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ID Date Author Type Category Subject
16031   Wed Apr 14 17:53:38 2021 AnchalUpdateSUSPlan for calculating filter banks for output matrix aka F2A aka F2P

### Plan of action

• Get the transfer functions of the suspension plant from actuated DOF to sensed DOF. We'll verify Bhavini's state-space model and get these transfer functions. Use the model TFs, not measured.
• For each of POS->POS, PIT->PIT, and YAW->YAW, we'll get the resonant frequency and Q of the resonance from these models. No, forget about the Q.
• We can correct the resonant frequencies from the measured ones in our free swinging data.
• Now, we'll repeat the following for each column of output matrix filters (inspired from scripts/SUS/F2Pcalc.py, but not fully understood how/why):
• Select col (eg. POS)
• Set f0 to the resonant frequency.
• Calculate $\large f_{UL} = f_0 * \sqrt{G_{UL}}$ where GUL is the corrected DC gain we got after output matrix optimization earlier. (Not sure how, why?). No, use the SS model.
• Calculate fUR, fLL, and fLR like above.
• Set $\large Q_{UL} = \sqrt{G_{UL}}$   (This just seems like a way of keeping some approximately low Q, ideally we should keep this same to what we got above but that might cause saturation issues like Rana mentioned in the meeting)
• Then, set the following filter in the output matrix element for UL:
$\dpi{200} G_{UL}\frac{1 + i\frac{f}{f_{UL}Q_{UL}} - \frac{f^2}{f_{UL}^2}}{1 + i\frac{f}{f_{0}} - \frac{f^2}{f_{0}^2}}$
which is in zpk form equivalent to:
$\dpi{150} z: \frac{f_0}{2 Q_{UL}} +/- i f_0 \sqrt{1 - \frac{1}{4Q_{UL}}} \quad, \quad p: \frac{f_0}{2} +/- i f_0 \frac{\sqrt{3}}{2} \quad, \quad k: G_{UL}$
• Repeat the above for UR, LL, LR.
• Note that this filter function takes values GUL at DC and at high frequencies while it would dip at the resonant frequency for POS with depth and narrowness directly proportional to QUL. No, the DC gain is different from the AC gain.
• However, the F2P filter plots we found in several places on elog look a bit different. Like here: 40m/4719. One important difference is that the filter magnitude always become 1 after the resonance at higher frequencies. Yes, this is  what we want, since you already did the balancing at high frequencies.
• A preliminary plot of the above calculation for the 1,1 output matrix filter bank (POS -> UL) is attached in Attachment 1.

### Discussion:

• We can make 12 such filters for the 12 numbers we got for the optimized output matrix. Is that the aim or should we do it only for the POS column as has been done in past?
• We are not sure how the choice of Q is made in setting the above filter function. We'll think more about it to understand this.
• We are also not sure how the choice of fUL is made above. It looks like depending on the correction gain, we want to slide the zero positions with respect to the pole positions which are fixed at the resonant frequency as expected. This seems to have some complex explanation.
• Please let us know if we are planning this right before we dive into these calculations/script writing. Thanks.

Edit Thu Apr 15 08:32:58 2021 :

Corrected the plot in the attachment. It shows the correct behavior at high frequencies now.

3576   Wed Sep 15 14:34:57 2010 josephbSummaryCDSPlan for RFM switch over

Steps for RFM switch over:

1) Ensure the new frame builder code is working properly:

A) Get Alex to finish compiling the frame builder and test on Megatron.

B) Test the new frame builder code on fb40m (which is running Solaris) in a reversible way.  Change directory structure away from Data1, Data2, to use actual times.

C) Confirm new frame builder code still records slow channels (c1dcuepics).

2) Ensure awg, tpman, and diagnostic codes (dtt) are working with the new front end code.

3) Physically move RFM cables from old front ends to the new front ends.  Remove excess connections from the network.

4) Merge the megatron/c1sus/c1iscex/c1ioo network with the main network.

A) Update all the network settings on the machines as well as Linux1

B) Remove the network switch separating the networks.

4) Start the new frame builder code on fb40m.

15654   Mon Nov 2 16:46:06 2020 gautamUpdateGeneralPlan for OMC chamber

To be a bit more clear about what we are going to do in the OMC chamber, I marked-up some photos, see Attachments #1 and #2.

1. OM5 will be rotated to bring the IFO AS beam straight out without any splitting to the OMC.
2. OMMT, OMC, DCPD, DCPD transimpedance amp, and all peripheral optics associated with these components, will be removed. Many of these components are mounted on a breadboard and so removing that breadboard will take care of it. These are marked with pink Xs.

