I can't explain the mechanical switching sound Gautam reported. The relay controlling power to the TP2 forepump is housed in the main AC relay box under the arm tube, not in the Acromag chassis, so it can't be from that. I've cycled through the pumpdown sequence several times and can't reproduce the effect. The Acromag switches for TP2 still work fine.
In any case, I've made modifications to the vacuum interlocks that will help with two of the issues:
C1:AUX-PSL_ShutterRqst --> 0
After finishing this vac work, I began a new pumpdown at ~4:30pm. The pressure fell quickly and has already reached ~1e-5 torr. TP2 current and temp look fine.
However, when opening V4 (the foreline of TP1 pumped by TP2), I heard a loud repeated click track (~5Hz) from the electronics rack. Shortly after, the interlocks shut down all the TPs again, citing "AC power loss". Something is not right, I leave it to Jon and Chub to investigate.
The interlocks tripped at ~630am local time. Jordan reported that TP2 was supposedly running at 52 C (!).
V1 was already closed, but TP2 was still running. With him standing by the rack, I remotely exectued the following sequence:
Jordan confirmed (by hand) that TP2 was indeed hot and this is not just some serial readback issue. I'll do the forensics later.
Here is the timeline. This suggests TP2 backing RP failure.
1st line: TP2 foreline pressure went up. Accordingly TP2 P, current, voltage, and temp went up. TP2 rotation went down.
2nd line: TP2 temp triggered the interlock. TP2 foreline pressure was still high (10torr) so TP2 struggled and was running at 1 torr.
3rd line: Gautam's operation. TP2 was isolated and stopped.
Between the 1st line and 2nd line, TP2 pressue (=TP1 foreline pressure) went up to 1torr. This made TP1 current increased from 0.55A to 0.68A (not shown in the plot), but TP1 rotation was not affected.
The foreline pressure of TP2 was 1.4 Torr this morning. This drypump worked well for ten months.
Recently rebuilt drypump with new seal was swapped in.
This is how you do it: close V1, V4 and turn off TP2. Replace drypump and start up TP2
Set pump speed to 50 K rpm and open V4 to TP1 Note that the Maglev was not turned off because V4 was closed off only 5-10 minutes.
Open V1 the status is Vac Normal.
TP2 is rotating at 50K rpm, current pick up 0.2A, the temp is 26C and its foreline pressure 33 mTorr
Dry fore pump of TP3 replaced by brand new Varian SH-110 at 1.1 Torr_75,208 hrs
The annuloses were closed off for 25 minutes. We are back to VACUUM NORMAL mode.
The TP3 fore line pressure dropped to 44 mTorr at 25 minutes in operation.......9.4mTorr at day 2 with full annulos load
I removed the forepump (Varian SH-110) for TP3 today to see why it had failed over the weekend. I tested it in the C&B lab and the ultimate pressure was only ~40torr. I checked the tip seals and they were destroyed. The scroll housing also easily pulled off of the motor drive shaft, which is indicative of bad bearings. The excess travel in the bearings likely led to significant increase in tip seal wear. This pump will need to be scrapped, or rebuilt.
I tested the spare Varian SH-110 pump located at the X-end and the ultimate pressure was ~98 mtorr. This pump had tip seals replaced on 11/5/18, and is currently at 55163 operating hours. It has been installed as the TP3 forepump.
Once installed, restarting the pump line occured as follows: V5 Closed, VA6 closed, VASE Closed, VASV closed, VABSSCI closed, VABS closed, VABSSCO closed, VAEV closed, VAEE closed,TP3 was restarted and once at normal operation, valves were opened in same order.
The pressure differential interlock condition for V5 was temporaily changed to 10 torr (by Gautam), so that valves could be opened in a controlled manner. Once, the vacuum system was back to normal state the V5 interlock condition was set back to the nominal 1 torr. Vacuum system is now running normally.
While the pumpspool is vented, I thought it would be a convenient time to change out the tip seal on the TP3 forepump. This one had not been changed since 2018, so as preventative maintence I had JC remove the pump and begin cleaning/installing the new tip seal.
Unfortunately the tip seal broke, but I have ordered another. We should have this pump ready to go late next week. If one is needed sooner, there is a spare IDP 7 pump we can install as the TP3 forepump.
