[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.
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
Pitch damping solution needed! It should be in the machine shop already.
Measurements for good fit were made. The new shelf will be installed on next Tuesday at 2pm
The reference cavity ion pump is in the way so the cavity will be moved 5" westward. The shelf height space will be 10" Under shelf working height 18" to optical table.
I have just received the scheduling of the PSL self work for tomorrow. Gautam and I agreed that if it is needed I will shut the laser off and cover the hole table with plastic.
While moving the RefCav to facilitate the PSL shelf install, I bumped the power cable to the AOM driver. I will re-solder it in the evening after the shelf installation. PMC and IMC have been re-locked. Judging by the PMC refl camera image, I may also have bumped the camera as the REFL spot is now a little shifted. The fact that the IMC re-locked readily suggests that the input pointing can't have changed significantly because of the RefCav move.
Johannes informed me that he touched up the PMC REFL camera alignment. I am holding off on re-soldering the AOM driver power as I could use another pair of hands getting the power cable disentangled and removed from the 1X2 rack rails, so that I can bring it out to the lab and solder it back on.
Is anyone aware of a more robust connector solution for the type of power pins we have on the AOM driver?
ETMX sus damping recovered. PSL enclousure is dusty at 20V rotation speed. Rainy days as outside condition.
The MET#1 particle counter was moved from CES wall at ITMX to PSL enclousure south west corner at 11am.
The HEPA filter speed at the Variac was turned down to 20V from 40
This counter pumps air for 1 minute in every 20 minutes. Soft foam in bags used to minimize this shaking as it is clamped.
I think we can put ø2mm × 10mm long magnetic material inside 4 holes with actuation magnets. Then magnetic field on the other side of the mirror will be close to one produced by actuation magnet. Magnetic cylinder center of inertia will be in the vertical plane where mirror's center of inertia is. So this should not change alignment significantly. Eddy current dumping will be applied to the end of the magnetic cylinder opposite to the magnet using aluminium disks, we have them in the clean room.
I've tested this approach. As we do not have required cylinders with high magnetic permittivity, I replaced them with magnets simular to actuator magnets ø2mm × 3mm long. Using them and aluminium disks from other TT I've made a "pitch dumping" construction.
Pitch Q reduced but not that much as I could expect. I did a ringdown test.
yaw ringdown using original construction | yaw ringdown with added pitch damping
pitch ringdown using original construction | pitch ringdown with added pitch damping
From this data I've estimated Q factor for yaw (135 vs 88) and pitch (192 vs 77) (original vs added pitch damping). Thess results diverges with the ones obtained by designes. They measured Q~40-50 for original construction. Pitch and yaw have 2 close resonances so this time domain method can not be very precise. I've measured the same with SR785.
In these comparison plots excitation was not the same as coils are not plugged in yet, but resonance Q factors can be compared.
From this data I've estimated Q factor for yaw (135 vs 88) and pitch (192 vs 77) (original vs added pitch damping).
I've made a more precise measurement of pitch damping using spectrum analyzer.
Measurements confirm that damping using small actuation magnets reduces pitch Q by a factor of 4 and is not enough.
I've tested the idea to use coils as eddy current dampers. I terminated them with a wire and measured Q factor during the ringdown test. Sadly, I did not see any significant damping and Q was ~150. We need stronger magnets if we want eddy current dumping down to Q~1.
We need stronger magnets if we want eddy current dumping down to Q~1.
I've inserted 10mm * 10mm magnets to the 4 corner holes on the front side of the mirror frame according to actuation magnets polarity. I realigned TT and measured Q factor for pitch and yaw, it was 5-10.
I was able to do it for 1 TT only, because others have smaller (~0.1 mm) hole diameter and magnets can't go inside. I tried to warm holes up to 850 F but still was not able to insert a magnet.
Too bad - I thought it would at least give a little damping. Since we want the viscous-like energy loss to be ~49x larger, we need to have the field modulation in the damper (not dumper) increase by ~7.
I've made SolidWorks models of damping bracket and eddy current disk. They will me manufactured and used instead of old ones. New bracket will be mounted in exactly the same place where the old one was. Drawings might not be complete but all dimensions are in the models so we can fix drawing tomorrow before going to machine shop.
I think we can use ring magnets for passive damping. Then we won't have the vent problem. I've found some at K&J Magnetics, we can get them any time. Magnets are Ni-Cu-Ni (fine for vacuum?) Diameter is 3/8'' with advertised tolerence 0.004'', so they should fit the holes.
Koji and Steve pointed out that previous design of a damping bracket was a bit complicated to manufacture. So I made it simpler and also added a tap hole for original yaw damping. We'll give drawing to Mike in the machine shop tomorrow morning.
