The signal that I get with the oscilloscope comes from Lock-in CH1 OUTPUT. It is much higher than the signal recorded by the vi (the AC signal in entry 252, for example).

I read the sr830 lock-in  manual and I found that the CH1 OUTPUT voltage is proportional to the AC signal according to the following formula:

Output = (signal/sensitivity - offset) x Expand x 10 V

The Expand factor is 1, the sensitivity is 1mV, as we can see in the picture of the front panel.

So in the case of signal = 15uV , for example, I get Output = 150mV, a factor 10^4 higher

[Manuel, Tatsumi]

We checked the wire connections for the coils. The pictures show the order of the wire connections on the suspension, and outside the tank.

[WORKERS]   Tatsumi, Takahashi, Manuel, Eleonora

(1) At TAMA south end room (EM2 tank)

* Install four coils.

* Connect in-vacuum cables for the coil

   Manual checked the cable connections. He will report soon.

(2) At TAMA center room (BS tank)

* Open the BS tank

* Remove the suspension with BS mirror

* Close the tank

Tatsumi will glue magnets on BS mirror in the next week.

And then we will install the mirror to the BS tank.

I calculated the beam size of the probe beam using OSCAR.

I used the distances I measured and summarized in the first drawing.

The plots show the beam waist along the optical path, cyan area is the sample, vertical lines are the optical component of the experiment, black line is a mirror, cyan line is the f=50mm lens, orange line is the small sphere f=1.25mm

The last image is a comparison of the beam spot size at the PD position with the PD size in the 3 cases.

[Eleonora, Manuel, Tatsumi, Raffaele]

We took two viewport shelves from NM1 tank and installed them at the North-West and South-West viewports of PR tank.

We placed a laser and a mirror on the North-West viewport shelf and placed a PSD on the South-West viewport shelf.

We tried to send the laser to the front surface of the mirror. Since the mirror suspension is not centered on the stack, there is not enough space to get the reflected beam on the other viewport.  We decided to send the laser on the back surface of the mirror.

We placed to mirrors as show in the picture. Part of the laser is transmitted and goes to hit the tank wall. Part of the transmitted beam is reflected by the second surface and goes to hit the tank wall on the other side.

We closed the tank.

Then we checked the T, X and Y signals of the PSD using an oscilloscope. The optical lever looks working fine. We remark that the X signal (Yaw motion) is strongly dominated by an oscillation at about 1Hz.

I installed a viewport on the flanges of the cryostat to test its vacuum compatibility. Right now, it looks quite good. The turbo pumb is working well and the viewport seems to be fine. I will leave the system on over the weekend to see whether we can reach the target pressure of 4*10^(-4) Pa.

(1) Wiring parts

See attached picture.

(2) Coil support plates

Given the fact that a thick sample changes the optical path of the probe, I wanted to see how and why the noise level changes when I change the position of the detection unit. The detection unit is made by one flat mirror at 45°, a f=50mm lens, a reflecting sphere f=2.5mm, and the photodetector.

I turned OFF the chopper to avoid any possible vibration, I set the lock-in internal oscillator as reference frequency (demodulation) at 420Hz.

I connected the oscilloscope at the photodetector (to see the DC signal), and at the output of the lock-in amp (to see the AC signal *1e6). I took some quick measurements, for different positions of the detection unit. The DC has a repeatability of 0.2V, the AC measurement is very rough, just an average of the signal in 10s. Every time I moved the detection unit I had to realign the beam on the PD, tuning the position of the 50mm lens to maximize the DC. The position can be changed only by 35mm, the length of the micrometer screw.

In the following table, there are the DC and AC values at different positions and for different samples. A higher position value means the detection unit is closer to the sample. Hence, 0mm is the furthest point where I could place the detection unit. To move it more it's necessary to unscrew the unit from the board.

I used three samples: the Sapphire small sample diam 1.5" x 5mm, the Sapphire Tama-sized  sample diam100mm x 60mm, and the glass KAGRA-sized sample.

Looking at those data, I can say:

• the DC decreases when the unit is placed further. This is reasonable considering the finite size of the PD and the divergence of the beam.
• In the case without any sample, when the unit position changes, the AC noise level doesn't change a lot.
• In the case with the small sample, when the unit distance increases, the AC noise level does decrease, maybe proportionally to the DC.
• In the case with the Tama-size sample, when the unit distance increases, the AC noise level changes a lot, compared to the DC.
• In the case with the KAGRA-size sample, when the unit distance increases, the DC is pretty constant and the AC noise level changes a bit.

The hypothesis I have in mind is that the probe spot size makes an important role when compared to the detector size.

I will use my simulations to try to reproduce the behavior shown in those measurements and try to find an  explanation.

Aoyama-san of National Institute of Polar Research warmed up the Iodine stabilized He-Ne laser.

