Attocube - Test Bench
Table of Contents
1 Estimation of the Spectral Density of the Attocube Noise
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') Ts = 0.1; % [s]
Figure 1: Long measurement time domain data
We can see in Figure 1 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 2.
t1 = 11; t2 = 17; % [h] x = x(t > t1*60*60 & t < t2*60*60); x = x - mean(x); t = t(t > t1*60*60 & t < t2*60*60); t = t - t(1);
Figure 2: Kept data (removed slow drifts during the first hours)
The Power Spectral Density of the measured displacement is computed
win = hann(ceil(length(x)/20)); [p_1, f_1] = pwelch(x, win, [], [], 1/Ts);
1.2 Short and Fast measurement
An second measurement is done in order to estimate the high frequency noise of the interferometer. The measurement is done with a sampling time of \(T_s = 0.1\,ms\) and a duration of ~100s.
load('./mat/test.mat', 'x', 't') Ts = 1e-4; % [s]
The time domain measurement is shown in Figure 3.
Figure 3: Time domain measurement with the high sampling rate
The Power Spectral Density of the measured displacement is computed
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
The computed ASD of the two measurements are combined in Figure 4.
Figure 4: Obtained Amplitude Spectral Density of the measured displacement