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MIF (ITF Control)
kazuya.yokogawa - 18:58 Thursday 14 March 2019 (8410) Print this report
Comment to Absolute frequency measurement of the old Prometheus Y (2143A) (8397)

I added the result for Prometheus 2143 A to the plot of the absolute frequency measurement (klog7375).

The raw data for each laser is attached as well.

Images attached to this comment
Non-image files attached to this comment
MIF (General)
kazuya.yokogawa - 18:16 Wednesday 23 January 2019 (7772) Print this report
Beat-note signal detection for Y arm

Today, I tried to get the beat-note signal between the PSL and the Prometheus laser for Y arm.

Firstly, I aligned the beam path using steering mirror so that the two beams interfere. Then I sweep the crystal temperature of the Prometheus with my hand and the beat-note signal was detected around 40 MHz when the crystal temperature was 25.22 deg.

When the above beat-note signal was detected, the lasers power in front of the PD are following.

  • PSL: 1 mW
  • Prometheus: 8 mW

Since the main laser power is lower than assumed, the amplitude of the beat-note was -17 dBm. (We require the beat-note with amplitude of -11 dBm.)

Images attached to this report
MIF (General)
kazuya.yokogawa - 17:39 Wednesday 23 January 2019 (7771) Print this report
Installation of POS optics for green

[Sugimoto, Yokogawa]

We brought dichroic mirrors(*2) and harmonic splitter(*1) from the PSL room to the POS table.

Dichroic mirrors are used for the periscope on the POS table. Harmonic splitter is used to separate IR and green on the POS table.

Images attached to this report
MIF (General)
kazuya.yokogawa - 21:21 Sunday 20 January 2019 (7728) Print this report
Fiber noise measurement

[Yokozawa, Enomoto, Sugimoto, Yokogawa]

We measured the fiber noise today.

Related log:

  • Jun. 28th 2018 (log5417): Fiber noise of 5m fiber
  • Jan. 10th 2019 (log7609): Preparation for the measurement of fiber noise

Experimental layout

The fist attachment is the layout of this measurement.

1. The green laser beam on the POP table is sent back to the PSL table using a spare fiber.

2. We detect the beat-note signal between two beams. One is through two fibers and the other is not through the fiber. There is a frequency difference of about 160 MHz for two beams since the beam passing through the fibers also passes through the AOM for shifting frequency. Therefore, the beat-note signal is obtained in 160 MHz. 

3. The frequency difference is controled by PLL. The beat-note signal is locked in 160 MHz by PLL using PFD, MC servo (for CARM loop) and AOM VCO.

4. The noise of the control signal is measured and calibrated to the fiber noise. The fiber frequency noise is obtained by multiplying the control signal by the actuator factor of AOM VCO (0.42 MHz/V).

Result

During this measurement, we swiched off all FFUs around MC, PR, BS areas, KOACH filters for PSL room and one precise air conditioner for PSL room.

This is the measured fiber noise. This is calibrated by multiplying the measured control signal by 0.42 MHz/V and dividing by 2 since the measured noise has the noise for two fibers.

There is the large structure at 10-100 Hz. We will incorporate this noise into the noise budget and compare to the measured ALS noise.

Images attached to this report
MIF (General)
kazuya.yokogawa - 21:22 Friday 28 December 2018 (7538) Print this report
Green beam for Y arm was coupled to the optical fiber

[Enomoto, Sugimoto, Yokogawa]

We tried to couple the green beam for Y arm to the optical fiber last week and this week.


What we did:

(on Dec. 21st)

  • aligned the steering mirrors and the colimeter lens position of the fiber coupler so that the beam is coupled to the test optical fiber with length of 5m. However, the transmittance of the fiber reached only 25%.

(on Dec. 26th)

  • measured the beam profile just before the fiber coupler, but the measured beam profile was dirty. We thought that the beam was clipped on the Iris.

(on Dec. 27th)

  • opend the iris slightly and measured the beam profile again. Then we found that the beam radius was smaller than that obtained from my mode match calculation. This seemed to be the effect of swapping the laser for the new one.
  • recalculated the mode match.

