40m QIL Cryo_Lab CTN SUS_Lab TCS_Lab OMC_Lab CRIME_Lab FEA ENG_Labs OptContFac Mariner WBEEShop
 40m Log, Page 52 of 344 Not logged in
ID Date Author Type Category Subject
5191   Thu Aug 11 14:22:00 2011 NicoleSummarySUSPhotosensor Head Calibration Curve for TT Frame

 Quote: I have re-calibrated the photosensor I used to measure the displacements of the TT frame (what I call "Photosensor 2"). As before, the linear region is about 15.2mm to 25.4mm. It is characterized by the slope -0.0996 V/mm (-0.1 V/mm). Recall that photosensor 1 (used to measure mirror displacements) has a calibration slope of -3.2V/mm. The ratio of the two slopes (3.2/0.1 = 32). We should thus expect the DC coupling level to be 32? This is not what we have for the DC coupling levels in our data (2.5 for flexibly-supported, fully-assembled TT (with EDC, with bar), 4.2 for EDC without bar, 3.2 for rigid EDC without bar, 3.2 for no EDC, with bar, 3.2 for no EDC without bar) . I think I may need to do my calibration plot for the photosensor at the frame?

I have redone the voltage versus displacement measurements for calibrating "Photosensor 2" (the photosensor measuring the motions of the TT frame). This time, I calibrated the photosensor in the exact position it was in during the experimental excitation ( with respect to the frame ). I have determined the linear region to be 15.2mm to 22.9mm (in my earlier post today, when I calibrated the photosensor for another location on the frame, I determined the linear region to be 15.2mm to 25.4mm). This time, the slope was -0.92 V/mm (instead of -0.1 V/mm).

This means that the calibration ratio for photosensor 1 (measuring mirror displacements) and photoensor 2 (measuring frame displacements) is 34.86.

Since this "unity" value should be 34.86 for my transfer function magnitude plots (instead of the ~3 value I have), do I need to scale my data? It is strange that it differs by an order of magnitude...

5192   Thu Aug 11 14:32:12 2011 KojiSummarySUSPhotosensor Head Calibration Curve for TT Frame

The entry was quite confusing owing to many misleading wordings.

- The PS2 should be calibrated "as is". (i.e. should be calibrated with the frame)

- The previous calibrations with the highly reflective surface were 0.32V/mm and 0.26V/mm, respectively.
This time you have 0.10V/mm (with an undescribed surface). The ratio is not 32 but 3.2.

- The DC output of PS2 on the shaking setup was 2.5V. The DC output seen in the plot is 3.5V-ish.
This suggests the possibiliteies:
1) The surface has slightly higher reflectivity than the frame
2) The estimation of the distance between the frame and the PS2 during the TF measurement was not accurate.

- The word "DC coupling level" is misleading. I guess you mean the DC value of the vbration isolation transfer function
of the suspension.

 Quote: I have re-calibrated the photosensor I used to measure the displacements of the TT frame (what I call "Photosensor 2"). As before, the linear region is about 15.2mm to 25.4mm. It is characterized by the slope -0.0996 V/mm (-0.1 V/mm). Recall that photosensor 1 (used to measure mirror displacements) has a calibration slope of -3.2V/mm. The ratio of the two slopes (3.2/0.1 = 32). We should thus expect the DC coupling level to be 32? This is not what we have for the DC coupling levels in our data (2.5 for flexibly-supported, fully-assembled TT (with EDC, with bar), 4.2 for EDC without bar, 3.2 for rigid EDC without bar, 3.2 for no EDC, with bar, 3.2 for no EDC without bar) . I think I may need to do my calibration plot for the photosensor at the frame?

5195   Thu Aug 11 16:09:05 2011 NicoleSummarySUSBode Plot for TT Suspension

All of my plots have already taken into account the calibration of the photosensor (V/mm ratio)

Here is a bode plot generated for the transfer function measurements we obtained last night/this morning. This is a bode plot for the fully-assembled T.T. (with flexibly-supported dampers and bottom bar). I will continue to upload bode plots (editing this post) as I finish them but for now I will go to sleep and come back later on today.

Here is a bode plot comparing the no eddy-current damper case with and without the bar that we suspected to induce some non-uniform damping. We have limited data on the NO EDC, no bar measurements (sine swept data from 7 Hz to 50 Hz) and FFT data from 0 Hz to 12.5 Hz because we did not want to induce too much movement in the mirror (didn't want to break the mirror).  This plot shows that there is not much difference in the transfer functions of the TT (no EDC) with and without the bar.

From FFT measurements of  the no eddy-current damper case without the bar (800 data points, integrated 10 times) we can define the resonance peak of the TT mirror (although there are still damping effects from the cantilever blades).

The largest resonance peak occurs at about 1.94 Hz. The response (magnitude) is 230.

The second-largest resonance peak occurs at about 1.67 Hz. The response (magnitude) is 153. This second resonance peak may be due to pitch motion coupling (this is caused by the fact that the clamping attaching the mirror to the wires occurs above the mirror's center of mass, leading to inevitable linear and pitch coupling).

Here is a bode plot of the EDC without the bar. It seems very similar to the bode plot with the bar

Here is a bode plot of the rigidly-supported EDC, without bar. I need to do a comparison plot of the rigid and flexibly-supported EDCs (without bar)

Attachment 1: flexwithbase.jpg
Attachment 3: stage1.jpg
5202   Fri Aug 12 03:49:45 2011 JennySummaryPSLNPRO PDH-Locked to Ref Cav

DMass and I locked the NPRO laser (Model M126-1064-700, S/N 238) on the AP table to the reference cavity on the PSL table using the PDH locking setup shown in the block diagram below (the part with the blue background):

A Marconi IFR 2023A signal generator outputs a sine wave at 230 kHz and 13 dBm, which is split. One output of the splitter drives the laser PZT while the other is sent to a 7dBm mixer. Also sent to the mixer is the output of a photodiode that is detecting the reflected power from off the cavity. (A DC block is used so that only RF signal from the PD is sent to the mixer). The output of the mixer goes through an SR560 low-noise preamp, which is set to act as a low pass filter with a gain of 5 and a pole at 30 kHz. That error signal is then sent to the –B port of the LB1005 PDH servo, which has the following settings: PI corner at 10kHz, LF gain limit of 50 dB, and gain of 2.7 (1.74 corresponds to a decade, so the signal is multiplied by 35). The output signal from the LB1005 is added to the 230 kHz dither using another SR560 preamp, and the sum of the signals drive the PZT.

I am monitoring the transmission through the cavity on a digital oscilloscope (not shown in the diagram) and with a camera connected to a TV monitor. I sweep the NPRO laser temperature set point manually until the 0,0 mode of the carrier frequency resonates in the cavity and is visible on the monitor. Then I close the loop and turn on the integrator on the LB1005.

The laser locks to the cavity both when the error signal is sent into the A port and when it is sent into the –B port of the PDH servo. I determined that –B is the right sign by comparing the transmission through the cavity on the oscilloscope for both ways.

When using the A port, the transmission when it was locked swept from ~50 to ~200 mV (over ~10 second intervals) but had large high frequency fluctuations of around +/- 50 mV. Looking at the error signal on the oscilloscope as well, the RMS fluctuations of the error signal were at best ~40 mV peak to peak, which was at a gain of 2.9 on the LB1005.