I anticipate that after this work, the only components on the table will be

1. IM1, to send the PSL beam to the IMC.
2. OMs 5 and 6 to bring the IFO AS beam out onto the AP table (in principle, we could try and eliminate both these optics, if the AS beam happens to exit through one of the viewports cleanly, we will not have any intervening objects in the way once the OMC and peripherals are removed).
3. MMT2 for mode-matching the IMC transmission to the interferometer mode.

Are we in agreement with this plan?

See #15656 for the updated photo

15655   Mon Nov 2 17:13:19 2020 KojiUpdateGeneralPlan for OMC chamber

I believe the mirror next to IM1 is for the green beams to be delivered to the PSL table. I think we still want to keep it. Otherwise, the plan looks fine.

15656   Mon Nov 2 17:32:05 2020 gautamUpdateGeneralPlan for OMC chamber

Good point - looking back, I also see that I already removed the mirror at the SW corner of the table in 2016. Revised photo in Attachment #1. There is an optic on the east edge of this table whose purpose I'm not sure of, but I'm pretty sure it isn't essential to the main functionality and so can be removed.

 Quote: I believe the mirror next to IM1 is for the green beams to be delivered to the PSL table. I think we still want to keep it. Otherwise, the plan looks fine.
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.

14801   Tue Jul 23 21:59:08 2019 JonUpdateCamerasPlan for GigE cameras

This afternoon Gautam and I assessed what to do about restoring the GigE camera software. Here's what I propose:

• Set up one of the new rackmount Supermicros as a dedicated camera feed server
• All GigE cameras on a local subnet connected to the second network interface (these Supermicros have two)
• Put the SnapPy, pypylon, and pylon5 binaries on the shared network drive. These all have to be built from source.
• All other dependencies can be gotten through the package managers, so create requirements files for yum and pip to automatically install these locally.

I've started resolving the many dependencies of this code on rossa. The idea is to get a working environment on one workstation, then generate requirements files that can be used to set up the rest of the machines. I believe the dependencies have all been installed. However, many of the packages are newer versions than before, and this seems to have broken SnapPy. I'll continue debugging this tomorrow.

10101   Wed Jun 25 14:52:22 2014 Andres MedinaUpdateelogPlacing a lens between the steering mirrors and another lens between the second steering mirror and the cavity

I was asked to calculate the lenses that we need in order to obtained a Gouy phase close to 90 degrees between the two mirrors that are in the Xend green. Yesterday, I measured the distances between the mirrors, and the distance between the mirror relative to the cavity as illustrate in the image attached below. I looked in to the 40m elog and Manasa did the last update on the length of the cavity. She measured 37.7 + 0.05m. The waist size of the beam that was measured by Annalisa in ID 8637 after the Faraday was w0=2.943e-5m @ -0.039m. I calculated the waist size inside the cavity, and I found a waist of w0=2.2 mm. My plan this week is to keep working in the calculation and finish all the calculation this week so that next week I can go inside and place the lenses.

4880   Fri Jun 24 21:21:46 2011 SureshUpdatePSLPlaced labels on the zig-zag mirrors on PSL table

I put labels on the pair of beam steering mirrors which are at the output end of the PSL table.  I had changed one of these mirrors (elog) and Jenne had changed the other (elog).  This was at about 3PM today

I just learned from Kiwamu that this has messed up the MC alignment.

16860   Tue May 17 18:43:38 2022 AnchalUpdateBHDPlaced SRM in ITMY Chamber

[Anchal, Paco, Yuta]

### SRM Placement

• SRM was moved from its parked location to the nominal position in the ITMY chamber.
• This imbalanced the table a lot as all SOS towers ended up on the south side of the table.
• I needed additionally three SOS tower side walls to recover the balance of the table.
• I initially tried to use a level meter on my phone which claimed to have 0.1 degrees of accuracy. But it turned out to be a bad idea.
• Eventually, I used the spirit bubble level meter we have, along with the OSEM values of ITMY, AS1, and AS4.
• At the end, the table is balanced as it was before, all SOS are damping usually.

