Alan and Alberto conducted a tour of 40 high-school students.
It may be the same tour that Rana found a spare PMC during the tour explanation as far as I remember...
There were no injuries...Now we need to get some new chairs.
The control room desk tops heights on the east side were lowered by 127 mm
I've created a 40m Google account. Please post all the 40m related photos to this site. If you don't already have it, download Picasa to make this easier.
40m Installation Photos">
the password is in the usual password place.
1/4" exposure, standard room lights 3" exposure, slowly moving LED bar light from ~60 cm distance
Because of the light behind, the focus was attracted by the far objects...
Evenso the magnet ball looks better in the right picture.
The technique is as follows:
Use longer exposure time, move the LED bar illumination through the area like painting the light everywhere.
It is supposed to provide a picture with more uniform light and the diminished shadow.
Before we installed the video switch box, we also took some photos of it. We uploaded them onto the 40m Picasa.
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.
I updated the photo of ETMY end table on the wiki.
Some pictures of "magnet inspection" from Picasa.
The coating of some magnets are chipped...
Were these magnets chipped before the Ni plating?
RA: Yes, it looks like this is the case. We also smashed some of the magnets against a metal surface and saw that a black grime was left. We should hold the magnets with a clean teflon clamp to measure the Gauss. Then we have to wipe the magnets before installing. I share Jenne's concern about the press-fit damaging the plating and so we need to consider using using glue or the ole magnetic attachment method. We should not rely on the structural integrity of the magnets at all.
One day I'll get to be part of the krew
Prof Alan Weistein guided the 24 student through the 40m. His performance was rated as an enthusiastic 9.5
I uploaded some pictures taken in the last and this week. They are on the Picasa web albums.
in vac work [Nov. 18 2010]
in vac work [Nov 23 2010]
CDS work [Nov 24 2010]
The 40m lab was visited by ~ 30 LSC members the end of last week.
Suresh is captivating his audience with gravity waves on last Friday, March 25
.....Happy.... Birthday.... to.... Joseph... and... Jamie...Happy....Birthday..... to.... You............sing with us........Happy Birthday.....to you
The little red all terrain cargo wagon 40" x 18" has just arrived on pneumatic wheels.
Model #29, 200 lbs max load at 26 PSI, minimum age requirement 1.5 years
Just for a record. This is the latest picture of the ETMY optical bench.
I will upload this picture on the wiki after the wiki gets up.
I didn't notice it the other day when I was working on putting in the trans QPD, but do we need to switch the mirror mount for the first turning mirror of the IR trans beam, which the green transmits through to go into the cavity? It seems like we've set ourselves up for potential clipping.
You are right. We should change or rotate the mirror mount.
Actually when Suresh and I were putting the mirror we rotated the mount by 90 deg such that the fat side of the mount is at left had side.
It was because the fat side had been clipping the oplev beam when the fat side is at right.
At that moment we were blocking the green beam to only see the faint IR beam with a sensor card, so we haven't checked the green beam.
Anyway the mount is apparently not good for the green beam.
While preping 1X4 for installation of c1lsc, we removed some old VME crates that were no longer in use. This freed up lots of space in 1X4. We then moved the SUS binary IO chassis 2 and 3, which plug into the 1X4 cross-connect, from 1X5 into the newly freed space in 1X4. This makes the cable run from these modules to the cross connect much cleaner.
Are we keeping these?
He has moved the levitation stuff for his surf student to Jan's lab in W-Bridge.
The pictures that we took are now on the Picasa web site. Check it out.
Also, we took photos (to be posted on Picasa in a day or two) of all the main IFO magnet-in-OSEM centering, as best we could. SRM, BS, PRM all caused trouble, due to their tight optical layouts. We got what we could.
After lots of trial and error, and a little inspiration from Koji, I have written a new script that will run when you select "update snapshot" in the yellow ! button on any MEDM screen.
Right now, it's only live for the OAF_OVERVIEW screen. View snapshot and view prev snapshot also work.
Next on the list is to make a script that will create the yellow buttons for each screen, so I don't have to type millions of things in by hand.
The script lives in: /cvs/cds/rtcds/caltech/c1/scripts/MEDMsnapshots, and it's called....wait for it....... "updatesnap".
