40m QIL Cryo_Lab CTN SUS_Lab TCS_Lab OMC_Lab CRIME_Lab FEA ENG_Labs OptContFac Mariner WBEEShop
  40m Log, Page 322 of 341  Not logged in ELOG logo
ID Date Authordown Type Category Subject
  14481   Sun Mar 17 13:35:39 2019 AnjaliUpdateALSPower splitter characterization

We characterized the power splitter ( Minicircuit- ZAPD-2-252-S+). The schematic of the measurement setup is shown in attachment #1. The network/spectrum/impedance analyzer (Agilent 4395A) was used in the network analyzer mode for the characterisation. The RF output is enabled in the network analyser mode. We used an other spliiter (Power splitter #1) to splitt the RF power such that one part goes to the network analzer and the other part goes to the power spliiter (Power splitter #2) . We are characterising power splitter #2 in this test. The characterisation results and comparison with the data sheet values are shown in Attachment # 2-4.

Attachment #2 : Comparison of total loss in port 1 and 2

Attachment #3 : Comparison of amplitude unbalance

Attachment #4 : Comparison of phase unbalance

  • From the data sheet: the splitter is wideband, 5 to 2500 MHz, useable from 0.5 to 3000 MHz. We performd the measurement from 1 MHz to 500 MHz (limited by the band width of the network analyzer).
  • It can be seen from attachment #2 and #4 that there is a sudden increase below ~11 MHz. The reason for this is not clear to me
  • The mesured total loss value for port 1 and port 2 are slightly higher than that specified in the data sheet.From the data sheet, the maximum loss in port 1 and port 2 in the range at 450 MHz are 3.51 dB and 3.49 dB respectively. The measured values are 3.61 dB and 3.59 dB respectively for port 1 and port 2, which is higher than the values mentioed in the data sheet. It can also be seen from attachment #1 (b) that the expected trend in total loss with frequency is that the loss is decreasing with increase in frequency and we are observing the opposite trend in the frequency range 11-500 MHz. 
  • From the data sheet, the maximum amplitude balance in the 5 MHz-500 MHz range is 0.02 dB and the measured maximum value is 0.03 dB
  • Similary for the phase unbalance, the maximum value specified by the data sheet in the 5 MHz- 500 MHz range is 0.12 degree and the measurement shows a phase unbalance upto 0.7 degree in this frequency range
  • So the observations shows that the measured values are slighty higher than that specified in the data sheet values.
Attachment 1: Measurement_setup.pdf
Measurement_setup.pdf
Attachment 2: Total_loss.pdf
Total_loss.pdf
Attachment 3: Amplitude_unbalance.pdf
Amplitude_unbalance.pdf
Attachment 4: Phase_unbalance.pdf
Phase_unbalance.pdf
  14482   Sun Mar 17 21:06:17 2019 AnjaliUpdateALSAmplifier characterisation

The goal was to characterise the new amplifier (AP1053). For a practice, I did the characterisation of the old amplifier.This test is similar to that reported in Elog ID 13602.

  • Attachment #1 shows the schematic of the setup for gain characterisation and Attachment #2 shows the results of gain characterisation. 
  • The gain measurement is comparable with the previous results. From the data sheet, 10 dB gain is guaranteed in the frequency range 10-450 MHz. From our observation, the gain is not flat pver this region. We have measured a maximum gain of 10.7 dB at 6 MHz and it has then decreased upto 8.5 dB at 500 MHz
  • Attachement #3 shows the schematic of the setup for the noise characterisation and Attachment # 4 shows the results of noise measurment. 
  • The noise measurement doesn't look fine. We probably have to repeat this measurement.
Attachment 1: Gain_measurement.pdf
Gain_measurement.pdf
Attachment 2: Amplifier_gain.pdf
Amplifier_gain.pdf
Attachment 3: noise_measurement.pdf
noise_measurement.pdf
Attachment 4: noise_characterisation.pdf
noise_characterisation.pdf
  14504   Sun Mar 31 18:39:45 2019 AnjaliUpdateAUXAUX laser fiber moved from AS table to PSL table
  • Attachment #1 shows the schematic of the experimental setup for the frequency noise measurement of 1 um laser source.

  • AUX laser will be used as the seed source and it is already coupled to a 60 m fiber (PM980). The other end of the fiber was at the AS table and we have now removed it and placed in the PSL table.

  • Attachment # 2 shows the photograph of the experimental setup. The orange line shows the beam that is coupled to the delayed arm of MZI and the red dotted line shows the undelayed path.

  • As mentioned, AUX is already coupled to the 60 m fiber and the other end of the fiber is now moved to the PSL table. This end needs to be collimated. We are planning to take the same collimator from AS table where it was coupled into before. The position where the collimator to be installed is shown in attachment #2. Also, we need to rotate the mirror (as indicated in attachment #2) to get the delayed beam along with the undelayed beam and then to combine them. As indicated in attachment #2, we can install one more photo diode to perform  balanced detection.

  • We need to decide on which photodetector to be used. It could be NF1801 or PDA255.

  • We also performed the power measurement at different locations in the beam path. The different locations at which power measurement is done is shown attachment #3

  • There is an AOM in the beam path that coupled to the delayed arm of MZI. The output beam after AOM was coupled to the zero-order port during this measurement. That is the input voltage to the AOM was at 0 V, which essentially says that the beam after the AOM is not deflected and it is coupled to the zero-order port. The power levels measured at different locations in this condition are as follows. A)282 mW B)276 mW C)274 mW D)274 mW E)273 mW F)278 mW G)278 mW H)261 mW I)263 mW J)260 mW K)131 mW L)128 mW M)127 mW N)130 mW

  • It can be seen that the power is halved from J to K. This because of a neutral density filter in the path of the beam

  • In this case, we measured a power of 55 mW at the output of the delayed fiber. We then adjusted the input voltage to the AOM driver to 1 V such that the output of AOM is coupled to the first order port. This reduced the power level in the zero-order port of AOM that is coupled to the delayed arm of the MZI. In this case we measured a power of 0.8 mW at the output of delayed fiber.

  •  We must be careful about the power level that is reaching the photodetector such that it should not exceed the damage threshold of the detector.

  • The power measured at the output of undelayed path is 0.8 mW.

  • We also must place the QWP and HWP in the beam path to align the polarisation.

Quote:

[anjali, gautam]

To facilitate the 1um MZ frequency stabilization project, I decided that the AUX laser was a better candidate than any of the other 3 active NPROs in the lab as (i) it is already coupled into a ~60m long fiber, (ii) the PSL table has the most room available to set up the readout optics for the delayed/non-delayed beams and (iii) this way I can keep working on the IR ALS system in parallel. So we moved the end of the fiber from the AS table to the SE corner of the PSL table. None of the optics mode-matching the AUX beam to the interferometer were touched, and we do not anticipate disturbing the input coupling into the fiber either, so it should be possible to recover the AUX beam injection into the IFO relatively easily.

Anjali is going to post detailed photos, beam layout, and her proposed layout/MM solutions later today. The plan is to use free space components for everything except the fiber delay line, as we have these available readily. It is not necessarily the most low-noise option, but for a first pass, maybe this is sufficient and we can start building up a noise budget and identify possible improvements.

The AUX laser remians in STANDBY mode for now. HEPA was turned up while working at the PSL table, and remains on high while Anjali works on the layout.

