BNC cable for old SRMF camera so that we can see it from the control room.
We also aligned AS-LO using LO1,LO2 and AS4.
We then aligned GRY injection to get maximum GTRY.

Maximum TEM00s right now are
 C1:SUS-ETMX_TRX_OUT_DQ ~0.1
 C1:SUS-ETMY_TRY_OUT_DQ ~0.05
 C1:ALS-TRX_OUT_DQ ~0.20
 C1:ALS-TRY_OUT_DQ ~0.18

  15284   Thu Mar 26 17:41:18 2020 JonOmnistructureBHDBHD docs compilation

Since there has been a proliferation of BHD Google docs recently, I've linked them all from the BHD wiki page. Let's continue adding any new docs to this central list.

  17056   Wed Aug 3 16:00:51 2022 yutaUpdateBHDBHD fringe aligned with reduced LO and AS beam clipping

Last week, we could find an alignment which realizes LO beam and AS beam both unclipped, but it was not consistent with an alignment which realize BHD fringe (40m/17046).
Today, we tweaked the alignment of SR2, AS1, AS4 to have BHD fringe with reduced LO and AS beam clipping.
AS beams on AP table and BHD both still look clipped, but much better now.
Ideally, SR2 and AS1 will unclip AS beam, and LO1, LO2, AS4 would make BHD fringe, but it is hard right now since LO beam seem to have little room and LO2 have little actuation range.
BHD optics on ITMY table, including camera, and AS55/ASDC were realigned after the aglinment work (Note that DCPD_A path have a pick-off for camera path, and this pick-off mirror have quite significant incident angle dependence of R/T ratio).

Current alignment scheme:
Current alignment scheme I figured out is the following.
 - Check Y green. If it is transmitted at good spot on GTRY camera, Yarm is OK. If not, tweak ITMY/ETMY. alignment.
 - Mis-align AS4, align TT1, TT2, LO1 to have DCPD_A_OUT of ~130 and DCPD_B_OUT of ~125.
 - Align PR3, PR2 to maximize TRY_OUT to ~1.05.
 - Tweak ITMY/ETMY if the beam spot on them are not good.
 - Align BS, ITMX to have good MICH fringe and TRX_OUT to ~1.1.
 - Tweak ITMX/ETMX if the beam spot on them are not good.
 - Misalign ETMY, ETMX, ITMY to have LO-ITMX fringe in BHD DCPDs, and align AS beam with SR2 and AS4 differentially, with ratio of AS4/SR2=3.6.

DC PD values in various configurations:
Both arms locked with POX/POY, MICH free, PRM/SRM misaligned

                          Mean     Max      Min
C1:IOO-MC_TRANS_SUM :     14088.57 13947.52 14167.04
C1:LSC-ASDC_OUT16 :           0.16    -0.02     0.34
C1:LSC-POPDC_OUT16 :        369.34   -74.88   854.34
C1:LSC-REFLDC_OUT16 :         0.03    -0.00     0.06
C1:LSC-TRY_OUT16 :            1.00     0.95     1.04
C1:LSC-TRX_OUT16 :            1.07     1.04     1.08

Only LO beam to BHD DCPDs
                          Mean     Max      Min
C1:IOO-MC_TRANS_SUM :     14121.32 14057.71 14159.38
C1:HPC-DCPD_A_OUT16 :       129.80   128.37   130.68 (Consistent with, 40m/17046. Power as expected within 20%. Squashed shape)
C1:HPC-DCPD_B_OUT16 :       123.42   121.92   124.48

ITMX single bounce (ITMY, ETMX, ETMY, PRM, SRM, LO misalgined)
                          Mean     Max      Min
C1:IOO-MC_TRANS_SUM :     14105.13 14000.89 14171.91
C1:HPC-DCPD_A_OUT16 :        92.54    91.45    93.30 (Consistent with 40m/17040, Power as expected within 40%. Clipped to the left in camera)
C1:HPC-DCPD_B_OUT16 :       137.70   136.55   138.53 (Note that DCPD_A/B ratio is different from LO, due to BHD BS R/T unbalance; 40m/17044)
C1:LSC-ASDC_OUT16 :           0.10     0.09     0.10 (Power as expected 40m/16952. Clipped to the right in camera)
C1:LSC-POPDC_OUT16 :        309.19   288.93   327.10 (Power as expected within 30% 40m/17042.)
C1:LSC-REFLDC_OUT16 :         0.02     0.01     0.02

