The manufacturer of a vacuum pump supplies a chart for each pump showing pumping speed (volume in unit time) vs pressure. The example, for a fictitious pump, shows the pumping speed is substantially constant over a large pressure range.
By multiplying pumping speed by pressure at which that pumping speed occurs, we get a measure called pump throughput. We can tabulate those results, as shown in the table below, or plot them as a graph of pressure vs pump throughput. As is clear from the chart, pump throughput (which might also be called mass flow) decreases proportionally with PRESSURE, at least over the pressure range where pumping speed is constant.
The roughing pump speed actually will reach 0 l/s at it's ultimate pressure performance.
Our roughing pump pumping speed will slowly drop as chamber pressure drops. Below 10 Torr this decrease is accelerated and bottoms out. This where the Root pump can help. See NASA evaluation of dry rough pumps...What is a root pump
We have been operating succsessfully with a narrow margin. The danger is that the Maglev forline peaks at 4 Torr. This puts load on the small turbo TP2, TP3 & large TP1
The temperature of these TP2 & 3 70 l/s drag turbos go up to 38 C and their rotation speed slow to 45K rpm from 50K rpm because of the large volume 33,000 liters
Either high temp or low rotation speed of drag turbo or long time of overloading can shut down the small turbo pumps......meaning: stop pumping, wait till they cool down
The manual gate valve installed helped to lower peak temp to 32C It just took too long.
We have been running with 2 external fans [one on TP1 & one on TP3] for cooling and one aux drypump to help lowering the foreline pressure of TP2 & 3
The vacuum control upgrade should include adding root pump into the zero pumping speed range.
Atm1, Pump speed chart: TP1 turbo -red, root pump -blue and mechanical pump green. Note green color here representing an oily rotory pump. Our small drypumps [SH-100] typically run above 100 mTorr
They are the forepump of TP2 & 3 Our pumpdown procedure: Oily Leybold rotory pumps ( with safety orifice 350 mT to atm ) rough to 500 mTorr
Here we switch over to TP2 & 3 running at 50k RPM with drypumps SH-100 plus Aux Triscroll
TP1- Maglev rotating full speed when V1 is opened at full volume at 500 mTorr
History: the original design of the early 1990s had no dry scroll pumps. Oil free dry scrools replaced the oily forepumps of TP2 & TP3 in ~2002 at the cost of degrading the forline pressure somewhat.
We had 2 temperature related Maglev failers in 2005 Aug 8 and 2006 April 5 Osaka advised us to use AUX fan to cool TP1 This helped.
Atm2, Wanted Root pump - Leybold EcoDry 65 plus
Atm3, Typical 8 hrs pumpdown from 2007 with TP2 & 3
Atm4, Last pumpdown zoomed in from 400 mT to 1mT with throttled gate valve took 9 hrs The foreline pressure of TP1 peaked at 290 mT, TP3 temperature peaked at 32C
This technic is workable, but 9 hrs is too long.
Atm5, The lowest pressure achived in the 40m Vacuum Envelope 5e-7 Torr with pumps Maglev ~300 l/s, Cryo 1500 l/s and 3 ion pumps of 500 l/s [ in April 2002 at pumpdown 53 day 7 ] with annuloses at ~ 10 mTorr
Atm6, Osaka TG390MCAB Throughput with screen ~300 L/s at 12 cfm backing pump
Atm1, ITMY and the SRM are on the same isolation stack. So why does the SRM move twice as much?
Atm2, We should check the ITMY SIDE_OSEM before pump down. Anatomically correct, beautiful picture taken by Kiwamu on August 22
Precondition: c1vac1 & c1vac2 all LED warning lights green [ atm3 ], the only error message is in the gauge readings NO COMM, dataviewer will plot zero [ atm1 ], valves are operational
When our vacuum gauges read " NO COMM " than our INTERLOCKS do NOT communicate either.
So V1 gate valve and PSL output shutter can not be triggered to close if the the IFO pressure goes up.
[ only CC1_HORNET_PRESSURE reading is working in this condition because it goes to a different compuer ]
Following the procedure in this elog, we effected a reset of the vacuum slow machines. Usually, I just turn the key on these crates to do a power cycle, but Steve pointed out that for the vacuum machines, we should only push the "reset" button.