Jordan recieved the new tip seal Friday afternoon and I continued the replacement process in the morning. Finishing up, we proceeded to test the pump in the Clean and Bake room. The pump's pressure lowered to 110 mTorr, and we continue pumping so the seal can recieve a good fitting.
Update: We have confirmed the pump is working great and have reinstalled this back into the vacuum system. Note: The same O-Rings were used.
I came to the campus and Gautam notified that he just had received the alert from the vac watchdog.
I checked the vac status at c1vac. PTP3 went up to 10 torr-ish and this made the diff pressure for TP3 over 1torr. Then the watchdog kicked in.
To check the TP3 functionality, AUX RP was turned on and the manual valve (MV in the figure) was opened to pump the foreline of TP3. This easily made PTP3 <0.2 torr and TP3 happy (I didn't try to open V5 though).
So the conclusion is that RP for TP3 has failed. Presumably, the tip-seal needs to be replaced.
Right now TP3 was turned off and is ready for the tip-seal replacement. V5 was closed since the watchdog tripped.
Disconcerting because those tip seals were just replaced . Maybe they were just defective, but if there is a more serious problem with the pump, there is a spare Varian roughing pump (the old TP2 dry pump) sitting at the X-end.
I reset the interlock error to unfreeze the vac controls (leaving V5 closed).
Gautam and I debugged a communications problem with TP3 that was causing its python service to fail. We traced the problem back to the querying of the pump controller for its operational parameters (speed, voltage, temp). Some small percentage of the time (~5%, indeterministically), the pump controller is returning an invalid response which causes the service to shut itself down and signal a NO COMM error.
As a temporary fix, I wrapped the failing query in an exception handler to continue past this particular error. However, we suspect the microprocessor in the TP3 controller may be beginning to fail. There is a spare controller sitting right next to it in the vacuum rack. We will ask Chub to install the replacement in the near future.
gautam: this pump is responsible for pumping the annular volume under normal operations. while this problem is being resolved, the annular volume is valved off (as it has been since July 2019 anyway which is when this problem first manifested).
PSL shutter closed at 6e-6 Torr-it
The foreline pressure of the drypump is 850 mTorr at 8,446 hrs of seal life
V1 will be closed for ~20 minutes for drypump replacement..........
9:30am dry pump replaced, PSL shutter opened at 7.7E-6 Torr-it
Valve configuration: vacuum normal as TP3 is the forepump of the Maglev & annuloses are not pumped.
TP3 drypump replaced at 655 mTorr, no load, tp3 0.3A
This seal lasted only for 33 days at 123,840 hrs
The replacement is performing well: TP3 foreline pressure is 55 mTorr, no load, tp3 0.15A at 15 min [ 13.1 mTorr at d5 ]
Valve configuration: Vacuum Normal, ITcc 8.5E-6 Torr
Dry pump of TP3 replaced after 9.5 months of operation.[ 45 mTorr d3 ]
The annulosses are pumped.
Valve configuration: vac normal, IFO pressure 4.5E-5 Torr [1.6E-5 Torr d3 ] on new ITcc gauge, RGA is not installed yet.
Note how fast the pressure is dropping when the vent is short.
IFO pressure 1.7E-4 Torr on new not logged cold cathode gauge. P1 <7E-4 Torr
Valve configuration: vac.normal with anunulossess closed off.
TP3 was turned off with a failing drypump. It will be replaced tomorrow.
All time stamps are blank on the MEDM screens.
The forline pressure of TP3 was 399 mTorr
It was replaced this morning at TP3 controller 134,638hrs with the "failed TP2 station" drypump. The foreline pressure now at TP3 is 100 mTorr at 6 hrs of operation.[ at day 3 63 mT ]
IFO pressure at CC Hornet 7.9e - 6 Torr
Valve configuration: vacuum normal as TP3 is the forepump of the Maglev & the annuloses are not pumped
The TP3 foreline pressure was 4.8 Torr, 50K rpm 0.54A and 31C........Maglev rotation normal 560 Hz....... IFO pressure 7.2e- 6 Torrit was not effected
V1 closed ......replaced drypump.........V1 opened
IFO 6.9e-6 Torrit at 19:55, TP3fl 18 mT, 50Krpm 0.15A 24C
VM1 is still closed
TP2's fore line - dry pump replaced at performance level 600 mTorr after 10,377 hrs of continuous operation.