 

Attachment 1: Schematic_of_experimental_setup_for_frequency_stabilisation_of_1_micron_source.png
Schematic_of_experimental_setup_for_frequency_stabilisation_of_1_micron_source.png
Attachment 2: 1_micron_setup_for_frequency_noise_measurement.JPG
1_micron_setup_for_frequency_noise_measurement.JPG
Attachment 3: 1_micron_setup_for_frequency_noise_measurement_power_levels.png
1_micron_setup_for_frequency_noise_measurement_power_levels.png
  14518   Fri Apr 5 11:40:57 2019 AnjaliUpdateFrequency noise measurementFrequency noise measurement of 1 micron source
  • Attachment #1 shows the present experimental setup. The photodiode is now replaced with PDA255. The farther end of the fiber (output of the delayed arm) is coupled through a collimator and aligned such that the beam from the delayed path fall on the detector along with the undelayed path of MZI. We tried to measure the frequency noise of the laser with this setup, but we didn’t get anything sensible.
  • One of the main draw backs of the measurement was the polarisation was not aligned properly in the setup. So, then the next step was to identify the polarisation at different locations in the beam path and to maximise the polarisation to either S or P component.

  • So, we introduced HWP at the input beam path after isolator as shown in attachment #1. Also, the polarisation was tested at positions P1, P2, P3, and P4 shown in attachment #1 by placing a polarisation beam splitter at these locations and then by observing the transmitted (P component) and reflected light (S component) using power meter.

  • The observations at different locations are as the follows

Position Input power (mW) P component (mW) S component (mW)
P1 279 145 123
P2 255 113 137
P3 129 67 58
P4 124 66 53

 

  • These observations show that the P and S components are almost equal, and this is not a good polarisation arrangement. At this point, we also had to check whether the incoming beam is linearly polarised or not.

  • To test the same, the PBS was placed at position P1 and the P and S components were observed with power meter as the HWP is rotated.Attachment # 2 shows the results of the same, that is the variation in P and S component as the HWP is rotated.

  • This result clearly shows that the input beam is linearly polarised. The HWP was then adjusted such that the P component is maximum and coupled to the MZI. With this orientation of HWP, the polarisation observed at different positions P1, P2, P3, and P4 are as follows.

Position Input (mW) P component (mW) S component (mW)
P1 283 276 5
P2 248 228 7
P3 126 121 2
P4 128 117 1
  • This shows that the polarisation is linearly polarised as well as it is oriented along the P direction (parallel to the optical table).

  • We have the polarisation maintaining fiber (PM 980) as the delay fiber. The polarisation of the light as it propagates through a PM fiber depends on how well the input beam is coupled to the axis (slow or fast) of the fiber. So, the next task was to couple the light to one of the axes of the fiber.

  • The alignment key on the fiber is a good indication of the axis of the fiber. In our case, the alignment key lines up with the slow axis of the fiber. We decided to couple the light to the fast axis of the fiber. Since the incoming beam is P polarised, the output fiber coupler was  aligned such that the fast axis is parallel to optical table as possible.

  • A PBS was then introduced after the fiber output collimator . There is a HWP (marked as HWP2 in attachment 1) in front of the input coupler of the fiber as well. This HWP was then rotated and observed the P and S component from the PBS that is now placed after the output coupler with a power meter.The idea was , when the light is coupled to the fast axis of the fiber, we will see the maximum at the P componet at the output

  • Attachment # 3 shows the observation. 

  • In this way I tried to find the orientation of the HWP2 such that the P component is maximum at the output. But I was not succeeded in this method and observed that the output was fluctuating when the fiber was disturbed. One  doubt we had was whether the fiber is PM or not . Thus we checked the fiber end with fiber microscope and confirmed that it is PM fiber. 

  • Thus, we modifed the setup as shown in attachement # 4.The photodetector (PDA55) was monitoring the S component and the output of the detector was observed on an oscilloscope. We rotated the HWP2 such that the S component is almost minimum. At the same time, we were disturbing the fiber and was observing whether the output is fluctuating. The HWP2 angle was tweaked around the minimum of S component and observed the output with disturbing the fiber. This way we found the orientation of HWP2  such that the light is coupled to the fast axis of the fiber and the output was not fluctuating while we disturb the fiber. We tested it  by heating the fiber with a heat gun as well and confirmed that the output is not fluctuating and thus the light is coupled to the fast axis of the fiber.

Attachment 1: Modified_experimental_setup.JPG
Modified_experimental_setup.JPG
Attachment 2: Checking_polarisation.pdf
Checking_polarisation.pdf
Attachment 3: Checking_the_polarisation_alignment_of_the_delay_fiber.pdf
Checking_the_polarisation_alignment_of_the_delay_fiber.pdf
Attachment 4: Setup_to_test_the_polarisation_alignment_of_delay_fiber.JPG
Setup_to_test_the_polarisation_alignment_of_delay_fiber.JPG
  14520   Sat Apr 6 02:07:40 2019 AnjaliUpdateFrequency noise measurementFrequency noise measurement of 1 micron source
  • The alignment of the output beam from the delayed path of MZI to the photodetector was disturbed when we did the polarisation characterisation yesterday. So, today we tried to align the output beam from the delayed path of MZI to the detector .
  • We then observed the beat output from the detector on oscilloscope.We initialy observed a dc shift . We then applied a frequency modulation on the input laser and observed the output on oscilloscope. We expected to see variation in output frequency in accordance with variation of input frequency modulation. But we didnt observe this and we were not really getting the interference pattern. 
  • We tried to make the alignment better. With a better alignment, we could see the interference pattern. We also observed that the output frequency was varying in accordance with variation in the input frequency modulation. We would expect a better result with proper mode matching of the two beams on the photodetector.
  14529   Wed Apr 10 00:33:09 2019 AnjaliUpdateFrequency noise measurementFrequency noise measurement of 1 micron source
  • Attachement #1 shows the input (ch4-green) modulation frequency and the photodiode output (ch1-yellow) when the modulation frequency is about 100 Hz
  • Attachement #2 shows the input (ch4-green) modulation frequency and the photodiode output (ch1-yellow) when the modulation frequency is about 30 Hz
  • The output frequency is varying in accordance with variation in modulation frequency. It is observed that, for a given modulation frequency also, the output frequency is fluctuating. There could be multiple reasons for this behaviour. One of the main reasons is the frequency noise of the laser itself. Also, there could be acoustic noise coupled to the system (eg, by change in length of the fiber).
  • The experimental setup is then modified as shown in attachment #3. The thick beam spliiter is replaced with a thinner one. The mount is also changed such that the transmitted beam can be now coupled to an other photodiode (earlier  the transmitted light was blocked by the mount). One more photodiode (PDA55) is introduced .So now the two photodiodes in the setup are PDA520 and PDA 55. 
  • We then applied frequency modulation on the input laser and observed the output of the two photodiodes. But we didn't get the results as we expected and observed earlier (shown in attachment #1 &2). Looks like, the problem is poor mode matching between the two beams. 
Quote:
  • The alignment of the output beam from the delayed path of MZI to the photodetector was disturbed when we did the polarisation characterisation yesterday. So, today we tried to align the output beam from the delayed path of MZI to the detector .
  • We then observed the beat output from the detector on oscilloscope.We initialy observed a dc shift . We then applied a frequency modulation on the input laser and observed the output on oscilloscope. We expected to see variation in output frequency in accordance with variation of input frequency modulation. But we didnt observe this and we were not really getting the interference pattern. 
  • We tried to make the alignment better. With a better alignment, we could see the interference pattern. We also observed that the output frequency was varying in accordance with variation in the input frequency modulation. We would expect a better result with proper mode matching of the two beams on the photodetector.
Attachment 1: Modulation_frequency_100Hz.jpg
Modulation_frequency_100Hz.jpg
Attachment 2: Modulation_frequency_30Hz.jpg
Modulation_frequency_30Hz.jpg
Attachment 3: Modified_setup.JPG
Modified_setup.JPG
  14534   Thu Apr 11 09:05:06 2019 AnjaliUpdateIOOSpooled fiber
  • Attchment #1,2,3 and 4 shows the results with frequency modulation of 32 Hz, 140 Hz , 300 Hz and without frequency modulation. I am trying to understand these results better.
  • A lot of fringing is there even when no modulation is applied. We hope to improve this by spooling the fiber and then encasing it in a box. 
  • As mentioned by Gautam, we have got a 50 m spooled fiber. Attachment #5 shows the photo of the same
Quote:

Steve had showed me some stock of long fibers a while back - they are from Oz Optics, and are 50m long, and are already spooled - so barring objections, we will try the MZ setup with the spooled fiber and see if there is any improvement in the fringing rate of the MZ. Then we can evaluate what additional stabilization of the fiber length is required. Anjali will upload a photo of the spooled fiber.