### SRM Sat Amp Box setup

• SRM Gold Box Sat Amp was found near the BS chamber.
• This box was moved to the ITMY chamber.
• The new flange on the East end was marked earlier for SRM. This flange on the vacuum side was connected with new in-vacuum blue ribbon cables.
• We had previously moved the cable post for SRM (40m/16849) behind AS2. This cable post is connected to the old in-vacuum cable.
• It would have changed the table balance to remove this cable post and connect new in-vacuum cables to it, so we decided to do this in the next vent when we put the BHD board on the table.
• For now, we connected the old in-vacuum cable to the new in-vacuum blue ribbon cables inside.
• Note, that the old in-vacuum cable has a gender flipping section which also mirrors the pin layout.
• We installed pin mirroring cables on the outside between the Sat Amp Box and the vacuum flange to revert back the additional mirroring.
• However it happened, now the Sat Amp Box is working, with all OSEMs and coils alive.
• One peculiarity we found was that the SRM face OSEMs have only about 250-300 um of range, which is roughly 3 times less than the other OSEMs in other SOSs.
• SRM side OSEM however behaves normally.
• After installment, at the free-hanging state, SRM LL OSEM is saturated (too bright) and other face OSEMs are close to total brightness state.
• We'll first put the alignment offsets to get the SRM perpendicular to the beam coming from SR2 and then center the OSEMs in this tiny range.
• The low OSEM range could be due to improper biasing from the Sat Amp Box. Hopefully, with new electronics, this issue would go away in future.
16863   Wed May 18 17:23:15 2022 AnchalUpdateBHDPlaced PRM in BS Chamber

[Anchal, Paco, Yuta, JC]

### SRM Oplev setup

• We setup SRM oplev path for the aligned position of SRM.
• This was bit hard, because the return beam was following almost the same path as the input beam, and the return beam had become about 1 cm in diameter.
• We replaced one of the in-air steering mirror of SRM op-lev input beam with a 1 inch BS on a non-steeerable mount.
• The returning oplev beam is picked at transmission from this BS.
• Note: we are not sure if this BS is actually coated for IR or Visible. We couldn't find a visible BS in the lab. We should order a 2 in diameter visible BS to be placed in this position.
• Half of the input beam would be used for PRM Oplev input.
• The returning beam was focused with a 100mm focal length lens. Again, this lens is not verified to be for visible wavelength. We think it might have an AR coating for IR. We should get a visible lens for this position also.

### PRM Placement

• PRM placed in nominal position + 2 cm, East.
• Currently, PRM SOS tower is blocking BS oplev input beam, this needs to be adjusted.
• Installed PRMOL at nominal position + 2 cm East (to clear path from TT2)
• I balanced the table succesfully, first using spirit bubble level and then OSEM levels of BS, SR2, PR3 and LO2.
• Note, that we need to adjust OSEM positions in many of these SOS before pumping down.
• Input beam from TT2 is going through center of PRM but the reflction is not coming back from PR2, maybe it is missing PR2 or PR2 alignment needs to be adjusted.
16474   Wed Nov 17 17:37:53 2021 AnchalUpdateGeneralPlaced Nodus and fb1 on UPS power

Today I placed nodus and fb1 on UPS battery backed supply. Now power glitches should not hurt our cds system.

5677   Mon Oct 17 11:06:31 2011 MirkoUpdateCDSPiping data from c1lsc to c1oaf

Changed, recompiled, installed and restarted c1rfm and c1oaf to get the MC1-3 Pitch and Yaw data into the c1oaf model.
Also changed c1oaf to use MCL as a witness channel (as well as an actuator).

174   Thu Dec 6 15:22:42 2007 AndreySummaryElectronicsPictures of the inside of He-Ne laser

Steve gave me an old "dead" He-Ne laser that long time ago was used for ETMX optical lever.

I dismantled it (cutting the metallic enclosure with a metallic saw), and these are two pictures of what is inside.
3261   Wed Jul 21 17:41:17 2010 GopalConfigurationOptic StacksPictures of Stacks

Now that venting is complete, this is a request for anyone who opens any chamber:

1) Please notify me immediately so I can take pictures of the stacks in that chamber.

2) If I'm not around, please take a few pictures for me. I'm most interested in the shape, number of layers, size, and damper arrangements of each stack.

This is most important for the MC1/MC3 chamber, MC2 chamber, and BS/ITMX/ITMY chambers.

Thanks!

8061   Mon Feb 11 18:39:10 2013 ChloeUpdateGeneralPictures of Circuitry in Photodiode

I am going to be making measurements to find the optical mounts with the least noise. I am using a quadrature photodiode to record intensity of laser light. These are pictures of the circuitry inside (both sides). I will be designing/making some circuitry on a breadboard in the next few days in order to add and subtract the signals to have pitch and yaw outputs.

3291   Mon Jul 26 11:15:23 2010 GopalHowToCOMSOL TipsPictures from Transfer Function Tutorial on the Wiki

The attached pictures give a brief overview of my transfer function measurement procedure in COMSOL. For more details, please see the Wiki.