Where are the foreline pressure gauges? These values are not on the vac.medm screen.
The new tip seal dry pump lowered the small turbo foreline pressure 10x
TP2fl after 2 day of pumping 65mTorr
TP2 dry pump replaced at fore pump pressure 1 Torr, TP2 50K_rpm 0.34A
Top seal life 6,362 hrs
New seal performance at 1 hr 36 mTorr,
Maglev at 560 Hz, cc1 6e-6 Torr
TP3 dry pump replaced at 540 mT as TP3 50K_rpm 0.3A with annulos load. It's top seal life time was 11,252 hrs
[Jenne, Kiwamu, and Steve via phone]
Around 9:30pm, Kiwamu and I came back from dinner, and were getting ready to begin the beam scan measurements. I noticed that one of the vacuum pumps was being very loud. Kiwamu noted that it is the fore pump for TP3's turbo, which he and Steve replaced in January (elog 2538). We had not noticed these noises before leaving for dinner, around 8pm.
We called Steve at home, and he could hear the noise through the phone. He said that even though it was really loud, since it was reading 3.3mTorr (on the display of the controller, in the vacuum rack just above head-height) which is close to the nominal value, it should be fine to leave. He will check it out in the morning. If it had been reading at or above ~1Torr, that's indicative of it being really bad, and we would have needed to shut it off.
For future reference, in case we need to turn it off, Steve said to use the following procedure:
1. Close VM3, to isolate the RGA, which is what this pump is currently (while we're at atmosphere) pumping on. I don't know if there are other things which would need to be shut at this stage, if we were at vacuum nominal.
2. Close VM5, which is right in front of TP3, so TP3's pump is just pumping on itself.
3. Push the "Stop" button on the Turbo controller for TP3, in the vacuum rack, about waist level. Turning off the turbo will also turn off the fore pump.
UPDATE, 1am: The controller in the rack is reading 3.1mTorr, so the pump, while still noisy, still seems to be working.
Is this one close to failure as well?
The foreline pressure of TP3 is 2.9 mTorr The drypump is loosing it's bearing and it is very noisy.
V3, V5 closed and TP3 small turbo controller off. This turned off the noisy forepump that has to be replaced.
RGA is running at cc4 2e-6 Torr
The RGA was turned off at cc4 1e-5 Torr
TP3 foreline's dry pump is getting noisier and noisier. Turbo TP3 is pumping on the annulos. The foreline pressure is 7.2 mTorr and it is not degrading. It was swapped in March 5, 2013
The seal is very good, but the bearing is dying.
The drypump is replaced at 95,781 hrs on TP3 controller time. The foreline pressure is 30 mTorr and dropping.
It is 13 mTorr after 17 hours of pumping.
For some time now, I've been puzzled by the unreliability of the ASS_X dither alignment servo. Leaving the servo on, TRX often begins to decay to a lower value, and even after freezing the dither at the maximum TRX values, I can manually align the mirrors to increase TRX. We have suspected some kind of clipping in the TRX path that is responsible for this behaviour. Today I decided to investigate this a bit further. To have the arm locked and to inspect the beam, we have to change the locking trigger - TRX is what is normally used, but I misaligned the Y arm completely, and used AS110 as a trigger instead. There is some strangeness in the triggering topology, but this deserves a separate elog.
Once the arm was locked (and relocks using the AS110 trigger in the event of an unlock), I was able to trace the beampath on the EX table with an IR card. The TRX beam is rather large and weak, so it is hard to see, but as best as I can tell, the only real danger of clipping (or perhaps the beam is already clipped) is on the final steering mirror before the beam hits the (Thorlabs) PD. Steve/Pooja are working on getting a photo of this, and will upload it here shortly. Options to mitigate this:
The EX QPD has stopped working since the Acromag install. If it were working, we wouldn't have to rely on the alternate triggering with AS110 and instead just use the QPD as TRX, while we debug the Thorlabs PD path.
I opted for the quickest fix - I raised the height of the offending steering mirror using a 0.25" shim. In the long term, we can get a taller post machined. After raising the mirror height, I then checked the DC centering of the spot on the DC PD using a scope.
Looking at the performance of the X arm ASS, I no longer see the strange oscillatory behaviour I described in my previous post . Moreover, the TRX level was ~1 before be raising the steering mirror - but it is now ~1.2. So we were certainly losing some power.