Attachment 1: Frequecy_modulation_32_Hz.pdf
Frequecy_modulation_32_Hz.pdf
Attachment 2: Frequecy_modulation_140_Hz.pdf
Frequecy_modulation_140_Hz.pdf
Attachment 3: Frequecy_modulation_300_Hz.pdf
Frequecy_modulation_300_Hz.pdf
Attachment 4: Without_modulation.pdf
Without_modulation.pdf
Attachment 5: New_fiber_spool.JPG
New_fiber_spool.JPG
  14540   Fri Apr 12 01:22:27 2019 AnjaliUpdateFrequency noise measurementFrequency noise measurement of 1 micron source

The alignement was disturbed after the replcement of the beam splitter. We tried to get the alignment back . But we are not succeeded yet in getting good interfernce pattern. This is mainly because of poor mode matching of two beams. We will also try with the spooled fiber.

Quote:

 

  • The experimental setup is then modified as shown in attachment #3. The thick beam spliiter is replaced with a thinner one. The mount is also changed such that the transmitted beam can be now coupled to an other photodiode (earlier  the transmitted light was blocked by the mount). One more photodiode (PDA55) is introduced .So now the two photodiodes in the setup are PDA520 and PDA 55. 
 
 
  14571   Thu Apr 25 03:32:25 2019 AnjaliUpdateFrequency noise measurementMZ interferometer ---> DAQ
  • Attachment #1 shows the time domain output from this measurement. The contrast between the maximum and minimum is better in this case compared to the previous trials.
  • We also tried to extract the frequency noise of the laser from this measurement. Attachment #2 shows the frequency noise spectrum. The experimental result is compared with the theoretical value of frequency noise. Above 10 Hz, the trend is comparable to the expected 1/f characteristics, but there are other peak also appearing. Similarly, below 10 Hz, the experimentally observed value is higher compared to the theory.
  • One of the uncertainties in this result is because of the length fluctuation of the fiber. The phase fluctuation in the system could be either because of the frequency noise of the laser or because of the length fluctuation of the fiber.  So,one of the reasons for the discrepancy between the experimental result and theory could be because of  fiber length fluctuation. Also, there were no locking method been applied to operate the MZI in the linear range.
  • The next step would be to do a heterodyne measurement. Attachment #3 shows the schematic for the heterodyne measurement. A free space AOM can be inserted in one of the arms to do the frequency shift. At the output of photodiode, a RF heterodyne method as shown in attachment #3 can be applied to separate the inphase and quadrature component. These components need to be saved with a deep memory system. Then the phase and thus the frequency noise can be extracted.
  • Attachment #4 shows the noise budget prepared for the heterodyne setup. The length of the fiber considered is 60 m and the photodiode is PDA255. I also have to add the frequency noise of the RF driver and the intensity noise of the laser in the noise budget.
Quote:
  1. Delay fiber was replaced with 5m (~30 nsec delay)
    • The fringing of the MZ was way too large even with the free running NPRO (~3 fringes / sec)
    • Since the V/Hz is proportional to the delay, I borrowed a 5m patch cable from Andrew/ATF lab, wrapped it around a spool, and hooked it up to the setup
    • Much more satisfactory fringing rate (~1 wrap every 20 sec) was observed with no control to the NPRO
  2. MZ readout PDs hooked up to ALS channels
    • To facilitate further quantitative study, I hooked up the two PDs monitoring the two ports of the MZ to the channels normally used for ALS X.
    • ZHL3-A amps inputs were disconnected and were turned off. Then cables to their outputs were highjacked to pipe the DC PD signals to the 1Y3 rack
    • Unfortunately there isn't a DQ-ed fast version of this data (would require a model restart of c1lsc which can be tricky), but we can already infer the low freq fringing rate from overnight EPICS data and also use short segments of 16k data downloaded "live" for the frequency noise measurement.
    • Channels are C1:ALS-BEATX_FINE_I_IN1 and C1:ALS-BEATX_FINE_Q_IN1 for 16k data, and C1:ALS-BEATX_FINE_I_INMON and C1:ALS-BEATX_FINE_I_INMON for 16 Hz.

At some point I'd like to reclaim this setup for ALS, but meantime, Anjali can work on characterization/noise budgeting. Since we have some CDS signals, we can even think of temperature control of the NPRO using pythonPID to keep the fringe in the linear regime for an extended period of time.

Attachment 1: Time_domain_output.pdf
Time_domain_output.pdf
Attachment 2: Frequency_noise.pdf
Frequency_noise.pdf
Attachment 3: schematic_heterodyne_setup.png
schematic_heterodyne_setup.png
Attachment 4: Noise_budget_1_micron_in_Hz_per_rtHz.pdf
Noise_budget_1_micron_in_Hz_per_rtHz.pdf
  14576   Thu Apr 25 15:47:54 2019 AnjaliUpdateFrequency noise measurementHomodyne v Heterodyne

My understanding is that the main advantage in going to the heterodyne scheme is that we can extract the frequecy noise information without worrying about locking to the linear region of MZI. Arctan of the ratio of the inphase and quadrature component will give us phase as a function of time, with a frequency offset. We need to to correct for this frequency offset. Then the frequency noise can be deduced. But still the frequency noise value extracted would have the contribution from both the frequency noise of the laser as well as from fiber length fluctuation. I have not understood the method of giving temperature feedback to the NPRO.I would like to discuss the same.

The functional form used for the curve labeled as theory is 5x104/f. The power spectral density (V2/Hz) of the the data in attachment #1 is found using the pwelch function in Matlab and square root of the same gives y axis in V/rtHz. From the experimental data, we get the value of Vmax and Vmin. To ride from Vmax to Vmin , the corrsponding phase change is pi. From this information, V/rad can be calculated. This value is then multiplied with 2*pi*time dealy to get the quantity in V/Hz. Dividing V/rtHz value with V/Hz value gives  y axis in Hz/rtHz. The calculated value of shot noise and dark current noise are way below (of the order of 10-4 Hz/rtHz) in this frequency range. 

I forgor to take the picture of the setup at that time. Now Andrew has taken the fiber beam splitter back for his experiment. Attachment #1 shows the current view of the setup. The data from the previous trial is saved in /users/anjali/MZ/MZdata_20190417.hdf5

 

Quote:

If I understand correctly, the Mach-Zehnder readout port power is only a function of the differential phase accumulated between the two interfering light beams. In the homodyne setup, this phase difference can come about because of either fiber length change OR laser frequency change. We cannot directly separate the two effects. Can you help me understand what advantage, if any, the heterodyne setup offers in this regard? Or is the point of going to heterodyne mainly for the feedback control, as there is presumably some easy way to combine the I and Q outputs of the heterodyne measurement to always produce an error signal that is a linear function of the differential phase, as opposed to the sin^2 in the free-running homodyne setup? What is the scheme for doing this operation in a high bandwidth way (i.e. what is supposed to happen to the demodulated outputs in Attachment #3 of your elog)? What is the advantage of the heterodyne scheme over applying temperature feedback to the NPRO with 0.5 Hz tracking bandwidth so that we always stay in the linear regime of the homodyne readout?