(on Dec. 28th)

  • moved the mode matching lens (f=250mm) about 40mm upstream based on the mode match clculation.
  • tried to couple the beam to the test fiber. The transmittance reached 68% (input power: 53mW, transmitted power: 36mW)
  • placed PDA100A on the POS table in order to measured the transmitted power of the fiber.
  • set the PD gain to 0dB.
  • measured the transmitted power of the long fiber. The measured value was about 2600cnt. This is equivalent to 3.31mW when converted to power and the transmittance of the fiber is expected to about 33mW considering that the PD receives the transmitted beam of the BS with transmittance of 10%.

Thus, the transmittance of the fiber is 62%. I think this is good value.

MIF (General)
kazuya.yokogawa - 23:33 Friday 14 December 2018 (7405) Print this report
PROMETHEUS X laser temperature was changed

[Sugimoto, Yokogawa]

Related log:

  • Sep. 21st 2018 (log6239): Frequencies of the main laser and the PROMETHEUS laser for X arm were measured.
  • Sep. 24th 2018 (log6270): The beat-note signal between the main laser and the PROMETHEUS X laser was found temporarily.
  • Sep. 26th 2018 (log6300): The temperature of the main laser was changed to 46.4 deg.
  • Sep. 26th 2018 (log6303): The beat-note signal was got by changing the temperature of the PROMETHEUS X.
  • Dec. 13th 2018 (log7375): The frequency of the new PROMETHEUS laser for Y arm was measured.
  • Dec. 14th 2018 (log7393): The temperature of the main laser was changed from 46.5 deg to 49.13 deg. 

Today, the main laser temperature was changed from 46.5 deg to 49.13 in order to get the beat-note signal between the main laser and the new PROMETHEUS laser for Y arm. Along with this, we changed the tamperature of the PROMETHEUS laser for X arm from 25.5 deg to 26.8 deg referencing this plot so that the frequency of the beat-note signal is 40 MHz.

Finaly, we got the beat-note signal and the PROMETHEUS X laser was phase-locked to the main laser by PLL without problems.

MIF (General)
kazuya.yokogawa - 22:51 Friday 14 December 2018 (7404) Print this report
Set up for ALSY system

[Izumi, Sugimoto, Yokogawa]

We proceeded with the preparation for the ALS Y arm system.


1. Installation of the optical fiber for ALSY

Related log about fiber installation:

  • Aug. 10th 2018 (log5774): The optical fiber was delivered and the fiber transmittance was measured.
  • Aug. 11th 2018 (log5785): The delivered fiber was laid by Fujitsu Fsas and the fiber transmittance was measured after fiber laying.

The optical fiber which transmit green beam for ALSY system from the PSL table to the POS table was laid to aroud the POP table and the rest of the fiber was rolled and placed on the LSC rack beacause the POS table had not been installed when the optical fiber was laid by Fujitsu Fsas. Since the POS table was installed on Nov. 9th (log6930), we laid the rest of the fiber to the POS table today.

What we did:

  1. covered the rest of the fiber using blue flexible tube.
  2. protected the fiber near the entrance and exit of the blue flexible tube using low-resistance cushioning materials.
  3. fixed the flexible tube to the I-shape pillar supporting the 2nd floor with C-shape clamp.
  4. installed a pillar post as a guide of the fiber from the top to the surface of the POS table.
  5. fixed fibers on the table using masking tape.

(I forgot to take pictures after the work of numbers 4 and 5.)

 

2. Setup of ALSY optics on the PSL table

Yesterday, the new PROMETHEUS laser was installed (log7384), so we aligned optics for ALSY system on the PSL table. Current status is following.

Green path: All the optics except the fiber coupler was aligned. It is necessary to bring the fiber coupler stored at Univ. of Toyama.

IR path: All the optics have not been aligned yet.

Images attached to this report
Comments to this report:
kiwamu.izumi - 3:00 Thursday 20 December 2018 (7454) Print this report

Kazuya, Ryousuke, Kiwamu,

--- An addendum.