These are the settings which determine the transmon (eg, TRX) amplitude, and which are updated by the matchTransMon scripts.
For the X arm
op440m:AutoDither>tdsread C1:LSC-TRX_GAIN C1:LSC-LA_PARAM_FLT_01 C1:LSC-LA_PARAM_FLT_00
For the Y arm
op440m:AutoDither>tdsread C1:LSC-TRY_GAIN C1:LSC-LA_PARAM_FLT_04 C1:LSC-LA_PARAM_FLT_03
[Jenne, Diego, Rana]
This is a note about work done last night.
We were starting to lock, and saw glitches in the Thorlabs TRY PD about once every 1/60th of a second. It is not a sine wave, so it is not 60Hz line noise directly. It looks like this:
Rana pointed out that this looks like it could be from a power supply that is converting AC to DC.
We went down to the Yend, and noticed some weird symptoms. So far, we do not know where the noise is coming from. Rather, we are just using the QPD for locking.
* The noise comes and goes, particularly if someone is moving around at the end station.
* Moving the Thorlabs power supply farther from the HeNe power supply didn't do much. Turning off and disconnecting the HeNe supply didn't make the noise go away, so we conclude that it is not the HeNe's fault.
* We suspected the loops of excess cable that were sitting on top of iscey, but moving the coils away from the computer did not make the noise go away.
* We removed a few disconnected BNC cables that were near or touching the end table, but that didn't fix things.
* We disconnected the PD's signal cable and pulled it out of the table enclosure, and then put it back. Noise was gone when cable was disconnected (good), but it was back after plugging the cable back in.
* The noise still comes and goes, but we don't have to use the Thorlabs PD for locking, so we leave it for another day.
RXA: also moved the Thorlabs power supply to a different power strip and tried putting it closer/farther to the Uniblitz shutter controller. Another suspect is that its some PWM type noise from the doubler crystal temperature driver. Need to try turning off the heater and the Raspberry PI to if it effects the noise.
A more permanent fix than a crocodile clip was implemented. Should probably look to do this for the X end unit as well.
Rich came by the 40m to photocopy some pages from Hobbs, and saw me working on the 60 Hz hunting. As I suspected, the problem was being generated in the D040060. This board receives the photodiode signal single-ended, but has a different power ground than the photodiode (even though the PD is plugged into a power strip that claims to come from 1Y4). The mechanism is not entirely clear - the presence of these 60 Hz features seemed to be dependent on the light level on the TRY photodiode (i.e. they were absent when the PSL shutter is closed, and were more prominent when TRY was 0.9 rather than 0.5) but the PD certainly wasn't saturated - the DC signal was only ~100 mV when viewed on a scope. In any case, Rich suggested the simplest test would be to ground the BNC shield bringing TRY to the rack, to the local ground on the board, which I did using a crocodile clip. This did the trick, the TRY signal RMS is now dominated by the ~1 Hz seismic-driven variation.
On a more pessimistic note - it looks like the elliptical reflector moving did not work, and the clipping in the Y arm persists . I am able to recover TRY~1 with the yaw offset on the ETM (which is still lower than the 1.06-1.07 Koji reported in Aug 2018, but I can believe that being down to the MC transmission being a few % lower at 15000cts rather than 15500), while the maximum I see without it is ~0.9. This is puzzling, because when the chamber was open, we saw that there was ~1.5" clearance between the edge of the reflector and the beam on an IR card. I suppose the input pointing could have been off by a small amount. So one of the primary vent objectives wasn't acheieved... But I will push ahead with the loss measurement.
P.S. I realigned the Y green to the arm and brought GTRY to 0.93
This evening, I was not able to successfully transition CARM from ALS to 1/sqrt(trans) signals. The TRY time series looked odd, so I took a spectra, and we have huge 60Hz noise in TRY.
I found a lock stretch from around 6:30pm that did not show the 60Hz noise, and then there was a lock stretch around 8pm that did have the noise. So, something happened at the Yend between 6:30 and 8pm tonight.
Asking around, this was the time frame in which Manasa was down at the Yend to realign the green beam, and to check cabling for the PZT_OUT and ERR_MON signals to the ADC.
Looking at the spectra, Rana noted that we have even as well as odd harmonics of the 60Hz line, which is unusual.