Also, what is the functional form of the curve labelled "Theory" in Attachment #2? How did you convert from voltage units in Attachment #1 to frequency units in Attachment #2? Does it make sense that you're apparently measuring laser frequency noise above 10 Hz? i.e. where do the "Dark Current Noise" and "Shot Noise" traces for the experiment lie relative to the blue curve in Attachment #2? Can you point to where the data is stored, and also add a photo of the setup?

 

Attachment 1: Experimental_setup.JPG
Experimental_setup.JPG
  14578   Thu Apr 25 18:14:42 2019 AnjaliUpdatePSLDoor broken

It is noticed that one of the doors (door # 2 ) of the PSL table is broken. Attachement #1 shows the image

Attachment 1: IMG_6069.JPG
IMG_6069.JPG
  14579   Fri Apr 26 12:10:08 2019 AnjaliUpdateFrequency noise measurementFrequency noise measurement of 1 micron source

From the earlier results with homodyne measurement,the Vmax and Vmin values observed were comparable with the expected results . So in the time interval between these two points, the MZI is assumed to be in the linear region and I tried to find the frequency noise based  on data available in this region.This results is not significantly different from that we got before when we took the complete time series to calculate the frequency noise. Attachment #1 shows the time domain data considered and attachment #2 shows the frequecy noise extracted from that. 

As discussed, we will be trying the heterodyne method next. Initialy, we will be trying to save the data with two channel ADC with 16 kHz sampling rate. With this setup, we can get the information only upto 8 kHz. 

Attachment 1: Time_domain_data.pdf
Time_domain_data.pdf
Attachment 2: Frequency_noise_from_data_in_linear_region.pdf
Frequency_noise_from_data_in_linear_region.pdf
  14586   Tue Apr 30 17:27:35 2019 AnjaliUpdateFrequency noise measurementFrequency noise measurement of 1 micron source

We repeated the homodyne measurement to check whether we are measuring the actual frequency noise of the laser. The idea was to repeat the experiment when the laser is not locked and when the laser is locked to IMC.The frequency noise of the laser is expected to be reduced at higher frequency  (the expected value is about 0.1 Hz/rtHz at 100 Hz ) when it is locked to IMC . In this measurement, the fiber beam splitter used is Non PM. Following are the observations

1. Time domain output_laser unlocked.pdf : Time domain output when the laser is not locked. The frequency noise is estimated from data corresponds to the linear regime. Following time intervals are considered to calculate the frequency noise (a) 104-116 s (b) 164-167 s (c) 285-289 s

2. Frequency_noise_laser_unlocked.pdf: Frequency noise when the laser is not locked. The model used has the functional form of 5x104/f as we did before. Compared to our previous results, the closeness of the experimental results to the model is less from this measurement. In both the cases, we have the uncertainty because of the fiber length fluctuation. Moreover, this measurement could have effect of polarisation fluctuation as well.

3.Time domain output_laser locked.pdf :Time domain output when the laser is locked. Following time intervals are considered to calculate the frequency noise (a) 70-73 s (b) 142-145 s (c) 266-269 s. 

4. Frequency_noise_laser_locked.pdf : Frequency noise when the laser is locked

5. Frequency noise_comparison.pdf : Comparison of frequency noise in two cases. The two values are not significantly different above 10 Hz. We would expect reduction in frequency noise at higher frequency once the laser is locked to IMC. But this result may indicate that we are not really measuring the actual frequency noise of the laser.

Attachment 1: Homodyne_repeated_measurement.zip
  14616   Fri May 17 10:12:07 2019 AnjaliSummaryEquipment loanBorrowed component

I borrowed one Marconi (2023 B) from 40 m lab to QIL lab.

  13686   Mon Mar 19 07:37:00 2018 Angelina PanSummary Proposed QPD Optical Arrangement

I am currently working on an optical arrangement consisting of a QPD that measures the fluctuations of an incoming HeNe laser beam that is reflected by a mirror. The goal is to add a second QPD to the optical arrangement to form a linear combination that effectively cancels out the (angular) fluctuations from the laser beam itself so that we can only focus on the fluctuations produced by the mirror.

In order to solve this problem, I have written a program for calculating the different contributions of the fluctuations of the HeNe laser and fluctuations from the mirror, for each QPD (program script attached). The goal of the program is to find the optimal combination of L0, L1, L2, and f2 that cancels the fluctuations from the laser beam (while retaining  solely the fluctuations from the mirror) when adding the fluctuations of QPD 1 and QPD 2 together. 

By running this program for different combinations of distances and focal lengths, I have found that the following values should work to cancel out the effects of the oscillations from the HeNe laser beam (assuming a focal length of 0.2 m for the lens in front of the original QPD):

  • L0 = 1.0000 m (distance from laser tube to mirror)
  • L1 = 0.8510 m (distance from mirror to lens in front of QPD 1)
  • L2 = 0.9319 m (distance from beamsplitter to lens in front of QPD 2)
  • f2 = 0.3011 m (focal length of lens in front of QPD 2)

Based on these calculations, I propose to try the following lens for QPD 2:

1’’ UV Fused Silica Plano-Convex Lens, AR-Coated: 350 - 700 nm (focal length 0.3011 m). https://www.thorlabs.com/newgrouppage9.cfm?objectgroup_id=6508

Attachment 1: angelinaCode.py.tar.bz2
  13699   Thu Mar 22 17:47:16 2018 Angelina PanSummary Proposed QPD Optical Arrangement
Attachment 1: IMG_0869.jpg
IMG_0869.jpg
  64   Mon Nov 5 22:24:38 2007 Andrey, SteveOmnistructureVACPumping down goes smoothly

We (Steve and Andrey) started pumping down at 3.25PM today. At 9 PM we turned off the rotary pump, and turned on turbomolecular pumps.

By 10.10PM we reached the pressure 1 milliTorr, and the current status is "Vacuum Normal". We leave the turbopumps on for the night, and as it is pretty late for Steve, we are going home.

P.S. Steve was very displeased with the standard selection of "Type" of messages, he would like to extend that list.
  489   Tue May 20 18:33:01 2008 Andrey, JohnConfigurationIOOMode Cleaner is locked again

It was noticed by Mr.Adhikari earlier today that the MC became unlocked at about 11AM.

There is no clear understanding what caused the problem.

Trying to restore the modecleaner locking, we noticed with John that the beam was not centered on the wavesensors (WFS1. WFS2 on the screen "C1IOO_LockMC.adl"). We decided to adjust the beam position moving slightly the bias sliders for pitch and yaw degrees of freedom for MC1.
This allowed to make the MC locked.

Old positions for the MC1 sliders: Pitch = 2.9934, Yaw = -0.6168;
New positions --------//---------: Pitch = 3.0604, Yaw = -0.7258.

At the same time, FSS for PSL is still showing the values in the range 0.720 - 0.750 which is lower than the usual values. The indicator for FSS value is yellow when it is below 0.750.
  11   Wed Oct 24 01:43:32 2007 Andrey RodionovOtherGeneralPDF-file -> Will report about first results for XARM during Wednesday meeting

Here is the pdf-file with some graphs showing first results for XARM optimization.

We will discuss alltogether during our Wednesday meeting which starts at 2.40PM. Probably it would be necessary to project this pdf-file to the big screen,
so someone should bring laptop and probably connect it to the projector. I do not have a laptop.