ITMY single bounce (ITMX, ETMX, ETMY, PRM, SRM, LO misalgined)
                          Mean     Max      Min
C1:IOO-MC_TRANS_SUM :     14112.09 14025.37 14154.51
C1:HPC-DCPD_A_OUT16 :        92.58    92.01    93.26
C1:HPC-DCPD_B_OUT16 :       137.68   136.81   138.27
C1:LSC-ASDC_OUT16 :           0.10     0.09     0.10
C1:LSC-POPDC_OUT16 :        308.48   290.49   319.73
C1:LSC-REFLDC_OUT16 :         0.02     0.01     0.02

MICH fringe only (ETMX, ETMY, PRM, SRM, LO misalgined)
                          Mean     Max      Min
C1:IOO-MC_TRANS_SUM :     14090.34 13979.15 14143.86
C1:HPC-DCPD_A_OUT16 :       325.60    91.92   714.57
C1:HPC-DCPD_B_OUT16 :       400.27    18.37   762.57
C1:LSC-ASDC_OUT16 :           0.19    -0.05     0.41
C1:LSC-POPDC_OUT16 :        595.66  -119.21  1334.11
C1:LSC-REFLDC_OUT16 :         0.03    -0.01     0.07

LO-ITMX fringe only (ITMY, ETMX, ETMY, PRM, SRM misalgined)
                          Mean     Max      Min
C1:IOO-MC_TRANS_SUM :     14062.58 13968.05 14113.67
C1:HPC-DCPD_A_OUT16 :       224.31    89.57   371.66
C1:HPC-DCPD_B_OUT16 :       259.74    85.37   421.86


Next:
 - Measure contrast (40m/17020) and estimate mode-matching of LO-AS again (40m/17041)
 - Now that we have better LO-AS fringe, lock LO phase in MICH (40m/17037)
 - Now that Dolphin issue was fixed, try double-demodulation to lock LO phase

  17067   Tue Aug 9 15:33:12 2022 yutaUpdateBHDBHD fringe contrast improved from 43% to 74%

[Anchal, Yehonathan, Yuta]

We did the constrast measurement with the method same as 40m/17020.
Contrast between ITM single bounce and LO beam increased to 74% (we had 43% before unclipping LO beam in 40m/17056).
From equations in 40m/17041 and measured ITM sigle bounce power (93 or 138 counts @ BHD DCPD) and LO power (130 or 124 counts @ BHD DCPD) from 40m/17056,  expected visibility for perfectly mode-matched case is 99%.
Measured constrast of 74% indicate mode-matching of 56%.

Both arms locked, MICH fringe (20% percentile)
Contrast measured by C1:LSC-ASDC_OUT is 80.66 +/- 0.20 %
Contrast measured by C1:LSC-POPDC_OUT is 92.27 +/- 0.66 %
Contrast measured by C1:LSC-REFLDC_OUT is 89.59 +/- 0.84 %
Contrast measured by all is 87.51 +/- 1.69 %

Both arms misaligned, MICH fringe (20% percentile)
Contrast measured by C1:LSC-ASDC_OUT is 82.50 +/- 0.61 %
Contrast measured by C1:LSC-POPDC_OUT is 94.18 +/- 0.26 %
Contrast measured by C1:LSC-REFLDC_OUT is 92.78 +/- 0.19 %
Contrast measured by all is 89.82 +/- 1.75 %

ITMX-LO fringe (40% percentile)
Contrast measured by C1:HPC-DCPD_A_OUT is 73.93 +/- 1.52 %
Contrast measured by C1:HPC-DCPD_B_OUT is 73.56 +/- 1.22 %
Contrast measured by all is 73.74 +/- 0.98 %

ITMY-LO fringe (40% percentile)
Contrast measured by C1:HPC-DCPD_A_OUT is 73.45 +/- 0.61 %
Contrast measured by C1:HPC-DCPD_B_OUT is 75.27 +/- 0.50 %
Contrast measured by all is 74.36 +/- 0.54 %

  17068   Tue Aug 9 15:50:22 2022 KojiUpdateBHDBHD fringe contrast improved from 43% to 74%

For both 40m/17020 and 40m/17024, what does the contrast mean if the numbers are leaking out to ~-100cnt?
Also how much is it if you convert this contrast into the mode matching?

