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R&D (FilterCavity)
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YuefanGuo - 10:41, Friday 19 February 2016 (222)Get code to link to this report
Progress of Squeezed light experiment
Member: Tatsumi. Yuefan

We tested the correspondence between the laser output power and the beam size.Then tested the beam profile to get the exact position of lens.Detail shows in the attachment.

But for now the beam size we got is not small enough for the SHG and the transmittance is a little bit low, so today we will reset the position of all components, add one more lens, mount the SHG and try to get the green light.

Non-image files attached to this report
R&D (FilterCavity)
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EleonoraCapocasa - 23:18, Wednesday 17 February 2016 (221)Get code to link to this report
NM2 optical lever installation

Today I installed an optical lever to sense the motion of the suspended input mirror of the filter cavity. Such lever uses a lens and a pair of PSD respectively placed in the focal plane and in the image plane. In these scheme the PSD in the focal plane is only sensitive to mirror tilts while the one on the image plane can only sense its shift. A picture of the optical lever is shown in the figure attached.

A first injection of white noise has been performend in order to excite mirror resonances. After identifying the degree of freedom (tilt or shift) at which each resonance belongs it could be possible to fine-tune the PSD positions to optimize the signal decoupling.

Images attached to this report
221_20160217151446_opticallever.jpg
KAGRA MIR (Absorption)
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ManuelMarchio - 22:43, Tuesday 16 February 2016 (220)Get code to link to this report
Beam profile measurement

I measured the beam profile of probe and pump near the crossing point.

Set a vertical blade to the translation stage and move it from PCI software.

Read data on the power meter and fit with erf function.

This table is a summary of the results.

    Probe   Pump
z (mm)   y_0 (mm) halfwidth (um)   y_0 (mm) halfwidth (um)
0   37.5 178   39.75 172
20   39.7 145   39.85 48
30   41 126   39.92 70
50   43 94   40 172

The probe waist is about 94um (radius at 1/e^2) but it is not near the crossing point. At the crossing point the beam size is about 290um (diameter).

The pump waist is about 48um (radius at 1/e^2) and is near the crossing point. At the crossing point the beam size is about 100um (diameter).

The angle between pump and probe is 0.105rad, or 6°.

The PCI manual said beamsizes of 200um and 70um. Which were the values I used until now in my simulations.

I will put those new measured parameters in the simulations.

Images attached to this report
220_20160216135751_blade.png 220_20160216140141_pumpbeam.png 220_20160216140157_probebeam.png 220_20160216142225_crossingpoint.png
R&D (FilterCavity)
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YuefanGuo - 11:10, Friday 12 February 2016 (219)Get code to link to this report
Squeezing light experiment progress: Laser property test
Members: Yuefan, Tatsumi

We tested two properties of the laser will be used in the squeezing light experiment:

1. The correspondence between the current of diode and the output power of Laser

2. The position of the laser beam waist

The reports will be shown in the attachment.
Non-image files attached to this report
R&D (FilterCavity)
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EleonoraCapocasa - 23:49, Wednesday 10 February 2016 (218)Get code to link to this report
Optical lever installation: preliminary work

Members: Eleonora, Manuel, Tatsumi, Yuefan

Some preliminary work has been done to prepare the installation of the oprical lever for controlling filter cavity input mirror (already suspended in NM2)

Mirror check      

The suspendend mirror  has been checked after the earthquakes of the past weekend. No damages have been found.

Coil drivers connection 

The four coil drivers to be used to move the mirror have been connected.

PSD electronics

The electronics necessary to power and to read signals from the two PSD need for the optical lever has been assembled and checked. (See picture attached)

PSD calibration

PSD have been calibrated by shining a laser to them and looking at the change in the output voltage when gradually varying their position in x and y direction.

In the plot attached the voltage value has been normalized using the total output value (SUM). The (normalized) calibration value found is  about 6.6*10-3 m/V

Laser check

We checked the dimension and the beam power of the  laser to be use for the optical lever. Dimensions of the beam (measured with a beam profile after 30 cm) are about 1.1 mm. The recommended dimensions for the PSD are beetween 0.2 and 7 mm.

We also checked the PSD output as a function of the laser power and we observed that the  signal saturates for a power higher than 0.15 mW. 

 

 

 

Images attached to this report
218_20160210034614_img20160210242505506.jpg 218_20160210034625_img20160210244430527.jpg 218_20160210035043_psd1cal.png
KAGRA MIR (Absorption)
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ManuelMarchio - 11:36, Wednesday 10 February 2016 (217)Get code to link to this report
Mirror mount delivered. Large translation stage disassembled and packed

The three mirror mounts has been delivered, unboxed and checked.

One mount for Kagra-size mirrors (ø220mm x 150mm)

One mount for Tama-size mirrors (ø100mm x 60mm)

One mount for 2inch samples (and smaller with adaptors that we already have).

