Conclusion
It is impossible to measure a displacement of IFI STM 2.
Details
・Introduction
We conducted several experiments. The first one was to measure the displacement of a mirror holder, and the second one is to do the displacement an IFI STM2. The following sections detail the findings of each experiment.
・Displacement Measurement of a mirror holder
By testing the setup in a configuration similar to actual IFI measurements, we aim to understand the difficulties and identify potential bottlenecks in the process.
We constructed the setup as shown in the first attached photo to determine if the displacement of the flat surface of the mirror holder could be measured from approximately one meter away. An accelerometer (TEAC 710) was attached on the mirror holder mount. The output results of the accelerometer and displacement sensor (LV-9300A) are shown in the second and third attached picture, respectively. The resolution of the displacement sensor was 0.3 nm and 0.15 nm, respectively. Given the high coherence at the resonance peak, we conclude that the measurements were performed appropriately.
・IFI STM 2 Measurement
Firstly, I want to show position of STM2 and a view port in IFI chamber. Could you see the fourth picture, please.
Unfortunately, we were unable to perform the IFI STM 2 measurement as planned. There is no place that the alignment of the reflected light from the IFI STM 2 can achieve the displacement sensor (LV-9300A).
Consequently, we used the LK-500 (made by KEYENCE) to measure the displacement using diffusely reflected light. A picture of setup is shown in the fifth attached one, and the result of this measurement is the seventh attached one. A resolution of the L
K-500 used in this experiment was 50 μm, which was insufficient for our purposes, so we can't get good results. The higher resolution modes (resolution: 10µm) could not be used due to the distance between the port and the IFI STM 2.
We think that it is impossible (very difficult) to measure a displacement of IFI STM 2 from the above situation.
Postscript
You can know the output voltage from LK-500 on K1:PEM-PORTABLE_MCF_RACK_MCF0_ADC1_DSUB21_OUT_DQ, and from the accelerometer on K1:PEM-PORTABLE_MCF_RACK_MCF0_ADC1_DSUB21_OUT_DQ.