We learned that there was a portion where the fibers were not covered by the yellow jacket under the black tubing presumably at each end of the duplex fiber.

The message here is that one can easily put himself or herself into a sad situation where the fiber is unintentionally damaged when he or she tries to remove a black tubing because of the facts that the black tubings are not easy to remove and the fibers are exposed under the tubings. So don't remove them unless you have a good reason to do it.

Since we didn't know this fact, we actually almost removed the black tubing at the end of the duplex green fiber on the POS table. We originally thought that removing the black tubing would enable us to further split the two fibers so that one can separately isolate them from some vibration in easier fashion. The black tubing seemed to have been glued on to the yellow jacket. So we used a wire cutter to carefully take the tubing off without damaging the fibers. Then realizing that a few mm long portion of the fibers were exposed out of the yellow jacket, we stopped removing it and subsequently re-wrapped the black tubings with the aid of Kapton tapes around it. See the first attachment for a picture of the fiber end that is now taped by Kapton. As seen in the picture, we also put a small caution label so that no one will remove the tubings in future.

After this, we additionally made sure that both A and B fibers can still transmit some light using a fiber checker which emits red-ish visible light.

kiwamu.izumi - 17:06 Thursday 20 December 2018 (7464) Print this report

For some reason, the picture that I attached disappeared. Hence this log with the same attachment.

Images attached to this comment
MIF (General)
kazuya.yokogawa - 22:58 Thursday 13 December 2018 (7384) Print this report
Comment to Frequency measurement of the new PROMETHEUS laser (7375)

Before saying about the frequency measurement, I should have mentioned about a important thing. The new PROMETHEUS laser was delivered to Mozumi in this morning, so we took it to the PSL room and swapped the problematic PROMETHEUS laser for the new one. The problematic one will be sent for repair to the manufacturer.

 NOTE 

Since we put the new laser loughly, we have to start the alignment from scratch.

Images attached to this comment
MIF (General)
kazuya.yokogawa - 18:47 Thursday 13 December 2018 (7375) Print this report
Frequency measurement of the new PROMETHEUS laser

[Izumi, Eleonora, Yokogawa]

Related klog: #6239

Today, the new PROMETHEUS laser for ALS (Y arm) system was delivered, so we measured frequency of this laser by tuning the crystal temperature.

The attached figure shows the result. Green dots show the measurement result of the new PROMETHEUS laser. Also, the measurement result of the main laser and the PROMETHEUS laser for X arm measured on Sep. 21st are shown in red and blue dots respectively. The frequency differences between the main laser and two PROMETHEUS lasers need to be around 40 MHz since the beat-note signal is locked to 40 MHz by PLL. However, the overlap range (gray region) is very narrow and the frequency of the main laser can be set only every 1.5 GHz in order to lock the main laser to the reference cavity. (FSR of the reference cavity is 1.5 GHz.)

I  believe that the beat-note signal for ALS Y arm system can be seen...

Images attached to this report
Comments to this report:
kazuya.yokogawa - 22:58 Thursday 13 December 2018 (7384) Print this report

Before saying about the frequency measurement, I should have mentioned about a important thing. The new PROMETHEUS laser was delivered to Mozumi in this morning, so we took it to the PSL room and swapped the problematic PROMETHEUS laser for the new one. The problematic one will be sent for repair to the manufacturer.

 NOTE 

Since we put the new laser loughly, we have to start the alignment from scratch.

Images attached to this comment
kiwamu.izumi - 11:11 Friday 14 December 2018 (7391) Print this report

For the book keeping purpose, here is a list of the log entries that describe the history the old Prometheus (2143A).

