In the following table, there is a summary of last measurements

"Depth" is the position of the incident sample surface with respect to the pump-probe cross point. According to the refraction effect, the cross point position inside the sample is double, so, given the sample thickness 60mm, the depth 30mm refers to the measurement at the opposite surface of the sample.

I attach the plots of the 6 sets of measurements.

Today I tried to do some measurements on a plane Beam splitter with the JASMINE setup.

Unfortunately, neither the laser nor the monitor were working... On the laser's power supply also no error signal has been shown. Just no signal at all. 

I wonder whether this is due to the humidity...

In order to test the configuration of the optical devices that will be used for the BS-OpLev in KAGRA, I simulated the basic setup of it on an optical table in the ATC.
For the position measurements, I have used a PSD (Position Sensing Detector) from Thorlabs (PDP90A).
The calibration of the PSD could be done in Y-direction only as the X-direction is not accessible due to the setup (for this I would need a 3-axis mount; the one used in the test was just a 2-axis mount). The resulting function Vy/Vsum is linear along the y-axis with a mean gradient of ca. 193 1/m (for comparison, the number that Eleonora has measured is 184 1/m for a PSD of the same type in TAMA).
A graph of the measured data along with a fit is shown in the attachment. Also shown are photos of the setup and a sketch of it.

I'm scanning the sample along the beam direction. I placed a translation stage with a micrometric screw below the mirror mount and set the sample height so that the pump goes at the centre of the sample.

Pictures 1,2,3 show how it was before.

Pictures 4,5 show the current setup.

I'm doing one measurement for each 5 mm of sample depth.

I did the same measurement for the 4th time but this time I covered better the pump path so that the scattered light is less.

The absorption value now is 4ppm/cm with a precision of 0.8 ppm/cm (after filtering).

This means that the pump stray light (1064nm) from outside the box gives a contribution of at least 2ppm/cm on the measure.

I couldn't cover the sample, but also the scattered light from the sample could give a significant contribution. So I would like to put a filter in front of the photodetector, to make only the probe light (633 nm) pass.

I ran another measurement with same experimental conditions as the ones in (entry 279), and made the same analysis of (entry 280) and (entry 281)

2016-07-25. Tama-size , 1h, rate: 100ms.

after filtering

I analyzed data of the two last measurements (entry 279), I made groups of 600 samples (1 minute) and I made the histogram for each group and the gaussian fit of the histograms.

I plot the fitted parameters of X/DC signal and Y/DC signal as a function of time (for each minute).

In blue the 0W pump data; in red the 9W pump data.

The thick line is the mean, the dashed lines are the mean ± sigma.

I did some analysis on the last absorption measurements (entry 279).

X, Y: output signal from Lock-in Amp.

I fitted the histograms of X and Y signals with gaussian. For raw data and for filtered data.

I calculated the precision of the measurement as std(sqrt( (X-Xo)^2 + (Y-Yo)^2 )) and used the calibration to get the ppm/cm

2016-07-20. Tama-size , 1h, rate: 100ms.

2016-07-21. Tama-size , 1h, rate: 100ms

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After average filtering, filter order: 600 (1min)

2016-07-20.

2016-07-21.

I removed again the translation stage and placed the tama-size mirror mount, tightly fixed to the optical board.

Yesterday I took 1h of data (rate 100ms) with the pump OFF and  1h of data with the pump ON (9W).

Today I repeated the same measurement: 1h at 0W and 1h at 9W.

I plot the raw data. Blue is the 0W data and red is the 9W data.

I will filter and calculate the ppm/cm.

I have calibrated the PSD used for the optical lever of the filter cavity mirrors. PSD model : PDP90A thorlab (see file attached).

I computed the calibration for 4 different values of the power (V_SUM should not exceed 4 V)

Mean = 0.00543 m  std = 0.00008 m

Normalised calibration seems reasonably independent of the power.

In order to recover the appropiate calibration ( m/V) to convert a voltage signal into a displacement of the beam on the PSD, this value shoud be dived by the measured V_SUM.

After closing the control loops of pitch and yaw of the telescope mirror in the PR tank, I tried to calibrated the signal in order to have an estimation of the angular motion of the mirror.

The displacement of the beam on the PSD given to a rotation in yaw on of an angle delta is given by

x  = 2* arm* delta

Where arm is the distance between the mirror and the PSD.  

A dispacement of the beam on the PSD of an amount x corresponds to a PSD voltage output of  x/cal.

So  delta = Vout*cal /(2*arm)

I measured the calibration factor of the PSD for 4 different powers in order to check if the normalized calibration (that is the calibration divided by the PSD voltage sum)  was constant.

I found 

mean (n_cal) = 0.0071      std (n_cal) = 0.0002     In order to recover the appropriate calibration (m/V) this value should be dived by the V_sum measured each time.

Assuming arm = 1.20 m +/- 0.15 m  (the precison on this measurement can be increased by measuring the optical lever arm next time we open PR tank)

and having measured V_sum = 13.3 V

we have

Cal_tot =  n_cal/(2*arm*V_sum) =  (2.2 +/- 0.3 ) e-4 [1/V]  (percentage error 13% to be improved by better measuring the arm)

The comparison between the calibrated spectra with open and closed loops for pitch and yaw is shown in figures 1 and 2.

Some remarks:

1)In both cases  the RMS seems to be dominate by the displacement in the region between 3-10 Hz.