8930   Sun Jul 28 19:39:04 2013 AnnalisaUpdateendtable upgradePicture

Yend table picture updated on the wiki page

7420   Thu Sep 20 14:55:06 2012 JenneUpdateGeneralPickoffs are hard to see

 Quote: My hope is that the DRMI flashes will be bright enough to see on the PO beams. IF we get 10 mW through the Faraday, you should get some buildup when the carrier resonates in the DRMI. If the recycling gain is 10 and the pickoff fraction is 100 ppm you ought to get ~10 uW on PO. How much of the recycling cavity power gets out of POP?

[Manasa, Jenne]

We think this math is wrong.

If we have P mW through the Faraday, PRM's transmission is 5.5%, BS transmission is 50%, Recycling gain is ~10, pickoff fraction is ~100ppm, we have:

P mW * 5.5e-2 * 0.5 * 10 * 100e-6 = P * 2750e-8 mW = P * 2.7e-5 mW.

So, if P=10 (10mW through the Faraday), we should have 2.7e-4 mW = 2.7e-7 W = 0.27 microwatts = not so many watts.

If P = 100 (100mW through the Faraday), we should have 2.7 microwatts. Still, not so many watts.

We have the Watec pointed at POY right now, DRMI is flashing, I'm waving the IR card in front of the mirror, and Manasa isn't able to see anything on the monitor.  The power into the vacuum is 100mW (we just measured and adjusted it), so even if we were getting a full 100mW through the Faraday, it would be hard to see.  If we're assuming we get ~half the power through the Faraday, then we should only have 1 microwatt

7422   Thu Sep 20 19:56:05 2012 JenneUpdateGeneralPickoffs are hard to see

Quote:

 Quote: My hope is that the DRMI flashes will be bright enough to see on the PO beams. IF we get 10 mW through the Faraday, you should get some buildup when the carrier resonates in the DRMI. If the recycling gain is 10 and the pickoff fraction is 100 ppm you ought to get ~10 uW on PO. How much of the recycling cavity power gets out of POP?

[Manasa, Jenne]

We think this math is wrong.

If we have P mW through the Faraday, PRM's transmission is 5.5%, BS transmission is 50%, Recycling gain is ~10, pickoff fraction is ~100ppm, we have:

P mW * 5.5e-2 * 0.5 * 10 * 100e-6 = P * 2750e-8 mW = P * 2.7e-5 mW.

So, if P=10 (10mW through the Faraday), we should have 2.7e-4 mW = 2.7e-7 W = 0.27 microwatts = not so many watts.

If P = 100 (100mW through the Faraday), we should have 2.7 microwatts. Still, not so many watts.

We have the Watec pointed at POY right now, DRMI is flashing, I'm waving the IR card in front of the mirror, and Manasa isn't able to see anything on the monitor.  The power into the vacuum is 100mW (we just measured and adjusted it), so even if we were getting a full 100mW through the Faraday, it would be hard to see.  If we're assuming we get ~half the power through the Faraday, then we should only have 1 microwatt

We can't mathdo

10636   Thu Oct 23 17:45:54 2014 JenneUpdateGeneralPianosa frozen

Not sure why, but Pianosa was frozen.  Also couldn't ssh or ping.  So, I hard power cycled it.

8775   Thu Jun 27 22:05:25 2013 ranaUpdateGeneralPianosa fixed

The keyboard on Pianosa workstation has been flaky for the last several days at least. Today, it was having troubles mounting the linux1 file system and was hanging on boot.

People in the control room emailed Jamie and then grew afraid of the computer. Annalisa suggested that we put garlic on it since was clearly possessed.

Typing 'dmesg' at the command prompt, I found that there were thousands of messages like these:

[ 3148.181956] usb 2-1.2: new high speed USB device number 68 using ehci_hcd
[ 3149.773883] usb 2-1.2: USB disconnect, device number 68
[ 3150.228900] usb 2-1.2: new high speed USB device number 69 using ehci_hcd
[ 3152.076544] usb 2-1.2: USB disconnect, device number 69
[ 3152.787391] usb 2-1.2: new high speed USB device number 70 using ehci_hcd
[ 3154.123331] usb 2-1.2: USB disconnect, device number 70
[ 3154.578459] usb 2-1.2: new high speed USB device number 71 using ehci_hcd

So I replaced the existing Dell keyboard with an older Dell keyboard and the bad messages have stopped. No garlic was used.

4969   Thu Jul 14 20:24:32 2011 NicoleSummarySUSPhotosensor Head Lessons

Today I tested the photosensor head combination (2 Hamamatsu S5971 photodiodes and 1 Hamamatsu L9337 LED). I discovered that I had burnt out the LED and the photodiodes when I soldered them to the PCB board.