  • Feb. 6th 2018 (4124); 2143A was installed on the POP table in order to test out TMSY. At this point no issue was found with 2143A
  • Aug. 6th 2018 (5724); the installation of the ALS optics in the PSL enclosure began.
  • Aug. 8th 2018 (5758); 2143A was moved from the POP table to the PSL table.
  • Aug.9th 2018 (5772); the issue was spotted for the first time.
  • Aug.11th 2018 (5786); the issue developed.
  • Aug.13th 2018 (5798); the situation momentarily improved.
  • Aug - Dec. 2018 (no logs); the laser was left off. Sometimes we switched it on, but it did't run for hours.
MIF (General)
kazuya.yokogawa - 22:42 Wednesday 28 November 2018 (7180) Print this report
Steps in order to reduce phase noise of optical fiber

[Enomoto, Yokogawa]

What we did:

1. re-fixed the optical fiber over the POP table. (Fig.1)

The optical fiber was re-fixed using the floor of BS booth 2nd floor, since the bar holding the fiber was flexible.

 

2. fixed the fiber to the POP table with masking tape. (Fig.2)

Images attached to this report
MIF (ITF Control)
kazuya.yokogawa - 10:11 Thursday 22 November 2018 (7086) Print this report
Comment to Frequency noise measured by Green with ALS CARM loop closed/opened (7071)

[Nakano, Enomoto, Sugimoto, Yokogawa]

(Yesterday work)

We suspected that the effect of RAM in phase modulation by Gr EOM is limiting the frequency stability (the above plot) and investigated the effect of RAM.

The attached figure is measured noise of the PDH error signal which taken at the I-phase output of I&Q demodulator for Gr PDHX. This is equivalent to the effect of RAM(Residual Amplitude Modulation) in phase modulation by Gr EOM. This noise seems to have the same shape as the noise of the PDH control signal (black line in above plot) especially at around 350 Hz and 1.x kHz. However, it was concluded that the factor of limiting the frequency stability is not the effect of RAM, since the effect of RAM should be a lower noise level in the frequency noise from simple calculations.

 

The data is stored at:

KAGRA Dropbox/Personal/Yokogawa/PDH/20181121

Images attached to this comment
MIF (General)
kazuya.yokogawa - 12:52 Thursday 15 November 2018 (6994) Print this report
Installation of the optics on the REFL table

[Miyoki, Enomoto, Sugimoto, yokogawa]

(Yesterday work)

We installed the optics on the REFL table and aligned those optics using the reflected beam from ITMX.

what we did:

  • assembled the optical mounts, posts and base plates.
    • The periscope, optical mount assemblies is the same as TMSX on this page.
  • installed the optics according to the layout design and aligned those optics.
    • The optical layout design is JGW-T1809238
    • The attached figure is the installed optics.

NOTE:

Since we did not have one RFPD and two QPDs, they have not installed yet.

Images attached to this report
MIF (General)
kazuya.yokogawa - 12:33 Monday 05 November 2018 (6850) Print this report
Comment to [ALS PLL] The strange noise was the free-run frequency noise of the PROMETHEUS laser (6818)

Hi Enomoto-san,

I ploted the free-run frequency noise of the PROMETHEUS laser considering the effect of the anti-whitening.

The blue line is the frequency noise measured last Thuersday and the orange line is the frequency noise considering the anti-whetening. This plot looks like 1/f shape. Also, the green line is the free-run frequency noise of the PROMETHEUS laser measured on Oct. 11th with Enomoto-san.

MIF (General)
kazuya.yokogawa - 2:00 Friday 02 November 2018 (6818) Print this report
[ALS PLL] The strange noise was the free-run frequency noise of the PROMETHEUS laser

[Izumi, Yokogawa]

Yesterday, it was confirmed that the broadband structure from 1 Hz to 100 Hz on the PLL feedback spectrum disappeared as we swiched off the KOACH air system (log6796), but there was flat noise after around 10 Hz.