  15295   Fri Apr 3 13:40:07 2020 JonUpdateBHDBHD front-end complication

I wanted to pass along a complication pointed out by K. Thorne re: our plan to use Gen1 (old) Dolphin IPC cards in the new real-time machines: c1bhd, c1sus2. The implication is that we may be forced to install a very old OS (e.g., Debian 8) for compatibility with the IPC card driver, which could lead to other complications like an incompatibility with the modern network interface.

Hardware is easy - you will also need a DX switch and the cables

As for the driver - the last update (version 4.4.5) was in 2016.  The notes on it say valid for Linux kernel 2.6 to 3.x.  This implies that it will not work with Linux kernel 4.x and greater

So - Gentoo with 3.0 kernel OK, SL7 (kernel 3.10)  - OK,   Debian 8 (kernel 3.16) - OK   

But Debian 9 (kernel 4.9),Debian 10 (kernel 4.19) - NOT OK

We have Gentoo with kernel 3.0  boot server, etc. [used in L1,H1 production right now, but not much longer] The hard part here will be making sure we have network drivers for the SuperMicro 5018-MR.

CDS was never able to get real-time builds to work well on Linux kernels from 3.2 on up until we got to Debian 9. This is not to say that the tricks and stripped-down RCG we found worked for real-time on Debian 9 and 10 won’t work on, say, Debian 8.  But we have not tried.

I have a query out to Dolphin asking:

  1. Have they done any testing of these old drivers on Linux kernel 4.x (e.g., Debian 9/10)?
  2. Is there any way to buy modern IPC cards for the two new machines and interface them with our existing Gen1 network?

I'll add more info if I hear back from them.

  15299   Tue Apr 7 10:56:39 2020 JonUpdateBHDBHD front-end complication
Quote:

I have a query out to Dolphin asking:

  1. Have they done any testing of these old drivers on Linux kernel 4.x (e.g., Debian 9/10)?
  2. Is there any way to buy modern IPC cards for the two new machines and interface them with our existing Gen1 network?

Answers from Dolphin:

  1. No, and kernel 4.x (modern Linux) definitely will not work with the Gen1 cards.
  2. No, cards using different PCIe chipsets cannot be mixed.

Since upgrading every front end is out of the question, our only option is to install an old OS (Linux kernel < 3.x) on the two new machines. Based on Keith's advice, I think we should go with Debian 8. (Link to Keith's Debian 8 instructions.)

  16475   Thu Nov 18 14:29:01 2021 KojiSummaryBHDBHD invac optics / opto-mechanics

I went through the optics list (in the BHD procurement google spreadsheet) and summarized how to build them.

The red ones are what we need to purchase. Because of the strange height of the LMR mounts, the post needs to have none half-integer inch heights.

They need to be designed as the usual SS posts are not designed to be vac compatible (not because of the material but the design like screw hole venting).

We also need to check how many clean forks we have.
-> The components were ordered except for the custom posts.
 