Using the –B port yielded a transmission that swept from 50 to 250 mV but had smaller high frequency fluctuations of around +/- 20 mV. The error signal RMS was at best 10mV peak to peak, which was at a gain of 2.7. (Although over the course of 10 minutes the gain for which the error signal RMS was smallest would drift up or down by ~0.1).

The open loop error signal peak-to-peak voltage was 180 mV, which is more than an order of magnitude larger than the RMS error signal fluctuations when the loop is closed, indicating that it is staying in the range in which the response is linear.

In the above plot the transmission signal is offset by 0.1 V for clarity.

Below is the closed loop error signal. The inset plot shows the signal viewed over a 1.6 ms time period. You can see ~60 microsecond fluctuations in the signal (~17 kHz)

The system remained locked for ~45 minutes, and may have stayed locked for much longer, but I stopped it by opening the loop and turning off the function generator. Below is a picture of the transmitted light showing up on a monitor, the electronics I'm using, and a semi-ridiculous mess of wires.

I determined that it’s not dangerous to leave the system locked and leave for a while. The maximum voltage that the SR560 will output to the PZT is 10Vpp. This means that it will not drive the PZT at more than +/-5 V DC. At low modulation rates, the PZT can take a voltage on the order of 30 Vpp, according to the Lightwave Series 125-126 user’s manual, so the control signal will not push the PZT too hard such that it’s harmful to the laser.

5205   Fri Aug 12 11:07:50 2011 NicoleSummarySUSMore TT Shaking Completed This Morning

This morning (about 10am to 11am), I have collected additional transfer function measurements for the T.T. suspension. I have finished taking my measurements. The SR785 has been returned to its place next the the seismometer racks.

The data has been backed up onto the cit40m computer

5206   Fri Aug 12 14:15:07 2011 NicoleSummarySUSBode Plot for TT Suspension

Here is my bode plot comparing the flexibly-supported and rigidly-supported EDCs (both with no bar)

It seems as if the rigidly-supported EDC has better isolation below 10 Hz (the mathematically-determined Matlab model predicted this...that for the same magnet strength, the rigid system would have a lower Q than the flexible system). Above 10 Hz (the resonance for the flexibly-supported EDCs seem to be at 9.8 Hz) , we can see that the flexibly-supported EDC has slightly better isolation? I may need to take additional measurements of the transfer function of the flexibly-supported EDC (20 Hz to 100 Hz?)  to hopefully get a less-noisy transfer function at higher frequencies. The isolation does not appear to be that much better in the noisy region (above 20Hz). This may be because of the noise (possibly from the electromagnetic field from the shaker interfering with the magnets in the TT?). There is a 3rd resonance peak at about 22 Hz. I'm not sure what causes this peak...I want to confirm it with an FFT measurement of the flexibly-supported EDC (20 Hz to 40 Hz?)

5208   Fri Aug 12 15:34:16 2011 NicoleSummarySUSBode Plot for TT Suspension

 Quote: Here is my bode plot comparing the flexibly-supported and rigidly-supported EDCs (both with no bar) It seems as if the rigidly-supported EDC has better isolation below 10 Hz (the mathematically-determined Matlab model predicted this...that for the same magnet strength, the rigid system would have a lower Q than the flexible system). Above 10 Hz (the resonance for the flexibly-supported EDCs seem to be at 9.8 Hz) , we can see that the flexibly-supported EDC has slightly better isolation? I may need to take additional measurements of the transfer function of the flexibly-supported EDC (20 Hz to 100 Hz?)  to hopefully get a less-noisy transfer function at higher frequencies. The isolation does not appear to be that much better in the noisy region (above 20Hz). This may be because of the noise (possibly from the electromagnetic field from the shaker interfering with the magnets in the TT?). There is a 3rd resonance peak at about 22 Hz. I'm not sure what causes this peak...I want to confirm it with an FFT measurement of the flexibly-supported EDC (20 Hz to 40 Hz?)

Since the last post, I have found from the Characterization of TT data (from Jenne) that the resonant frequency of the cantilever springs for TT #4 (the model I am using) have a resonant frequency at 22 Hz. They are in fact inducing the 3rd resonance peak.

Here is a bode plot (CORRECTLY SCALED) comparing the rigidly-supported EDCs (model and experimental transfer functions)

Here is a bode plot comparing the flexibly-supported EDCs (model and experimental transfer functions). I have been working on this graph for FOREVER and with the set parameters, this is is close as I can get it (I've been mixing and matching parameters for well over an hour > <). I think that experimentally, the TTs have better isolation than the model because they have additional damping properties (i.e. cantilever blades that cause resonance peak at 22 Hz). Also, there may be a slight deviation because my model assumes that all four EDCs are a single EDC.

5214   Fri Aug 12 17:27:49 2011 YoichiSummaryCDSToggle button for RCG
Bottom line: I made an RCG block to realize a toggle button easily.

Read on if you need such a button, or if you want to know how to
write a new RCG block with C.

-----------------
When I was making MEDM screens for FFC, I wanted to have a toggle
button to enable/disable the FFC path.
I wanted to have something like the ON/OFF buttons of the filter bank
screens, the one changes its state every time I click on it.
However, I could not find an easy way to realize that.

From MEDM, I can send a value to an EPICS channel using a "Message Button".
This value is always the same, say 1.
In the RCG model, I used a cdsEpicsMomentary block so that whenever the channel
gets 1, it stays to be 1 for a while and turns back to 0 in a second or so.
This generates a pulse of 1 when I click on a message button on a MEDM screen.
Then I needed a block to keep its internal state (0 or 1), and flips its state
whenever it receives a pulse of 1.
Since I couldn't find such a block in the current RCG library, I implemented one
using the cdsFunctionCall block. It allows you to implement a block with C code.

There is a good explanation of how to use this block in the CDS_PARTS library.
Here is basically what I did.

(1) Drag and drop thee cdsFunctionCall block to my model.

(2) In the "Block Properties", I put the following line in the Description field.
inline cdsToggle /opt/rtcds/caltech/c1/userapps/release/cds/common/src/cdsToggle.c

This means to call a function cdsToggle(), whose code is in the file indicated above.

(3) The contents of the source code is very simple.
void cdsToggle(double *in, int inSize, double *out, int outSize){
static double x = 0;
static double y = 0;

if (*in != y){
y = *in;
if (y == 1){
x = (x == 1) ? 0 : 1;
*out = x;
}
}
}

The function prototype is always the same. *in and *out are the pointers to the arrays of doubles
for input and output signals of the block. In simuLink, the signals have to be
multiplexed so that the RCG can know how many signals are handed to or returned from the function.
In order to keep the internal state of my custom block, I used "static" keyword in the
declaration of the variables. The rest of the code should be obvious.

(4) Just compile the model as usual. The RCG will automatically include the source code and put
a call to the function in the proper place.

I made the block a library so that people can use it.
/opt/rtcds/caltech/c1/userapps/trunk/cds/common/models/cdsToggle.mdl
is the one.
For the usage of it, please have a look at
/opt/rtcds/caltech/c1/userapps/trunk/isc/c1/models/c1lsc
5217   Fri Aug 12 20:33:57 2011 DmassSummaryPSLNPRO PDH-Locked to Ref Cav

To aid Jenny's valiant attempt to finish her SURF project, I did some things with the front end system over the last couple days, largely tricking Jamie into doing things for me lest I ruin the 40m RCG system. Several tribulations have been omitted.