Currently the update snapshot script looks at the 3 letters after "C1" to determine what folder to put the snapshots in. (It can also handle the case when there is no C1, ex. OAF_OVERVIEW.adl still goes to the c1oaf folder). If the 3 letters after C1 are SYS, then it puts the snapshot into /opt/rtcds/caltech/c1/medm/c1sys/snap/MEDM_SCREEN_NAME.adl
Mostly this is totally okay, but a few subsystems seem to have incongruous names. For example, there are screens called "C1ALS...." in the c1gcv folder. Is it okay if these snapshots go into a /c1als/snap folder, or do I need to figure out how to put them in the exact same folder they currently exist in? Or, perhaps, why aren't they just in a c1als folder to begin with? It seems like we just weren't careful when organizing these screens.
Another problem one is the C1_FE_STATUS.adl screen. Can I create a c1gds folder, and rename that screen to C1GDS_FE_STATUS.adl? Objections?
Many photos were taken by many different people....most of the fuzzy ones are by yours truely (doing a reach-around to get to hard-to-reach places), so sorry about that.
I put all the photos from yesterday and today into 6 new albums on Picasa: https://picasaweb.google.com/foteee
The album titles are generally descriptive, and I threw in a few comments where it seemed prudent.
Big note: The tip tilt on the ITMX table does, in fact, have the arrow pointing in the correct direction. Photo is in the TT album from today.
Notes of stuff we discussed @ today's meeting, and afterwards, towards measuring ponderomotive squeezing at the 40m.
I have been looking into whether we can observe squeezing on a short timescale. The simulations I show here say that we can get 2 dBvac of squeezing at about 120 Hz using extreme signal recycling.
The parameters used here are
The first attachment shows the displacement noise. The red curve labeled vacuum is the standard unsqueezed vacuum noise which we need to beat. The second attachment shows the same noise budget as a ratio of the noise sources to the vacuum noise.
This homodyne angle and SRC detuning give about the maximum amount of squeezing. However, there's quite a bit of flexibility and if there are other considerations, such as 100 Hz being too low, we should be able to optimize these angles (even with more pessimistic values of the above parameters) to see at least 0.2 dBvac around 400 Hz.
We can get 1.1 dBvac at 210 Hz.
The first two attachments are the noise budgets for these optimized angles. The third attachment shows squeezing as a function of homodyne angle and SRC detuning at 210 Hz. To stay below -1 dBvac, the homodyne angle must be kept between 88.5 and 89.7 degrees and the SRC detuning must be kept between -0.04 and 0.03 degrees. This corresponds to fixing the SRC length to within a range of 0.07/360 * 1064 nm = 200 pm.
Interesting. My understanding is that this is close to signal recycling, rather than resonant sideband extraction. Is that correct?
For signal recycling, we need to change the resonant condition of the carrier in the SRC. Thus the macroscopic SRC length needs to be changed from ~5.4m to 9.5m, 6.8m, or 4.1m.
In the case of 6.8m, SRC legnth= PRC length. This means that we can use the PRM (T=5%) as the new SRM.
Does this T(SRM)=5% change the squeezing level?
Yes, this SRC detuning is very close to extreme signal recycling (0° in this convention), and the homodyne angle is close to the amplitude quadrature (90° in this convention).
For T(SRM) = 5% at the optimal angles (SRC detuning of -0.01° and homodyne angle of 89°), we can see 0.7 dBvac at 210 Hz.
Maybe you've accounted for this already in the Optickle simulations - but in Finesse (software), the "tuning" corresponds to the microscopic (i.e. at the nm level) position of the optics, whereas the macroscopic lengths, which determine which fields are resonant inside the various cavities, are set separately. So it is possible to change the microscopic tuning of the SRC, which need not necessarily mean that the correct resonance conditions are satisfied. If you are using the Finesse model of the 40m I gave you as a basis for your Optickle model, then the macroscopic length of the SRC in that was ~5.38m. In this configuration, the f2 (i.e. 55MHz sideband) field is resonant inside the SRC while the f1 and carrier fields are not.
If we decide to change the macroscopic length of the SRC, there may also be a small change to the requirements on the RoCs of the RC folding mirrors. Actually, come to think of it, the difference in macroscopic cavity lengths explains the slight differences in mode-matching efficiencies I was seeing between the arms and RCs I was seeing before.
In fact, that is my point. If we use signal recycling instead of resonant sideband extraction, the "tuning" of the SRC is opposite to the current setup. We need to change the macro length of the SRC to make 55MHz resonant with this tuning. And if we make the SRC macro length together with the PRC macro length for this reason, we need to thing again about the mode matching. Fortunately, we have the spare PRM (T=5%) which matches with this curvature. This was the motivation of my question. We may also choose to keep the current SRM because of its higher T and may want to evaluate the effect of expected mode mismatch.