ssome partssss
Name Optic Mount Mount OH Post Post OH Fork / Base Base OH Total Height Notes
POP_SM5  Previous POYM1 / 2" Y1-2037-0 LMR2V Thorlabs 1.36 Custom Post 4.14 SS Fork 0 5.5  
POP_SM4 New CM254-750-E03 Thorlabs LMR1V Thorlabs 0.87 Newport 9953+PLS-T238 3.88 BA1V / BA2V 0.75 5.5  
BSOL1 New 2" VIS BB2-E02 LMR2V Thorlabs 1.36 Custom Post 4.14 SS Fork 0 5.5  
ITMYOL1 New 2" VIS BB2-E02 LMR2V Thorlabs 1.36 Custom Post 4.14 SS Fork 0 5.5  
ITMYOL2 New 2" VIS BB2-E02 LMR2V Thorlabs 1.36 Custom Post 4.14 SS Fork 0 5.5  
SRMOL1 New 2" VIS BB2-E02 LMR2V Thorlabs 1.36 Custom Post 4.14 SS Fork 0 5.5  
ASL LA1779-C Thorlabs or KPX217AR.33 Newport LMR2V Thorlabs 1.36 Custom Post 4.14 SS Fork 0 5.5  
GRY_SM1 Y2-2037-0 (in hand) DLC   DLC Post   DLC Fork   5.5  
BHDBS CVI (In hand) DLC 2 DLC Post   DLC Fork   5.5 (3" post for BHD)
LO3 Lambda (in hand) POLARIS-K1-2AH Thorlabs 1 Custom Post 4.5 SS Fork 0 5.5 (3" post for BHD)
LO4 Lambda (in hand) POLARIS-K1-2AH Thorlabs 1 Custom Post 4.5 SS Fork 0 5.5 (3" post for BHD)
AS3 Lambda (in hand) POLARIS-K1-2AH Thorlabs 1 Custom Post 4.5 SS Fork 0 5.5 (3" post for BHD)
OMC1R3 Y1-1025-45P (in hand) POLARIS-K1-2AH Thorlabs 1 Custom Post 4.5 SS Fork 0 5.5 (3" post for BHD)
OMC1R4 Y1-1025-45P (in hand) POLARIS-K1-2AH Thorlabs 1 Custom Post 4.5 SS Fork 0 5.5 (3" post for BHD)
OMC2R3 Y1-1025-45P (in hand) POLARIS-K1-2AH Thorlabs 1 Custom Post 4.5 SS Fork 0 5.5 (3" post for BHD)
OMC2R4 Y1-1025-45P (in hand) POLARIS-K1-2AH Thorlabs 1 Custom Post 4.5 SS Fork 0 5.5 (3" post for BHD)
                   
OMC1R1 Y1-1025-45P (in hand) LMR1V Thorlabs 0.87 Custom Post 4.63 SS Fork 0 5.5 (3.13" post for BHD)
OMC2R1 NB1-K14 Thorlabs LMR1V Thorlabs 0.87 Custom Post 4.63 SS Fork 0 5.5 (3.13" post for BHD)

 

  15336   Mon May 18 18:00:16 2020 HangUpdateBHDBHD mode-matching study

[Jon, Tega, Hang]

We proposed a few BHD mode-matching telescope designs and then preformed a few monte-carlo experiments to see how the imperfections would change the story. We assumed a 2 mm (1-sigma) error on the location of the components and 1% (1-sigma) fractional error on the RoC of the curved mirrors. The angle of incidence has not yet been taken into account (no astigmatism at the moment but will be included in the follow-up study.)

For the LO path things are mostly fine. We can use LO1 and LO2 as the actuators (Sec. 2.2 of the note), and when errors are taken into account more than 90% of times we can still achieve 98% mode matching. The gouy phase separation between LO1 and LO2 > 34 deg for 90% of the time, which corresponds to a condition number of the sensing matrix of ~ 3. 

The situation is more tricky for the AS path. While the telescopes are usually robust against 2 or 3 mm of positional error, the 1% RoC does affect the performance quite significantly. In the note we choose two best-performing ones but still only 50% of the time they can maintain a power-overlap of > 99%. In fact, the 1% RoC error assumed should be quite optimistic... Not sure if we could achieve this in reality. 

One potential way out is to ignore the MM for the first round of BHD. Here anyway we only need to test the ISC schemes. Then in the second round when we have the whole BHD board suspended, we can then use AS1 and the BHD board as the actuators. This might be able to make things more forgiving if we don't need to shrink the AS beam very fast so that it could be separated from AS4 in gouy phase.

  15337   Tue May 19 15:24:06 2020 ranaUpdateBHDBHD mode-matching study

It would be good to have a corner plot with all the distances/ RoCs. Also perhaps a Jacobian like done in this breathtaking and seminal work.

  15339   Wed May 20 18:45:22 2020 HangUpdateBHDBHD mode-matching study--corner plot & adjustment requirement

As Rana suggested, we present the scattering plot of the AS path mode matching for various variables. The plot is for the AS path, Plan 2 (whose params we summarize at the end of this entry).