We concluded that these noise is freerun frequency noise of the PROMETHEUS laser.


what we did:

  1. made a comparison of the relationship  between the measured PLL feedback spectrum and the spectrum obtained from the noise budget.
    • Here is the plot of these spectra. The pink line is the measured PLL feedback spectrum and the gray line is the spectrum obtained from the noise budget culculation. We assumed that the free-run frequency noise of the PROMETHEUS is 1e6/f as a typical value. These are matched at 1 to 10 Hz, but there are strange noises after 10 Hz.
  2. tried to do PLL by using the low noise VCO instead of the laser frequency and evalueted the sensing noise of PLLX loop.
    • We saw that there is no relationship between the strange noises and the sensing noise of PLL.
  3. made a comparison of the relationship between the PLL feedback spectrum and the PDH feedback spectrum
    • If the PLL works well, the free-run frequency noise of the PROMETHEUS laser and the sensing noise of PLL should be seen in the PDH feedback spectrum multiplied by 1/(1+G) and G/(1+G) respectivelly. (G is the olg of PLLX loop.) Here is the screenshot of these spectra. We indeed see that the PDH feedback spectrum is limited by the PLL sensing noise around 100 Hz and the free-run frequency noise of PROMEHTEUS laser is suppressed by the factor 1/(1+G) after 1 kHz. Therefore, the strange noise in the PLL feedback spectrum is the freerun frequency noise of the PROMETHEUS laser.
Comments to this report:
yutaro.enomoto - 11:05 Friday 02 November 2018 (6821) Print this report

Hi Yokogawa-kun,

Which channel did you use as a monitor of the feedback signal of PLLX? K1:ALS-PLLX_SLOW_DAQ_OUT(_DQ)?
If so, we haven't implemented an anti-whitening filter for this channel, which means that value of this channel is different from the voltage of the feedback signal in the real world, by a 2nd order whitening filter (two zeros at 10Hz and two poles at 100Hz, DC gain of 2).
We need an anti-whitening filter same as the one implemented in the filter module K1:ALSPDH_PDHX_SLOW_DAQ. 
(I implemented such filters only for K1:ALS-PDH{X|Y}_SLOW_DAQ_OUT. Sorry for this confusion.)

And my implementation of the anti-whitening filter by eyes to the spectrum gives me less-structured 1/f shape. This must be free-run noise! 

Images attached to this comment
kazuya.yokogawa - 12:33 Monday 05 November 2018 (6850) Print this report

Hi Enomoto-san,

I ploted the free-run frequency noise of the PROMETHEUS laser considering the effect of the anti-whitening.

The blue line is the frequency noise measured last Thuersday and the orange line is the frequency noise considering the anti-whetening. This plot looks like 1/f shape. Also, the green line is the free-run frequency noise of the PROMETHEUS laser measured on Oct. 11th with Enomoto-san.

yutaro.enomoto - 18:20 Monday 05 November 2018 (6852) Print this report

Great!
(By the way, the plot has disappeared at some point.)

To avoid further confusion, I implemented anti-whitening filters for CMSBs named as PLLX, PLLY, Summing node, and CARM servo.
Then updated the safe.snap of k1alspll

MIF (General)
kazuya.yokogawa - 21:36 Wednesday 31 October 2018 (6796) Print this report
[ALS PLL]

[Izumi, Sugimoto, Yokogawa]

The noise of PLLX

Yesterday, Izumi-san found that the noise of the PLLX control signal are higher than before. Since, these noise had coherence with the microphone in the PSL room, we assumed that the couse of noise increse was acoustic noise. We confirmed the folloing two points.

  • The alignmet of the beatnote
    • It was suspected that the alignment of the beatnote got worse, so we aligned the beam path using the steering mirrors for taking the beatnote. However, it turned out that the alignment was not getting worse.
  • The influence of the wind from the KOACH in the PSL room
    • It was supected that the noise increased due to the wind from the KOACH, so we turned off the KOACH and measured the noise. By doing so, the noise decresed. (I forgot saving the noise plot in my tablet.)

Since it was found that the noise increased due to the wind from the KOACH, we confirmed the noise when we knocked the optics for IR beam path in order to see if the wind was shaking the optics. However, even if we knocked the optics, there was no change in the noise. Also, even when the KOACH is on, the noise sometimes became peliodically smaller. That was strange.

 

The amplitude of the beatnote

Since the power of the main IR beam was raised about 3 times by Nakano-san, we adjusted the beam power before the RFPD for detecting the beatnote. The folloing table shows the beam power of the main laser (MEPHISTO) side and the AUX laser (PROMETHEUS) side before the RFPD and the amplitude of the beatnote before and after adjusting the power.