We stole a channel in the frontend, in the proccess:

1. Modified the C1GFD simulink model (now analog) to be "ADC -> TMP -> DAC" where TMP is a filter bank
• C1GFD_TMP.adl (in /opt/rtcds/caltech/c1/medm/c1gfd) is the relevant part which connects the ADC to the DAC in the frontend
2. Confirmed that the ADC was working by putting a signal in and seeing it in the frontend
3. Could not get a signal out of the anti aliasing board
4. Looked sad until Kiwamu found a breakout board for the SCSI cable coming from the DAC
5. Used SR560 to buffer DAC output
• drove a triangle wave with AWG into the TMP EXC channel (100 counts 1 Hz) and looked at it after the ~25 ft of BNC cable running between the DAC and the NRPO driver
• wave looked funny (not like a triangle wave), maybe the DAC is not meant to push a signal so far, so added buffer
6. Took the control signal going to the fast input of the NPRO driver (using the 500 Ohm SR560 output - see Jenny's diagram) and put it into the anti aliasing board of the ADC
7. Added switchable integrator to filter bank with Foton
• I couldn't get the names to display in the filter bank, so I looked sad again
• Jamie and Koji both poked at the "no name displayed" problem but had no conclusions, so I decided to ignore it
• I confirm that when the two filters were toggled "on" that the transfer function was as expected: simple integrator with a unity gain at ~10mHz - agrees with what Foton's Bode Plot tool says it should be (see attached DTT plot)
8. I got Jamie to manually add the two epics channels from the TMP model to the appropriate .ini file so they would be recorded
• C1:GFD-TMP_OUTPUT  (16 Hz)
• C1:GFD-TMP_INMON    (16 Hz)
9. RefCav heater servo seems to still be set up, so we can use existing channels:
• C1:PSL-FSS_RCPID_SETPOINT (temp setpoint - will do +/-1C steps about 35 C)
• C1:PSL-FSS_MINCOMEAS (In loop temp sensor - in C)
• C1:PSL-FSS_RCTEMP (out of loop temp sensor - in C)
• C1:PSL-FSS_TIDALSET (Voltage to heater - rails @ +/- 2V)
10.  Closed loop on the control signal for the NPRO driver with an integrator, saw error signal go to zero
• Turned up gain a little bit, saw some oscillations, then turned gain down to stop them, final gain = 2
11. Left system on for Jenny to come in and do step responses
Attachment 1: TMP_INT_TF.pdf
5222   Sat Aug 13 15:40:38 2011 NicoleSummarySUSTT Shaking Today and Hopefully More?

As reported in my  previous entry of TT supsension bode plots, I found that my experimental data had what appears to be very noise peaks above 20 Hz (as mentioned earlier, the peak at 22 Hz is likely due to vertical coupling, as 22 Hz is the resonant frequency of the cantilever blades). This is very unusual and needs to be explored further. I would like to vertically-shake the TTs to obtain more data on possible coupling. However, I am leaving on Monday and will not return until Thursday (day of SURF talks). I am leaving campus Friday afternoon or so. I would may need some help coming up with an assembly plan/assembling set-up for vertical shaking (if it is possible to do so in such a limited time frame).

Today I wanted to see if the "noisy peaks" above 30 Hz were due to EM noise coupling. I tested this hypothesis today, seeing if EM fields generated by the coil at higher frequencies were injecting noise into my transfer function measurements. I found that the "noisy peaks" above 30 Hz are NOT DUE TO EM NOISE COUPLING. I am very curious as to what is causing the high peaks (possibly coupling from other degrees of freedom)?

5223   Sat Aug 13 15:47:47 2011 NicoleSummarySUSTT Optimization Curves

Using my Matlab model of the flexibly-supported eddy current damping system, I have changed parameters to see if/how the TTs can be optimized in isolation. As I found earlier, posted in my bode plot entry, there is only a limited region where the flexibly-supported system provides better isolation than the rigidly-supported system.

Here is what I have found, where \gamma is the scale factor of the magnetic strength (proportional to magnetic strength), \beta is the scale factor of the current damper mass (estimated by attempting to fit my model to the experimental data), and \alpha is the scale factor of the current resonant frequency of the dampers.

Here are my commentaries on these plots. If you have any commentaries, it would be very helpful, as I would like to incorporate this information in my powerpoint presentation.

It seems as if the TT suspensions are already optimized?

It may be difficult to lower the resonant frequency of the dampers because that would mean changing the lengths of the EDC suspensions). Also, it appears that a rather drastic reduction (at most 0.6*current EDC resonant frequency --> reduction from about 10 Hz to 6 Hz or less) is required . Using the calculation that the resonant frequency is sqrt(g/length), for my single-suspended EDC model, this means increasing the wire length to nearly 3 x its current value. I'm not sure how this would translate to four EDCs...

The amplification at resonance caused by increasing the magnet strength almost offsets the isolation benefits of increasing magnet strength. From my modeling, it appears that the magnet strength may be very close (if not already at) isolation optimization.

Lowering the mass to 0.2 the current mass may be impractical. It seems as if the benefits of lowering the mass only occur when the mass is reduced by a factor of 0.2 (maybe 0.4)

5224   Sat Aug 13 19:08:01 2011 KojiSummarySUSTT Optimization Curves

What are the parameters you are using? As you have the drawings of the components, you can calculate the masses of the objects.

Reducing the ECD resonance from 10Hz->6Hz looks nice.

The resonant freq of the ECDs are not (fully) determined by the gravitational energy but have the contribution of the elastic energy of the wire.

Q1: How much is the res freq of the ECDs if the freq is completely determined by the grav energy? (i.e. the case of using much thinner wires)

Q2: How thin should the wires be?

5225   Sat Aug 13 21:15:47 2011 NicoleSummarySUSTT Optimization Curves

 Quote: What are the parameters you are using? As you have the drawings of the components, you can calculate the masses of the objects.   Reducing the ECD resonance from 10Hz->6Hz looks nice. The resonant freq of the ECDs are not (fully) determined by the gravitational energy but have the contribution of the elastic energy of the wire. Q1: How much is the res freq of the ECDs if the freq is completely determined by the grav energy? (i.e. the case of using much thinner wires) Q2: How thin should the wires be?

The drawings do not have the masses of the objects.

For the resonant frequency:

Instead of sqrt (g/l) would the numerator in the square root be[ g + (energy stored in wire)/(mass of damper)] ?

5226   Sat Aug 13 21:48:17 2011 KojiSummarySUSTT Optimization Curves

1) Drawing has the dimensions => You can calculate the volume => You can calculate the mass
Complicated structure can be ignored. We need a rough estimation.

2) Your restoring force can have two terms:
- one comes from the spring constant k
- the other from the gravity

5227   Sun Aug 14 00:26:51 2011 NicoleSummarySUSTT Optimization Curves

 Quote: 1) Drawing has the dimensions => You can calculate the volume => You can calculate the mass Complicated structure can be ignored. We need a rough estimation. 2) Your restoring force can have two terms: - one comes from the spring constant k - the other from the gravity

Thank you.

The wire used to suspend the EDCs is tungsten?

To verify, for my model, the EDC will be the mass of all four dampers or a single damper? The length of the wire used to suspend the EDC will be the combined length of 4 wires or length of  a single wire?