All parts go well on the large translation stage and the stage can move without any obstruction.

-----------------------------------------------------------------------------------------------------------------------

The large translation stage, has been disassebled and packed.

Today the company person pick it up to clean it and to grease it.

Images attached to this report
217_20160210033233_img20160208142516.jpg 217_20160210033244_img20160208142523.jpg 217_20160210033250_img20160208143017.jpg 217_20160210033258_img20160208143026.jpg 217_20160210033307_img20160208143521.jpg 217_20160210033316_img20160208143526.jpg
KAGRA MIR (Absorption)
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ManuelMarchio - 04:33, Friday 05 February 2016 (216)Get code to link to this report
Simulation scan along bulk reference sample

I simulated the signal of the absorption system, in order to be able to compare the measurement reported in this post .

The reference sample is made of silica and absorbs 116%/cm. Thickness is 3.6mm. Chopper frequency 400Hz.

I attach an animated gif to show three aspects:

1. The colored image represents the temperature distribution inside the bulk reference sample, heated by the horizontal pump beam. The shadow represents the probe beam at an angle of 7° to the pump.

Moving the sample along the z axis (along the pump beam) make the crossing point of pump and probe to scan the depth of the sample, and it is equivalent to move the probe vertically respect to the pump.

2. The interference pattern is the difference between the intensity of the probe passing through the heated sample and the intensity of the probe not passing through the sample. This is because the heating is modulated. The signal is given by the integral of the interference pattern in the area of the photodetector. The area of the photodetector is represented by the black square.

3. The plot is the calculated signal from the lock-in as a function of the sample depth. The 0 is when the pump-probe crossin point is at the surface of the sample.

Images attached to this report
216_20160204203441_scanbulk.gif
R&D (FilterCavity)
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ManuelMarchio - 15:34, Tuesday 02 February 2016 (214)Get code to link to this report
Temporary input mirror suspended in NM2 tank

Members: Takahashi, Tatsumi, Guo, Manuel.

We suspended a temporary mirror in the NM2 vacuum tank.

Set the earthquake stoppers at about 1mm from the mirror. 

Set the 4 coil actuators coaxially aligned to the magnets.

Closed the vacuum tank.

R&D (FilterCavity)
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DaisukeTatsumi - 21:17, Saturday 30 January 2016 (213)Get code to link to this report
Magnet glueing on a LISM mirror

I made glueing of four magnets on a LISM mirror.

See attched PDF file.

Page 1: Magnet polarity check

Page 2: Anti-Reflection coating check by green lase pointer

Page 3: Overall view of the glueing JIG

Page 4, 5: Closer view of Magnet clamping parts

 

See JPEG file:

This is TAMA traditional magnet configuration.

I also follow this.

Images attached to this report
213_20160130131428_mirrormagnet.jpg
Non-image files attached to this report
R&D (FilterCavity)
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ManuelMarchio - 21:23, Wednesday 27 January 2016 (212)Get code to link to this report
Optical table moving

Members: Tatsumi, Guo, Manuel.

We moved and clean an optical table in the central room of TAMA. The attached image shows from where to where.

Images attached to this report
212_20160127132020_screenshotfrom20160127211927.png
KAGRA AOS (General)
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SimonZeidler - 14:20, Wednesday 20 January 2016 (211)Get code to link to this report
JASMINE manual

I and Torii-san finished writing a manual for the JASMINE scatterometer in the ATC.
It is uploaded on the JGW website and available in Japanese and English.

R&D (FilterCavity)
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DaisukeTatsumi - 12:59, Thursday 07 January 2016 (210)Get code to link to this report
Modulation frequency for SHG cavity

I study on modulation frequency for SHG cavity.

Because the cavity is very short (30mm or less),

it has FSR of 4 GHz and has a finesse of 75.

These correspond to resonant width of 53 MHz.

By using FINESSE simulator,

I checked the PDH signals for each modulation frequency.

fmod                  merit                                                    demerit

600MHz            non-resonant sideband                   modulation frequency is too high

15MHz              TAMA used this freq.                        The PDH signal get smaller by a factor of 10.

I think that modulation frequency of 15 MHz is acceptable for us.

Non-image files attached to this report
KAGRA VIS (Mirror Assemble)
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DaisukeTatsumi - 18:16, Thursday 24 December 2015 (209)Get code to link to this report
Test samples for Sapphire wire breaker removing

I made four test samples as shown in bellows.

Before the glueings, mirror surfaces were cleaned up by First Contact

(mainly to remove oils on these).

I will send sample A and C to Hirose-san on 25 December (tomorrow).