  Before                     After                    
MEPHISTO side IR beam power 2.5 mW 7 mW
PROMETHEUS side IR beam power 8.5 mW 8 mW
Beatnote amplitude -17 dBm -11 dBm
Comments to this report:
kiwamu.izumi - 23:26 Wednesday 31 October 2018 (6804) Print this report

Some additional data:

Here is a screenshot of the PLL feedback spectrum with and without KOACH on, taken in this after noon. The broadband structure from 1-100 Hz and a peak at around 200 Hz disappeared as we switched off the KOACH air system. Also, when the KOACH is on, we see high coherence in the same frequency band, indicating somehow the wind couples to the PLL.

By the way, we believe that noise 1 Hz is free-run frequency noise of the Prometheus laser.

The data is stored in the xml format at:

/users/Commissioning/ALS/PLL/ALS_PLLX_with_without_KOACH_20181031.xml

Images attached to this comment
kiwamu.izumi - 14:09 Monday 04 October 2021 (18435) Print this report

Erratum:

The diaggul xml file was stored in the following page. Sorry for any confusion.

/users/Commissioning/data/ALS/PLL/ALS_PLLX_with_without_KOACH_20181031.xml

MIF (General)
kazuya.yokogawa - 20:47 Wednesday 24 October 2018 (6702) Print this report
[ALS PLL] Noise of MC servo for PLLX

[Izumi, Sugimoto, Yokogawa]

In preparation for the characterization of PLL, we measured noise of Common Mode Servo Board (CMB) for PLLX. The condition of CMB in our measurement are following.

  • The input gain is -23 dB.
  • Common compensation (40Hz/4kHz pole/zero): ON
  • Common boost1 (0Hz/10Hz pole/zero): OFF
  • Common boost2&3 (20Hz/2kHz pole/zero): OFF
  • Slow boost(4Hz/400Hz pole/zero): ON
  • Slow conpensation (4Hz pole): OFF

We could not turn on the common boost (1, 2 and 3) because the slow output of CMB saturated. The other settings are the same as when PLL is locked.

The attached is the noise of CMB for PLLX measured by Agilent 35670A. The graph is plotted by connecting the data measured three times while varying the stop frequency of the measuring instrument at 100Hz, 1.6kHz and 51.2kHz.

The data are uploaded in /KAGRA/Dropbox/Personal/Yokogawa/PLL/noise/20181024.

Images attached to this report
MIF (General)
kazuya.yokogawa - 16:30 Thursday 18 October 2018 (6596) Print this report
[ALS PLL] Automation of PLLX

[Enomoto, Sugimoto, Yokogawa]

(Yesterday work)

We tried automating the PLL and succeeded!

The procedure of PLL;

  1. bring the beatnote frequency close to 40 MHz.
  2. trun on SLOWBOOST filter of MC servo. (Set INPUT GAIN of MC servo as -23 dB.)
  3. sweep the PROMETHEUS temperature so that the beatnote is locked to the local frequency(40 MHz).
  4. trun on COMMON CONPESASION filter of MC servo.
  5. trun on COMMON BOOST filter of MC servo.
  6. close the temperature loop. (Refer to log6543 for setting of low path filter of the temperature loop)

It is difficult to judge the lock because the Phase Frequency Discriminator (PFD) outputs a sawtooth wave. (The output signal of the PFD is an error signal for PLL.) PFD outputs -4 V when the beatnote frequency is higher than the local frequency and outputs +4 V when the beatnote frequency is lower than the local frequency. If the beatnote frequency is close to the local frequency, the PFD outputs a sawtooth wave.

So, we decided that PLL is locked when the PROMETHEUS frequency is 40MHz lower than the main laser frequency and the beatnote frequency approaches the local frequency from the lower ferequency side by sweeping the PROMETHEUS temperature. Specifically, when the current and the previous value of the error signal and the direction of sweeping temperature satisfy the following expression, PLL is locked.