While TP1 was spun down, we took the opportunity to replace the TP1 controller with a spare unit the company has sent us for use while our unit is sent to them for maintenance. The procedure was in principle simple (I only list the additional ones, for the various valve closures, see the slow machine reset procedure elog):
However, we were foiled by a Philips screw on the DB37 connector labelled "MAG BRG", which had all its head worn out. We had to make a cut in this screw using a saw blade, and use a "-" screwdriver to get this troublesome screw out. Steve suspects this is a metric gauge screw, and will request the company to send us a new one, we will replace it when re-installing the maintaiend controller.
Attachments #1 and #2 show the Vacuum MEDM screen before and after the reboot respectively - evidently, the fields that were reading "NO COMM" now read numbers. Attachment #3 shows the main volume pressure during this work.
The problem will be revisited on Monday.
I forgot to mention about the whitening filter for the ALS digital control system.
As usual I used a whitening filter to have a good SNR against ADC noise, but this time our whitening scheme is little bit different from the usual our systems.
I used two ADC channels for one signal and put a digital summing point and digital filters to keep good SNR over the frequency range of interest.
It's been working fine but it's still primitive, so I will study more about how to optimize this scheme.
The diagram above shows our scheme for the signal whitening.
Basically the SNR at DC is bad when we use only a whitening filter as shown on the bottom part of the diagram because the signal is quite tiny at DC.
On the other hand if we take raw signal into ADC as 'DC path' shown above, the SNR is better at DC but not good at intermediate frequencies (30 mHz - 1kHz).
So the idea to keep the good SNR over the frequency range of interest is to combine these 'DC path' and 'AC path' in a clever way.
In our case, the 'DC path' signal is not as good as the 'AC path' signal above 30 mHz, so we cut off those high frequency signals by using a digital low pass filter.
In addition to it, I put a gain of 1000 in order to match the relative gain difference between 'DC path' and 'AC path'.
Then the resultant signal after the summing point keeps the good SNR with a flat transfer function up to 1 kHz.
Two different measurement have been performed for a test of the green locking last night.
Everything is getting better. yes. yes.
Yesterday I failed to take good pictures of ETMY resonant arm of 1064 nm with Cannon Rebel T3i in RAW 22-27Mp & JPG dual- format. UFRaw file converter worked well. The IR blocker filter seems to be too good.
Today I used Olympus SP-570UZ ( without IR blocker), in raw format of 15Mp, fl 22.4mm, 15s including 2-3s flashlight, f/8 and auto focus This is just too much scattered IR for the Olympus.
Overexposed raw picture' jpg is shown at the PSL with diffraction patter of the camera.
I'll go back using the Nikon D40 with zoom 55-200mm as this Atm2 of May 2007 : manual focus, 15s, f/4-5.6, ISO 560, 826KB
RFAMPD_DCMON disappered on Nov 5, 2009
Photo diodes stored in the east arm cabinet E4: ALL PDs meet here, fast or slow......
Reminder: I will be on vacation next week. We would have to put the access connector in tonight if I'm pumping down Friday, tomorrow.
It turned out that the DC alignment of MC2 from epics doesn't helathily work.
For example, the pitch slider does drive the yaw alignment as well.
Is this somehow related to the unknown MC2 jump happened around September 10th ?? (see the trend below)
[Yuta, Suresh, Rana and Kiwamu]
The DC alignment problem of MC2 was fixed.
There were some loosely connected cables on the backside of a VME rack which contains the MC2 SOS driver.
We pushed those connectors to make them tightly connected. And then the problem disappeared.
(voltage unbalance on coils)
Before fixing it Yuta opened the satellite box and measured the voltage across the coils using a voltmeter.
At that time UL and LR showed 20 times smaller voltages than that of the other two when we moved the DC alignment slider from min. to max. on the medm screen.
This behavior is exactly consistent with the wired motion of a beam spot which we saw when we were aligning MC2.
(diagnostic using optical lever)
After pushing the connectors, we made an optical lever using a red laser pointer in order to check the actual motion of MC2.
We confirmed that MC2 respond correctly to the alignment slider.
It turned out that the DC alignment of MC2 from epics doesn't helathily work.