Taking into account the densities for each material (specific material of each component was listed, so I looked up the densities), and trying my best to approximate the volumes of each component, I have determined

the mass of the mirror + mirror holder to be ~100 g and the mass of a single EDC to be ~19 g

5229   Sun Aug 14 13:57:52 2011 NicoleSummarySUSTT Optimization Curves

Quote:

 Quote: 1) Drawing has the dimensions => You can calculate the volume => You can calculate the mass Complicated structure can be ignored. We need a rough estimation. 2) Your restoring force can have two terms: - one comes from the spring constant k - the other from the gravity

Thank you.

The wire used to suspend the EDCs is tungsten?

To verify, for my model, the EDC will be the mass of all four dampers or a single damper? The length of the wire used to suspend the EDC will be the combined length of 4 wires or length of  a single wire?

Taking into account the densities for each material (specific material of each component was listed, so I looked up the densities), and trying my best to approximate the volumes of each component, I have determined

the mass of the mirror + mirror holder to be ~100 g and the mass of a single EDC to be ~19 g

I am thinking that perhaps my mass estimations were off? The model that I have used fits the data better than the model that I have made (changing the masses to fit my estimations of the values)

5231   Sun Aug 14 17:47:39 2011 NicoleSummarySUSTT Shaking Today and Hopefully More?

 Quote: As reported in my  previous entry of TT supsension bode plots, I found that my experimental data had what appears to be very noise peaks above 20 Hz (as mentioned earlier, the peak at 22 Hz is likely due to vertical coupling, as 22 Hz is the resonant frequency of the cantilever blades). This is very unusual and needs to be explored further. I would like to vertically-shake the TTs to obtain more data on possible coupling. However, I am leaving on Monday and will not return until Thursday (day of SURF talks). I am leaving campus Friday afternoon or so. I would may need some help coming up with an assembly plan/assembling set-up for vertical shaking (if it is possible to do so in such a limited time frame).   Today I wanted to see if the "noisy peaks" above 30 Hz were due to EM noise coupling. I tested this hypothesis today, seeing if EM fields generated by the coil at higher frequencies were injecting noise into my transfer function measurements. I found that the "noisy peaks" above 30 Hz are NOT DUE TO EM NOISE COUPLING. I am very curious as to what is causing the high peaks (possibly coupling from other degrees of freedom)?

I have been redoing the noise test multiple times today. Here is the best plot that I got

5233   Sun Aug 14 20:04:40 2011 Keiko, Anamaria, Jenne, and KiwamuSummaryLockingcentral part ifo locking plan
GOAL : To lock the central part of ifo

Here is the plan:

Mon - assemble all the cables from PDs and mixers, and check the CDS channels. Prepare the beamsplitters.

Tue - The current paths to REFL11 and REFL55 will be modified to the four paths to REFL11, 33, 55, 165. And the PDs will be placed.
Wed, Thu - during waiting for the ifo available with vacuum, help aligning the POP, POX, POY. In parallel, a simulation to find the PRC length SRC
length tolerance will be proceeded.

Fri - When the ifo becomes available with vacuum, the sensing signals by 3-f scheme will be obtained with proper demodulation phases.

Sat - Try to lock the central part of the ifo with the new 3-f signals.
5243   Mon Aug 15 21:43:29 2011 Anamaria and KeikoSummaryLockingcentral part ifo locking project

REFL33 and REFL165 cables were connected from the AP table to the rack.  Cables on the rack for REFL33I, 33Q, 165I, 165Q ports were connected, too. Connections were confirmed by the data viewer. Two SMA cables which will be used for the two PDs on the AP tabl were built. We will be able to place the two PDs tomorrow. The beamsplitters to split the laser to REFL33 and REFL165 ports were mounted and ready to be placed.

5350   Tue Sep 6 22:51:53 2011 ranaSummaryCamerasAll Camera setups a need upgrading

I just tried to adjust the ETMY camera and its not very user friendly = NEEDS FIXING.

* Camera view is upside down.

* Camera lens is contacting the lexan viewport cover; this means the focus cannot be adjusted without misaligning the camera.

* There's no strain relief of the camera cables at the can. Needs a rubber cable grommet too.

* There's a BNC "T" in the cable line.

Probably similar issues with some of the other setups; they've had aluminum foil covers for too long. We'll have a camera committee meeting tomorrow to see how to proceed.

5358   Wed Sep 7 13:28:25 2011 steveSummaryCamerasAll Camera setups a need upgrading

 Quote: I just tried to adjust the ETMY camera and its not very user friendly = NEEDS FIXING. * Camera view is upside down. * Camera lens is contacting the lexan viewport cover; this means the focus cannot be adjusted without misaligning the camera. * There's no strain relief of the camera cables at the can. Needs a rubber cable grommet too. * There's a BNC "T" in the cable line. Probably similar issues with some of the other setups; they've had aluminum foil covers for too long. We'll have a camera committee meeting tomorrow to see how to proceed.

ITMY has been upgraded  here I have the new lenses on hand to do the others when it fit into the schedule.

5459   Mon Sep 19 14:57:36 2011 kiwamuSummaryIOOIP POS is back

IPPOS is back. A cable had been disconnected at the 1Y2 rack. So I put it back to place.

The cartoon below shows the current wiring diagram. I think this configuration is exactly the same as it it used to be.

 Quote from #5455 + Fixing IPPOS (volunteers)

5468   Mon Sep 19 20:56:36 2011 PaulSummarySUSRemaining SRM and ITMY OSEMs calibrations

I've now taken data for the pitch and yaw calibrations for the OSEMs of SRM and ITMY. Until such time as I know what the calibrated oplev noise spectra are like, I'm leaving the servo gains at zero.

I estimate the length of the lever arm from SRM to measurement position to be 3.06m, and the length of the lever arm from the ITMY to the measurement position to be 3.13m.

From the fits shown on the attached plots, this gives the following calibration factors for the SRM and ITMY OSEMs pitch and yaw counts (i.e. counts from channels such as SUS-ITMY_ULSEN_SW2 multiplied by a matrix of 1s and -1s) to pitch and yaw angle:

SRM PITCH: 1 OSEMs pitch count = 11.74 microradians

SRM YAW: 1 OSEMs yaw count = 12.73 microradians

ITMY PITCH: 1 OSEMs pitch count = 13.18 microradians

ITMY YAW: 1 OSEMs yaw count = 13.52 microradians

Next step is to do some DC offsets with the oplev paths back in place to get the final calibration between OSEMs counts and oplev counts, thus finally getting a conversion factor from oplev counts to radians.

I noticed while taking these measurements that the DC offsets I put on ITMY caused around 5 times larger change in angle than those on the SRM. The different path length is not enough to account for this, so I propose that the actuation is working differently for the two. I guess this should be taken into account when designing the output matrices (unless the control is passed through a different output matrix than the DC offsets?). I'll quantify the difference shortly, and write a conversion factor between output alignment count (e.g. SUS-ITMY_PIT_COMM) and angle.

Attachment 1: SRM_PITCH_calib_curve.png
Attachment 2: SRM_YAW_calib_curve.png
Attachment 3: ITMY_PITCH_calib_curve.png
Attachment 4: ITMY_YAW_calib_curve.png
5492   Tue Sep 20 23:59:53 2011 KojiSummaryLSCPlan to update the LSC code for multiple lock-ins

DRMI team needs to use at least three lockins on LSC

• Increase the number of the lockin matrix  done
• Duplicate lockin modules in the LSC code  done
• modify the main LSC screen done
• modify the lockin screen done
• modify the lockin matrix screen done
5495   Wed Sep 21 02:49:39 2011 KeikoSummaryLSCLSC matrices

I created 3 kinds of LSC matrices, PRMI condition with carrier resonant in PRC, PRMI condition with SB resonant in PRC, and DRMI with SB resonant in PRC. The matrices are with AS55 and REFL11 which are used for locking right now. The signal numbers are written in log10, and the dem phases are shown in degrees.