See you on that meeting.
Attachment 1: Andrey_October_24.pdf
Andrey_October_24.pdf Andrey_October_24.pdf Andrey_October_24.pdf Andrey_October_24.pdf Andrey_October_24.pdf Andrey_October_24.pdf Andrey_October_24.pdf Andrey_October_24.pdf
  38   Wed Oct 31 10:31:23 2007 Andrey RodionovRoutineVACVenting is in progress

We (Steve, David, Andrey) started venting the vacuum system at 9.50AM Wednesday morning.
  41   Wed Oct 31 19:26:08 2007 Andrey RodionovRoutineGeneralPhotographs of "Mode-Cleaner Entrance"

Here are the pictures of "inside the chamber".
Attachment 1: MC-Pictures-1.pdf
MC-Pictures-1.pdf MC-Pictures-1.pdf MC-Pictures-1.pdf MC-Pictures-1.pdf
Attachment 2: MC-Pictures-2.pdf
MC-Pictures-2.pdf MC-Pictures-2.pdf MC-Pictures-2.pdf MC-Pictures-2.pdf
Attachment 3: MC-Pictures-3.pdf
MC-Pictures-3.pdf MC-Pictures-3.pdf MC-Pictures-3.pdf MC-Pictures-3.pdf
Attachment 4: MC-Pictures-4.pdf
MC-Pictures-4.pdf MC-Pictures-4.pdf MC-Pictures-4.pdf MC-Pictures-4.pdf
Attachment 5: MC-Pictures-5.pdf
MC-Pictures-5.pdf MC-Pictures-5.pdf MC-Pictures-5.pdf MC-Pictures-5.pdf
Attachment 6: MC-Pictures-6.pdf
MC-Pictures-6.pdf MC-Pictures-6.pdf MC-Pictures-6.pdf MC-Pictures-6.pdf
Attachment 7: MC-Pictures-7.pdf
MC-Pictures-7.pdf MC-Pictures-7.pdf MC-Pictures-7.pdf MC-Pictures-7.pdf
Attachment 8: MC-Pictures-8.pdf
MC-Pictures-8.pdf MC-Pictures-8.pdf MC-Pictures-8.pdf MC-Pictures-8.pdf
Attachment 9: MC-Pictures-9.pdf
MC-Pictures-9.pdf MC-Pictures-9.pdf
  46   Thu Nov 1 16:34:47 2007 Andrey RodionovSummaryComputersLimitation on attachment size of E-LOG

I discovered yesterday when I was attaching photos that it is NOT possible to attach files whose size is 10Mb or more. Therefore, 10Mb or something very close to that value is the limit.
  47   Thu Nov 1 16:42:48 2007 Andrey RodionovSummaryEnvironmentEnd of Daylight Saving Time this weekend
Useful information for everyone, as a friendly reminder:

According to the web-page

http://www.energy.ca.gov/daylightsaving.html,

this coming weekend there will be the end of Daylight Saving Time.

Clocks will be adjusted backward one hour.
  50   Thu Nov 1 19:53:02 2007 Andrey RodionovBureaucracyPhotosTobin's picture
Attachment 1: DSC_0053.JPG
DSC_0053.JPG
  51   Thu Nov 1 19:53:34 2007 Andrey RodionovBureaucracyPhotosRobert's photo
Attachment 1: DSC_0068.JPG
DSC_0068.JPG
  52   Thu Nov 1 19:54:22 2007 Andrey RodionovBureaucracyPhotosRana's photo
Attachment 1: DSC_0120.JPG
DSC_0120.JPG
  53   Thu Nov 1 19:55:03 2007 Andrey RodionovBureaucracyPhotosAndrey's photo
Attachment 1: DSC_0055.JPG
DSC_0055.JPG
  54   Thu Nov 1 19:55:59 2007 Andrey RodionovBureaucracyPhotosAndrey, Tobin, Robert - photo
Attachment 1: DSC_0092.JPG
DSC_0092.JPG
  55   Thu Nov 1 19:58:07 2007 Andrey RodionovBureaucracyPhotosSteve and Tobin's picture
Attachment 1: DSC_0023.JPG
DSC_0023.JPG
  56   Thu Nov 1 20:03:00 2007 Andrey RodionovSummaryPhotosProcedure "Drop and Drag" in pictures
Attachment 1: DSC_0072.JPG
DSC_0072.JPG
Attachment 2: DSC_0083.JPG
DSC_0083.JPG
Attachment 3: DSC_0099.JPG
DSC_0099.JPG
Attachment 4: DSC_0100.JPG
DSC_0100.JPG
  75   Wed Nov 7 02:14:08 2007 AndreyBureaucracyIOOMore information about MC2 ringdown
As Tobin wrote two hours ago, we (Andrey, Tobin, Robert) made a series of ringdown measurements for MC2
in the spirit of the measurement described by Rana -> see
entry from Mon Oct 29 23:47:29 2007, rana, Other, IOO, MC Ringdowns.

I attach here some pictures that we saw on the screen of the scope, but I need to admit that I am not experienced enough to present a nice fit to these data, although I attach fits that I am able to do today.

I definitely learned a lot of new Matlab functions from Tobin - thanks to him!, but I need to learn two more things:

Firstly, I do not know how to delete "flat" region (regions before the ringdown starts) in Matlab ->
I needed to delete the entries for times before the ringdown ("negative times") by hand in the text-file, which is extremely non-elegant method;

Secondly, I tried to approximate the ringdown curve by a function ydata=a*exp(b*xdata) but I am not exactly sure if this equation of the fitting curve is a good fit or if a better equation can be used.

It seems, in this situation it is better for me to ask more experienced "comrades" on November 7th.

P.S. It seems I really like the type of message "Bureaucracy" - I put it for every message. As Alain noted, maybe that is because some things are very bureacratized in the former USSR / Russia. By the way, when I was young, November 7th was one of two most important holidays in the USSR - I liked that holiday because I really liked military parades on the red square. I attach a couple of pictures. November 7 is the anniversary of the Revolution of 1917.
Attachment 1: image-attempt_1.png
image-attempt_1.png
Attachment 2: image-attempt_2.png
image-attempt_2.png
Attachment 3: image-attempt_3.png
image-attempt_3.png
Attachment 4: image-attempt_4.png
image-attempt_4.png
Attachment 5: image-attempt_5.png
image-attempt_5.png
Attachment 6: Fit-1st_attempt.jpg
Fit-1st_attempt.jpg
Attachment 7: Fit-5th_attempt.jpg
Fit-5th_attempt.jpg
Attachment 8: 7_Nov_1941-parad-na-krasnoy-ploschadi.jpg
7_Nov_1941-parad-na-krasnoy-ploschadi.jpg
Attachment 9: parad1984-moskva.jpg
parad1984-moskva.jpg
  130   Wed Nov 28 12:43:53 2007 AndreyBureaucracy Here was the PDF-file of my presentation

I was making a report with powerpoint presentation during that Wednesday's 40-m meeting.

Here was the pdf-file, but LATER IN THE EVENING I CREATED A WIKI-40M-page describing the algorithm, and now the pdf-file is ON THAT WIKI-40M PAGE.


NOTE ADDED AFTER THE PRESENTATION: I double checked, I am indeed taking the root-mean-square of a difference, as we discussed during my talk.

My slide #17 "Calculation of differential length" was wrong, but now I corrected it.
  135   Wed Nov 28 19:02:41 2007 AndreyBureaucracyWIKI-40M UpdateNew WIKI-40M page describing Matlab Suspension Modeling

I created the WIKI-40m page with some details about my today's talk on the 40-m lab meeting.

The address is:

http://lhocds.ligo-wa.caltech.edu:8000/40m/Modeling_of_suspensions

(or you can go to the main page, http://lhocds.ligo-wa.caltech.edu:8000/40m/ , and click on the link "Modeling of suspensions").

The WIKI-40m page describes my transfer functions and contains the pdf-file of my presentation.
  151   Fri Nov 30 20:17:26 2007 AndreyConfigurationPEMAccelerometers and alum.plates for them
All 6 accelerometers which were located near the ITMX are turned off and disconnected from the power cords.
Actually these accelerometers are now in the office area on the electronics bench (to the left from Steve Vass' place).

I made today 4 new aluminum mounting plates for the accelerometers (I drilled holes and made threads in them). On Monday I will buy short screws and install accelerometers on these new mounting plates. These mounting plates will be screwed directly into the metallic frame which is firmly cemented to the ground. Before yesterday accelerometers were mounted on top of blue stack towers, not on the ground directly, so we hope that new measurements of the ground noise will be more realistic.

