NAOJ GW Elog Logbook 3.2
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.
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.
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.
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.
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.
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).
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
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.
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.
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.
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):
- A baseplate (see picture 1)
- A three layer stack made of rubber and metal blocks (see picture 2)
- A top-plate
- 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.
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.
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...
We star by checked the double-pendulum system which were moved form warehouse to TAMA central room.
We found that coil mass and electric cable were missing (fig 1-2).
We opened PD vacuum chamber and we found a completely assembled isolator stack with a double-pendulum system (fig 3).
(It was meant to be used to suspend a signal recycling mirror in TAMA.)
We checked this system too and we found that just the electric connectig cable was missing.
Since this vibration isolation system (both double pendulum and stack isolator) is in a better condition than the one stored in the warehouse,
we planned to use this one for suspending filter cavity input mirror in NM2 vacuum tank.
In order to do that, we checked that system dimensions were compatible with the ones needed for NM2 tank (fig 4-5).
Next week we will remove current TAMA SAS system from NM2 vacuum tank and we will replace it with the vibration isolation system at present placed in PD vacuum chamber.
On 11 November, we finished the following works.
1) fixing the TAMA SAS system,
2) unscrewing TAMA SAS system from the bottom of the vacuum tank. and
3) we found a hanging frame for TAMA SAS system at TAMA west-end room.
Ishizaki-san will move it to TAMA center room.
4) a double-pendulum system and bottom plate of the stack isolator
were moved from warehouse to TAMA center room.
Now TAMA SAS system is ready to remove.
Workers: Eleonora, Tatsumi
[ WORKERS ] Tatsumi and Takahashi
We opened the tank and then check TAMA SAS system
to remove from the tank.
You can find the procedure to air explosure of NM2 tank
bellow.
I did again measurements on the surfaces of some new SiC samples.
The number of samples this time was 6 from two companies: 3 samples from "NihonFineCeramics" and 3 samples from "Coorstek".
The average surace height distribution (Sa) has been found with Zygos NewView instrument to be 10 ~ 12 nm, for all samples. The measured window has been chosen to be 3x3 mm (2.5x mag.). Thus, the resolution is not particular high. Therefore, and also as we found some irregularities in the measured Sa values at higher resolutions (50x mag.), we made an additional measurement with the AFM in ATC on a randomly chosen spot of the third sample from "Croostek". The determined value of Sa with the AFM is 16.2 nm.
Attached to this report are the taken pictures of the height profiles. The first three are from "Croostek", the other three from "NihonFineCeramics". In black/white, the AFM picture is shown.
I used the Fresnel laws to determine wether or not the angle 12° would affect the Reflection measurement.
If the light was polarized the difference between 12° and 0° would be 2.5%
But the spectrophotometer SolidSpec-3700 have unpolarized light, and the difference between 12° and 0° is a factor of 1.5e-5 (0.0015%).
Not enough to affect the measurement, unless the light was polarized for some reason.
Members: Tatsumi-san, Manuel
Before making the glueing work it is necessary to pour First Contact polymer on the central area of mirror surface. We tried to do that but we had some troubles. I attach the pictures to show the problem. If the flow from the bottle is not continuous, the liquid splatters around and so we got some droplets in the area which is not to be covered by FirstContact. So we had to add FirstContact on the droplets and peel it up to clean them. The droplets went also on the edge and we had to apply the FirstContact with a brush. and using a smaller bottle.