For example, the pitch slider does drive the yaw alignment as well.
It appears that the old PSL fast channels never made it into the new DAQ system. We need to figure out what to do with them.
A D990155 DAQ Interface card in far right of the 1X1 PSL EuroCard ("VME") crate is supposed output various PMC/FSS/ISS fast channels, which would then connect to the 1U "lemo breakout" ADC interface chassis. Some connections are made from the DAQ interface card to the lemo breakout, but they are not used in any RTS model, so they're not being recorded anywhere.
An old elog entry from Rana listing the various PSL DAQ channels should be used as reference, to figure out which channels are coming out, and which we should be recording.
The new ALS channels will need some of these DAQ channels, so we need to figure out which ones we're going to use, and clear out the rest.
Fibox FBAI-M 20bit units were connected with multimode fibre. This pair of fiber is not protected in the cable tray.
SUS-ETMY_QPD is not responding. It is reading zero in dataviewer and 4,400 counts on QPD MEDM screen.......must be wrong cable connected
IP-POS is sick. Last time alive 7-19-2011
IP-ANG beam is clipping on pick-up mirror at ETMY chamber. This will have to be fixed at the vent. The qpd itself is responding to light.
We hypothesize that the systematic error in the loss measurement can come from the fact that the requirement on the alignment of the cavity mirrors is not stringent enough.
We repeat the loss measurement with 50 measurements. This time we change the thresholds for the error signals of the dither-align in the measureArmLoss.py file from 0.5 to 0.3.
We repeat the analysis done before:
We plot the reflected power of the two states on top of each other:
This time it appears there was no drift. The histogram of the loss measurement:
The mean is 104ppm and the variation is 27%.
What I notice this time is that the PD readings in the aligned and misaligned states are anti-correlated. This is also true in the previous run (where there was drift) when looking in the short time scales. I plot several time series to demonstrate:
I wonder what can cause this behaviour.
Kiwamu, Koji, Yutah, Rana, Jan and Steve
We removed the west access connector this afternoon.
Fire-smoke sensors in the vertex area #2-31, 2-30 east, 2-32 south/MC2 and 2-37 old control room area are turned off to accommodate the welding
activity of folding crane. These sensors will be reactivated at 3:30pm today.
Stay out of the 40m lab: IFO room till 6 pm today.
IP_POS is back.
I reconnected the cable to an interface card : D030238-A which has been labeled as "IP POS".
The card currently resides on the third crate rack from the top at the very right side in 1Y2. Also a rear side connection was modified a little bit.
I will clean up some cables because I tried some cables to see which was which.
Hopefully I will make a simple wiring diagram such that we will never forget the connections.
A cable for IP_POS has been disconnected at the LSC rack, 1Y2. Due to it currently no IP_POS signal shows up on the digital side.
I will check how it used to be and reconnect it.
I found the disconnected cable, but I do not see the interface board at the LSC rack
in the rack next to the printer. It sounds like a fan is hitting something.
Weekly Project Update:
We are studying Haixing's circuit diagram for the quadrant maglev control circuit. We have analyzed several of the sub-circuits and plotted transfer functions for these in MatLab. To check the circuit, we will compare the calculated transfer functions with those obtained from the HP control systems analyzer.
To learn how to use the control systems analyzer, we are reading App Note 243 as well as an online manual (477 pages in the first volume). We are beginning with a simple test circuit, and are comparing its measured frequencyresponse with calculated transfer functions. We currently have obtained a response graph beginning at 100 Hz (which we have not yet figured out how to print), and we are planning to investigate behavior at lower frequencies.
We also have been continuing our reading on control systems after a failed attempt at magnetic levitation.
This past week, we levitated our small cylindrical magnet (with the flag made from heat shrink). Though the levitated magnet didn't appear very jittery to the eye, we looked at the PD current on the scope and could see oscillations that corresponded to the flag hitting the sides of the OSEM. The oscillations were more pronounced as we gently hit/vibrated the lab bench, and by pounding on the bench Rana knocked the levitated magnet completely out of the setup. So, we're currently working on building a new, stabler mount. The biggest challenge here is fixing the OSEM in place, but we're experimenting with different optics pieces to see which is the most stable for our purposes. Jenne taught us how to make through holes using the drill press so we can add slats of aluminum to adjust the height of the OSEM mount. We also plan to fix some heavy plates to the bottom of our system to decrease its vibration frequency.