The 4 mounting plates are on the same desk -> on the electronics bench (to the left from Steve Vass' place). Please do not displace them.

Attached is a drawing of the aluminum mountain plate.
Attachment 1: Scheme_Aluminum_Piece-inches.pdf
Scheme_Aluminum_Piece-inches.pdf
  168   Wed Dec 5 18:08:36 2007 AndreyUpdateASCOptical Lever laser for ETMX is installed

A new laser with \lambda=633nm has been intalled and the mirror adjusted so that the signal hits the center of the photodetector.

Output power level of that laser is 3.45 +- 0.05 mW.

Only about 0.29mW hits the photodetector.

Cable clips have been used to firmly fix the power supply cable for the laser.

See attached photopicture of the ETMX - "oplev" - optical - table.
Attachment 1: DSC_0199.JPG
DSC_0199.JPG
  172   Wed Dec 5 23:19:03 2007 AndreyConfigurationPEMAccelerometers are turned on

All accelerometers have been turned on, as Alan asked during Wednesday meeting.

Typical power spectra and coherence plots are attached below.

"East" in the name means that the previous location of accelerometrs was to the east from "Beamsplitter" (the location for "east" accelerometers was not changed, actually, it is still near ITMX), while "west" means that previously accelerometers were to the west from the BS, but now their new location is near the ETMX.

I will change the names of the channels tomorrow (Thursday) when someone (Tobin?) will show to me how to do it.

P.S. (addition made on Dec. 19th, 2007, by Andrey) I intended to change the names of accelerometers the next day, Thursday Dec. 06,
but I did not do it that day (did not understand how to do it), then I fell ill, and eventually
I changed the names of accelerometers on December 19th, see entry to ELOG #204)
Attachment 1: Power_Sp_and_Coh_XY-EAST.pdf
Power_Sp_and_Coh_XY-EAST.pdf
Attachment 2: Coherence-ZX_East.pdf
Coherence-ZX_East.pdf
Attachment 3: Coherence-ZY_East.pdf
Coherence-ZY_East.pdf
Attachment 4: Power_Sp_WEST.pdf
Power_Sp_WEST.pdf
Attachment 5: Coherence-ZX_West.pdf
Coherence-ZX_West.pdf
Attachment 6: Coherence-XY_West.pdf
Coherence-XY_West.pdf
Attachment 7: Coherence-YZ_West.pdf
Coherence-YZ_West.pdf
  174   Thu Dec 6 15:22:42 2007 AndreySummaryElectronicsPictures of the inside of He-Ne laser

Steve gave me an old "dead" He-Ne laser that long time ago was used for ETMX optical lever.

I dismantled it (cutting the metallic enclosure with a metallic saw), and these are two pictures of what is inside.
Attachment 1: DSC_0226.JPG
DSC_0226.JPG
Attachment 2: DSC_0228.JPG
DSC_0228.JPG
  176   Thu Dec 6 19:19:47 2007 AndreyConfigurationSUSSuspension damping Gain was restored

Suspension damping gain was disabled for some reason (all the indicators in the most right part of the screen C1SUS_ETMX.adl were red), it is now restored.
  191   Thu Dec 13 23:56:02 2007 AndreyConfigurationComputer Scripts / ProgramsOvernight measurements

After my disease (fever, vomitting, nose problem, overall weakness) I returned to LIGO today for the first time after the weekend, and I am running the script for the XARM-measurements over this night.

So, suspension dumping gains should undergo changes in the interval from 1 to 10 in both ITMX and ETMX.

XARM has been of course locked.

I started running the script for the first time at about 10PM, but I realized after an hour and a half that my step of gain increase 0.2 was too shallow, too small to execute my program during one night. Therefore, I needed to terminate the program, change my program so that it increases the gain with increment 0.5, not 0.2, and started it again around midnight.

Going home.

P.S. The red pump that I borrowed from the lab (Steve's pump?) is back at its previous place. The tire-worker tells me that I absolutely need to change all four tires for almost 500 dollars. I regret a lot about that huge money loss.
  194   Mon Dec 17 23:42:08 2007 AndreyConfigurationComputer Scripts / ProgramsOvernight measurements in X-arm

I am making overnight measurements this night (from Monday to Tuesday) in XARM.

The X-arm is now locked, and the values for suspension damping gain will be changed in the interval from 1 to 7 with the step 0.5 in both ITMX and ETMX.

This is the second, repeated measurement. The results of the first measurement from Saturday to Sunday night will be reported in the separate ELOG entry (sorry, I did not make an ELOG entry on Saturday evening about running the program overnight).

The very first attempt to run the script in the night from Thursday to Friday was not successful.
  195   Tue Dec 18 00:51:39 2007 AndreyUpdateComputer Scripts / ProgramsResults of Saturday overnight measurements

As I indicated in the previous e-log entry (#194), I made overnight measurements in XARM in the night from Saturday to Sunday.

Root-mean-square values of the peaks in calibrated spectra were calculated, and I plotted them as functions of suspension gains in ITMX and ETMX "position" degrees of freedom.
More specifically, Q_ITMX means the value in the channel "C1:SUS-ITMX_SUSPOS_GAIN", while Q_ETMX means the value in the channel "C1:SUS-ETMX_SUSPOS_GAIN".

Root-mean-square values (RMS) were calculated during that night in three intervals:

1) around 0.8 HZ in the interval (0.6 Hz <-> 1.0 Hz);

2) around 3.0 Hz in the interval (2.0 Hz <-> 3.6 Hz);

3) in the broad interval from 0.6Hz to 3.6Hz.


I plotted three results for RMS in the abovementioned three intervals in three different ways:

1) view from the top in the axes (Q_{ITMX}+Q_{ETMX})/2 and (Q_{ITMX}-Q_{ETMX}) -> first three graphs (attachments 1 -3);

2) view from the side in the same sum- and difference-axes -> next three graphs (attachments 4-6);

3) view from the side in Q_{ITMX} and Q_{ETMX} axes -> next three graphs (attachments 7-9), above accelerometer spectra (attachments 10-11).


Also, I compared the ground noise level by comparing spectra of accelerometer signals at different times during that night. As a reminder, before my disease I installed one accelerometer near ITMX and another accelerometer near ETMX (see entries 161 and 172 in ELOG). The plots of ratios of accelerometer signals at different times (pairs of times that were used: 12AM and 3AM, 12AM and 6AM, 12AM and 9AM) are given below, see attachments 10-11.

Tomorrow I will try to compare the results with the second measurements that are being taken tonight.
Attachment 1: RMS_08Hz_top_view.png
RMS_08Hz_top_view.png
Attachment 2: RMS_3Hz_top_view.png
RMS_3Hz_top_view.png
Attachment 3: RMS_broad_top_view.png
RMS_broad_top_view.png
Attachment 4: RMS_08Hz_Qsum-Qdiff-axes.png
RMS_08Hz_Qsum-Qdiff-axes.png
Attachment 5: RMS_3Hz_Qsum-Qdiff-axes.png
RMS_3Hz_Qsum-Qdiff-axes.png
Attachment 6: RMS_broad_Qsum-Qdiff-axes.png
RMS_broad_Qsum-Qdiff-axes.png
Attachment 7: RMS_08Hz_Qaxes.png
RMS_08Hz_Qaxes.png
Attachment 8: RMS_3Hz_Qaxes.png
RMS_3Hz_Qaxes.png
Attachment 9: RMS_broad_Qaxes.png
RMS_broad_Qaxes.png
Attachment 10: Accel_ITMX.png
Accel_ITMX.png
Attachment 11: Accel_ETMX.png
Accel_ETMX.png
  198   Tue Dec 18 23:27:36 2007 AndreyConfigurationComputer Scripts / ProgramsNew overnight measurements (this night from Tue to Wed)

I am making overnight measurements in XARM tonight.

