Received additional front/rear panels. Updated the original entry and Wiki [Link]
Missed to note: The IF test was done at TP7 and TP6 using pomona clips i.e. brefore the preamp.
The parts will be ordered by Koji The components for the additional BIO I/F have been ordered.
I believe the aLIGO style invac dsub cables and the conventional 40m ones are incompatible.
While the aLIGO spec is that Pin1 (in-vac) is connected to the shield, Pin13 (in-vac) is the one for the conventional cable. I still have to check if Pin13 is really connected to the shield, but we had trouble before for the IO TTs https://nodus.ligo.caltech.edu:8081/40m/7864.
(At least one of the existing end cables did not show this Pin13-chamber connection. However, the cables OMC/IMC chambers indicated this feature. So the cables are already inhomogenious.)
- Which way do we want to go? Our electronics are updated with aLIGO spec (New Sat amp, OMC electronics, etc), so I think we should start making the shift to the aLIGO spec.
- Attachment Top: The new coil drivers can be used together with the old cables using a custom DB25 cable (in-air).
- Attachment Mid: The combination of the conventional OSEM wiring and the aLIGO in-vac cable cause the conflict. The pin1 which is connected to the shield is used for the PD bias.
- Attachment Bottom: This can be solved by shifting the OSEMs by one pin.
o The aLIGO cables have 12 twisted pair wires, but paired signals do not share a twisted pair.
--- No. This can't be solved by rotating the connectors.
o This modification should be done only for the new suspension.
--- In principle, we can apply this change to any SOSs. However, this action involves the vent. We probably want to install the new electronics for the existing suspensions before the vent.
o ^- This means that we have to have two types of custom DB25 in-air cables.
--- Each cable should handle "Shield wire" from the sat amp correctly.
Active TT Pin Issue
and the thread
Active TT Pin Swapping (December 21, 2012)
TT Wiring Diagram (Wiki)
How were the statistics of them? i.e. # of Good OSEMs, # of OK OSEMs, etc...
I just saw the PRM watchdog tripped at ~15:20 local (23:20UTC). I restored the PRM but I saw only the side watchdog tripped.
Again at 15:27
17:55 I found the PRM was oscillating while the watchdogs were not tripped. I turned off the OPLEV servos and this made the PRM calmed down. But I didn't turn on the OPLEVs for the past two trips. How were the OPLEVs turned on???
Ah, I'm sorry, I missed the line that Gautam was running the free-swinging test on the PRM.
The two kicks starting from 23:08:50 and from 23:26:31 were spoiled. Did it make the measurement completely waisted?
Stephen and I discussed the nominal heights of the BHD platform components.
Per Gautam's request, I've checked the coil resistances and inductances.
A DSUB25 breakout was directly connected to the flange (Attachment 1).
The impedance meter was nulled every time the measurement range and type (R or L) were changed.
Feedthru connector: PRM1
Pin1 - flange: R = 0.8Ω
Pin11-23 / R = 1.79Ω / L=3.21mH
Pin 7-19 / R = 1.82Ω / L=3.22mH
Pin 3-15 / R = 1.71Ω / L=3.20mH
Feedthru connector: BS1
Pin1 - flange: R = 0.5Ω
Pin11-23 / R = 1.78Ω / L=3.26mH
Pin 7-19 / R = 1.63Ω / L=3.30mH
Pin 3-15 / R = 1.61Ω / L=3.29mH
Feedthru connector: SRM1
Pin1 - flange: R = 0.5Ω
Pin11-24 / R = 18.1Ω / L=3.22mH
Pin 7-20 / R = 18.8Ω / L=3.25mH
Pin 3-16 / R = 20.3Ω / L=3.25mH
Feedthru connector: PRM2
Pin1 - flange: R = 0.6Ω
Pin11-23 / R = 1.82Ω / L=3.20mH
Pin 7-19 / R = 1.53Ω / L=3.20mH
Pin 3-15 / R = N/A
Feedthru connector: BS2
Pin1 - flange: R = 0.6Ω
Pin11-23 / R = 1.46Ω / L=3.27mH
Pin 7-19 / R = 1.54Ω / L=3.24mH
Pin 3-15 / R = N/A
Feedthru connector: SRM2
Pin1 - flange: R = 0.7Ω
Pin11-24 / R = N/A
Pin 7-20 / R = 18.5Ω / L=3.21mH
Pin 3-16 / R = 19.1Ω / L=3.25mH
The SRM pinouts seem mirrored compared to the others. In fact, these two connectors are equipped with mirror cables (although they are unshielded ribbons) (Attachment 2).