To try to diagnose the problem, Rana and I tried to make sure no cables' connectors were touching, and that no equipment was plugged in that shouldn't be. We noticed that none of: the shutter, the Thorlabs TRY PD, or the QPD TRY are isolated from the table. To see if perhaps the shutter was the problem, I turned off the power to the Yend green shutter, and unplugged the cable. The cable is laying on the table, with the connector sitting on a piece of plastic to isolate it. Removing the shutter from the system did not change anything.
We don't see the 60Hz noise in the Xarm, so it's not on the laser light itself. Also, we don't see the 60Hz lines in the Yarm feedback signal, so we're not putting the lines onto the mirror, and thus onto the Yarm's light.
Manasa, can you please take a look, and see if you can figure out what is going on? We need TRY so that we can transition to 1/sqrt(trans) signals for CARM. Thanks!!
This evening, I was not able to successfully transition CARM from ALS to 1/sqrt(trans) signals. The TRY time series looked odd, so I took a spectra, and we have huge 60Hz noise in TRY.
I went to the Y end to look at the TRY 60Hz noise situation this morning. While looking at TRY noise on dtt, I found that just lifting the cable away from the cable bunch that runs out of the table suppressed the noise drastically.
I removed the unwanted bnc connector in the path of the already long TRY cable running from the PD to the 1Y4 rack and isolated it from the bunch. TRY became less noisy.
But the noise was back again earlier in the evening and it looks like the noise is very much related to the TRY cable. TRY cable might have moved from its sweet spot while I was around checking cable connections yesterday.
I couldn't find a spare to replace it right away today (We need a BNC to 4 pin lemo).
The detectors and electronics on this table are not properly isolated. To reduce the 60 Hz and ground loops, photodiodes and shutter must be isolated by using plastic spacers as we usually do elsewhere - this table just seems to have a few oversights.
Steve can start assembling all of the pieces to do this in the morning and then we can start the swapping after the meeting.
The high gain Transmon cable should be a regular BNC. There's no need for 4-pin LEMO in this usage, so the best move is to modify the board and replace the 4-pin LEMO connector with an isolated panel mount BNC female.
The AC adapter for this diode (and all of the detectors on the table) should get their power from a power strip which gets plugged into the rack with the whitening boards. The SHG oven, the Uniblitz shutter, and any cameras can get their power from another power strip if needed/wanted.
To find noise source
1. Swapped the power cable of the PD and checked that it is connected to the right power source.
2. Changed the aluminium base of the post holding the diode so that the diode is floating
3. Grounded the table and the rack
4. Routed the cable on the other side of the beam tube to isolate it from other cables.
After all the above, we still found that shaking the cable was making TRY noisy.
I pulled out the PD whitening board to replace the 4 pin lemo connector with a bnc connector so that we can swap the cable with a new one. So there is no TRY right now.
This is an effort to get rid of our ground loops by isolating the electronic components from the optical table.
Aluminum mounting base plates of Thorlabs BA2 and Newport B-2 were replaced by plates or post made out of delrin material.
This is an insulator. DELRIN base plates were installed 6 places. The oplev-qpd has Nylon base plate.
The NPRO and HE/NE lasers are not isolated from the table. S8 and S9
I'm not sure about the doubling oven S10
The optical table is grounded at G11 through ~1 Mohms to the ETMY chamber.
Alignment touch up needed at all D-marked component!
D: component delrin isolated
N: component nylon isolated ( or Delrin )
S: component shell is shorting to optical table (except oven)
G: optical table ground
I failed to maximize TRY the pds.
I worked at the ETMY-ISCT this morning and late afternoon. I will continue the 60 Hz noise hunt tomorrow.
The Y arm was locked with the TRY DC signal.
The handing off process is too complicated because there is no path from ALS to the LSC error.
The TRY DC error signal & the gain determination
- The error signal was produced by the operation 1/SQRT(TRY) - OFFSET. The initial offset was -5.
- The sign of the TRY DC error signal depends on which side of the resonance the arm is.
By looking at the strip chart, I determined that the sign is opposite of the ALS.
The ALS had the gain of -25, so the TRY control gain was to be positive.
- From the strip chart on the previous entry , the slope difference between the PDH error and the TRY DC error was x500.
The arm control with POY11 PDH had the gain of 0.2. So the target gain for the TRY DC was determined to be +100.