This is the third night of measurements in XARM, but tonight I am scanning the narrower region between values of damping gain 1.00 and 4.50 with the smaller step 0.25. (for comparison, during two previous measurements the region was between 1.0 and 7.0 with the step 0.5).

I have relocked the XARM before the start of the measurements.

I started running the program at 9.30PM, and it should collect all the data by 9.00AM wednesday morning.

Below are explanations why I chose these different parameters for the interval and step:

I am going to put the results of previous night measurements into the next ELOG entry, and it we be pretty obvious from those graphs that results in XARM from the two previous (different) nights agree well with each other, and the approximate positions of minima and areas of "big growth" of the surfaces are pretty obvious from those graphs. It is clear that RMS are too big for the values of the damping gain bigger than 4.0, and that minima are somewhere near the values of 2.0. But those graphs were too rough to locate a somewhat precise value for the minima. Therefore, I am studying tonight the interval of gains between 1.00 and 4.50 with a smaller step.

A short note how I estimate time that is necessary to collect the experimental data.

there are 15 experimental points for each ETMX and ITMX suspension gains in the interval between 1.00 and 4.50 with the step 0.25. They are: 1.00, 1.25, 1.50, 1.75, 2.00, ..., 3.75, 4.00, 4.25, 4.50. As I am changing both ETMX and ITMX gains, I have an array of 15*15=225 elements.
It takes 3 minutes for each point to collect the data (I wrote the program that way). Therefore, the total time it takes to run the program is: 225*3=675 minutes, or 675/60=11.25 hours, almost 11 and a half hours.
  199   Tue Dec 18 23:41:00 2007 AndreySummaryComputer Scripts / ProgramsResults of Mon/Tue overnight measurements (entry #194)

Here I inform our community about the results of the measurements of RMS values in XARM during the previous night from Monday to Tuesday (I announced those measurements in ELOG entry #194).

All the plots in today's report seem to agree well with the analogous plots from the night from Saturday to Sunday (those results are given in ELOG entry # 195).

All the intervals in which RMS have been calculated are the same as in yesterday's ELOG entry #195.

I plotted three results for RMS in the abovementioned three intervals in three different ways:

1) view from the top in the axes (Q_{ITMX}+Q_{ETMX})/2 and (Q_{ITMX}-Q_{ETMX}) -> first three graphs (attachments 1 -3);

2) view from the side in the same sum- and difference-axes -> next three graphs (attachments 4-6);

3) view from the side in Q_{ITMX} and Q_{ETMX} axes -> next three graphs (attachments 7-9, also attch. 12), above accelerometer spectra (attachments 10-11).

Also, I compared the ground noise level by comparing spectra of accelerometer signals at different times during that night. As a reminder, before my disease I installed one accelerometer near ITMX and another accelerometer near ETMX (see entries 161 and 172 in ELOG). The plots of ratios of accelerometer signals at different times (pairs of times that were used: 11PM and 2AM, 11PM and 5AM, 11PM and 8AM) are given below, see attachments 10-11. The program was running from 11PM on Monday till 9AM on Tuesday.

As I explained in the previous ELOG entry # 198, tonight I am taking experimental data in the narrowere interval from 1.00 to 4.50 with a smaller step 0.25.
Attachment 1: RMS_08HZ_Top_View.png
RMS_08HZ_Top_View.png
Attachment 2: RMS_3HZ_Top_View.png
RMS_3HZ_Top_View.png
Attachment 3: RMS_broad_Top_View.png
RMS_broad_Top_View.png
Attachment 4: RMS_08HZ_Side_View.png
RMS_08HZ_Side_View.png
Attachment 5: RMS_3HZ_Side_View.png
RMS_3HZ_Side_View.png
Attachment 6: RMS_broad_Side_View.png
RMS_broad_Side_View.png
Attachment 7: RMS_08HZ_Q_E_Q_I_Axes.png
RMS_08HZ_Q_E_Q_I_Axes.png
Attachment 8: RMS_3HZ_Q_E_Q_I_Axes.png
RMS_3HZ_Q_E_Q_I_Axes.png
Attachment 9: RMS_broad_Q_E_Q_I_Axes.png
RMS_broad_Q_E_Q_I_Axes.png
Attachment 10: Accelerometer_ITMX.png
Accelerometer_ITMX.png
Attachment 11: Accelerometer_ETMX.png
Accelerometer_ETMX.png
Attachment 12: RMS_broad_Q_E_Q_I_Axes.png
RMS_broad_Q_E_Q_I_Axes.png
  201   Wed Dec 19 15:51:00 2007 AndreyUpdateComputer Scripts / ProgramsDaytime measurements in XARM and their results

I was making measurements in XARM for three different nights. All the results agree with each other (I will put the results from the last night soon).

Steve Vass recommended to me to compare those results with the daytime data, in order to see if there is a real necessity to run the scripts overnight or if daytime results will yield similar results.

XARM has been locked, and I am taking measurements today from 3.30PM till 11.30PM.

I will be changing the suspension damping gains in ETMX and ITMX "position" degrees of freedom in the interval from 1.0 to 3.75 with the step 0.25.

BELOW: RESULTS OF MEASUREMENTS WERE ADDED ON THURSDAY, DEC. 20.

All the meaning of the attachments 1-3, 4-6, 7-9, 10-11 is the same as in previous ELOG entries # 195, # 199, # 202, see in those entries which graph corresponds to which coordinate axes orientation.
Attachment 1: RMS-08Hz-Top_View.png
RMS-08Hz-Top_View.png
Attachment 2: RMS-3Hz-Top_View.png
RMS-3Hz-Top_View.png
Attachment 3: RMS-broadband-Top_View.png
RMS-broadband-Top_View.png
Attachment 4: RMS-08Hz-Side-View.png
RMS-08Hz-Side-View.png
Attachment 5: RMS-3Hz-Side_View.png
RMS-3Hz-Side_View.png
Attachment 6: RMS-broadband-Side_View.png
RMS-broadband-Side_View.png
Attachment 7: RMS-08Hz-Q_I-Q_E-Axes.png
RMS-08Hz-Q_I-Q_E-Axes.png
Attachment 8: RMS-3Hz-Side_View.png
RMS-3Hz-Side_View.png
Attachment 9: RMS-broadband-Side_View.png
RMS-broadband-Side_View.png
Attachment 10: Accelerometer_ETMX.png
Accelerometer_ETMX.png
Attachment 11: Accelerometer_ITMX.png
Accelerometer_ITMX.png
  202   Wed Dec 19 16:07:37 2007 AndreySummaryComputer Scripts / ProgramsResults of overnight measurements Tue/Wed night (entry #198)

As indicated in ELOG entry 198, I was making overnight measurements during last night from Tuesday to Wednesday.

I was changing the suspension damping gain in ETMX and ITMX in "position" degree of freedom between values of 1.00 and 4.50 with the step 0.25.

Results for RMS of peaks (A) at 0.8Hz, (B) at about 3.0Hz and (C) in the range from 0.6Hz to 3.7Hz ("RMS in a broad interval") are given below:

I plotted three results for RMS in the abovementioned three intervals in three different ways:

1) view from the top in the axes (Q_{ITMX}+Q_{ETMX})/2 and (Q_{ITMX}-Q_{ETMX}) -> first three graphs (attachments 1 -3);

2) view from the side in the same sum- and difference-axes -> next three graphs (attachments 4-6);

3) view from the side in Q_{ITMX} and Q_{ETMX} axes -> next three graphs (attachments 7-9)

Attachments 10 and 11 show ratios of accelerometer signals at different times of the night/morning.


A little discussion about these graphs:

1) The areas of minima and of rapid growth are the same for all the measurements during all three nights.