The SRM sus is located on the ITMY table. There is a long in vacuum DSUB25 cable between the ITMY and BS tables. I suspect that the cable mirrors the pinout and this needs to be corrected by the in-air mirror cables.
I went around the lab and did not find any other suspensions which have the mirror cable.
WIth the BHD configuration, we will move the feedthru for the SRM to the one on the ITMY chamber. So I believe the situation is going to be improved.
For magnet strength measurement: There is a gaussmeter in the flukes' drawer (2nd from the top). It turns on and reacts to a whiteboard magnet.
I've brought 4 DO-32L-PE cards from WB for BHD upgrade for Jon.
I want to emphasize the followings:
I'm going to remove REFL11 demod for the noise check/circuit improvement.
First I checked the noise levels and the transfer functions of the daughterboard preamp were checked. The CH-1 of the SR785 seemed funky (I can't comprehensively tell yet how it was), so the measurement maybe unreliable.
For the replacement of AD797, I tested OP27 and TLE2027. TLE2027 is similar to OP27, but slightly faster, less noisy, and better in various aspects.
The replacement of the AD797 and whatever-film resistors with LTE2027 and thin-film Rs were straightforward for the I phase channel, while the stabilization of the Q phase channel was a struggle (no matter I used OP27 or TLE2027). It seems that the 1st stage has some kind of instability and I suffered from 3Hz comb up to ~kHz. But the scope didn't show obvious 3Hz noise.
After a quite bit of struggle, I could tame this strange noise by adjusting the feedback capacitor of the 1st stage. The final transfer functions and the noise levels were measured. (To be analyzed later)
Now the REFL11 LO cable was replaced from the soft low noise audio coax (Belden 9239) to jacketed solder-soaked coax cable (Belden 1671J - RG405 compatible). The original cable indicated the delay of -34.3deg (@11MHz, 8.64ns) and the loss of 0.189dB.
I took 80-inch 1671J cable and measured the delay to be ~40deg. The length was adjusted using this number and the resulting cable indicated the delay of -34.0deg (@11MHz, 8.57ns) and the loss of 0.117dB.
The REFL11 demod module was restored and the cabling around REFL11 and AS110 were restored, tightened, and checked.
I've removed the PD mon cables from the NI RF switch. The open ports were plugged with 50Ohm temirnators.
Attachment 1: Transfer Functions
The original circuit had a gain of ~20 and the phase delay of ~1deg at 10kHz, while the new CH-I and CH-Q have a phase delay of 3 deg and 2 deg, respectively.
Attachment 2: Output Noise Levels
The AD797 circuit had higher noise at low frequency and better noise levels at high frequency. Each TLE2027 circuit was tuned to eliminate the instability and shows a better noise level compared to the low-frequency spectrum of the AD797 version.
RXA: AD797 , all hail the op-amps ending with 27 !
I've worked on packing the components for the following chassis
- 5 16bit AI chassis
- 4 18bit AI chassis
- 7 16bit AA chassis
- 8 HAM-A coil driver chassis
They are "almost" ready for shipment. Almost means some small parts are missing. We can ship the boxes to the company while we wait for these small parts.
And some more additional items to fill the emptying stock.
We have received 9x 18bit DAC adapter boards (D1000654)
I think the PSL HEPA (both 2 units) are not running. The switches were on. And the variac was changed from 60% to 0%~100% a few times but no success.
I have no troubleshooting power anymore today. The main HEPA switch was turned off.
- Last week we found both of the PSL HEPA units were not running.
- I replaced the capacitor of the north unit, but it did not solve the issue. (Note: I reverted the cap back later)
- It was found that the fans ran if the variac was removed from the chain.
- But I'm not certain that we can run the fans in this configuration with no attendance considering fire hazard.
@3AM: UPON LEAVING the lab, I turned off the HEPA. The AC cable was not warm, so it's probably OK, but we should wait for the continuous operation until we replace the scorched AC cable.
The capacitor replacement was not successful. So, the voltages on the fan were checked more carefully. The fan has the three switch states (HIGH/OFF/LOW). If there is no load (SW: OFF), the variac out was as expected. When the load was LOW or HIGH, it looked as if the motor is shorted (i.e. no voltage difference between two wires).
