diff --git a/index.html b/index.html index 98ffb03..47c7508 100644 --- a/index.html +++ b/index.html @@ -3,7 +3,7 @@ "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd"> - + Attocube - Test Bench @@ -35,72 +35,72 @@

Table of Contents

-
-

1 Estimation of the Spectral Density of the Attocube Noise

+
+

1 Estimation of the Spectral Density of the Attocube Noise

-
+

test-bench-shematic.png

Figure 1: Test Bench Schematic

-
+

IMG-7865.JPG

Figure 2: Picture of the test bench. The Attocube and mirror are covered by a “bubble sheet”

-
-

1.1 Long and Slow measurement

+
+

1.1 Long and Slow measurement

The first measurement was made during ~17 hours with a sampling time of \(T_s = 0.1\,s\).

-
load('./mat/long_test2.mat', 'x', 't')
+
load('./mat/long_test_plastic.mat', 'x', 't')
 Ts = 0.1; % [s]
-
+

long_meas_time_domain_full.png

Figure 3: Long measurement time domain data

-Let’s fit the data with a step response to a first order low pass filter (Figure 4). +Let’s fit the data with a step response to a first order low pass filter (Figure 4). 

f = @(b,x) b(1)*(1 - exp(-x/b(2)));
 
-y_cur = x(t < 17*60*60);
-t_cur = t(t < 17*60*60);
+y_cur = x(t < 17.5*60*60);
+t_cur = t(t < 17.5*60*60);
 
 nrmrsd = @(b) norm(y_cur - f(b,t_cur)); % Residual Norm Cost Function
 B0 = [400e-9, 2*60*60];                        % Choose Appropriate Initial Estimates
@@ -112,26 +112,26 @@ B0 = [400e-9, 2*60
 
-2.0576
+2.0658
 

 
 
 
-

+

 
long_meas_time_domain_fit.png
 

 
Figure 4: Fit of the measurement data with a step response of a first order low pass filter

 

 
 

-We can see in Figure 3 that there is a transient period where the measured displacement experiences some drifts.
+We can see in Figure 3 that there is a transient period where the measured displacement experiences some drifts.
 This is probably due to thermal effects.
 We only select the data between t1 and t2.
-The obtained displacement is shown in Figure 5.
+The obtained displacement is shown in Figure 5.
 

 
 

-
t1 = 11; t2 = 17; % [h]
+
t1 = 10.5; t2 = 17.5; % [h]
 
 x = x(t > t1*60*60 & t < t2*60*60);
 x = x - mean(x);
@@ -141,7 +141,7 @@ t = t - t(1);
 

 
 
-

+

 
long_meas_time_domain_zoom.png
 

 
Figure 5: Kept data (removed slow drifts during the first hours)

@@ -176,8 +176,8 @@ f_1 = f_1(f_1 < 2);
 

 

 
-

-
1.2 Short and Fast measurement

+

+
1.2 Short and Fast measurement

 

 

 An second measurement is done in order to estimate the high frequency noise of the interferometer.
@@ -196,11 +196,11 @@ Ts = 1e-4; % [s]
 

 
 

-The time domain measurement is shown in Figure 6.
+The time domain measurement is shown in Figure 6.
 

 
 
-

+

 
short_meas_time_domain.png
 

 
Figure 6: Time domain measurement with the high sampling rate

@@ -210,22 +210,22 @@ The time domain measurement is shown in Figure 6.
 The Power Spectral Density of the measured displacement is computed
 

 

-
win = hann(ceil(length(x)/10));
+
win = hann(ceil(length(x)/20));
 [p_2, f_2] = pwelch(x, win, [], [], 1/Ts);
 

 

 

 

 
-

-
1.3 Obtained Amplitude Spectral Density of the measured displacement

+

+
1.3 Obtained Amplitude Spectral Density of the measured displacement

 

 

-The computed ASD of the two measurements are combined in Figure 7.
+The computed ASD of the two measurements are combined in Figure 7.
 

 
 
-

+

 
psd_combined.png
 

 
Figure 7: Obtained Amplitude Spectral Density of the measured displacement

@@ -234,22 +234,22 @@ The computed ASD of the two measurements are combined in Figure 
-
2 Effect of the “bubble sheet” and Aluminium tube

+

+
2 Effect of the “bubble sheet” and Aluminium tube

 

 
-

+

 
IMG-7864.JPG
 

 
Figure 8: Aluminium tube used to protect the beam path from disturbances

 

 

 
-

-
2.1 Aluminium Tube and Bubble Sheet

+

+
2.1 Aluminium Tube and Bubble Sheet

 

 

-
load('./mat/long_test_plastic.mat');
+
load('./mat/short_test_plastic.mat');
 Ts = 1e-4; % [s]
 

 

@@ -267,11 +267,11 @@ Ts = 1e-4; % [s]
 

 

 
-

-
2.2 Only Aluminium Tube

+

+
2.2 Only Aluminium Tube

 

 

-
load('./mat/long_test_alu_tube.mat');
+
load('./mat/short_test_alu_tube.mat');
 Ts = 1e-4; % [s]
 

 

@@ -282,7 +282,7 @@ Ts = 1e-4; % [s]
 

 
 

-The time domain measurement is shown in Figure 6.
+The time domain measurement is shown in Figure 6.
 

 

 
win = hann(ceil(length(x)/10));
@@ -292,15 +292,36 @@ The time domain measurement is shown in Figure 6.
 

 

 
-

-
2.3 Nothing

+

+
2.3 Nothing

+

+

+
load('./mat/short_test_without_material.mat');
+Ts = 1e-4; % [s]
+

 

 
-

-
2.4 Comparison

+

+
x = detrend(x, 0);
+

+

+
+

+The time domain measurement is shown in Figure 6.
+

+

+
win = hann(ceil(length(x)/10));
+[p_3, f_3] = pwelch(x, win, [], [], 1/Ts);
+

+

+

+

+
+

+
2.4 Comparison

 

 
-

+

 
asd_noise_comp_bubble_aluminium.png
 

 
Figure 9: Comparison of the noise ASD with and without bubble sheet

@@ -311,7 +332,7 @@ The time domain measurement is shown in Figure 6.
 

 

 
Author: Dehaeze Thomas

-
Created: 2020-11-02 lun. 16:06

+
Created: 2020-11-03 mar. 11:21

 

 
 
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