updates

main/laserstab.tex

@@ -41,7 +41,7 @@ The control noise will become negligible above 5Hz because the bandwidth for the
 \begin{figure}[h!]
 \centering
 \includegraphics[scale=0.7]{images/6dsens.PNG}
-\caption[6D sensitivity curve]{A comparison of the expected performance of the 6D isolator and that of current STS-2 seismometers (Figure taken from \cite{6d}).}
+\caption[6D sensitivity curve]{A comparison of the expected performance of the 6D isolator and that of current seismometers (Figure taken from \cite{6d}).}
 \label{6dsens}
 \end{figure}
 
@@ -71,7 +71,7 @@ The laser chosen as source for 6D is a 1064 nm RIO ORION Laser Module (see Fig.
 \label{rio}
 \end{figure}
 \noindent
-What we want from this source is a low-noise readout for the HoQIs inside the 6D tank, and thus the laser source needs to be as low noise in frequency fluctuations as possible at frequencies arond 10 mHz, because this is the range of frequencies where the 6D isolator is aimed to detect and control seismic noise: we are going to use two Rio Orion laser modules to obtain a frequency stabilization suitable for 6D requirements. Constraints to these requirements are mainly given by the HoQIs. For 6D readout, HoQIs are built in such a way that the arm length mismatch is as small as practically possible, e.g. L$_{6D}$ $<$ 3 mm. Limitations to this number are given by BOSEM size ($\pm$ 2 mm) and the ability to adjust it, once the devices are in vacuum. Another parameter to take into account is the noise of HoQIs, which is H = 6 $\times$ 10$^{-14}$ m/$\surd{Hz}$ at about 1 Hz \cite{hoqi}. Frequency fluctuations depend on both these parameters and we want it to meet the following requirement:
+What we want from this source is a low-noise readout for the HoQIs inside the 6D tank, and thus the laser source needs to be as low noise in frequency fluctuations as possible at frequencies arond 100 mHz, because this is the range of frequencies where the 6D isolator is aimed to detect and control seismic noise: we are going to use two Rio Orion laser modules to obtain a frequency stabilization suitable for 6D requirements. Constraints to these requirements are mainly given by the HoQIs. For 6D readout, HoQIs are built in such a way that the arm length mismatch is as small as practically possible, e.g. L$_{6D}$ $<$ 3 mm. Limitations to this number are given by BOSEM size ($\pm$ 2 mm) and the ability to adjust it, once the devices are in vacuum. Another parameter to take into account is the noise of HoQIs, which is H = 6 $\times$ 10$^{-14}$ m/$\surd{Hz}$ at about 1 Hz \cite{hoqi}. Frequency fluctuations depend on both these parameters and we want it to meet the following requirement:
 
 \begin{equation}
 \centering
@@ -199,7 +199,7 @@ The lasers can then be controlled via input modulation through the feedback cont
 \begin{figure}[h!]
 \centering
 \includegraphics[scale=0.3]{images/filter.png}
-\caption[Controller filter]{Bode plot of the three-step controller filter installed into the CDS (green) and of the closed-loop expected gain when this filter is applied (magenta). Since we want to lower the frequency noise below 0.1 Hz, the filter has been designed with a pole at 0.1 Hz: this design should push the gain from below 0.1 Hz, assuring stability when applied at lower frequencies. The resulting controller filter is the product of the three different filters applied.}
+\caption[Controller filter]{Bode plot of the three-step controller filter installed into the CDS (green) and of the closed-loop expected gain when this filter is applied (magenta). This design should push the gain from below 0.1 Hz, assuring stability when applied at lower frequencies.}
 \label{filter}
 \end{figure}
 
@@ -277,7 +277,7 @@ A picture of the experiment is in Fig. \ref{expsetup}.
 \begin{figure}[h!]
 \centering
 \includegraphics[scale=0.3]{images/result.png}
-\caption[Results of frequency stabilization tests]{Results of frequency stabilization with respect to th free running frequency noise: the in-loop red trace shows the frequency stabilized lasers as detected by the frequency counter, monitoring the beat-note between the two lasers in the lower frequency range. This trace is the best measurement we obtained below 1 Hz, where we reached 1.67 $\times$ 10$^4$ Hz/$\sqrt{Hz}$ at 0.05 Hz; The green trace is a test taken with the counter set to a higher frequency range: this test shows a result of 3.6 $\times$ 10$^3$ Hz/$\sqrt{Hz}$ at 1 Hz. This is also the test which showed the quietest results above 10 Hz, demonstrating that the HoQIs can reach a good level of stability in air. The black trace is the expected gain activated by the controllers, which is set to maximise the stabilization below 1 Hz.}
+\caption[Results of frequency stabilization tests]{Results of frequency stabilization with respect to the free running frequency noise: the in-loop red trace shows the frequency stabilized lasers as detected by the frequency counter, monitoring the beat-note between the two lasers in the lower frequency range. This trace is the best measurement we obtained below 1 Hz, where we reached 1.67 $\times$ 10$^4$ Hz/$\sqrt{Hz}$ at 0.05 Hz; The green trace is a test taken with the counter set to a higher frequency range: this test shows a result of 3.6 $\times$ 10$^3$ Hz/$\sqrt{Hz}$ at 1 Hz. This is also the test which showed the quietest results above 10 Hz, demonstrating that the HoQIs can reach a good level of stability in air. The black trace is the expected gain activated by the controllers, which is set to maximise the stabilization below 1 Hz.}
 \label{test}
 \end{figure}