I thought the motors may have been shorted. But if the load resistance was measured with the fluke meter, it showed some resistance
- North Unit: SW LOW 4.6Ohm / HIGH 6.0Ohm
- South Unit: SW LOW 6.0Ohm / HIGH 4.6Ohm (I believe the internal connection is incorrect here)
I believed the motors are alive! Then the fans were switched on with the variac removed... they ran. So I set the switch LOW for the north unit and HIGH for the south unit.
Then I inspected the variac:
So, this scorched AC plug/cable connected directly to the AC right now. I'm not 100% confident about the safety of this configuration.
Also I am not sure what was wrong with the system.
So, while I'm in the lab today, I'll keep the HEPA running, but upon my taking off, I'll turn it off. We'll discuss what to do in the meeting tomorrow.
Basically I went around all the chambers and all the DB25 flanges to check the invac cable configurations. Also took more time to check the coil Rs and Ls.
Exceptions are the TTs. To avoid unexpected misalignment of the TTs, I didn't try to disconnect the TT cables from the flanges.
Upon the disconnection of the SOS cables, the following steps are taken to avoid large impact to the SOSs
After the measurement, IMC was lock and aligned. The two arms were locked and aligned with ASS. And the PRM alignment (when "misalign" was disengaged) was checked with the REFL CCD.
So I believe the SOSs are functioning as before, but if you find anything, please let me know.
5x 16bit ADC adapter boards (D0902006) assembled.
We received 10x 16bit ADC adapter boards from Todd. S2100687~S2100696
The number of soldered resistors seems to be less than that on the schematics. They are related to duotone, so check if it's OK upon use.
I was looking at the laser head/amp and somehow decided to open the glue freezer. And it was stuck. I've managed to open it but the upper room was completely frozen.
Some of the batteries were embedded in a block of ice. I think we should throw them out.
Can the person who comes in the morning work on defrosting?
- Coordinate with Yehonathan and move the amps and the wooden crate so that you can move the freezer.
- Remove the contents to somewhere (it's OK to be room temp for a while)
- Unplug the freezer
- Leave the freezer outside with the door open. After a while, the ice will fall without care.
- At the end of the day, move it back to the lab. Continue defrosting the other day if the ice remains.
PSL Shutter closed / MC Autolocker disabled / PSL mechanical shutter closed / Laser injection current turned to zero / Laser turn off (red button) / Laser key turned off
The laser stat before the shutdown:
- LD Temp A: Set 22.07 (Untouched)
- LD Temp B: Set 21.03(Untouched)
- Laser Injection Current: Dial 9.53, Actual 2.100 -> Dial was moved to zero upon shutting down
- Laser Crystal Temp: Dial 3.34 (untouched) Set 30.57 Actual 30.60 (Untouched)
PSL Table covering
- Because of the so many cables going up and down, sealing the PSL table with the metalized sheet was not easy. Therefore, the sheets have been just softly laid above the optics. (Attachment 1)
- The largest sheet which covers the east half of the table was taped to the table at the bottom, so that the air from the chimneys (see below) does not come up to the table
- The large dust could come from the opening of the enclosure during the filter replacement. So it was considered to be easier to seal the openings. (Attachment 2)
- Of course, the HEPAs are going to be tested after the maintenance work. It means that vent paths were needed so that the seals do not explode with the pressure (together with dust).
- Thus, the tubes of the sheets are attached to the seals to form "chimneys" for guiding the airflow beneath the table. (Attachment 2/3/4)
- This configuration was not meant to be sufficiently strong for a continuous run of the fans. Long running of the HEPAs may cause the failure of the seal tapes.
Therefore the HEPA test should be done with a low flow rate and/or a short period of high flow.
- Once the work has been done, all the sheets should be carefully removed without scattering the fallouts onto the optics.
I also located the (possible) HEPA filters in the lab. (Attachments 1~3)
Oh! This is NO-NO! We can't place anything in front of the mains breakers. (Attachment 2)
I relocated the objects (Attachment 3)
It's probably too late to say but there are/were two boxes. (just for record)
The new HEPA speed controllers are attached at the middle of the HEPA unit (not at the edge of the unit)... (Attachment 1)
You still need a step./stool to touch the knob and need a ladder for a more precise setting.
We still don't know the optimal speed of the nominal IFO operation. For now, the HEPAs are running at the max speed (Attachment 2).
Once we know the optimal setting, we mark the knobs so that we can see them only with the step.