In the corner plot, we color-coded each realization according to the mode matching. We use (purple, olive, grey) for (MM>0.99, 0.98<MM<=0.99, MM<=0.98), respectively. From the plot, we can see that it is most sensitive to the RoC of AS1. The plot also shows that we can compensate for some of the MM errors if we adjust the distance between AS1-AS3 (note that AS2 is a flat mirror). The telescope is quite robust to other errors.

The compensation requirement is further shown in the second plot. To correct for the 1% RoC error of AS1, we typically need to adjust AS1-AS3 distance by ~ 1 cm (if we want to go back to MM=1; the window for >0.99 MM spans also about 1 cm). This should be doable because the nominal distance between AS1-AS3 is 115 cm. 

The story for plan1 is similar and thus not shown here. 

==============================================================

AS path plan2 nominal params:

label     z (m)     type             parameters  
-----     -----     ----             ----------  
SRMAR          0    flat mirror      none:     
AS1       0.7192    curved mirror    ROC: 2.5000 
AS2       1.2597    flat mirror      none:     
AS3       1.8658    curved mirror    ROC: -0.5000
AS4       2.5822    curved mirror    ROC: 0.6000  
OMCBS1    3.3271    flat mirror      none:   
  15151   Fri Jan 24 13:56:21 2020 JonUpdateBHDBHD optics specifications

I've started a spreadsheet for the BHD optics specifications and populated it with my best initial guesses. There are a few open questions we still need to resolve, mostly related to mode-matching:

  • PR2 replacement: What transmission do we need for a ~100 mW pickoff? Also, do we want to keep the current curvature of -700 m?
  • LO mode-matching telescope: What are the curvatures of the two mirrors?
  • Lenses: We have six of them in the current layout. What FLs do we need?

The spreadsheet is editable by anyone. If you can contribute any information, please do!

  15305   Thu Apr 16 21:13:20 2020 JonUpdateBHDBHD optics specifications

Summary

I've generated specifications for the new BHD optics. This includes the suspended relay mirrors as well as the breadboard optics (but not the OMCs).

To design the mode-matching telescopes, I updated the BHD mode-matching scripts to reflect Koji's draft layout (Dec. 2019) and used A La Mode to optimize ROCs and positions. Of the relay optics, only a few have an AOI small enough for curvature (astigmatism) and most of those do not have much room to move. This reduced the optimization considerably.

These ROCs should be viewed as a first approximation. Many of the distances I had to eyeball from Koji's drawings. I also used the Gaussian PRC/SRC modes from the current IFO, even though the recycling cavities will both slightly change. I set up a running list of items like these that we still need to resolve in the BHD README.

Optics Specifications

At a glance, all the specifications can be seen in the optics summary spreadsheet.

LO Telescope Design

The LO beam originates from the PR2 transmission (POP), near ITMX. It is relayed to the BHD beamsplitter (and mode-matched to the OMCs) via the following optical sequence:

  • LM1 (ROC = +10 m, AOI 3°)
  • LM2 (Flat, AOI  45°)
  • MMT1 (Flat, AOI  5°)
  • MMT2 (ROC = +3.5 m, AOI  5°)

The resulting beam profile is shown in Attachment 1.

AS Telescope Design

The AS beam is relayed from the SRM to the BHD beamsplitter (and mode-matched to the OMCs) via the following sequence:

  • AS1 (ROC = +1.5 m, AOI  3°)
  • AS2 (Flat, AOI  45°)
  • Lens (FL = -125 mm)

A lens is used because there is not enough room on the BHD breadboard for a pair of (low-AOI) telescope mirrors, like there is in the LO path. The resulting beam profile is shown in Attachment 2.

  15334   Fri May 15 09:18:04 2020 JonUpdateBHDBHD telescope designs accounting for ASC

Hang and I have reanalyzed the BHD telescope designs, with the goal of identifying sufficiently non-degenerate locations for ASC actuation. Given the limited room to reposition optics and the requirement to remain insensitive to small positioning errors, we conclude it is not possible put sufficient Gouy phase separation between the AS1/AS2 and LO1/LO2 locations. However, we can make the current layout work if we instead actuate AS1/AS4 and LO1/LO4. This would require actuating one optic on the breadboard for each relay path. If possible, we believe this offers the simplest solution (i.e., least modification to the current layout).