From CR reso PRMI to SB reso PRMI, demodulation phases change  ----

PRMI - Carrier resonant in PRC

PRCL      MICH  SRCL

 REFL11 7.7079 2.9578 0 REFL33 5.2054 3.2161 0 REFL55 7.7082 2.9584 0 REFL165 3.9294 2.5317 0 AS11 1.0324 3.5589 0 AS33 1.0286 1.6028 0 AS55 1.1708 4.2588 0 AS165 1.1241 0.9352 0 POP11 2.8015 -1.3331 0 POP33 0.2989 -1.6806 0 POP55 2.8017 -0.6493 0 POP165 -0.9769 -2.3708 0 POX11 3.7954 -0.3363 0 POX33 1.293 -0.7058 0 POX55 3.796 0.355 0 POX165 0.0187 -1.3837 0 Dem Phase REFL11 3 179 0 REFL33 165 -172 0 REFL55 13 170 0 REFL165 86 177 0 AS11 -32 73 0 AS33 176 -72 0 AS55 -41 12 0 AS165 -7 146 0 POP11 -11 -116 0 POP33 124 147 0 POP55 -54 -146 0 POP165 -117 -25 0 POX11 -87 15 0 POX33 -105 -80 0 POX55 -76 16 0 POX165 180 -91 0

PRMI - SB resonant in PRC

 SB reso PRMI PRCL MICH SRCL REFL11 7.6809 5.2777 0 REFL33 5.2465 3.1565 0 REFL55 7.2937 5.589 0 REFL165 4.3892 2.6857 0 AS11 1.3123 3.545 0 AS33 0.9331 1.6022 0 AS55 1.7425 4.0514 0 AS165 1.5838 1.1344 0 POP11 2.7745 0.3791 0 POP33 0.3401 -1.7392 0 POP55 2.3872 0.6904 0 POP165 -0.5171 -2.2279 0 POX11 3.7684 1.3574 0 POX33 1.3341 -0.7664 0 POX55 3.3815 1.6688 0 POX165 0.4785 -1.2163 0
Dem Phase
 REFL11 155 -115 0 REFL33 -8 3 0 REFL55 91 -178 0 REFL165 -62 28 0 AS11 109 62 0 AS33 -39 99 0 AS55 13 -38 0 AS165 -155 168 0 POP11 141 -128 0 POP33 -48 -38 0 POP55 24 115 0 POP165 95 -176 0 POX11 65 155 0 POX33 83 95 0 POX55 2 92 0 POX165 32 123 0

DRMI - SB resonant in PRC

 REFL11 7.6811 5.0417 4.2237 REFL33 5.2751 4.1144 3.7766 REFL55 7.2345 7.0288 6.6801 REFL165 4.3337 4.1266 3.7775 AS11 1.1209 3.512 0.9248 AS33 0.9159 1.6323 0.7971 AS55 2.6425 5.3915 2.5519 AS165 2.6423 2.4881 2.3272 POP11 2.7747 0.1435 -0.6846 POP33 0.3687 -0.7849 -1.122 POP55 2.3244 2.1302 1.7815 POP165 -0.5833 -0.8 -1.1548 POX11 3.7676 3.261 0.8086 POX33 1.3896 0.2372 0.2333 POX55 3.4619 3.0097 3.1326 POX165 0.782 0.6668 0.4357
Dem Phase
 REFL11 154 -16 4 REFL33 -5 12 51 REFL55 129 -166 -123 REFL165 -23 40 83 AS11 132 79 69 AS33 -92 -127 -83 AS55 -33 -55 -5 AS165 154 179 -144 POP11 141 -29 -9 POP33 -46 -27 12 POP55 62 127 170 POP165 135 -161 -117 POX11 64 -102 -83 POX33 85 143 118 POX55 57 103 124 POX165 99 155 -164

5498   Wed Sep 21 14:28:25 2011 KojiSummaryLSCThe LSC code/screen modification for LSC LOCKINs

## The LSC code has been modified

- The code was modified, compiled, and installed.

- The code is now running. FB was restarted to deal with the change of the channel names.

- Now we have LOCKIN1, 2, and 3. This required the change of the names from C1:LSC-LOCKIN_.... to C1:LSC-LOCKIN1_...

- The LSC screen has also modified. It has three lockins on the screen.

- The corresponding matrix screens have been modified/created and linked from the main screen.

- I need to make the screens more cool but the locking team can start to use those lockins.

5522   Thu Sep 22 18:33:01 2011 KojiSummaryLSCThe LSC screen modification

As per the request of Anamaria, I have added the slider of the demodulation phase for each RF PD screens.

Attachment 1: PD_screen.png
5528   Thu Sep 22 23:18:51 2011 KojiSummaryLSCThe LSC screen modification

Attachment 1: C1LSC_RFPD.png
5589   Fri Sep 30 18:06:24 2011 kiwamuSummaryIOOPZTs straing guage

5592   Sat Oct 1 17:47:21 2011 KojiSummaryGeneralRecovery from the power shutdown

[Steve Koji Kiwamu]

- The storage on linux1 and linux1 itself (with this order) were turned on at 10:30am

- Kiwamu restored the vacuum system

=> opened V4, started TP1 (maglev) and opened V1.

The pressure went downfrom 2.5 mTorr to the normal level in about 20 minutes.

- A regular fsck of linux1 was completed at 5pm

- Nodus was turned on. Mounting /cvs/cds succeeded

- The control room computers were turned on

- The rack power for FB turned on, FB and megatron started.

- Kiwamu and Koji went through all of the rack powers and started the slow and fast machines.
As we found Solensen for -15V at ETMX was current limited. +/-15V were turned off for now.
==> Kiwamu turned on Solensen again for investigation and found it became okay.
It's now ON.

- c1sus and c1ioo had many red lamps on the FE status screen.
Ran killc1XXX for all of the FE codes on c1lsc and c1ioo.
Then, made software reboot (sudo shutdown -r now)
All of the FEs shows green (after some randome clicking of DIAGRESETs)

- HVs on 1X1 were turned on. The are not vacuum HV, but used only in the air

- Turned on the RF generation box and the RF distribution box

- burtrestore slow machines (c1psl, c1susaux, c1iool0, c1iscaux, c1iscaux2, c1auxex, c1auxey)

5593   Sat Oct 1 22:53:49 2011 kiwamuSummaryGeneralRecovery from the power shutdown : lockable

Found the Marconi for the 11 MHz source had been reset to its default.

=> reset the parameters. f = 11.065910 MHz (see #5530) amp = 13 dBm.

Interferometer became lockable. I checked the X/Y arm lock, and MICH lock, they all are fine.

5596   Sun Oct 2 13:45:13 2011 ranaSummaryGeneralRecovery from the power shutdown: apache / svn

Restarted Apache on nodus using Yoichi's wiki instructions. SVN is back up.

5599   Mon Oct 3 08:38:21 2011 steveSummaryVACRecovery from the power shutdown is completed

I failed to start Rana's favorit anciant desktop computer at the vac rack. He has to baby this old beast just a little bit more.

Vacuum status: Vac Normal was reached through Farfalla: Rga was switched back to IFO and and Annuloses are beeing pumped now.