New HV power supply from Company 'M' has been delivered. So I decided to compare the noise levels of some HV supplies in the lab. There are three models from companies 'H', 'K', and 'M'.
The noise level was measured with SR785 via Gautam's HP filter with protection diodes.
'H' is a fully analog HV supply and the indicator is analog meters.
'K' is a model with a LCD digital display and numerical keypad.
'M' is a model with a knob and digital displays.
All the models showed that the noise levels increased with increased output voltage.
Among these three, H showed the lowest noise. (<~1uV/rtHz@10Hz and <50nV/rtHz@100Hz) (Attachment 1)
K is quite noisy all over the measured freq range and the level was <50uV/rtHz. Also the PSD has lots of 5Hz harmonics. (Attachment 2)
M has a modest noise level (<~30uV/rtHz@10Hz and <1uV/rtHz@100Hz)except for the noticeable line noise (ripple). (Attachment 3)
The comparison of the three models at 300V is Attachment 4. The other day Gautam and I checked the power spectrum of the HV coil driver with KEPCO and the output noise level of the coil driver was acceptable. So I expect that we will be able to use the HV supply from Company M. Next step is to check the HV driver noise with the model by M used as the supply.
I believe that there is an internal setting for the minimum flow, so the flow is not linear ("0%" is not zero), but we should mark this flow speed once you find this is sufficiently low for the locking too.
The other day I felt hot at the X end. I wondered if the Xend A/C was off, but the switch right next to the SP table was ON (green light).
I could not confirm if the A/C was actually blowing or not.
I also noticed some sound in the control room. (didn't open the MP3 yet)
I'm afraid that the hard disk in the control room iMac is dying.
Did you match the local PC time with the GPS time?
No, this is the property of the suspension assembly. The mass says 10kg
Could you do the same for the testmass assembly (only the suspended part)? The units are good, but I expect that the values will be small. I want to keep at least three significant digits.
I believe I did the identical test with the one in [40m ELOG 15786]. The + input of PA95 was shorted to the ground to exclude the noise from the bias input. The voltage noise at TP6 was measured with +/-300V supply by two HP6209 and two Matsusada R4G360.
With R4G360, the floor level was identical and 60Hz line peaks were less. It looks like R4G360 is cheap, easier and precise to handle, and sufficiently low noise.
Calculation for the SOS POS/PIT/YAW resonant frequencies
- Nominal height gap between the CoM and the wire clamping point is 0.9mm (cf T970135)
- To have the similar res freq for the optic with the 3" metal sleeve is 1.0~1.1mm.
As the previous elog does not specify this number for the current configuration, we need to asses this value and the make the adjustment of the CoM height.
HP HV power supply ( HP6209 ) were returned to Downs
11 new Satellite Amps were picked up from Downs. 7 more are coming from there. I have one spare unit I made. 1 sat amp has already been used at MC1.
We had 8 HAM-A coil drivers delivered from the assembling company. We also have two coil drivers delivered from Downs (Anchal tested)
DC Power Strip Assemblies delivered and stored behind the Y arm tube (Attachment 1)
I also moved the spare 1U Chassis to the same place.
Differential misalignment of the OMCs
40m BHD will employ two OMCs on the BHD platform. We will have two SOSs for each of the LO and AS beams. The challenge here is that the input beam must optimally couple to the OMCs simultaneously. This is not easy as we won't have independent actuators for each OMC. e.g. The alignment of the LO beam can be optimally adjusted to the OMC1, but this, in general, does not mean the beam is optimally aligned to the OMC2.
When a beam with the matched mode to an optical cavity has a misalignment, the power coupling C can be reduced from the unity as
where is the waist radius, is the divergence angle defined as , and are the beam lateral translation and rotation at the waist position.
The waist size of the OMC is 500um. Therefore = 500um and = 0.68 mrad. If we require C to be better than 0.995 according to the design requirement document (T1900761). This corresponds to (only) to be 35um and (only) to be 48urad. These numbers are quite tough to be realized without post-installation adjustment. Moreover, the OMCs themselves have individual differences in the beam axis. So no matter how we set the mechanical precision of the OMC installation, we will introduce a maximum of 1mm and ~5mrad uncertainty of the optical axis.
Suppose we adjust the incident beam to the OMC placed at the transmission side of the BHD BS. The reflected beam at the BS can be steered by picomotors. The distance from the BS to the OMC waist is 12.7" (322mm) according to the drawing.