- The arm was stabilized by ALS. The ALS gain was -25 with FM2/3/5/6/7/10
- YARM configuration: no trigger / no FM trigger / gain =+0 / FM5 ON / OFFSET -5
- Start handing off:
YARM: Turned up the gain to +50
- ALS: Turned off FM6/7
- YARM: Turned on FM6/7
- ALS: Turned off FM2
- YARM: Turned on FM4
- ALS: Turned off FM3/10
- YARM: Turned on FM2/3/8/9 ON
- ALS: Reduced the gain to -15
- YARM: Increased the gain to +70
- ALS: Reduced the gain to 0
- YARM: Increased the gain to +100
HANDING OFF - DONE
Changing the offset
The offset of -5 gave the TRY of <0.1.
The detuning was reduced by giving the offset of -4. TRY went up to ~.1
The offset of -3 made TRY 0.13
The offset of -2 made TRY 0.25
The offset of -1.5 made TRY 0.4. And the arm could not be held by this error signal anymore.
I don't know why, but TRY has somehow gotten a 0.3 count offset in the last hour.
Rana and I are witnesses for each other that neither of us has gone into the IFO room in the last several hours (and we're the only ones here). For some reason though, the TRY PD now has a 0.3 count offset. We have been doing some ALS locks, but we have not run the offset script in the last several hours. Closing the green shutter doesn't change things, and we still see the offset when the MC loses lock, so it's not to do with the end or the PSL laser. We haven't been in there, so there hasn't been a change in the room lights.
TRY signals are all gone! Both the PD and the camera show no signal. I went down there to turn off the lights, and look to see what was up, and I don't see any obvious things blocking the beam path on the table. However, Steve has experimentally bungeed the lids down, so I didn't open the box to really look to see what the story is.
Absent TRY, I redid the IFO alignment. Yarm locked, so I assumed it was close enough. I redid Xarm alignment pretty significantly. Transmission was ~0.5, which I got up to ~0.85 (which isn't too bad, since the PMC transmission is 0.74 instead of the usual 0.83). I then aligned MICH, and PRM. After fixing up the BS alignment, the POP beam wasn't hitting the POP PD in the center any more. I centered the beam on the PD, although as Gabriele pointed out to me a week or two ago, we really need to put a lens in front of POP, since the beam is so big. We're never getting the full beam when the cavity flashes, which is not so good.
Den is still working on locking, so I'll let him write the main locking report for the night.
We see that the PRC carrier lock seems to be more stable when we lock MICH with +1 for ITMY and -1 for ITMX, and PRCL with -1 for both ITMs. This indicates that we need to revisit the systematic problem with using the PRM oplev to balance the coils, since that oplev has a relatively wide opening angle. I am working on how to do this.
Again unknown, but about 6 hours ago (so ~8am) the offset disappeared.
Here's a 1-day trend:
One question answered, but another raised. The offset came from LSC-TRY switching to the ETMY-QPD signal from ETMY-TRY (Hi gain pd).
The TRY (TRansmitted light from Y arm ) path was a bit realigned because there had been a small clipping.
This clipping was introducing offsets on the error signals of the C1ASS servo.
During I was running the C1ASS servo on the Y arm I found every time after the auto-alignment is done there still remained a slight offset in the beam pointing,
I looked at the CCD camera which looks at the transmitted light and then introduced an intentional misalignment in ETMY in order to find an obvious clipping.
Indeed there was a clipping in horizontal direction. I checked through the optics on the Y end optical bench.
On the second mirror (beam splitter) the beam was on a very edge. So I steered the first steering mirror to fix it,
In addition to that an iris which is placed between the first and second mirror was also clipping the beam,
So I fully opened the aperture of the iris.
[Suresh / Kiwamu]
We installed the TRY photo diode (Thorlabs one) and the ETMYT CCD camera in place on the ETMY table.
Now we can see a signal on the TRY digital channel.
It will be quite useful for the Y arm locking, for instance we can do a triggered locking and the maximization of the intracavity power.
Someone has to install the EMTY trans QPD at some point.
Koji noticed that earlier this afternoon the Yarm ASS was working, but then after dinner it was no longer working. I saw that the ETMY trans camera beam was clipped. These things precipitated a visit to the Yend station.