( (Error signal CURRENT value) - (Error signal PREVIOUS value) ) * (Temperature sweep direction) < 0

MIF (General)
kazuya.yokogawa - 1:38 Friday 12 October 2018 (6517) Print this report
[ALS PLL] OLTF and noise spectrum

[Enomoto, Yokogawa]

We measured OLTF and noise spectrum of PLL.

OLTF

This is the measured OLTF of PLL. UGF was 35.6 kHz.

Noise spectrum

We measured noise spectrum of the control signal and error signal by 35670A (Agilent). I will post the details such as caliblation tomorrow, but I post frequency fluctuation of a Prometheus laser estimated by measured noise spectrum. The frequency fluctuation of a Prometheus laser is obtained by multiplying the noise spectrum of the control signal and the actuator efficiency of laser PZT (1.4 MHz/V) if we assume that the open loop gain is much larger than 1. Below is an estimated Prometheus laser frequency fluctuation.

Images attached to this report
MIF (General)
kazuya.yokogawa - 10:53 Saturday 06 October 2018 (6441) Print this report
Prometheus (green laser) was phase locked to the main laser!

[Enomoto, Midooka, Yokogawa]

We did phase lock a Prometheus to the main laser!!coolThe attached figure is the beatnote signal during control.

What we did;

  • put jumper pins in the Dsub-BNC Converter (DAC) chassis in order to ground the outside of BNC.
  • created filter bank so that the temperature of a Prometheus can be varied by offset.
  • Yesterday, the peak of the beatnote was -18 dBm, but it had dropped to about -30 dBm today. So, we raised the power of Prometheus side from about 3mW to 15mW so that the peak of the beatnote is -11dBm. (The phase frequency discriminator (PFD) requires a beatnote signal with a peak of -11dBm)
  • locked the beatnote at 40MHz. (This means the frequency of Prometheus was locked at 40MHz away from the main laser.)

Next;

  • We will measure OLTF.
Images attached to this report
MIF (General)
kazuya.yokogawa - 18:25 Thursday 27 September 2018 (6298) Print this report
Real time model of C.M.B. for ALS PDH is running

[Izumi, Enomoto, Midooka, Yokogawa]

log on 26th.

We set up the Common Mode Servo Board for ALS PDH to run with realtime model.

  1. installed two BIO boards to the LSC0 I/O chassis.
  2. connected the cable to the port on the left side of the BIO board as seen from the back of the I/O chassis.
  3. prepared the environment on Simulink.
  4. confirmed the signal using the BIO checker whether the signal from the BIO board is linked with the realtime model of the CMB for ALS PDH.

It seems that the signal is correctly output!

MIF (General)
kazuya.yokogawa - 17:42 Thursday 27 September 2018 (6325) Print this report
Today's work

[Midooka, Yokogawa]

Shelves for ALS signal generator

We installed shelves for ALS signal generator. (See the attached picture1.)

Beatnote between the main laser and a Prometheus

  • We checked the beatnote signal using an oscilloscope. This signal is nice.
  • We measured the beam power. The laser of both the main laser side and a Prometheus side ware 3.8 mW.
  • Amplitude was -18dBm when obserbing this beatnote with Moku:Lab.

.

DCPD for monitoring power of fiber transmitted beam

We installed the a DCPD on the POP table in order to monitor the power of fiber transmitted beam. But the cable has not been connect yet.

Images attached to this report
MIF (General)
kazuya.yokogawa - 19:58 Wednesday 26 September 2018 (6303) Print this report
Beatnote between the main laser and a Prometheus

[Midooka, Yokogawa]

Related log: 6239, 6270

The crystal temperature of the main laser (Mephisto) was changed from 27 degree to 46.4 degree by Nakano-san. Then we found the beatnote between the main laser and a Prometheus by sweeping the Prometheus temperature.

  • Mephisto temperature was at 46.4 degree.
  • We found the beatnote at about 40 MHz when Prometheus temperature are at 23.4 degree and 25.5degree.
  • Mode hop of a Prometheus seem to occur at between 24.2deg to 24.6deg.
  • Amplitude of the beatnote was about -22 dBm. (I forgot to measure the incident laser power to the RFPD.)