LO Telescope Design (Attachment 1)

Radius of curvatures:

  • LO1: +10 m
  • LO2: flat
  • LO3: +15 m
  • LO4: flat

AS Telescope Design (Attachment 2)

Radius of curvatures:

  • AS1: +3 m
  • AS2: flat
  • AS3: -1 m
  • AS4: flat
  16849   Thu May 12 20:11:18 2022 AnchalUpdateBHDBHDBS Output beams steered out to ITMY table

I successfully steered out the two output beams from BHD BS to ITMY table today. This required significant changes on the table, but I was able to bring back the table to balance coarsely and then recover YARM flashing with fine tuning of ITMY.

  • The counterweights were kept at the North end of the table which was in way of one of the output beams of BHD.
  • So I saved the level meter positions in my head and removed those counterweights.
  • I also needed to remove the cable post for ITMY and SRM that was in the center of the table.
  • I installed a new cable post which is just for SRM and is behind AS2. ITMY's cable post is next to it on the other edge of the table. This is to ensure that BHD board can come in later without disturbing existing layout.
  • I got 3 Y1-45P and 1 Y1-0 mirror. The Y1-0 mirror was not installed on a mount, so I removed an older optic which was unlabeled and put this on it's mount.
  • Note that I noticed that some light (significant enough to be visible on my card) is leaking out of the 45P mirrors. We need to make sure we aren't loosing too much power due to this.
  • Both beams are steered through the center of the window, they are separating outside and not clipping on any of the existing optics outside. (See attachment 1, the red beam in the center is the ITMY oplev input beam and the two IR beams are the outputs from BHD BS).
  • Also note that I didn't find any LO beam while doing this work. I only used AS beam to align the path.
  • I centered the ITMY oplev at the end.

Next steps:

  • LO path needs to be tuned up and cleared off again. We need to match the beams on BHD BS as well.
  • Setup steering mirrors and photodiodes on the outside table on ITMY.
  16188   Sun Jun 6 16:33:47 2021 JonUpdateCDSBI channels on c1auxey

There is still an open issue with the BI channels not read by EPICS. They can still be read by the Windows machine though.

I looked into the issue that Yehonathan reported with the BI channels. I found the problem was with the .cmd file which sets up the Modbus interfacing of the Acromags to EPICS (/cvs/cds/caltech/target/c1auxey1/ETMYaux.cmd).

The problem is that all the channels on the XT1111 unit are being configured in Modbus as output channels. While it is possible to break up the address space of a single unit, so that some subset of channels are configured as inputs and another as outputs, I think this is likely to lead to mass confusion if the setup ever has to be modified. A simpler solution (and the convention we adopted for previous systems) is just to use separate Acromag units for BI and BO signals.

Accordingly, I updated the wiring plan to include the following changes:

  • The five EnableMon BI channels are moved to a new Acromag XT1111 unit (BIO01), whose channels are configured in Modbus as inputs.
  • One new DB37M connector is added for the 11 spare BI channels on BIO01.
  • The five channels freed up on the existing XT1111 (BIO00) are wired to the existing connector for spare BO channels.

So, one more Acromag XT1111 needs to be added to the c1auxey chassis, with the wiring changes as noted above. I have already updated the .cmd and EPICS database files in /cvs/cds/caltech/target/c1auxey1 to reflect these changes.

  16189   Mon Jun 7 13:14:20 2021 YehonathanUpdateCDSBI channels on c1auxey

I added a new XT1111 Acromag module to the c1auxey chassis. I sanitized and configured it according to the slow machines wiki instructions.

Since all the spare BIOs fit one DB37 connector I didn't add another feedthrough and combined them all on one and the same DB37 connector. This was possible because all the RTNs of the BIOs are tied to the chassis ground and therefore need only one connection. I changed the wiring spreadsheet accordingly.

I did a lot of rewirings and also cut short several long wires that were protruding from the chassis. I tested all the wires from the feedthroughs to the Acromag channels and fixed some wiring mistakes.

Tomorrow I will test the BIs using EPICs.