V1 was closed for about a day and the pressure reached  ~2.8 mTorr in the IFO.  This leakrate plus outgassing is normal

The ref cavity 5000V was turned on.

The only thing that has to be done is to restart the RGA. I forgat to turn it off on Friday.

Attachment 1: poweroutage.jpg
5628   Fri Oct 7 11:45:24 2011 KojiSummaryLSCPOY11 installed, 55MHz PD at POY removed

POY11 PD was installed last night. The lock of the Y arm was confirmed with the POY11I signal.

- The DC transimpedance was modified to be 1010V/A as the incident power is tiny.

- The demodulation phase of the roughly adjusted (148deg) to have PDH signal at the I-phase.
The comparison with AS55I signal exhibits that POY11I have ~150 times weaker signal with 45dB whitening.
(In total 25000 times weaker.)

On the way to make POY11 functioning, there were many fixes at the LSC rack...

Details:

- The PD interface cards (power supply for the RFPDs) were checked:
So far the two card at the right hand side were checked.
Desipite the previous entry reported the issues on those boards, they did not show any problem yesterday.
One hypothetical possibility is the enabling switches that is controlled from the old slow epics targets.

- POY55 was removed
This 55MHz PD is supposed to be installed at POP.
The PD, an RF cable, an RF amp, the power supply of the RF amp were removed.

- POY11 was installed
The PD was placed where the 55MHz was placed.
The beam was aligned on the diode using the IR viewer and the digital multimeter.
The power supply cable and the RF cable for POY on the ITMY table were used.
There were an ND filter on the POY beam path. It was removed.

- On the LSC rack
The PD RF was connected to the patch panel at the top of the rack.
There were loose connectors on the patch panel. Some connectors were tightened on the panel.

I found that POY11 and POX11 had I&Q signal reversely connected to the whitening board.
==> These were fixed but
require the orthogonality test again for those channels.

The I phase output of the AS11 demod board had a broken connector.
The onboard SMA has got disintegrated because of too much twist on the connector.
The board was once removed from the rack and the connector was fixed using a heat gun and soldering.

The DC signals were checked. POYDC was not correctly connected. POYDC were correctly connected to the POYDC channel.

- CDS
c1lsc was found with the RFM frozen.
The c1lsc machine was soft-rebooted after stopping all of the RT processes.
Once the RT processes came back, they were all burtrestored.

- PDH locking
Restored Y-arm. Locked it with AS55Q.
Ran ASS alignment for Y-arm. 100cnt 150Hz sinusoidal signal is applied to ETMY
Measured the PSD of AS55Q, POY11I, and POY11Q.
Adjusted the demod phase so that the excitation could be minimized in POY11Q.

5662   Thu Oct 13 21:40:59 2011 ranaSummaryVACRecovery from the power shutdown is completed

As it turns out Steve is not crazy in this particular instance: the vacuum computer, linux3 , has some issues. I can login just fine, but trying to open a terminal makes the CPU rail and the RAM max out and eventually the machine freezes.

Under KDE, I can open a terminal OK as root, but if I then try a 'su controls', the same issue happens. Let's wait for Jamie to fix this.

5686   Tue Oct 18 15:20:03 2011 kiwamuSummaryIOORFAM plan

[Suresh / Koji / Rana / Kiwamu]

Last night we had a discussion about what we do for the RFAM issue. Here is the plan.

(PLAN)

1. Build and install an RFAM monitor (a.k.a StochMon ) with a combination of a power splitter, band-pass-filters and Wenzel RMS detectors.

=> Some ordering has started (#5682). The Wenzel RMS detectors are already in hands.

2. Install a temperature sensor on the EOM. And if possible install it with a new EOM resonant box.

=> make a wheatstone bridge circuit, whose voltage is modulated with a local oscillator at 100 Hz or so.

3. Install a broadband RFPD to monitor the RFAMs and connect it to the StochMon network.

=> Koji's broadband PD or a commercial RFPD (e.g. Newfocus 1811 or similar)

4. Measure the response of the amount of the RFAM versus the temperature of the EO crystal.

=> to see whether if stabilizing the temperature stabilizes the RFAM or not.

5.  Measure the long-term behavior of the RFAM.

=> to estimate the worst amount of the RFAM and the time scale of its variation

6. Decide which physical quantity we will stabilize, the temperature or the amount of the RFAM.

7. Implement a digital servo to stabilize the RFAMs by feeding signals back to a heater

=> we need to install a heater on the EOM.

8. In parallel to those actions, figure out how much offsets each LSC error signal will have due to the current amount of the RFAMs.

=> Optickle simulations.

9. Set some criteria on the allowed amount of the RFAMs

=> With some given offsets in the LSC error signal, we investigate what kind of (bad) effects we will have.

5703   Wed Oct 19 17:21:16 2011 KojiSummaryLSCModification on the RFPD interface cards

I have modified all of the three RFPD interface cards to be enabled permanently.
This prevents an accidental disabling caused by a stray voltage of the logic input (or whatever),
which was reported in multiple occasions by Anamaria and me.

The logic ICs (74LS04) for buffering of the EPICS switches were removed by 14pin sockets with additional wires soldered.
The modification shorts the inputs to the second logic chips, resulting in the permanent enabling of the PD circuit.

Attachment 1: D990543-B_mod.pdf
5708   Thu Oct 20 01:40:33 2011 KojiSummarySUSMC2 Misaligned 2:27PM on Wednesday

There looks some activity at around MC2 on Wednesday afternoon.
It caused the misalignment of MC2. Misalignment was not found in MC1/3.

It seems that the incident beam on the MC was aligned in the evening.
This increased the MC transmission but it is vibible that the spot on MC2 is shifted from the center.

We need an action on this issue tomorrow in the daytime.

Attachment 1: MC2_misalign.png
5716   Thu Oct 20 18:57:35 2011 SureshSummarySUSMC2 Misaligned 2:27PM on Wednesday

 Quote: There looks some activity at around MC2 on Wednesday afternoon. It caused the misalignment of MC2. Misalignment was not found in MC1/3. It seems that the incident beam on the MC was aligned in the evening. This increased the MC transmission but it is vibible that the spot on MC2 is shifted from the center. We need an action on this issue tomorrow in the daytime.

I am working on fixing this.  You might some strange stuff going on in the control room screens.  Pls ignore it till I am done.

5717   Fri Oct 21 02:36:44 2011 SureshSummarySUSMC2 Misaligned 2:27PM on Wednesday : MC Realigned

Quote:

 Quote: There looks some activity at around MC2 on Wednesday afternoon. It caused the misalignment of MC2. Misalignment was not found in MC1/3. It seems that the incident beam on the MC was aligned in the evening. This increased the MC transmission but it is vibible that the spot on MC2 is shifted from the center. We need an action on this issue tomorrow in the daytime.

I am working on fixing this.  You might some strange stuff going on in the control room screens.  Pls ignore it till I am done.

I have realigned the MC by recentering the spots on all the MC optics.  The current spot positions (in mm) are:

MC1P     MC2P     MC3P      MC1Y      MC2Y     MC3Y

0.2245    0.3364   -0.2801   -1.8891    0.1631   -1.744

Initially the lockins 2 and 5 showed very small outputs.  This was traced to the fact that we have recently switched on a 28Hz ELP filter module in the MC2 ASC filter bank which introduces an extra phase of about 75deg..  See this elog.