Images attached to this report
209_20151224102047_samplea.jpg 209_20151224102055_sampleb.jpg 209_20151224102102_samplec.jpg 209_20151224102109_sampled.jpg
KAGRA VIS (Mirror Assemble)
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DaisukeTatsumi - 21:41, Monday 14 December 2015 (208)Get code to link to this report
Inspection of Sapphire Wire Breaker

Because we found that Sapphire Wire Breakers are broken in the curing process of the glueing,

(see k-log http://klog.icrr.u-tokyo.ac.jp/osl/?r=451)

we inspected the remaining eight Sapphire WBs.

 

I cannot find any obvious cracks in these.

Due to the sand surfaces of that, I cannot inspect micro-cracks.

 

[RELATED ENTRY]

http://www2.nao.ac.jp/~gw-elog/osl/?r=45

JGW-T1503409 http://gwdoc.icrr.u-tokyo.ac.jp/cgi-bin/private/DocDB/ShowDocument?docid=3409

KAGRA VIS (Mirror Assemble)
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DaisukeTatsumi - 21:31, Monday 14 December 2015 (207)Get code to link to this report
Inspection of Sapphire Wire Breaker

Because we found that Sapphire Wire Breakers are broken in the curing process of the glueing,

(see k-log http://klog.icrr.u-tokyo.ac.jp/osl/?r=451)

we inspected the remaining eight Sapphire WBs.

 

I cannot find any obvious cracks in these.

Due to the sand surfaces of that, I cannot inspect micro-cracks.

Images attached to this report
207_20151214132339_rimg00011024x743.jpg 207_20151214132348_rimg00071024x767.jpg 207_20151214132402_rimg00111024x764.jpg 207_20151214132413_rimg00131024x758.jpg
KAGRA AOS (General)
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SimonZeidler - 22:52, Tuesday 08 December 2015 (206)Get code to link to this report
Offset in back-scatterometer?

A gap between the data of VB measured with our back-scatterometer and the data provided by SurreyNanoSystems made me curious about a possible offset in our data (our data were constantly 10 x higher). So I searched for systematical errors and ended up on the beam-splitter. It seems that by illuminating it with the laser, the PD gets a signal of 0.252nA even when the backscattering is cut of.

My interpretation is that this additional signal is actually scattering from the beam-splitter.

I am now thinking how we can get rid of this influence without violating the SNR too much severely.

R&D (FilterCavity)
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EleonoraCapocasa - 20:41, Friday 27 November 2015 (205)Get code to link to this report
Change of double pendulum suspension

Workers: Eleonora and Tatsumi

 

Today we replaced the double pendulum installed in NM2 vacuum tank with the one used to suspend the TAMA power recycling mirror (placed In RM vacuum chamber)

Power recycling mirror was still suspended and we succeded in moving the suspension with the mirrorr hanged. In the next days we planned to take a spectrum of the mirror motion to check the effectiveness of the stack and suspension system.

We also started preparing an optical lever needed to measure this spectrum.

Images attached to this report
205_20151127123741_1.png 205_20151127123759_2.png
R&D (FilterCavity)
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EleonoraCapocasa - 19:18, Tuesday 17 November 2015 (204)Get code to link to this report
Vibration isolation system installation

Workers: Eleonora, Tatsumi, Takahashi

Today we completed the installation of the vibration isolation system needed to suspend the filter cavity input mirror in the NM2 vacuum tank.

Such a system is composed by (from bottom to top):

  1. A baseplate (see picture 1)
  2. A three layer stack made of rubber and metal blocks (see picture 2)
  3. A top-plate
  4. A double pendulum system

In picture 3 the empty bottom of the vacuum tank is showed while in picture 4 the complete system can be seen.

Some test of vibration isolation are planned for the next days.

Images attached to this report
204_20151117111300_1.png 204_20151117111304_2.png 204_20151117111310_3.png 204_20151117111315_4.png
R&D (FilterCavity)
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EleonoraCapocasa - 17:34, Monday 16 November 2015 (203)Get code to link to this report
TAMA SAS system removed from NM2 vacuum tank

Workers: Eleonora and Tatsumi

Today current TAMA SAS system has been safely removed from NM2 vacuum tank. The vibration isolation system to be installed at its place is currently placed in PD vacuum tank ( e-log 201) and can be now moved in NM2 vacuum tank.

KAGRA AOS (General)
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SimonZeidler - 20:00, Friday 13 November 2015 (202)Get code to link to this report
VB measurements

I have measured the new VB-S sample and again the original VB-plate in order to compare these two.
Surprisingly, the VB-S sample is more "black" than the original sample although the other way around should have been occured. Also, it seems that the VB-plate-blackness altered when comparing this with a measurement from January...

In all these, I have to add that the data in the measurement from January may be not comparable as the system was still under reconstruction at that time. Also, as it is the first time for me to use Torii-sans setup, I am not sure whether there is still a mistake in the absolute values...

Images attached to this report
202_20151113120031_beamdumper.jpg