We also calculated the transfer function of our circuit, which seems to match the measured frequency response to within a small factor. We're playing with Rana's Simulink models and are currently modeling our own system to determine what gains we would expect to use and get a better understanding of our circuit.
Once our system is successfully mounted stably, we plan to experimentally observe the effects of changing the gain and integrator by looking at time series measurements of the PD current, as well as using the spectrum analyzer to compare the frequency response of our system at different gain settings.
Summary of the week ending Aug 8th. Number of elog entries = 56
+ The vent started Wednesday morning
+ Repositioning of the green periscopes and associated mirrors are done.
+ Got both of the green beams coming out from the chambers
+ Moved the ETMX suspension tower by -8.09 inch (away from vertex)
+ Fixed the alignment of the ETMX CCD mirrors
+ Recovered the X green beam axis for the latest ETMX position
+ oplev centered prior to the vent
+ ETMY_TRANS_QPD didn't respond at all, needs to be fixed
+ Old MZ PD (InGaAs 2mm, @29.5MHz) has been modified for REFL33.
The 11MHz notch circuit is at the amp side instead of the diode side. This is ready for the installation
+ REFL165 PD has been made from the old 166MHz PD.
+ IPPOS has been sick since 19th of July, 2011
+ IPANG is clipped on a pick-up mirror on the ETMY table. QPD itself is healthy.
+ The spot positions on the MC mirrors were measured prior to the vent.
The results are almost the same as before within a few percent difference expect for the MC2 yaw.
+ An attenuator, consisting of two HWPs and a PBS, has been installed on the PSL table for the MC low power state.
+ a 10% BS in front of the MCREFL_RFPD was replaced by a perfect reflector for the low power mode.
+ The incident power for MC was decreased to 20 mW
+ The beam axis going to MC was misalgned due to the attenutor.
Then the beam was aligned by touching two steering mirrors on the PSL table
+ MC is able to be locked in air. The reflection DC goes from 1.4 to 0.13 V when the MC is locked.
+ With the mass-kicking technique, the arm lengths were measured.
Xarm = 37.5918 m, Yarm = 37.5425 m.
- Green locking
+ Y green beam is aligned to the Y arm
+ Locking of the Y green is not robust, it needs to be revisited
+ Wiener Filtering was applied on the data collected from the X-arm for a duration of 1500 seconds.
+ The hazardous waste people are moving chemicals around outside our door, and have roped off our regular front door.
+ The horizontal trolley drive of the east end crane stopped working. It will be fixed.
It's been a miserable week for lock acquisition, with each night worst than the last. The nadir was around Sunday night, when I couldn't even get a PRM to lock stably, which meant that the auto-alignment scripts could not finish successfully. It now appears that was due to some XYCOM mis-settings.
We've also been having problems with timing for c1susvme2. Attached is a one-hour plot of timing data for this cpu, known as SRM. Each spike is an instance of lateness, and a potential cause of lock loss. This has been going on for a quite a while.
Tonight we also encountered a large peak in the frequency noise around 485 Hz. Changing the MZ lock point (the spot in the PZT range) solved this.
Today Steve and I tried to recenter the Guralps. The breakout box technique didn't work for us, so we just turned the leveling screws until we got the mass position outputs within +/-50 mV for all DoF as read out by the breakout box.
The attachment shows the 6 channels after our work. You can see that GUR2_X/Y still look deadish. I tried wiggling the cables at the interface box and powering on/off, but no luck. Next, we swap cables.
Tried to bring the weather station back to life, but no luck. The unit on the wall is alive and so is the EPICS IOC (c1pem1). But there is apparently no communication between them. telnet into c1pem and the error message repeating at the prompt is:
Weather Monitor Output: NO COMM
Might be related to the flaky connector situation that Liz and I found there a couple summers ago, but I tried jiggling and reseating that one with no luck. Looks like it stopped working around 8 PM on March 24, 2014. That's the same time as a ~30s power outage, so perhaps we just need some more power cycling? Tried hitting the reset button on the VME card for c1pem1, but didn't change anything.