After looking up soldering information on Hamamatsu photodiodes, I learned that I need to solder at least 2 mm away from the head. I checked the pins of my burnt-out photodiodes and I had soldered 1.5 mm away from the head. To prevent this problem from happening again, Suresh suggested that I clip a lead onto photodiode/LED pin while I solder on connections to help dissipate some of the heat.

Today I was able to get a single photodiode (not attached to the PCB) to measure light emitted from an LED and I observed how voltage fluctuated as I moved the photodiode around the LED.

Suresh and Jamie also helped me to fix my photosensor head design (to make it more electrically-stable). Originally, I had planned to solder the LED and photodiodes onto a PCB and to mount that PCB to the front of a small metal Pomona Electronics box (with a whole cut out for the photodiodes and LED) using spacers, screws, and nuts.  However, the PCB I am using to solder on the LED and photodiodes has metal connections that may cause problems for the LED and photodiodes lying on the surface. Now, the plan is to have the LED and photodiodes mounted to the PCB with an insulatory PCB in between. Below is an explanatory picture.  I will determine the placement of the LED and photodiodes after making screws holes in the two PCBs to attach to the metal face of the box. I want to attach the screw holes first to make sure that the PCBs (and attached photosensor) are centered.

4970   Fri Jul 15 01:11:21 2011 KojiSummarySUSPhotosensor Head Lessons

Rotate the PDs and the LED so that you can put them as close as possible.
This is to increase the sensitivity of the sensor. Think why the closer the better.

4971   Fri Jul 15 08:48:36 2011 JamieSummarySUSPhotosensor Head Lessons

Nicole: I thought we had decided to use teflon as the insulator between the PCB (yellow) and the LED/PDs?  I don't think you should use another circuit board with copper on it.  The copper will short the LED/PD heads to the metal box, which might be problematic.

Otherwise the design looks pretty good.  I think the PDs have three leads each, yes?

4974   Fri Jul 15 14:23:30 2011 NicoleSummarySUSPhotosensor Head Lessons

Ah! I see! Thank you!

I should put the LEDs and photodiodes closer together so that more of the reflected light falls on the photodiodes and the photodiodes have a higher response.

Also the reflectivity of the mirror will be optimized if the incident light is normal to the mirror surface. We will be setting up the photosensor and mirror so that the LEDs

emit light normal to the mirror surfaceDuring displacement, this light may be slightly off-normal but still close to normal incidence. We want the photodiodes to be close to the LED since we want

them to detect light that is close to the path of normal incidence (small angles of reflection). [Thanks to Jenne for helping me figure this one out!]

Thank you for the suggestion ^___^

4975   Fri Jul 15 14:29:30 2011 NicoleSummarySUSPhotosensor Head Lessons

You are right Jamie! Thank you for the correction! I will now use the Teflon sheet instead of the PCB piece.

The photodiodes do have three legs, but I imagined the third one lying on a different plane, since it is spaced apart from the two I have drawn.

I should include this third leg in my drawing?

5188   Thu Aug 11 12:31:39 2011 NicoleSummarySUSPhotosensor Head Calibration Curve for TT Frame

I have re-calibrated the photosensor I used to measure the displacements of the TT frame (what I call "Photosensor 2").

As before, the linear region is about 15.2mm to 25.4mm. It is characterized by the slope -0.0996 V/mm (-0.1 V/mm). Recall that photosensor 1 (used to measure mirror displacements) has a calibration slope of -3.2V/mm. The ratio of the two slopes (3.2/0.1 = 32). We should thus expect the DC coupling level to be 32? This is not what we have for the DC coupling levels in our data (2.5 for flexibly-supported, fully-assembled TT (with EDC, with bar), 4.2 for EDC without bar, 3.2 for rigid EDC without bar, 3.2 for no EDC, with bar, 3.2 for no EDC without bar) . I think I may need to do my calibration plot for the photosensor at the frame?

5191   Thu Aug 11 14:22:00 2011 NicoleSummarySUSPhotosensor Head Calibration Curve for TT Frame

 Quote: I have re-calibrated the photosensor I used to measure the displacements of the TT frame (what I call "Photosensor 2"). As before, the linear region is about 15.2mm to 25.4mm. It is characterized by the slope -0.0996 V/mm (-0.1 V/mm). Recall that photosensor 1 (used to measure mirror displacements) has a calibration slope of -3.2V/mm. The ratio of the two slopes (3.2/0.1 = 32). We should thus expect the DC coupling level to be 32? This is not what we have for the DC coupling levels in our data (2.5 for flexibly-supported, fully-assembled TT (with EDC, with bar), 4.2 for EDC without bar, 3.2 for rigid EDC without bar, 3.2 for no EDC, with bar, 3.2 for no EDC without bar) . I think I may need to do my calibration plot for the photosensor at the frame?