I've purchased K&J magnets for eddy current damping, they should be here in 2 days.
Den mentioned that the disks will have threaded holes, and that he has made a note to that effect on the paper copy of the drawing that he will bring to Mike at the shop. Also, all threaded holes in the new plate are marked on the paper copy.
Wow... This is even more complicated than the original "Y" design...
We've received all parts that we need for eddy current damping. I've made an estimate of Q with dirty tip-tilt. It looks fine (Q~1)
We need to check ring magnets for vacuum compatibility. Bob start baking on Friday.
Just a reminder that a film crew will be here Monday morning, filming Christian Ott for some Discovery channel show.
They are slated to be here from 8am to 12:30pm or so. They will take a couple of shots inside the lab, and the rest of the filming should be of Christian in the control room (which they will "clean up" and fit with "sexy lighting"). I will try to be here the whole time to oversee everything.
Konecrane Fred was early this morning. He diagnosed the ETMY crane horizontal drive gear box dead and left just before the film crew showed up.
New gear box should be here by the end of this week for installation.
The lab air quality is high ~20,000 counts of particles of 0.5 micron. Keep an eye on this before you open the chamber.
This is the third morning in a row that the MC2 was tripped. Would you look at it Koji?
This may be cause by the impact of crazy WFS signal after the lock loss.
The auto locker is not fast enough to shut the WFS down before the mirrors are kicked.
Jenne and I discussed the issue and agreed that this can be solved by implementing
the same triggering algorithm as the LSC triggers.
Give us a bit more time to work on this.
This is the third morning in a row that the MC2 was tripped.
MC2 was tripped again. I think the answer is that watchdog's critical value was too small C1:SUS-MC2_PD_MAX_VAR = 10, so seismic could trip MC2. I've changed the value to 100.
The Napa earth quake magnitude 6 did not have any effect on the suspensions.
The Goy phase upgrade was done nicely. The IOO pointing did not change. Credit owned to Nick and Andres.
IFO is locked right on.
IN VACUUM beam heights are ALL 5.5" This is measured from the top of the optical table to the center of all TMs, mirrors and other optical components. This beam is ~36" above the floor.
PSL (inside of enclosure) main-output beam: PMC, MZ, RC and ISS are at 3" heights. IOO Angle & Position, MC-Trans and RFAM qpds are at 4"
ALL OTHER beam heights at atmosphere and different ISCT (interferrometer sensing, control optical table)s are at 4"
Alex and Steve,
Old halogen chamber illuminator cabling disconnected and potenciometer board removed at 1Y1 in order to give room for pd calibration fibre set up.
During the process, they had also removed the power cable to the ITMY camera. Steve and I fixed this...so the camera is back.
We'll follow LIGO policy:
Our policy is to use first contact within 1 year of purchase for use in the interferometers. For inspection use I am comfortable with out-of-date use.
GaryLinn offered their indate First Contact for use.
Enclosure is at the east end. It has it's bottom o-ring in place. It will be ready for optics tomorrow around 5pm
I have to shim out the enclosure, finish leveling the table and cut surgical tubing O-ring for the top.
Glued surgical latex tubing with super glue into O-ring shape. The existing in place tubing K-100, OD 0.125" (actual size 0.140"), wall 0.031", ID 0.062".
I have just found out that tolerances on tubing OD are + - 0.026" by the manufacturer. I'm getting larger tubing for better fit.
The table is ready for optics.
Things left to do:
1, finalize o-ring size 2, finish cable feedthrough 3, finalize window connection 4, IR-Thermashield strips for bridge sides 5, replace bridge support post with solid one
I'm working on to improve the quality of the enclosure.
The short comings are: more cable feedthroughs needed, latches to anchor top covers air tight and posts to support bending bridges.
Red triangles are compression latches at 10 places to hold the top air tight on surgical tubing
Green lines represent 4 posts of Al 1" OD to support the covers and maximize their eigenfrequencies.
Black crosses are 4 spring loaded push-bottom quick release pins to anchor the top covers to the bridges. This connection will not be air tight.
(quarter-turn wing head fastener have the same problem) I'm thinking of some solution to minimize the leak.
Violet _ steel plate (1" wide, 15" long, 0.125" thick) between the two posts will anchor the quick release pins and make bridge rigid.
Blue rectangle is an other cable feedthrough exiting on the chamber side.
Planning to substitute window with soft - air tight ( Aluminized thin wall hose ) connection to vacuum view port where white circle is representing the Al adaptor ring.
Updated after Wednesday meeting 4-24-2013
ETMX table layout uploaded with beam paths to the wiki.