2) Since the optical lever makes use of two steering mirrors directly fixed on the stack (see entry 262), this could not be a real motion of the mirror but a motion of the stack

3) This shoud be understood in order to improove the filter shape (Shoud we gain in that region or not?)

NB. For the pitch calibration we need to take into account an additional factor, equal to the the cosine of the incidence angle of the beam on the mirror (see 3rd attache picture)

y  = 2* arm* delta* cos(alpha)

THIS FACTOR  HAS NOT BEEN TAKEN INTO ACCOUNT IN THE PITCH PLOT WHICH SHOULD HAVE BEEN MULTIPLIED BY A FACTOR 1.412 (since alpha is 45°)

I ckecked the dimensions of BS intermediate mass.

I found that clamp parts are common for NM, EM ans BS itermediate masses.

Therefore, I can conclude that a hanging jig for NM and EM mirror can use for BS.

Since the fans of the booth have been off for a couple of months. I had to clean everything from the dust. I started from the top shelves, wiping one by one all the objects. I moved the boxes made of paperboard out of the clean booth because paperboard  is known to produce dust. I cleaned the optical table and all the objects on it. Wiping with a wet tissue was not enough because the tissue releases fibers and dust. So I used the strong green lamp to watch the dust particles, the spray air to blow on the surfaces to make the dust fly and the vacuum cleaner to blow it up from the air. The vacuum cleaner was outside, I only brought the pipe inside.  After that, I measured again the particles number.

This afternoon I measured the spectra and the transfer functions of the mirror installed on in the PR tank (to be used as a part of the injection telescope of the filter cavity).

The mirror motion in pich and yaw is sensed by means of a optical lever. The spectrum of the motion in the two degree of freedom is shown in fig1 and 2 of the attached file.

In order to measure the transfer functions, I injected white noise in pitch and yaw (with an amplitude of 3 V ).  To improve the diagonalization of the sensing, I changed the the sensing matrix appying a rotation of 0.04 rad. I have also slightly changed the driving matrix, to reduce the excitation of the yaw resonance when injecting noise on pitch. The comparison between the TFs before and after these changes are shown in fig 3-4 and 5-6 for yaw and pitch respectively.

When we install the BS suspension,

(1) one magnet came off, and

(2) the lower suspsnsion wires were broken.

Since one possible explanation of the  noise is dust, I used the particle counter to quantify the dust.

Instrument name: MET ONE Airborne Particle Counter HHPC6+

Acquisition time: 10 minutes

Volume: 28.36L

Inside the clean booth of Tama central room.

Almost the same order of a normal room. Indeed I realized that the fans of the clean booth were OFF since a couple of month ago, when I checked whether the acoustic noise was important.

I switched ON the fan and wait half an hour

After one hour

The morning after I came inside the clean booth and run the count

So it looks that an entire night doesn't clean the air much more than an hour.

Moving very gently I repeated the count

I think there is some dust on the everything, so when I move the air, the dust flies and make the count higher.

Then I moved the particle counter in the small clean booth on the small optical table that is used for gluing work

Very clean...

And then I went to clean room of ATC

I got some information about TAMA Faraday Isolator from Takahashi-san.

I upload these files here.

In the past days I have implemented the control of the end mirror of the filter cavity, following what was already done for the input mirror.

The transfer functions of the mirror motion, measured injecting white noise (with amplitude 3 V) in each degree of freedom, are plotted in the first figures of the attached document. In figure 4,open loop transfer functions are shown. In the last figures the comparison between the spectra with closed and open loops has been plotted.

I made a scan of the bulk reference sample for many positions of the detection unit as I did in this post for other samples.

The position closest to the sample is 34mm, which is the usual position. Other positions are gradually further from the sample.

Modulation reference is from the chopper at 430Hz. Pump power is 30mW before the sample.

Plot1 shows the scan of the sample for different positions of the detection unit. AC signal

Plot2 shows the scan of the sample for different positions of the detection unit. AC signal / DC

For each scan, I took the point at which the calibration value is taken (3^rd mm of the scan) and I took 10 minutes of data to check how the noise looks like with a large signal.

Plot3 shows  the calibration signal and noise (Y/DC vs X/DC) for each detection unit position.

Plot4 is a zoom of Plot3 

The following table is a summary of the values.

Error values are the size of the clouds of points on the XY plane (standard deviations)

I notice that

 - the calibration factor (R=AC/DC/abs/Power) doesn't change more than 10% when moving the detection unit and doesn't show a clear trend

 - the noise on the XY plane is more on the AC value rather than on the Phase value (in other words the cloud is squeezed )

 - both the AC and DC get smaller when putting the detection unit further.

 - the measurement at 10mm is not reliable because the reflection of the probe on the prism after the sample was on the boundary of the prism.

I placed back the magnetic translation stage and measure again the noise of the small sapphire sample. 

I took the measurement in two cases: with and without the small sapphire sample.

Acquisition time: 10 minutes, Rate 100ms, demodulation with the lockin internal oscillator frequency 420Hz.

Plot1 shows the 2D plot of the AC signal from the lockin after demodulation, divided by the DC.

Plot2 is a zooming of the first plot, the circles are centered on the mean of the signal over all the acquisition time and have a radius equal to the standard deviation.

It looks the system is noisier without the sample, this makes me think that vibrations of the sample don't make a lot of difference. I have the idea that most of the noise comes from the dust, and it depends on how we move the air during replacing of the sample or working inside the box.