In light of the discussion at today's meeting, Guantanamo and I looked at how the series resistance for the test mass coil drivers limits the amount of squeezing we could detect.
The parameters used for the following calculations are:
Since we need to operate very close to signal recycling, instead of the current signal extraction setup, we will need to change the macroscopic length of the SRC. This will change the mode matching requirements such that the current SRM does not have the correct radius of curvature. One solution is to use the spare PRM which has the correct radius of curvature but a transmissivity of 0.05 instead of 0.1. So using this spare PRM for the SRM and changing the length of the SRC to be the same as the PRC we can get
This lower transmissivity for the SRM also reduces the achievable squeezing from the current transmissivity of 0.1. For an SRM with a transmissivity of 0.15 (which is roughly the optimal) we can get
The minimum achievable squeezing moves up from around 205 Hz at 1 W to 255 Hz at 5 W because the extra power increases the radiation pressure at lower frequencies.
Note that for Signal Recycling, which is what Kevin tells us we need to do, there is a DARM pole at ~150 Hz.
To be quantitative, since we are looking at smaller squeezing levels and considering the possibility of using 5 W input power, it is possible to see a small amount of squeezing below vacuum with no SRM.
Attachment 1 shows the amount of squeezing below vacuum obtainable as a function of homodyne angle with no SRM and 5 W incident on the back of PRM. The optimum homodyne angle at 210 Hz is 89.2 deg which gives -0.38 dBvac of squeezing. Figure 2 is the displacement noise at this optimal homodyne angle and attachment 3 is the same noise budget shown as the ratio of the various noise sources to the unsqueezed vacuum.
The other parameters used for these calculations are:
So maybe it's worth considering going for less squeezing with no SRM if that makes it technically more feasible.
We have been working on double checking the noise budget calculations. We wanted to evaluate the amount of squeezing for a few different scenarios that vary in cost and time. Here are the findings:
All calculations done with
Main unbudgeted noises:
Threat matrix has been updated.
On the call last week, I claimed that there isn't much hope of directly measuring Ponderomotive Squeezing in aLIGO without some significant configurational changes. Here, I attempt to quantify this statement a bit, and explicitly state what I mean by "significant configurational changes".
The I/O relations will generally look something like:
The. magnitudes of the matrix elements C_12 and C_21 (i.e. phase to amplitude and amplitude to phase coupling coefficients) will encode the strength of the Ponderomotive squeezing.
For the inital study, let's assume DC readout (since there isn't a homodyne readout yet even in Advanced LIGO). This amounts to setting in the I/O relations, where the former angle is the "homodyne phase" and the latter is the "SRC detuning". For DC readout, the LO quadrature is fixed relative to the signal - for example, in the usual RSE operation, . So the quadrature we will read out will be purely (or nearly so, for small detunings around RSE operation). The displacement noises will couple in via the matrix element. Attachment #1 and Attachment #2 show the off-diagonal elements of the "C" matrix for detunings of the SRC near RSE and SR operation respectively. You can see that the optomechanical coupling decays pretty rapidly above ~40 Hz.
In this particular case, there is no benefit to detuning the SRC, because we are assuming the homodyne angle is fixed, which is not an unreasonable assumption as the quadrature of the LO light is fixed relative to the signal in DC readout (not sure what the residual fluctuation in this quantity is). But presumably it is at the mrad level, so the pollution due to the orthogonal anti-squeezed quadrture can be ignored for a first pass I think. I also assume ~10 degrees of detuning is possible with the Finesse ~15 SRC, as the linewidth is ~12 degrees.
To see how this would look in an actual measurement, I took the data from Lee's ponderomotive squeezing paper, as an estimate for the classical noises, and plotted the quantum noise models for a few representative SRC detunings near RSE operation - see Attachment #3. The curves labelled for various phis are the quantum noise models for those SRC detunings, assuming DC readout. I fudged the power into the IFO to make my modelled quantum noise curve at RSE line up with the high frequency part of the "Measured DARM" curve. To measure Ponderomotive Squeezing unambiguously, we need the quantum noise curve to "dip" as is seen around 40 Hz for an SRC tuning of 80 degrees, and that to be the dominant noise source. Evidently, this is not the case.
The case for balanced homodyne readout:
I haven't analyzed it in detail yet - but it may be possible that if we can access other quadratures, we might benefit from rotating away from the DARM quadrature - the strength of the optomechanical coupling would decrease, as demonstrated in Attachments #1 and #2, but the coupling of classical noise would be reduced as well, so we may be able to win overall. I'll briefly investigate whether a robust measurement can be made at the site once the BHD is implemented.