Let's try power cycling that crate (which has c1pem1, c0daqawg, and some GPS receiver)...nope - no luck.
Also tried power cycling the weather box which is near the BS chamber on the wall. This didn't change the error message at the c1pem1 telnet prompt.
After a brief look this morning, I called it and declared that we were ok to close up. The access connector is almost all buttoned up, and both ETM doors are on.
Basically nothing moved since last night, which is good. Jenne and I were a little bit worried about how the input pointing might have been effected by our moving of the green periscope in the MC chamber.
First thing this morning I went into the BS chamber to check out the alignment situation there. I put the targets on the PRM and BS cages. We were basically clear through the PRM aperture, and in retro-reflection.
The BS was not quite so clear. There is a little bit of clipping through the exit aperture on the X arm side. However, it didn't seem to me like it was enough to warrant retouching all the input alignment again, as that would have set us back another couple of days at least.
Both arm green beams are cleaning coming out, and are nicely overlapping with the IR beams at the BS (we even have a clean ~04 mode from the Y arm). The AS and REFL spots look good. IPANG and IPPOS are centered and haven't moved much since last night. We're ready to go.
The rest of the vertex doors will go on after lunch.
steve, rob, alberto
Steve installed two rotary flow meters into the MOPA chiller system--one at the chiller flow output and one in the NPRO cooling line. After some hijinks, we discovered that the long, insulated chiller lines have the same labels at each end. This means that if you match up the labels at the chiller end, at the MOPA end you need switch labels: out goes to in and vice-versa. This means that, indubitably, we have at some point had the flow going backwards through the MOPA, though I'm not sure if that would make much of a difference.
Steve also installed a new needle valve in the NPRO cooling line, which works as expected as confirmed by the flow meter.
We also re-discovered that the 40m procedures manual contains an error. To turn on the chiller in the MOPA start-up process, you have to press ON, then RS-232, then ENTER. The proc man says ON, RS-232, RUN/STOP.
The laser power is at 1.5W and climbing.
The chiller HT alarm started blinking, as the water temperature had reached 40 degrees C, and was still rising. We turned off the MOPA and the chiller. Maybe we need to open the needle valve a bit more? Or maybe the flow needs to be reversed? The labels on the MOPA are backwards?
The chiller appears to be broken. We currently have it on, with both the SENSOR and RS-232 unplugged. It's running, circulating water, and the COOL led is illuminated. But the temperature is not going down. The exhaust out the back is not particularly warm. We think this means the refrigeration unit has broken, or the chiller computer is not communicating with the refrigerator/heat exchanger. Regardless, we may need a new chiller and a new laser.
steve, alberto, rob
After some futzing around with the chiller, we have come to the tentative conclusion that the refrigeration unit is not working. Steve called facilities to try to get them to recharge the refrigerant (R-404a) tomorrow, and we're also calling around for a spare chiller somewhere in the project (without luck so far).
We will start preparing for pumping down. Main goal for this is to demonstrate PRFPMI using ALS.
Here are to-dos before we pump down.
Feb 18 eveing
- check input beam and Y arm alignment again
- IPPOS/IPANG alignment
- check all oplevs
Feb 19 morning
- open ETMX chamber heavy door
- align BS to X end
- adjust OSEM values (added by YM)
- center beam on all AS optics
- make sure AS/REFL is clear
- take picture of flipped PR2 (added by YM)
- make sure green is not clipped by new PRM oplev mirrors (added by YM)
- center all oplevs
Feb 19 afternoon - Feb 20 morning
- close PSL shutter
- close all heavy doors and put the access connector back
- start pumping down
Feb 20 evening
- start aligning IFO
I added ~500 cc of distilled water to the laser chiller yesterday.
rob, koji, steve
We noticed some water (about a cup) on the floor under the NESLAB chiller today. We put the chiller up on blocks and took off the side panel for a cursory inspection, but found no obvious leaks. We'll keep an eye on it.
The culprit has been found: One of the bottles of chiller water had a tiny leak in it, and apparently the floor is sloped just right to make it look like the water had been coming from under the chiller. All is well again in the world of chilled water.
