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AOS (Beam Reducing Telescopes)

kazuya.yokogawa - 20:31 Thursday 29 March 2018 (4589)

Installation of the GPT for green

[ Akutsu, K. Nagano, Ko. Yamamoto, Sugimoto, Yokogawa ]

Summary

We installed GPT(Gouy Phase Telescope) optics for the green beam. (Fig 1)

installed a periscope and the steering mirror1
measured the beam profile of the reflected beam from the steering mirror1
installed the GPT lens and the steering mirror2
measured the beam profile of the beam passed through the GPT lens
installed two QPDs and confirmed the signal from QPDs (The serial numbers of QPDs are '013' and '035'.)

Beam profile

I show the beam profile of the beam passed through the GPT lens.

180329tmsprofile2.png

The parameters obtained from the fitting are as follows.

Direction	M²	w₀[mm]	The waist position from the steering mirror1 [mm]
Horizontal	1.122	0.139477	708.516
Vertical	1.191	0.165963	826.164

From this result, we decided to install QPDs at the position of 600mm and 950mm from the first steering mirror.

Signal from QPDs

Finally, we confirmed the signal from QPDs (maybe Nagano-san will explain the detail).

Images attached to this report

Comments to this report:

koji.nagano - 23:25 Thursday 29 March 2018 (4592)

[K. Nagano, Yokogawa, Sugimoto, Ko. Yamamoto, Akutsu]

After placing two QPDs on TMSY bench, we checked signals from them.
Temporarily, we used EY0 ADC1 ch28--31 and IOP channels since RT model and cables for TMS were not prepared.
(Nominal TMS channels are ADC1 ch4--19.)
For both QPDs whose gain switch was turned to larger one, the measured mean counts in each channel (i.e. each element) are ~-220 when green light was on the QPD and about ~-200 when it was off.
This means green light corresponds to about 20 counts.
(In this measurement, room light was on but LED light was off.)

Tomorrow, we will connect two QPDs to the nominal channels and investigate their signals more after centering light.

koji.nagano - 8:12 Friday 30 March 2018 (4594)

Error correction

X (Nominal TMS channels are ADC1 ch4--19.) --> O (Nominal TMS channels are ADC0 ch4--19.)

kazuya.yokogawa - 1:32 Saturday 31 March 2018 (4606)

I forgot to report on the beam shape.

This is the shape of the passed through the GPT lens.

The beam was elliptical.

In addition, the beam shape occasionally spread to the lower right during the measurement.

Images attached to this comment