So we can absorb the misalignment mode of (, ) = (0.322 , ). This is a bit unfortunate. 0.322m is about 1/2 of the rayleigh range. Therefore, this actuation is still angle-dominated but a bit of translation is still coupled.
If we enable to use the third picomotor on the BHD BS mount, we can introduce the translation of the beam in the horiz direction. This is not too huge therefore we still want to prepare the method to align the OMC in the horiz direction.
The difficult problem is the vertical alignment. This requires the vertical displacement of the OMC. And we will not have the option to lower the OMC. Therefore if the OMC2 is too high, we have to raise the OMC1 so that the resulting beam is aligned to the OMC2. i.e. we need to maintain the method to raise both OMCs. (... or swap the OMCs). From the images of the OMC beam spots, we'll probably be able to analyze the intracavity axes of the OMCs. So we can always place the OMC with a higher optical axis at the transmission side of the BHD BS.
Can you just cut the viton tips smaller? If you cut it to have some wedge (or say, taper), it can get stuck with the vent hole.
How about to use the non-Ag coated threaded shaft + the end SS masses with helicoils inserted? Does this save the masses to get stuck?
- Could you explain what is the blue thing in Attachment 1?
- To check the validity of the signal chain, can you make a diagram summarizing the path from the fast BO - BO I/F - Acromag - This opto-isolator - the coil driver relay? (Cut-and-paste of the existing schematics is fine)
This RTS also use the BO interface with an opto isolator. https://dcc.ligo.org/LIGO-D1002593
Could you also include the pull up/pull down situations?
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.
If my understanding is correct, the (photo receiving) NPN transistor of the optocoupler is energized through the acromag. The LED side should be driven by the coil driver circuit. It is properly done for the "enable mon" through 750Ohm and +V. However, "Run/Acquire" is a relay switch and there is no one to drive the line. I propose to add the pull-up network to the run/acquire outputs. This way all 8 outputs become identical and symmetric.
We should test the configuration if this works properly. This can be done with just a manual switch, R=750Ohm, and a +V supply (+18V I guess).
I made a flow sensor with a stick and tissue paper to check the airflow.
- The HVAC indicator was not lit, but it was just the blub problem. The replacement bulb is inside the gray box.
- I went to the south arm. There are two big vent ducts for the outlets and intakes. Both are not flowing the air.
The current temp at 7pm was ~30degC. Max and min were 31degC and 18degC.
- Then I went to the vertex and the east arm. The outlets and intakes are flowing.
25 HAM-A coil driver units were fabricated by Todd and I've transported them to the 40m.
2 units we already have received earlier.
The last (1) unit has been completed, but Luis wants to use it for some A+ testing. So 1 more unit is coming.
It is a belated report: We received 5 more sat amps on June 4th. (I said 7 more but it was 6 more) So we still have one more sat amp coming from Todd.
- 1 already delivered long ago
- 8 received from Todd -> DeLeone -> Chub. They are in the lab.
- 11 units on May 21st
- 5 units on Jun 4th
Total 1+8+11+5 = 25
1 more unit is coming
Then, can we replace the four small EQ stops at the bottom (barrel surface) with two 1/4-20 EQ stops? This will require drilling the bottom EQ stop holders (two per SOS).
The issue of the PD output was that the PD whitened outputs of the sat amp (D080276) are differential, while the successive circuit (D000210 PD whitening unit) has the single-ended inputs. This means that the neg outputs (D080276 U2) have always been shorted to GND with no output R. This forced AD8672 to work hard at the output current limit. Maybe there was a heat problem due to this current saturation as Anchal reported that the unit came back sane after some power-cycling or opening the lid. But the heat issue and the forced differential voltage to the input stage of the chip eventually cause it to fail, I believe.
Anchal came up with the brilliant idea to bypass this issue. The sat amp box has the PD mon channels which are single-ended. We simply shifted the output cables to the mon connectors. The MC1 sus was nicely damped and the IMC was locked as usual. Anchal will keep checking if the circuit will keep working for a few days.
We held the lab cleaning for the first time since the campus reopening (Attachment 1).
Now we can use some of the desks for the people to live! Thanks for the cooperation.
We relocated a lot of items into the lab.
We still want to make some more cleaning:
- Electronics workbenches
- Stray setup (cart/wagon in the lab)
- Some leftover on the desks
- Instruments scattered all over the lab
- Ewaste removal