A Caltech maintenance staff dropped by at around noon today, and told me that he had seen a small puddle of water on the other side of the door along the Y-arm that is kept locked (about 10m from the end-table, on the south side of the arm). He suspected a leak in the lab. Koji and I went down to the said door and observed that there was indeed a small puddle of water accumulated there. There isn't any obvious source of a leak on our side of the door, although the walls tiles in the area suggest that there could be a leak in one of the pipes running through the wall/under the floor. In any case, the leak doesn't seem too dramatic, and we have decided to consult Steve as to what is to be done about this once he is back on Wednesday.
The leak was found inside the wall. Fortunately the plumbers were able to access it from CES room 108
This has been leaking for sometimes. The damaged wall area is about 18 ft long and 1 ft high.
I am leaving ITMX and ETMX freely swinging, so that later I can take the spectra and diagonalize the input matrices.
Please don't restore the watchdogs until tomorrow morning.
Tonight, swing again.
Please do not restore the watchdogs until tomorrow (Dec.9) morning.
The watchdogs' issue has been solved and they are now working fine.
It was just because one of the Sorensens had been off.
Tonight we noticed that, in fact, the watchdogs don't work for any of the corner optics (I confirmed that they do work for the ETMs).
Please do not touch the watchdogs for all SUSs except for MCs,
because I am going to measure the free swinging spectra for ITMs, ETMs, BS, PRM, SRM tonight.
Today, it is good chance to summarize those data under atmospheric pressure.
I've changed the watchdog rampdown script so it brings the SUS watchdogs to 220, instead of the 150 it previously targeted. This is to make tripping less likely with the jackhammering going on next door. I've also turned off all the oplev damping.
The wasp nest will be removed tomorrow from from the out side of the east arm window.
The resonant frequency of the newly arrived gravity bee detector is not known.
since the summary pages are working again, I was clicking through and noticed that there's a wandering peak in the whitened IMC spectrogram that goes from 10-30 Hz over the course of a day.
anyone know what this is ?
Theoretically the waist position of a Gaussian beam (1064) in our PPKTP crystal differs by ~6.7 mm from that of the incident Gaussian beam.
So far I have neglected such position change of the beam waist in optical layouts because it is tiny compared with the entire optical path.
But from the point of view of practical experiments, it is better to think about it.
In fact the result suggests the rough positioning of our PPKTP crystals;
we should put our PPKTP crystal so that the center of the crystal is 6.7 mm far from the waist of a Gaussian beam in free space.
The calculation is very very simple.
The waist position of a Gaussian beam propagating in a dielectric material should change by a factor of n, where n is the refractive index of the material.
In our case, PPKTP has n=1.8, so that the waist position from the surface of the crystal becomes longer by n.
Now remember the fact that the maximum conversion efficiency can be achieved if the waist locates at exact center of a crystal.
Therefore the waist position in the crystal should be satisfied this relation; z*n=15 mm, where z is the waist position of the incident beam from the surface and 15 mm is half length of our crystal.
Then we can find z must be ~8.3 mm, which is 6.7 mm shorter than the position in crystal.
The attached figure shows the relation clearly. Note that the waist radius doesn't change.
The mode profile of Gaussian beams in our PPKTP crystals was calculated.
I confirmed that the Rayleigh range of the incoming beam (1064 nm) and that of the outgoing beam (532 nm) is the same.
And it turned out that the waist postion for the incoming beam and the outgoing beam should be different by 13.4 mm toward the direction of propagation.
These facts will help us making optical layouts precisely for our green locking.
The result is shown in the attached figure, which is essentially the same as the previous one (see the entry).
The horizontal axis is the length of the propagation direction, the vertical axis is the waist size of Gaussian beams.
Here I put x=0 as the entering surface of the crystal, and x=30 mm as the other surface.
The red and green solid curve represent the incoming beam and the outgoing beam respectively. They are supposed to propagate in free space.
And the dashed curve represents the beams inside the crystal.
A trick in this calculation is that: we can assume that the waist size of 532 nm is equal to that of 1064 nm divided by sqrt(2) .
If you want to know about this treatment in detail, you can find some descriptions in this paper;
"Third-harmonic generation by use of focused Gaussian beams in an optical super lattice" J.Opt.Soc.Am.B 20,360 (2003)"