When the MC ASS lockins were initially setup, the phase was set with this filter module switched off.  Since quite some time has passed since the last calibration of these phases, I readjusted the phases to minimise the  Q_OUTPUT and I also adjusted the GAINs in the SIG filter banks  of all the six lockins so that their I_OUT's drop by the calibration value of -2.65 when an offset of 0.1 is introduced into the MC suspension output matrices.  Two short scripts in the $scripts$/ASS/ directory help in setting and removing these offsets.  They are called MCxoffsetOn and MCxoffsetOff.   They have to be edited appropriately to address each DoF of the MC.

The $scripts$/ASS/mcassUp script., which sets up everything to make the MC spot decentering measurement, has been edited to set these new phases and gains.  The old settings have been commented out.

I then centered the spots on the WFS sensors and the MC_TRANS QPD.  We are now ready to make the MC WFS output matrix transfer coef measurement again, but this time with the WFS loops closed.

5718   Fri Oct 21 02:57:38 2011 SureshSummarySUSMC2 Misaligned 2:27PM on Wednesday : cause traced

Quote:

 Quote: There looks some activity at around MC2 on Wednesday afternoon. It caused the misalignment of MC2. Misalignment was not found in MC1/3. It seems that the incident beam on the MC was aligned in the evening. This increased the MC transmission but it is vibible that the spot on MC2 is shifted from the center. We need an action on this issue tomorrow in the daytime.

I am working on fixing this.  You might some strange stuff going on in the control room screens.  Pls ignore it till I am done.

While chatting with Jenne I learnt that some substantial amount of work had taken place yesterday around the MC2 chamber.  This was associated with the relocating of seismometers.  ref elog

I reiterate what is well known for quite sometime:  MC2 table is not well isolated from the ground.  And we should not approach this chamber unless absolutely necessary. I have blocked off the area around it which we should avoid.  It is a serious waste of time and effort to realign the MC each time the MC2 table decides to settle into a new position.

Steve tells me that the mild-steel frame supporting the chamber+MC2_table sits with two legs on one concrete slab while the other two legs sit on another one.   The frame is also quite weak without sufficient gussets or cross connects.  The next time we have a major shutdown we must replace this frame with a more sturdy one which sits on one slab (preferably the one on which the rest of the MC sits).

Till we improve this mounting, I suggest that we avoid that area as much as possible.

5745   Thu Oct 27 03:32:45 2011 KojiSummaryIOORFAM monitor progress

[Suresh, Mirko, Koji]

A cable from the stochmon box to the cross connect for the EPICS ADCs is installed.

The power supply and the signal outputs are concentrated in a single DSub 9pin connector
that is newly attached on the box.

The connection from the stochmon side of the cable and the EPICS value was confirmed.
The calibration of them looks fine.

To do:
- Once the stochmon box is completed we can immediately test it.
- The EPICS channel names are still as they were. We need to update the database file of c1iool0, the chans file for the slow channel.

The pinout is as following

------------- | 1 2 3 4 5 |   Female / Inside View \  6 7 8 9  /  \---------/

1 - 11MHz Signal
2 - 30MHz Signal
3 - 55MHz Signal
4 - NC
5 - +5V supply
6 - 11MHz Return
7 - 30MHz Return
8 - 55MHz Return
9 - Supply ground

5747   Thu Oct 27 18:00:38 2011 kiwamuSummaryLSCOffsets in LSC signals due to the RFAMs : Optickle simulation

The amount of offsets in the LSC signals due to the RFAMs have been estimated by an Optickle simulation.

The next step is to think about what kind of effects we get from the RFAMs and estimate how much they will degrade the performance.

(Motivation)

We have been having relatively big RFAM sidebands (#5616), which generally introduce unwanted offsets in any of the LSC demodulated signals.
The motivation was that we wanted to estimate how much offsets we've been having due to the RFAMs.
The extreme goal is to answer the question : 'How big RFAMs do we allow for operation of the interferometer?'.
Depending on the answer we may need to actively control the RFAMs as already planed (#5686).
Since the response of the interferometer is too complicated for analytic works, so a numerical simulation is used.

(Results : Offsets in LSC error signals)

Figure: Offsets in unit of meter in all the LSC demodulated signals.  Y-axis is the amount of the offsets and the X-axis represents each signal port.
In each signal port, the signals are classified by color.
(1) Offsets in the PRCL signal. (2) Offsets in the MICH signal. (3) Offsets in the SRCL signal.

Roughly the signals showed offsets at a 0.1 nm level.
The numerical error was found to be about 10-10 nm by running the same simulation without the AM sidebands.
Here is a summary of the amount of the offsets:

 offsets [nm] (1f signal port) offsets [nm] (3f signal port) biggest offsets [nm] (signal port) PRCL 0.3 (REFL11) 0.2 (REFL33) 1 (REFL55) MICH 0.00009 (AS55) 0.8 (REFL33) 7 (POP11) SRCL 0.1 (REFL55) 0.1 (REFL165) 40 (POX11)
In the SRCL simulation  REFL11I, REFL11Q, POP11I, POP11Q and POX11I didn't show any zero crossing points within 100 nm range around the resonance.
It is because that the SRCL doesn't do anything for the 11MHz sidebands. So it is the right behavior.
However POX11 was somewhat sensitive to the SRCL motion and showed a funny signal with a big offset.

(Simulation setup)

I applied the current PM/AM ratio according to the measurement (#5616, #5519)
The modulation indices used in the simulation are :
+ PM index in 11MHz = 0.17
+ PM index in 55MHz = 0.14
+ AM index in 11MHz = 0.17 / 200 = 8.5x10-4
+ AM index in 55MHz = 0.14 / 200 = 7.0x10-4
Note that the phases of the AM and PM sidebands are the same.

For clarity, I also note the definition of PM/AM ratio as well as how the first order upper sideband looks like.

The optical parameters are all at ideal length although we may want to check the results with more realistic parameters:
+ No arm cavities
+ PRCL length = 6.75380
+ SRCL length = 5.39915
+ Schnupp asymmetry = 3.42 cm
+ loss in each optic = 50 ppm
+ PRCL = resonant for 11 and 55MHz
+ MICH = dark fringe
+ SRCL = resonant for 55 MHz
The matlab script will be uploaded to the cvs server.

 Quote from #5686 8. In parallel to those actions, figure out how much offsets each LSC error signal will have due to the current amount of the RFAMs.     => Optickle simulations.

5849   Wed Nov 9 14:49:07 2011 kiwamuSummaryLSCCharacterization of the Power Recycled Michelson

EDIT by KI:

The definition of the recycling gain is wrong here.

See the latest entry (

Here is a summary about the Power Recycled Michelson (PRMI).

It seems the mode matching is also one of the greatest contributor on the low recycling gain.

(Estimated parameters)

Loss = 5.3% (or effective reflectivity of  93.28% in Michleson) => Under coupling !!

+  Mode matching efficiency = 47.4 %  => Really bad !!

With these values we end up with a recycling gain of 7 and a normalized REFLDC of  0.5 as observed (#5773).

Also according the incident beam scan measurement (#5773) the loss is NOT a local effect like a clipping, it is more like uniformly distributed thing.

As for the mode matching, the number indicates that approximately the half of the incident light is coming back to the REFL port without interacting with PRMI.

This is bad because the non-mode-matched light, which is just a junk light, is entering into the photo detectors unnecessarily.

In the worst scenario, those junk light may create a funny signal, for example a signal sensitive to the alignment of PRM.

