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Last modified by rangeadm on 2025/04/23 16:13
From version 10.1
edited by cpassow
on 2020/09/22 14:02
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To version 9.1
edited by sndueste
on 2020/07/07 16:55
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1 -XWiki.cpassow
1 +XWiki.sndueste
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2 2  
3 3  The only input parameters are the center wavelength, spectral bandwidth and the pulse duration.
4 4  
5 -Below you can find a python implementation (by (% class="twikiNewLink" %)MartinB(%%)) of the partial coherence method as described in:
5 +Here you can find a small python script (by (% class="twikiNewLink" %)MartinB(%%)) implementing the partial coherence method as described in:
6 6  
7 -(% style="margin-left: 60.0px;" %)
8 -**Thomas Pfeifer et al. //Partial-coherence method to model experimental free-electron laser pulse statistics,// Opt. Lett. 35, 3441-3443 (2010);** [[link to the paper>>url:http://dx.doi.org/10.1364/OL.35.003441||shape="rect"]]
7 +* **Thomas Pfeifer et al. //Partial-coherence method to model experimental free-electron laser pulse statistics,// Opt. Lett. 35, 3441-3443 (2010);** [[link to the paper>>url:http://dx.doi.org/10.1364/OL.35.003441||shape="rect"]]
9 9  
10 -==
11 -Examples: ==
9 +\\
12 12  
13 -[![Binder]([[https:~~/~~/mybinder.org/badge_logo.svg>>url:https://mybinder.org/badge_logo.svg||shape="rect"]])]([[https:~~/~~/mybinder.org/v2/git/https%3A%2F%2Fgitlab.desy.de%2Fchristopher.passow%2Fsase-pulses/master?filepath=simulating_SASE_pulses.ipynb>>url:https://mybinder.org/v2/git/https%3A%2F%2Fgitlab.desy.de%2Fchristopher.passow%2Fsase-pulses/master?filepath=simulating_SASE_pulses.ipynb||shape="rect"]])
11 +The pulse shapes in time AND corresponding spectral distribution can be easily created with:
14 14  
13 +* (((
14 +a python script
15 +
16 +{{expand title="Click here to expand the script ..."}}
17 +import numpy as np
18 +import matplotlib.pyplot as plt
19 +
20 +def GetSASE(CentralEnergy, dE_FWHM, dt_FWHM, samples=0, Axis=True):
21 +h=4.135667662 #in eV*fs
22 +dE=dE_FWHM/2.355 #in eV, converts to sigma
23 +dt=dt_FWHM/2.355 #in fs, converts to sigma
24 +if samples == 0:
25 +samples=int(400.*dt*CentralEnergy/h)
26 +else:
27 +if (samples < 400.*dt*CentralEnergy/h):
28 +print("Number of samples is a little small, proceeding anyway. Got", samples, "prefer more than",400.*dt*CentralEnergy/h)
29 +
30 +EnAxis=np.linspace(0.,20.*CentralEnergy,num=samples)
31 +EnInput=np.zeros(samples, dtype=np.complex64)
32 +EnInput=np.exp(-(EnAxis-CentralEnergy)~*~*2/2./dE~*~*2+2*np.pi*1j*np.random.random(size=samples))
33 +En_FFT=np.fft.fft(EnInput)
34 +TAxis=np.fft.fftfreq(samples,d=(20.*CentralEnergy)/samples)*h
35 +TOutput=np.exp(-TAxis~*~*2/2./dt~*~*2)*En_FFT
36 +EnOutput=np.fft.ifft(TOutput)
37 +if (Axis):
38 +return EnAxis, EnOutput, TAxis, TOutput
39 +else:
40 +return EnOutput, TOutput
41 +
42 +\\
43 +
44 +# set the main parameters here:
45 +CentralEnergy=80. # in eV
46 +bandwidth=0.5 # bandwidth in %
47 +dt_FWHM=30. # FWHM of the temporal duration on average
48 +
49 +dE_FWHM=CentralEnergy/100 *bandwidth # calculate bandwidth of the spectrum in eV
50 +
51 +# calculate 3 SASE pulses
52 +EnAxis, EnOutput, TAxis, TOutput = GetSASE(CentralEnergy=CentralEnergy, dE_FWHM=dE_FWHM, dt_FWHM=dt_FWHM)
53 +EnAxis2, EnOutput2, TAxis2, TOutput2 = GetSASE(CentralEnergy=CentralEnergy, dE_FWHM=dE_FWHM, dt_FWHM=dt_FWHM)
54 +EnAxis3, EnOutput3, TAxis3, TOutput3 = GetSASE(CentralEnergy=CentralEnergy, dE_FWHM=dE_FWHM, dt_FWHM=dt_FWHM)
55 +
56 +
57 +# plot spectrum
58 +ax1 = plt.subplot(1, 2, 1)
59 +plt.plot(EnAxis,np.absolute(EnOutput),EnAxis2,np.absolute(EnOutput2),EnAxis3,np.absolute(EnOutput3) )
60 +plt.xlim(CentralEnergy-2.*dE_FWHM,CentralEnergy+2.*dE_FWHM)
61 +plt.title('Average pulse duration: %.1f fs' % dt_FWHM )
62 +ax1.set_xlabel('Photon energy in eV')
63 +ax1.set_ylabel('spectral intensity')
64 +
65 +# plot time structure
66 +ax1 =plt.subplot(1, 2, 2)
67 +plt.plot(TAxis,np.absolute(TOutput),TAxis2,np.absolute(TOutput2), TAxis3,np.absolute(TOutput3))
68 +plt.xlim(-2.*dt_FWHM,+2.*dt_FWHM)
69 +ax1.set_xlabel('time in fs')
70 +ax1.set_ylabel('pulse amplitude')
71 +
72 +plt.show()
73 +{{/expand}}
74 +)))
75 +* or the same as a Jupyter Notebook** [[attach:GenerateSASE.ipynb]] **
76 +
77 +==
78 +Some examples: ==
79 +
15 15  //CentralEnergy=80 # in eV//
16 16  
17 17  //bandwidth=0.5 # bandwidth in %//