2) Tonight there was a strange spike for the values of Q_{ETMX}=2.5 and Q_{ITMX}=4.0. I interpret that as an error of experiment.

3) On all the plots from all three nights there is a wide area of minimum on the plots for RMS at 0.8Hz and for "RMS in the broad interval",
and the graph for "RMS at 3Hz" indicates a clearer minimum in a localized area for Q_{ITMX}=2+-1, Q_{ETMX}=2+-1. Note that this area 2+-1
is included into the wide region of minimum for "RMS at 0.8Hz" and "RMS in a broad range".

Therefore, my guess at this stage is that we can choose the optimized value of suspension damping gains for both Q_{ITMX} and Q_{ETMX} somewhere
around 2+-1. I would like to make another overnight measurement (tonight) in that narrowed region with a small step to have more certainty.

By the way, I realized that I was a little bit careless and at some plots Q_I stands for {Q_ITMX}, and Q_E stands for Q_{ETMX}.
Attachment 1: RMS_08Hz_Top_view.png
RMS_08Hz_Top_view.png
Attachment 2: RMS_3Hz_Top_view.png
RMS_3Hz_Top_view.png
Attachment 3: RMS_broad_Top_view.png
RMS_broad_Top_view.png
Attachment 4: RMS_08Hz_Side_view.png
RMS_08Hz_Side_view.png
Attachment 5: RMS_3Hz_Side_view.png
RMS_3Hz_Side_view.png
Attachment 6: RMS_broadband_Side_view.png
RMS_broadband_Side_view.png
Attachment 7: RMS_08Hz_Q_I-Q_E-axes.png
RMS_08Hz_Q_I-Q_E-axes.png
Attachment 8: RMS_3Hz_Q_I-Q_E-axes.png
RMS_3Hz_Q_I-Q_E-axes.png
Attachment 9: RMS_broadband_Q_I-Q_E-axes.png
RMS_broadband_Q_I-Q_E-axes.png
Attachment 10: Accelerom_ETMX.png
Accelerom_ETMX.png
Attachment 11: Accelerom_ITMX.png
Accelerom_ITMX.png
  204   Wed Dec 19 20:28:27 2007 AndreyDAQPEMNames for all 6 accelerometers have been changed

I eventually changed the names for all 6 accelerometers (see my ELOG entry # 172 from Dec. 05 about my intent to do that).

I removed the word "BS" from their names,
and I changed the word combination "ACC_BS_EAST" in the old name for "ACC_ITMX" in the new name;
as well "ACC_BS_WEST" is now replaced by "ACC_ETMX".
(the reasoning behind such a change should become clear from my ELOG entry #172).

New accelerometer names are:
(note: there are no spaces (nowhere!) in the names of accelerometers, but ELOG replaces ": P" written without a space by a strange symbol Tongue)

C1 : PEM - ACC _ ETMX _ X ;
C1 : PEM - ACC _ ETMX _ Y ;
C1 : PEM - ACC _ ETMX _ Z ;
C1 : PEM - ACC _ ITMX _ X ;
C1 : PEM - ACC _ ITMX _ Y ;
C1 : PEM - ACC _ ITMX _ Z .

One can find them in "C1 : PEM - ACC" in Dataviewer.

  205   Thu Dec 20 02:04:09 2007 AndreyUpdateComputer Scripts / ProgramsNew overnight measurements in XARM and their results

I ran in the daytime/evening time my program, changing the damping gains in suspension "position" degree of freedom for ETMX and ITMX
in the interval from 1.00 to 3.75 with the step 0.25 (see entry # 201).

Now I am running overnight (from 2AM till 9AM) the program changing the gains in the interval from 1.3 to 3.5 with the step 0.20,
12 X 12 = 144 experimental points. I started so late because I fell asleep after my Wednesday evening dinner, then woke up half an hour ago and hurried to the lab.

BELOW: RESULTS OF MEASUREMENTS WERE ADDED ON THURSDAY EVENING, DEC. 20.

All the meaning of the attachments 1-3, 4-6, 7-9, 10-11 is the same as in previous ELOG entries # 195, # 199, # 202, see in those entries which graph corresponds to which coordinate axes orientation.
Attachment 1: RMS-08Hz-Top-View.png
RMS-08Hz-Top-View.png
Attachment 2: RMS-3Hz-Top-View.png
RMS-3Hz-Top-View.png
Attachment 3: RMS-broadband-Top-View.png
RMS-broadband-Top-View.png
Attachment 4: RMS-08Hz-Side_View.png
RMS-08Hz-Side_View.png
Attachment 5: RMS-3Hz-Side_View.png
RMS-3Hz-Side_View.png
Attachment 6: RMS-broadband-Side_View.png
RMS-broadband-Side_View.png
Attachment 7: RMS-08Hz-Q_I-Q_E-Axes.png
RMS-08Hz-Q_I-Q_E-Axes.png
Attachment 8: RMS-3Hz-Q_I-Q_E-Axes.png
RMS-3Hz-Q_I-Q_E-Axes.png
Attachment 9: RMS-broadband-Q_I-Q_E-Axes.png
RMS-broadband-Q_I-Q_E-Axes.png
Attachment 10: Accelerometer-ETMX.png
Accelerometer-ETMX.png
Attachment 11: Accelerometer-ITMX.png
Accelerometer-ITMX.png
  208   Thu Dec 20 21:57:34 2007 AndreyUpdateComputer Scripts / ProgramsMeasurements in XARM today

Today at 2PM I started a program, it should change the suspension gains in the interval from 1.0 to 3.8 with the step 0.2. Estimated running time is till 3.30AM coming night.

Results will be reported on Friday.

BELOW: ADDITION MADE ON FRIDAY EVENING.

Due to some unforeseen circumstances, I was unable to add results on Friday. I have so far accelerometer spectra only, which I add to this ELOG entry.

I have files with the measurement results, and I will process them after Christmas and add to this ELOG entry. I might not be in the lab on Dec. 24 and 25.
Attachment 1: Accelerom_ETMX.png
Accelerom_ETMX.png
Attachment 2: Accelerom_ITMX.png
Accelerom_ITMX.png
  209   Thu Dec 20 21:58:28 2007 AndreySummaryComputer Scripts / ProgramsResults for 2 previous XARM measurements have been added

I attached results (plots) of yesterday's daytime and overnight measurements to the initial reports about those measurements.

These are ELOG entries # 201 and # 205.
  251   Mon Jan 21 23:30:03 2008 AndreyUpdateComputer Scripts / ProgramsMatlab Program for Q-factor measurements (XARM -> ITMX and ETMX)

Finally I overcame difficulties with adapting Sonia's Matlab programs for XARM (Sonia's program was for MC),

and now there exists a Matlab program that makes a fit of a ringdown curve and calculates Q-factor for a mirror ITMX.

Specifically, this program allows to measure ringdown, fit it and calculate Q-factor for the ITMX-mirror for a specific value of
"C1:SUS-ITMX_SUSPOS_GAIN".

Attached is a plot of a ringdown curve and its fit for the value 4.0 in channel "C1:SUS-ITMX_SUSPOS_GAIN".

Calculations yield the result Q=3.7+-0.2 for the value 4.0 in channel "C1:SUS-ITMX_SUSPOS_GAIN".

As Robert started 10 minutes ago the long procedure of the whole interferometer locking,
I cannot disturb the interferometer now, so I will measure Q-factors for various combinations of suspension damping gain on Tuesday.

I will also easily modify the program for measuring Q-factors of ETMX-mirror and make measurements with ETMX on Tuesday.

The Matlab scripts are in directory /cvs/cds/caltech/users/rodionov/Q-Factors/
Attachment 1: Example-ITMX_POS_40.png
Example-ITMX_POS_40.png
ELOG V3.1.3-