  16193   Tue Jun 8 11:54:39 2021 YehonathanUpdateCDSBI channels on c1auxey

I tested the digital inputs the following way: I connected a DB9 breakout to DB9M-5 and DB9M-6 where digital inputs are hosted. I shorted the channel under test to GND to turn it on.

I observed the channels turn from Disabled to Enabled using caget when I shorted the channel to GND and from Enabled to Disabled when I disconnected them.

I did this for all the digital inputs and they all passed the test.

I am still waiting for the other isolator to wire the rest of the digital outputs.

Next, I believe we should take some noise spectra of the Y end before we do the installation.

Quote:

Tomorrow I will test the BIs using EPICs.

 

  15248   Wed Mar 4 12:25:11 2020 gautamUpdateCDSBIO1 on c1psl is dead

There was some work done on the Acro crate this morning. Unclear if this is independent, but I found that the IMC servo board IN1 slider doesn't respond anymore, even though I had tested it and verified it to be working. Patient debugging showed that BIO1 (and only that acromag unit with the static IP 192.168.114.61) doesn't show up on the subnet in c1psl. Hopefully it's just a loose network cable, if not we will switch out the unit in the afternoon. 

Jon is going to make a python script which iteratively pings all devices on the subnet and we will put this info on an MEDM screen to catch this kind of silent failure.

  5567   Wed Sep 28 18:39:50 2011 MirkoUpdatePEMBLRM seismic channels in c1pem

[Mirko,Jenne]

Created 5-band BLRMS for seismometer data (Gur1, Gur2 and STS1 each in x,y,z respectively) and accelerometer 1 through 6.

Bands are:
0.1Hz-0.3Hz
0.3Hz-1Hz
1Hz-3Hz
3Hz-10Hz
10Hz-30Hz
each with a fitting 4th order butterworth bandpass.

Data is recorded at 256Hz as e.g. C1:PEM-ACC1_RMS_RMS_0p3_1_OUT_DQ. For the 75 channels we have that corresponds to the data rate of just 1.2 16kHz channels.

c1pem execution time increased fom 6-7us to 15-16us out of 480us available.

  6523   Wed Apr 11 22:48:39 2012 ranaUpdateEnvironmentBLRMS

seis_blrms.png

  7183   Tue Aug 14 21:01:51 2012 ranaUpdatePEMBLRMS

Screenshot-Untitled_Window.png

I fixed up the seismic.stp file for the StripTool display:

  1. All BLRMS channels now have a y-axis range of 3 decades. So they all are displaying the same relative changes.
  2. So the 0.01-0.1 Hz band which is all over the place is real, sort of. Masha says that it is due to the seismometer signal being dominated by noise below 0.1 Hz. She is going to fix this somehow.
  3. I changed the samping time from 1 sec. to 10 sec. to make the traces less fuzzy.
  4. We (Masha / Liz) should harmonize the colors of this file with what's on the summary pages.
  8764   Thu Jun 27 15:50:03 2013 JenneUpdatePEMBLRMS are going crazy

The BLRMS are totally crazy today!  I'm not sure what the story is, since it's been this way all day (so it's not an earthquake, because things eventually settle down after EQs).  It doesn't seem like anything is up with the seismometer, since the regular raw seismic time series and spectrum don't look particularly different from normal.  I'm not sure what's going on, but it's only in the mid-frequency BLRMS (30mHz to 1Hz).

Here are some 2 day plots:

 

WeirdBLRMSincrease_27June2013_rawSeis.png

WeirdBLRMSincrease_27June2013_Gur1xBLRMS.png

WeirdBLRMSincrease_27June2013_lowFreqBLRMS.png

  8773   Thu Jun 27 21:45:48 2013 ranaUpdatePEMBLRMS are going crazy

Its an increase in the microseismic peak. Don't know what its due to though.

  7745   Mon Nov 26 18:36:17 2012 JenneUpdatePEMBLRMS back

Quote:

 I got two seismometers and one microphone back from Tara.

They are now near the Gurlap under the MC.

 I have finally plugged GUR1 back in....it is down at ETMY for now, since that's where the cable was.  BLRMS are back up on the projector.

ELOG V3.1.3-