I have redone the voltage versus displacement measurements for calibrating "Photosensor 2" (the photosensor measuring the motions of the TT frame). This time, I calibrated the photosensor in the exact position it was in during the experimental excitation ( with respect to the frame ). I have determined the linear region to be 15.2mm to 22.9mm (in my earlier post today, when I calibrated the photosensor for another location on the frame, I determined the linear region to be 15.2mm to 25.4mm). This time, the slope was -0.92 V/mm (instead of -0.1 V/mm).

This means that the calibration ratio for photosensor 1 (measuring mirror displacements) and photoensor 2 (measuring frame displacements) is 34.86.

Since this "unity" value should be 34.86 for my transfer function magnitude plots (instead of the ~3 value I have), do I need to scale my data? It is strange that it differs by an order of magnitude...

5192   Thu Aug 11 14:32:12 2011 KojiSummarySUSPhotosensor Head Calibration Curve for TT Frame

The entry was quite confusing owing to many misleading wordings.

- The PS2 should be calibrated "as is". (i.e. should be calibrated with the frame)

- The previous calibrations with the highly reflective surface were 0.32V/mm and 0.26V/mm, respectively.
This time you have 0.10V/mm (with an undescribed surface). The ratio is not 32 but 3.2.

- The DC output of PS2 on the shaking setup was 2.5V. The DC output seen in the plot is 3.5V-ish.
This suggests the possibiliteies:
1) The surface has slightly higher reflectivity than the frame
2) The estimation of the distance between the frame and the PS2 during the TF measurement was not accurate.

- The word "DC coupling level" is misleading. I guess you mean the DC value of the vbration isolation transfer function
of the suspension.

 Quote: I have re-calibrated the photosensor I used to measure the displacements of the TT frame (what I call "Photosensor 2"). As before, the linear region is about 15.2mm to 25.4mm. It is characterized by the slope -0.0996 V/mm (-0.1 V/mm). Recall that photosensor 1 (used to measure mirror displacements) has a calibration slope of -3.2V/mm. The ratio of the two slopes (3.2/0.1 = 32). We should thus expect the DC coupling level to be 32? This is not what we have for the DC coupling levels in our data (2.5 for flexibly-supported, fully-assembled TT (with EDC, with bar), 4.2 for EDC without bar, 3.2 for rigid EDC without bar, 3.2 for no EDC, with bar, 3.2 for no EDC without bar) . I think I may need to do my calibration plot for the photosensor at the frame?

Here is the calibration curve (displacement versus voltage output) for the photosensor head that I made with the S5971 photodiodes and L9337 LEDs. This was made using a regular mirror. The linear region appears to be between 0.4 and 0.75cm. I will need to arrange the photosensor head so it measures displacements in the linear region of this plot. This plot was made using a 287 ohm resistor.

2465   Tue Dec 29 13:57:20 2009 Rana, Kiwamu, and HaixingUpdatePhotosPhotos of video switch box

Before we installed the video switch box, we also took some photos of it. We uploaded them onto the 40m Picasa.

Video Matrix

The first photo is the an entire view of the switch box. The following four photos are the details of the switch matrix.

The slideshow below is a dump of the last several months of photos from the Olympus. The originals have been deleted.

2535   Thu Jan 21 10:09:27 2010 KojiSummaryIOOPhotos of the optical tables

I made a wiki page dedicated for the photos of the optical tables.

http://lhocds.ligo-wa.caltech.edu:8000/40m/Optical_Tables

819   Sun Aug 10 16:57:02 2008 ranaSummaryPhotosPhotos from Vent 8/4 - 8/8
http://www.ligo.caltech.edu/~rana/40m/VentAug08/

I've added the D40 pictures from last week to this web page. I have done some cropping and
rotating to make things look better.

On page 3, there are some over head shots of the Michelson area so that one can use screw holes
to judge what the spacing between the suspensions is and also possibly the cavity lengths. Lets
also remember to measure the ITM-BS distance accurately using a tape measure or ruler while we
have the thing open.
41   Wed Oct 31 19:26:08 2007 Andrey RodionovRoutineGeneralPhotographs of "Mode-Cleaner Entrance"

Here are the pictures of "inside the chamber".
2129   Wed Oct 21 15:07:45 2009 AlbertoUpdateWIKI-40M UpdatePhotodiodes' configuration for the Upgrade

I uploaded on the Wiki (here) the results of an inventory over our current PDs, a list of the new ones that we're going to need for the new control scheme.