MIF (General)
kazuya.yokogawa - 0:19 Tuesday 25 September 2018 (6274) Print this report
Comment to Green beam alignment (6082)

[Michimura, Enomoto, Sugimoto, Yokogawa]

Yesterday, Michimura-san and Enomoto-san found that the DAC chassis (Ser. Num JGW-S1605872 ) gives an oscillated signal at ~1MHz. So, we changed to the new DAC chassis (Ser. Num JGW-S1605870) and used Low Path Filter in order to avoid the oscillation at 1MHz.

However, it was not the real reason why the beam shutter does not work in trigger mode. The point of the real reason was at ground. We found that outside the BNCs of the DAC chassis are not grouded in default. So, we connected the outside of BNC to the ground of DC power supply. (See the attached picture.) By doing so, the beam shutter worked with trigger mode!!

But this is not cool. We will drop the outside of BNC to ground using jumper pin.

Summary

  • Probably the DAC chassis (S1605872) we used before was not broken.
  • The beam shutter for green laser is working without problem with trigger mode.
  • We will drop the outside the BNC of the previous DAC chassis (S1605872) using jumper pin and exchange with S1605870.
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MIF (General)
kazuya.yokogawa - 18:24 Friday 21 September 2018 (6239) Print this report
Laser frequency measurement

[Izumi, Sugimoto, Yokogawa]

We measured the frequency of the KAGRA main laser and the Prometheus(Xarm) with respect to the laser crystal temperature. We used wavelength meter(Highfinesse WS Ultimate 30) for this measurement. Blue marker is the KAGRA main laser and green marker is the Prometheus for Xarm. For reference, I plotted the data of Mephisto in U. Toyama which was measured last year as red marker.

In order to take beatnote between the main laser and the Prometheus, it is nessesary to bring frequencies of two laser closer. However it seems that the frequencies approach only when the main laser temperature is very high and the Prometheus temperature is very low. Furthermore, the overlap range is narrow.

Images attached to this report
MIF (General)
kazuya.yokogawa - 2:46 Friday 14 September 2018 (6143) Print this report
Initial alignment: We found the beams at X end!!

[Michimura, Enomoto, Takeda, Sugimoto, Yokogawa]

We found the beams at X end !!

What we did:

  1. At the beginning, the reflected beams of PR3 were about 5 cm higher than the height of the center of PR2. So we aligned PR3 PIT so that the height of the reflected beams were the same as the height of PR2 center.
  2. We aligned PR3 PIT and YAW so that the beams hit at the center of ITMX.
  3. Since the IR and green slightly off at this time, we aligned PR2 so that the IR beam matched to the green beam.
  4. We further aligned PR3 so that the green beam path through the NAB at IXA. (The IR beam could not be seen at this time because the transmittance of ITMX is 0.4% for IR.)
  5. We swept PR3 and waited the response of X end PD. However we could not confirned any response.
  6. We went to X end and discovered the power of AA shassis was down. So we turned on the AA chassis.
  7. We changed the gain of X end PD from 50dB to 70dB(Max).
  8. When we retruned to the center area, we discovered the green beam hits the PD! 

  9. We shut the green beam with beam shutter and swept PR3 in order to find response of PD to the IR beam. 
  10. When we retruned to the control room, we discovered the IR beam hits the PD!! 

The oplev values of PR3 when the beams hit the PD are folloing.

  Green IR
PIT -83 -180
YAW -140 -341

It is a taugh day, but we were very happy to find the beams at X end!cool

Images attached to this report
Comments to this report:
tomotada.akutsu - 6:51 Friday 14 September 2018 (6144) Print this report

Omedetogozaimasu!

keiko.kokeyama - 11:29 Friday 14 September 2018 (6148) Print this report

Great job!yes

kiwamu.izumi - 11:00 Saturday 15 September 2018 (6164) Print this report

I liked the title so much in that the word "beam" is in the plural form. I nominate this as the klog title of the year.cheeky

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