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

The direction of the probe changes inside the sample according to the Snell's law. As I calculated in this post

I included this effect in the optical part of my simulations. I show the simulation of the scan of the silica bulk reference sample, with and without the refraction effect.

The sample thickness is 3.6mm. With the refraction effect, the simulation is more similar to the measurement. Apart from the unknown scale factor.

I attach the slides that I presented at the last meeting on May 18 (slides from 1 to 6)

and the slides about the progress I did in these these days (slides from 7 to 11).

Slides 8 and 9 have two animations which don't move in the pdf.

I attach also the GIFs.

X axis unit of the histograms in the GIFs is ppm/cm

I couldn't upload the pdf file at once, so I had to split it in two.

We got the SiC samples back from KEK last week. Unfortunately, I discovered some dark spots on the polished surface on at least 3 of 7 samples. 

The pictures below show these spots on a NFC (first picture) and Covalent (second one) sample.

I made a calculation that might explain why I couldn't see any absorption signal.

The cross point between pump and probe changes position when there is a thick sapphire sample.

Details are in the attached slide.

This might also explain why in my simulations the simulated scan shows a thicker sample than the measured scan. I will include this effect in the simulations and check the result.

I attach a report about the measurements I did this week

I set the parameters thresholds on the controller (CLD1015) as specified in the butterfly package specs (FPL1053P):

LD max current: 450mA

TEC max current: 500mA

There are two possible operation modes: "Constant Current mode" and "Constant Power mode"

- The "Constant Current" mode keeps the LD current constant (and is used for fast laser modulation)

- The "Constant Power" mode uses the current of a PD placed inside the butterfly package to monitor the output power. 

I set the operation mode on "Costant Current" and make measurements of the optical power using a powermeter. I attach the pdf of the  measurements.

I couldn't use the "Constant power" mode because as soon as I switch on the laser, the  LD current reaches immediately the maximum (450mA as set before), even if I set the minimum PD current. It looks the controller is not able to measure the PD current, I attach a picture of this situation (pic1).

I also noticed that the PAF-X-11-C is bent (pic2) like Pisa's tower, I disassembled the clamp plate (pic3) and removed the "Bulkhead", which is the bent part, I think it is a fabrication defect.

Because Manuel claimed that the optical chopper has some problems,

I checked the chopper before sending it back.

[ CONCLUSION ]

The chopper has no problems and works well.