7794   Wed Dec 5 17:38:41 2012 RijuHowTo Photodiode transimpedance

I have started making the circuit to measure the transimpedance for the photodiode PDA10CF using Jenne's laser. I will continue it tomorrow.

7834   Fri Dec 14 14:40:31 2012 RijuUpdate Photodiode transimpedance

Photodiode PDA10CF was under test. The RF out signal of AG4395A had been divided by splitter with one output of the splitter going to R channel of the network analyzer and the other to the laser. The splitted laser beams - splitted with beam splitter - fall on two photodiodes - one reference and the other on PDA10CF. The outputs of these two photodiodes go to channel B and A respectively of the network analyzer. The measured transimpedance data had been collected using the GPIB connection.

The result is as follows:

7854   Tue Dec 18 16:44:00 2012 rijuUpdate Photodiode transimpedance

Today I measured the dark current of the PDA10CF. The output of the PD was connected to the A channel of the network analyzer, when there was no light falling on it. The response is collected using GPIB.

I will upload the result shortly.

7870   Fri Dec 21 19:49:39 2012 RijuUpdate Photodiode transimpedance

I have repeated the transimpedance measurement of PDA10CF. Also made the dark current noise measurement by connecting the PDA10CF output to the A channel of network analyzer.  The results are as follows. I I started to take the reading for shot noise intercept current using a light bulb in front of the PD, changing the current through the bulb, but at higher current the bulb filament got broken, so the experiment is incomplete.

7874   Thu Jan 3 20:34:43 2013 RijuUpdate Photodiode transimpedance

Today I have measured the transimpedance and dark-noise of the MC-REFL PD.

For transimpedance measurement I first collected the data of the reference Newfocus PD connecting it at channel B of Network-analyzer using the set-up of Jenne's laser. The data for the MC-REFL PD had been collected by connecting it to the A channel of Network Analyzer. To do that I shifted the Jenne's Laser to the table of MC-REFL PD, I moved the laser output on the table and fixed a lens and a mirror on the table. Taking the ratio of the two sets of datas I got the required trans-impedance.

Dark-noise readings were taken keeping the laser off.

I will upload the corresponding plots tomorrow.

7875   Fri Jan 4 13:23:10 2013 ranaUpdateElectronicsPhotodiode transimpedance

You have to correct this transimpedance ratio by correcting for the different levels of DC photocurrent in the two devices.

For the dark noise, you must always include a trace showing the noise of the measurements device (i.e. the analyzer noise must be less than the dark PD noise) with the same input attenuation setting.

7880   Tue Jan 8 14:01:21 2013 RijuUpdate Photodiode transimpedance

Here I upload the plots corresponding to my last day's measurements.

7881   Tue Jan 8 14:07:04 2013 RijuUpdateElectronicsPhotodiode transimpedance

 Quote: You have to correct this transimpedance ratio by correcting for the different levels of DC photocurrent in the two devices. For the dark noise, you must always include a trace showing the noise of the measurements device (i.e. the analyzer noise must be less than the dark PD noise) with the same input attenuation setting.

Hi,

The correction for different levels of DC photocurrent in the two devices had been taken care by one MATLAB code, the code that originally was made by Koji.

The analyzer noise I had not recorded; today I am going to record it.

Riju

7882   Tue Jan 8 15:28:41 2013 RijuUpdateElectronicsPhotodiode transimpedance

Quote:

 Quote: You have to correct this transimpedance ratio by correcting for the different levels of DC photocurrent in the two devices. For the dark noise, you must always include a trace showing the noise of the measurements device (i.e. the analyzer noise must be less than the dark PD noise) with the same input attenuation setting.

Hi,

The correction for different levels of DC photocurrent in the two devices had been taken care by one MATLAB code, the code that originally was made by Koji.

The analyzer noise I had not recorded; today I am going to record it.

Riju

Here is the data for AG4395A network/spectrum analyzer noise data. I collected the data by putting 50ohm terminator on channel A with same input attenuation setting (0dB attenuation).

7887   Wed Jan 9 19:32:24 2013 RijuUpdate Photodiode transimpedance

Summary:

Today I have tested the MC transmission-end RF photodiode PDA255 for transimpedance and dark noise using Jenne's Laser and AG4395A network/spectrum analyzer. The dark noise voltage distribution for the transmission and reflection PDs of MC and the analyzer has been compared.

