From 7e6ff243037b074a65e144ff02877d5ac2533a0e Mon Sep 17 00:00:00 2001
From: Laurent Mercadier <laurent.mercadier@xfel.eu>
Date: Mon, 14 Mar 2022 21:52:49 +0100
Subject: [PATCH] add fluence calibration routine
---
doc/changelog.rst | 2 +-
src/toolbox_scs/misc/laser_utils.py | 90 +++++++++++++++++++++++++++--
2 files changed, 87 insertions(+), 5 deletions(-)
diff --git a/doc/changelog.rst b/doc/changelog.rst
index ee15b95..ed49140 100644
--- a/doc/changelog.rst
+++ b/doc/changelog.rst
@@ -19,7 +19,7 @@ unreleased
- improve SLURM scripts with named arguments :mr:`176`
- **New Features**
-
+ - add routine for fluence calibration :mr:`180`
1.5.0
-----
diff --git a/src/toolbox_scs/misc/laser_utils.py b/src/toolbox_scs/misc/laser_utils.py
index b284999..99698e1 100644
--- a/src/toolbox_scs/misc/laser_utils.py
+++ b/src/toolbox_scs/misc/laser_utils.py
@@ -1,10 +1,14 @@
__all__ = [
'degToRelPower',
'positionToDelay',
+ 'fluenceCalibration',
]
+import numpy as np
+import matplotlib.pyplot as plt
-def positionToDelay(pos, origin=0, invert = False, reflections=1):
+
+def positionToDelay(pos, origin=0, invert=True, reflections=1):
''' converts a motor position in mm into optical delay in picosecond
Inputs:
pos: array-like delay stage motor position
@@ -15,18 +19,96 @@ def positionToDelay(pos, origin=0, invert = False, reflections=1):
Output:
delay in picosecond
'''
- c_ = 299792458 *1e-9 # speed of light in mm/ps
+ c_ = 299792458 * 1e-9 # speed of light in mm/ps
x = -1 if invert else 1
return 2*reflections*(pos-origin)*x/c_
-
+
+
def degToRelPower(x, theta0=0):
''' converts a half-wave plate position in degrees into relative power
between 0 and 1.
Inputs:
x: array-like positions of half-wave plate, in degrees
theta0: position for which relative power is zero
-
+
Output:
array-like relative power
'''
return np.sin(2*(x-theta0)*np.pi/180)**2
+
+
+def fluenceCalibration(hwp, power_mW, npulses, w0x, w0y=None,
+ train_rep_rate=10, fit_order=1,
+ plot=True, xlabel='HWP [%]'):
+ """
+ Given a measurement of relative powers or half wave plate angles
+ and averaged powers in mW, this routine calculates the corresponding
+ fluence and fits a polynomial to the data.
+
+ Parameters
+ ----------
+ hwp: array-like (N)
+ angle or relative power from the half wave plate
+ power_mW: array-like (N)
+ measured power in mW by powermeter
+ npulses: int
+ number of pulses per train during power measurement
+ w0x: float
+ radius at 1/e^2 in x-axis in meter
+ w0y: float, optional
+ radius at 1/e^2 in y-axis in meter. If None, w0y=w0x is assumed.
+ train_rep_rate: float
+ repetition rate of the FEL, by default equals to 10 Hz.
+ fit_order: int
+ order of the polynomial fit
+ plot: bool
+ Plot the results if True
+ xlabel: str
+ xlabel for the plot
+
+ Output
+ ------
+ F: ndarray (N)
+ fluence in mJ/cm^2
+ fit_F: ndarray
+ coefficients of the fluence polynomial fit
+ E: ndarray (N)
+ pulse energy in microJ
+ fit_E: ndarray
+ coefficients of the fluence polynomial fit
+ """
+ power = np.array(power_mW)
+ hwp = np.array(hwp)
+ E = power/(train_rep_rate*npulses)*1e-3 # pulse energy in J
+ if w0y is None:
+ w0y = w0x
+ F = 2*E/(np.pi*w0x*w0y) # fluence in J/m^2
+
+ fit_E = np.polyfit(hwp, E*1e6, fit_order)
+ fit_F = np.polyfit(hwp, F*1e-1, fit_order)
+ x = np.linspace(hwp.min(), hwp.max(), 100)
+ if plot:
+ fig, ax = plt.subplots(figsize=(6, 4))
+ ax.set_title(f'w0x = {w0x*1e6:.0f} $\mu$m, w0y = {w0y*1e6:.0f} $\mu$m')
+ ax.plot(hwp, F*1e-1, 'o', label='data')
+ fit_label = 'F = '
+ for i in range(len(fit_F)-1, 1, -1):
+ fit_label += f'{fit_F[i]:.2g}x$^{i}$ + '
+ if i % 2 == 0:
+ fit_label += '\n'
+ fit_label += f'{fit_F[-2]:.2g}x + {fit_F[-1]:.2g}'
+ ax.plot(x, np.poly1d(fit_F)(x), label=fit_label)
+ ax.set_ylabel('Fluence [mJ/cm$^2$]')
+ ax.set_xlabel(xlabel)
+ ax.legend()
+ ax.grid()
+
+ def eTf(x):
+ return 1e-7*2*x/(np.pi*w0x*w0y)
+
+ def fTe(x):
+ return 1e7*x*np.pi*w0x*w0y/2
+ ax2 = ax.secondary_yaxis('right', functions=(fTe, eTf))
+ ax2.set_ylabel(r'Pulse energy [$\mu$J]')
+ fig.tight_layout()
+ return F*1e-1, fit_F, E*1e6, fit_E
--
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