(Estimation method)

The method to estimate the loss and the MM (Mode-Matching efficiency) is essentially the same as before (#5541).

One difference from the previous estimation is that the I used more realistic parameters on the transmissivity of ITMs and PRM :

PRM : T = 5.637 %  (see the 40m wiki)

ITM : T = 1.384 %  (see the 40m wiki)

In addition to the basic calculations I also made plots which are handy for figuring out where we are.

Quantities we can measure are the reflected light from PRMI and the recycling gain using the REFL PD and the POY PD respectively.

So I wanted to see how the loss and MM can be estimated from the measured REFL DC and recycling gain.

The plots below are the ones.

[Loss map]

The first figure shows a contour map of the loss as a function of the measured REFL DC and recycling gain.

The white area is a place where no proper solutions can be found (for example MM can get to more than 100 or loss becomes negative).

The star mark in the plot corresponds to the place where we are now. Obviously the loss is about 5%.

If we somehow decrease the amount of the loss the star mark will mostly go up in the plot.

[MM map]
The second figure shows a contour map of the MM as a function of the measured REFL DC and recycling gain.

The X and Y axis are exactly the same as that of the first plot. Again the star mark represents the place where we are.

We are currently at MM=47%

(Solutions)

Here are some solutions to bring the recycling gain higher.

We don't work on these things immediately since it requires opening of the chambers again and it will take some times.

But we should think about those options and prepare some stuff for a coming vent.

+ Refinement of the position of the mode matching telescopes.  => The Recycling gain can go up to 15.

=> Assuming the loss in the cavity doesn't change, the star mark in the first plot will go to the left hand side along the "0.05" black solid line.

=> However PRMI will be still under coupled.

=> Needs an estimation about which way we move the telescopes.

+ Locate the place of the dominant loss source and reduce it somehow.

=> The recycling gain will be more than 18 if the loss reduces by a factor of more than 5.

=> Needs a clever way to find it otherwise we have to do it in the classical way (i.e. white light and trying to find dirty surfaces)

5850   Wed Nov 9 16:03:21 2011 kiwamuSummaryGeneralGoal this week

Goal of this week :  ALS on the Y arm

Minimum success : Detection of the green beatnote between the freq-doubled PSL and the Y arm transmitted light

5851   Wed Nov 9 16:29:36 2011 KojiSummaryLSCCharacterization of the Power Recycled Michelson

Difficult to understand.

The mode matching does not change the recycling gain. It changes the coupling of the incident light into the cavity.
It changes the reflected and accumulated power, but the recycling gain is not affected.

The recycling gain is determined by the optical configuration and the optical loss in the cavity.

In the actual measurement, of course, we should take both of the loss and the mode matching into account.
But this is the issue of the measurement method.

The essential questions are:
How much is the actual recycling gain? And how does it affect the signal extraction?

5875   Fri Nov 11 14:55:47 2011 kiwamuSummaryLSCCharacterization of the Power Recycled Michelson : take 2

 Quote from #5851 The recycling gain is determined by the optical configuration and the optical loss in the cavity. How much is the actual recycling gain? And how does it affect the signal extraction?

As Koji pointed out I made a wrong definition on the recycling gain of PRMI (Power-Recycled Michelson Interferomter).

In the correct definition the estimated recycling gain is 15.
In order to answer Koji's second question,which is about the effect on the signal extraction,
I need to scratch my head for a while.
( Give me some time..)

The value what I called "Recycling gain" must have been called "measured power build up" or something like that.
For clarity I put the definitions of the quantities.
Recycling gain :

Reflectivity of PRMI (measured by REFLDC):

Power build up (measured by POY DC) :

Mode Matching (MM) efficiency :

Loss in the PRMI cavity :

(Results of Measurement and Estimation)

Estimated recycling gain = 15

Estimated MM efficiency = 47.4%

Estimated Loss = 5.3%

Measured power build Up = 7

Measured reflectivity of PRMI = 0.5

5885   Mon Nov 14 11:32:02 2011 kiwamuSummaryGeneralGoal this week

Goal of this week : Noise budgeting on the Y arm ALS

Minimum success : bring the Y arm to the resonance by using ALS  NOISE BUDGETING!!!

=> as a preparation the incident beam pointing needs to be fixed by steering the MC suspensions.

 Quote from #5850http://nodus.ligo.caltech.edu:8080/40m/5850 Goal of this week :  ALS on the Y arm (DONE)

5980   Tue Nov 22 18:42:10 2011 kiwamuSummaryGreen LockingSome issues on the Y end green PDH locking

[Rana / Kiwamu]

As a part of the ALS noise budgeting we took a look at the Y end PDH setup to see if we are limited by an effect from the Amplitude Modulation (AM).

Then we found two issues :
(1) a big variation in AM transfer function from the laser PZT to the intensity of the frequency-doubled laser. We haven't figured out the reason yet,
(2) some of the optics and their mounts need to be refined.

(AM transfer function)

One of the suspicious noise source of the Y arm ALS was an AM effect in the Y end green PDH locking.
A possible scenario is that: there is some amount of the offset in the PDH signal due to the AM at the modulation frequency,
and it allows the intensity noise to couple to the laser frequency, which we want to suppress.
So we wanted to check if the measured AM (#2799) at 1064 nm  is still true at 532 nm.
The problem right now is that : every time we measured the AM transfer function by exciting the laser PZT with swept sine,
the transfer function varied by 20 dB, with average response of 50 dB. And there was no repeatability.
We were using the PD which is for the green PDH signal and the single-bounced light from ETMY.
The measurement was done in a frequency band of 100 - 400 kHz where we expect a couple of sharp notches.
Perhaps we should try the same measurement with IR first to make sure we are doing a right thing, and then do it with the frequency-doubled laser.

(Y table setup needs more improvements)

We found some optics and their mounts which need to be refined.
Here is a list which we briefly made at the time.
• Use washers
• Beam clipping in Green Faraday and the very last mirror
• Use two screws and wide base plate
• Tune PPKTP PID parameters
• Remove flipper mirror
• Move the mechanical shutter to where the beam size is smaller
• Put a beam damp for the reflected light from the PD
• Cable rack
• Improve the incident angle on the last two launching mirrors
5983   Wed Nov 23 00:00:53 2011 ZachSummaryGreen LockingSome issues on the Y end green PDH locking

 Quote: (AM transfer function)  One of the suspicious noise source of the Y arm ALS was an AM effect in the Y end green PDH locking. A possible scenario is that: there is some amount of the offset in the PDH signal due to the AM at the modulation frequency, and it allows the intensity noise to couple to the laser frequency, which we want to suppress.  So we wanted to check if the measured AM (#2799) at 1064 nm  is still true at 532 nm. The problem right now is that : every time we measured the AM transfer function by exciting the laser PZT with swept sine, the transfer function varied by 20 dB, with average response of 50 dB. And there was no repeatability. We were using the PD which is for the green PDH signal and the single-bounced light from ETMY. The measurement was done in a frequency band of 100 - 400 kHz where we expect a couple of sharp notches. Perhaps we should try the same measurement with IR first to make sure we are doing a right thing, and then do it with the frequency-doubled laser.

What is meant by the "average response of 50 dB"? Is this dB[ RIN / Hz ] or something? Also, do you mean the average over a broad band or the average response at the chosen modulation frequency over several trials? I don't really understand what measurement was done.

ELOG V3.1.3-