Motivation:

I am to do the input mode cleaner cavity mode scan. The electronic and shot noise of the components used , particularly photodiode noise, will affect the peak position  of the modes, indicating the uncertainty in the measured frequencies of the modes. That will in turn give the uncertainty in the measured change of radius of curvature of the mirrors in presence of the laser beam, from which we will be able to calculate the uncertainty in the mirror-absorption  value.

Method:

For PD transimpedance measurement I used Jenne's laser along with AG4395 network analyzer. The RF out signal of AG4395A had been divided by splitter with one output of the splitter going to R channel of the network analyzer and the other to the laser. The splitted laser beams - splitted with beam splitter - fall on two photodiodes - one reference(Newfocus1617? PD, the DC and RF transimpedance values were taken from its datasheet ) and the other on PDA255. The outputs of these two photodiodes go to channel B and A respectively of the network analyzer. The measured transimpedance data had been collected using the GPIB connection. It had been ensured that the PD under test is not going to saturation, for that the source power level was kept to -40dBm. transimpedance measurements were compensated by the ratio of DC photocurrent.

For dark noise measurement the output of the PD was connected to the A channel of the AG4395A, when there was no light falling on it. The response is collected using GPIB. The attenuation of channel A was made 0dB. ( AG4395A was kept in Spectrum analyzer mode in Noise Format).

Results:

The plots corresponding to the measurements are attached.

Discussion:

The comparison for the dark noise voltage levels of the MC transmission PD (PDA255) with MC REFL PD has been made with analyzer dark noise voltage. It is shown in the attachment (I will upload the dark noise current comparison too....since the output darknoise depends on the gain of the circuit, it is important to divide this voltage spectra by transimpedances.)

7907   Wed Jan 16 18:58:08 2013 RijuUpdate Photodiode transimpedance

Today I have taken the reading for shot noise intercept current for the PDA255 - MC transmission RF PD. To do that I have put an incandescent bulb (JKL lamps, 222 bulbs, voltage and current rating 2.25V and 0.25A) in front of the PD and varied the current through it from 0A to 0.29A at 2.2V. I measured the corresponding DC voltage and took the noise data (4395A spectrum analyzer/ format noise, channel attenuation 0dB) through GPIB .

I will process the data and upload the result soon.

7926   Tue Jan 22 17:29:29 2013 RijuUpdate Photodiode transimpedance

Riju

Summary:  I am stuck with the measurement of shot-noise-intercept-current of PDA255. Seeking help.

Motivation: It is to measure the shot noise intercept current for PDA255 - the MC transmission RF photodiode to get an idea for the noise current for the detector.

Method: It is as described in the elog  7907

Result: The plot is attached here.

Discussion: The result I got is really unexpected, the noise voltage should increase with the DC current level that corresponds to the increment of light level too. But actually it is decreasing. Three times I have repeated this experiment and got the same result. I want some suggestion on this regard.

7927   Tue Jan 22 19:51:52 2013 KojiUpdate Photodiode transimpedance

- The data should be plotted in a log-log scale.
- The data points were only taken in the high current region.

- The plot may suggest that the amplifier saturate at the RF.

PDA255 has the nomial transimpedance gain of 10^4 Ohm.
The DC current of 10^-3 gives the output of 10V.
This plot may tell that the saturation starts even at the 1/10 of the full DC range.

The plot doesn't have many points below 0.1mA.
Consult with my plots for the similar measurements.
The measured points are logarithmically spaced. Use the same technique.

- It is also very unknown that how the noise level is calculated. No info is supplied in the plot or the elogs.

7929   Wed Jan 23 11:43:19 2013 RijuUpdate Photodiode transimpedance

 Quote: - The data should be plotted in a log-log scale. - The data points were only taken in the high current region. - The plot may suggest that the amplifier saturate at the RF. PDA255 has the nomial transimpedance gain of 10^4 Ohm. The DC current of 10^-3 gives the output of 10V. This plot may tell that the saturation starts even at the 1/10 of the full DC range. The plot doesn't have many points below 0.1mA. Consult with my plots for the similar measurements. The measured points are logarithmically spaced. Use the same technique. - It is also very unknown that how the noise level is calculated. No info is supplied in the plot or the elogs.

Here I am attaching the plot in loglog scale. I have taken the data-points from no light condition to the maximum light condition, the minimum variation possible in the current supply was 0.01A. The noise was visibly decreasing at higher light level.

For the noise level calculation I took the average of total noise in the range 7-60MHz. For each range the formula used was

noisevalue= sqrt(data(:,2)*100)/sqrt(2)/sqrt(channel BW);     -- this conversion is needed since the data was collected in the 2 column format: frequency, spectrum(W).

ELOG V3.1.3-