I saw that the beam on the optic that steers the camera beam to the camera was very, very low, almost falling off the optic. The only mirror which steers to this optic is the harmonic separator which reflects the IR, and transmits the green. I turned the pitch knobs on the harmonic separator until the beam was roughly centered on all 3 optics between the separator and the camera (BS to QPD, BS to TRYDC and Y1 for camera). The yaw was fine, so I didn't touch it.
I then adjusted the steering mirror to the camera, and the BS pointing to the DC PD. I have not touched the BS pointing to the QPD. Once the beam was on the TRY PD, Koji ran the ASS script, and I recentered the beam on the DC PD. During this time, Koji had the Yarm triggering using -1 in the POYDC element of the matrix.
The harmonic separator is not mounted in a nice way (I'm assuming that Annalisa is in the middle of things, and she'll get back to it after the green work), so the TRY PD and camera will need to be aligned again, so I didn't do any ASS-recentering-ASS iteration tonight.
The Yarm ASS works nicely again, getting TRY to ~0.89 .
[Koji, Steve, Den]
TT alignment is fine, yaw damping is satisfactory, pitch damping is slow. We might want to add magnets to the mirror and attach blades to the frame for pitch edge current damping.
We are moving towards electronics testing.
D - UL
B - UR
A - LR
C - LL
First plug in only one of the quadrupus cables, find out what coil it corresponds to according to screen, then plug in 2nd cable, don't test already-determined cable, but all other 3, find what cable it corresponds to according to the screen. Repeat for other 2 cables.
C = LL, not UR, not UL, not LR
D = UL, not UR, not LR
A = LR, not UR
B = UR
After confirming that the correct quadrupus cables were plugged in to the correct coils, I suspected that our problems could be coming from a (or some) magnet(s) touching the inside of the OSEM. We tested this a little bit, with the goal of finding the range of values where no magnets are touching.
All matrix values are either +1000 or -1000, so, with an example pitch slider value :
Pit slider | 1000 1000 | ---> -22000 UL
-22.2 | -1000 1000 | ---> +22000 LL
Yaw slider | 1000 -1000 | ---> -22000 UR
0 | -1000 -1000 | ---> +22000 LR
Trying some values for pitch, keeping yaw constant:
0 yaw, Pitch bias = 5 -> UR is touching on left side of its osem.
0 yaw, Pitch 0, UR is touching left side.
0 yaw, -1.2 pitch, UR just came off from touching left side. More neg from here should be non-touching. all others are fine.
0 yaw, -32.2 pitch, LR not quite touching right side of osem, but is close (much less than 1mm clearance). UR fine. all others fine.
0 yaw, -22.2 pitch, all 4 are fine.
Trying some yaw values, keeping pitch constant:
1. -22.2 pitch, -32 yaw, LR touching. UR touching.
2. -22.2 pitch, -12 yaw, LR barely not touching, UR still touching.
3. -22.2 pitch, 0 yaw, UR still touching.
4. -22.2 pitch, 16 UR barely not touching.
5. -22.2 pitch, 32, none touching.
6. -22.2 pitch, 12, UR close, not touching.
7. -22.2 pitch, 0, UR touching.
8. -22.2 pitch, 32 (or 30?) UR came off.
9. -22.2 pitch, -25, UR close
10. -22.2 pitch, -32 UR touching.
11. -22.2 pitch, -4 UR not touching.
12. -22.2 pitch, 0 yaw, UR not touching.
Here is a graphical semi-representation for the yaw data:
The motion of the magnets (~1.5mm estimated by looking at the magnets moving) correspond to ~2deg. tilt of the mirror. This would mean almost 1.5m shift at the ETM end (~45m from the TT).
That seems like easily enough range; as long as we can put the TT into the middle of their range to start with we should be OK.
We should consider instrumenting the leakage transmission through all TT with a bare QPD on a stick. We can then use those sensors to monitor the spot positions within the input mirrors as well as the PRC / SRC.
Atm1, TT 1.5" high adaptor base will be back from the shop in 10 days.
Atm2, There is no PITCH damping, YAW edie current damping works well at 0.5 mm gap
Atm3, Adjustable Al -disc that contains a small magnet is purely designed.
We have to come up with a solution to have damping in PITCH
We can only decide the need of pitch damping when the coils are activated.
Could you tell us why? Are you thinking about induced current damping?
I was wrong The instability will be the same when the coils are actuated.