Given the effect on the contrast defect, the consensus at the meeting Wednesday 6-22 was that we should continue to use the existing ETMX optic.
(on tower )
NOT finished, last edited 6-28
JDSU 1103P. sn T8070866, made March 2007, output power 2.7 mW, on pd 17,750 counts,
GV 17 March 3pm: I found the Innolight NPRO was off when I walked down to the X end earlier, possibly was accidentally tripped during the Oplev laser replacement. I turned it back on.
ETMX oplev laser is dead. It will be replaced this after noon. Sus damping recovered.
This 3 years old HeNe [ JDS 1103P, sn 351889 ] has been dying for some time or just playing possum at age 1,126 days
I did not replace the ETMX oplev laser because I was unable to bring up the the C1ASC_ETMX_OPTLEV_SERVO medm screen on laptops.
In the attached photo from 2012, one can see the installed black glass baffle. According to the drawings (LIGO-DNNNXXX) this one has a clear aperture of 40 mm.
In (someplace ?) we have clean baffles with a 50 mm aperture which can be installed during this vent. In order to be more conservative, let us choose to swap these out for all 4 test masses during the upcoming vent using the green laser as an alignment guide, as Koji described at today's lunch meeting.
They are located at the top of E1 drawer cabinet
No sign of damage
No suspention lost damping.
EQ 5.2 mag at Jun 10, 8:04 am UTC, Borego Spring, CA ~150 mi away.........no obvoius damage, damping restored, MC is locking, arms are flashing
In order to better understand how the composite signal would behave in the presence of noise, I decided to do a simple analysis of the cavity signals while sweeping through resonance.
My noise model was to just assume that a given signal has some rms uncertainty (error bars) and use linear error propagation to propagate from simple signals to more complicated ones.
I used the python package uncertainties to do the error propagation.
I assumed that the ALS signal, the cavity transmission, and the cavity PDH error signal all have some constant noise that is independent of the cavity detuning. Below is a sweep through resonance (x axis is cavity detuning in units of radians).
The shaded region represents the error on each signal.
Next I calculated the 'first order' calculated error signals. These being a raw PDH, normalized PDH, an inverse square root trans, and the normal ALS again. I tuned the gains so they match appropriately.
Here, one can see how the error in the trans signal propagates to the normalized and trans signals and becomes large are the fractional error in the trans signal becomes large.
Next I did some optimization of linear combinations of these signals. I told the code to maximize the total signal to noise ratio, while ensuring that the overall signal had positive gain. I did this again as a function of the cavity detuning.
Each curve represents the optimized weight of the corresponding signal as a function of detuning.
So this is roughly doing what we expect, it prefers ALS far from the resonance, and PDH close to the resonance, while smoothly moving into square root trans in the middle.
It's a little fake, but it gives us an idea of what the 'best' we can do is.
Finally I used these weights to recombine the signals into a composite, to get an idea of the noise of the overall signal. At the same time, I plot the weighting proposed by Koji's mathematica notebook (using trans and 1-trans, and a hard switch to ALS).
So as one can see, at least for the noise levels I chose, the koji weighting is not much worse than the 'optimal' weighting. While it is much simpler.
The code for all this is in the svn at 40mSVN/nicolas/workspace/2014-03-06_compositeerror
CC1 and CC2 are working again. Why did they start working again ?
Lenses removed from oplev beam path at elog entry 11246
The pdf file is uploaded into the wiki.
SUS- BS, ITMX, ITMY, PRM, SRM, ETMX & ETMY_OLPIT transfer funtion with sine wave excitation 0.1 amplitude:
OL_YAW transfer functions are here.
I had two PHDs helping me to overlap the EXML files in DTT. We failed. This job requires professorial help.
We have 6 of these boards now in cabinet E7
I wired all 32 channels going to the AA board directly to the ADC as described in the previous log. However, instead of using the old AA board and bypassing the whole circuit, I just used a breakout board as is shown in the first attachment. I put the board back in the rack and reconnected all of the cables.
The seismic BLRMs appear to be working again. A PSD of the BS seismometers is shown in attachment 2. Tomorrow I'll look at how much the ADC alone is suppressing the common mode 60 Hz noise on each of the channels.
Steve: 5 of ADC DAC In Line Test Boards [ D060124 ] ordered. They should be here within 10 days.
Vacuum normal valve condition was changed to accommodate SRS-RGA calibration.
VM1 was closed to isolate the RGA from the IFO.
Vacuum valve configuration is back to VACUUM NORMAL condition. RGA calibration completed.
RGA scan attached is the backgroud of the rga with std cal leak open, sn 08581
Krypton at amu 84 and Argon at amu 40 are the cal signals.