But they found trouble on the laser.

Now we are waiting for the warming-up run

and for the stable operation.

We will check the laser in tomorrow morning.

I add some pictures of  tama PR and tama BS.

First picture (tamabs1.jpg) shows that three magnets are clearly absent, but regarding the bottom left one, it's not clear: maybe is still attached, or maybe it is lying in the inner plastic part of the coil.

I add some pictures of  tama PR and tama BS.

First picture (tamabs1.jpg) shows that three magnets are clearly absent, but regarding the bottom left one, it's not clear: maybe is still attached, or maybe it is lying in the inner plastic part of the coil.

Tatsumi and Takahashi successfully installed the mirror into PR vacuum tank.

Also one additional optical window was installed for Optical Lever system.

Instead of that, a turbo pump was removed from the port.

ToDo list:

* In-vacuum coil actuator cables are temporary connected to the panel fixed at the suspension frame.

We should check the connection later.

We installed an old PR mirror into EM2 vacuum tank.

In-vacuum cables were salvaged from TAMA SAS.

ToDo list:

(1) South end room / mirror installation

Because a stand-off came off the mirror, we postponed the installation to Thursday.

(2) South end room / Coil

Tatsumi has 20 of coils with bobin.

Pin connectors should be swaged to the coil wires. Takahashi-san has a swage tool and pins.

Tatsumi will make swage works tomorrow.

The pins will be connected to BNC connectors. Tatsumi cannot find the connector.

Takahashi-san will look for at KAGRA site in next week.

Coil support plates are also not found. We hope to find these at KAGRA.

(3) PR tank at center room

Stand-off for this mirror is also troubled. We will install the mirror on Friday.

We found that one pico-motor is missing for the suspension.

Takahashi-san installed the motor today.

(4) BS mirror

We checked BS mirror with opening the vacuum tank.

We found that all of four magnets came off the mirror. 

Glueing jig for TAMA BS is at KAGRA site. Takahashi-san will send it back in next week.

And then we need the glueing and installation work.

Manuel will upload some pictures. 

In last report, I showed that to fix tightly the samples to the board doesn't change the noise level. http://www2.nao.ac.jp/~gw-elog/osl/?r=247

This is still in progress.
However, important measurements were done already on three samples of SiC (after the outgassing measurements at KEK). We now have the reflectivities and the BRDF for the JGW 1 (NFC) and two "Covalent" samples.

I prepared a document for report the results. It cannot be attached to this entry but can be downloaded from the JGW document server instead.

[Raffaele, Manuel]

We took a viewport shelf from the IMC end mirror vacuum tank, and placed it on the south-east viewport of the BS vacuum tank.

We assembled an optical lever to test the components. Since the mirror is placed at 45°, the laser cannot reach the center of the mirror because of the suspension leg in front of the mirror. So we pointed the laser to about half of the radius of the mirror. The PSD position is about at the center of the viewport. We could see a good signal of X and Y channels (we jumped on the floor), but the "Total" channel saturates at 15V, because the laser power is too high. Putting an OD filter in front of the laser makes the signal do not saturate anymore.

[Takahashi, Tatsumi, Ishizaki, Manuel]

We removed the SAS from the vacuum tank in South end room.

We installed the stack and the suspension for the filter cavity end mirror. See the picture.

And closed the tank.

In last measurements, we noticed a larger noise when measuring the Tama-size sapphire sample.

I did some measurement of the AC signal from the lock-in, in different conditions with two samples: small sapphire sample and Tama-size sapphire sample.

Acquisition time: 1h

Sampling rate: 100ms.

Pump OFF

Probe ON

In order to check if the blocks vibrations were the noise source, I placed the small sample on the blocks .

Plot1: Comparison of small sample sitted on the blocks and small sample attached at the translation stage. The noise is almost the same

To be sure the vibrations don't cause the noise, I removed the translation stage to make enough room, and I placed the Tama-size sample tightly fixed at the optical board. Picture1

Plot2: Comparison of Tama-size sample sitted on the blocks and Tama-size sample fixed at th eoptical board. The noise is almost the same.

Plot3: Comparison between small sample and Tama-size sample, both tightly fixed. The larger sample gives a larger noise.

Conclusion:

The only different thing is the thickness.

Let me make an hypotesis. Let's suppose the noise comes from the angle fluctuations of the probe, which cause a fluctuation of the spot position on the photodetector. The probe passing through a thick sample have a longer optical path. This is like if the detector was further. And a further detector sees more angular fluctuation, like in an optical lever. So, next check, I will see how the noise change when I change the detector distance.

I wrote a python script to record the frequency value from the lockin amplifier through the serial port.

Sample rate: 1Hz

Acquisition time: 8h

I attach a plot of the entire acquisition (0 - 480min)

and a plot of the first 1000 seconds