Topic better picmi gaus laser

lib/python/picongpu/picmi/gaussian_laser.py

@@ -1,7 +1,7 @@
 """
 This file is part of PIConGPU.
 Copyright 2021-2024 PIConGPU contributors
-Authors: Hannes Troepgen, Brian Edward Marre, Alexander Debus
+Authors: Hannes Troepgen, Brian Edward Marre, Alexander Debus, Richard Pausch
 License: GPLv3+
 """
 
@@ -13,6 +13,7 @@
 
 import typeguard
 import typing
+import logging
 
 
 @typeguard.typechecked
@@ -87,21 +88,15 @@ def __init__(
             **kw,
         )
 
-    def get_as_pypicongpu(self) -> laser.GaussianLaser:
-        util.unsupported("laser name", self.name)
-        util.unsupported("laser zeta", self.zeta)
-        util.unsupported("laser beta", self.beta)
-        util.unsupported("laser phi2", self.phi2)
-        # unsupported: fill_in (do not warn, b/c we don't know if it has been
-        # set explicitly, and always warning is bad)
-
+    def check(self) -> None:
+        # polarization direction is normalized
         assert self.testRelativeError(
             1,
             self.scalarProduct(self.polarization_direction, self.polarization_direction),
             1e-9,
         ), "the polarization direction vector must be normalized"
 
-        # check for excessive phase values to avoid numerical precision errors
+        # phase values not excessive to avoid numerical precision errors
         assert abs(self.picongpu_phase) <= 2 * math.pi, "abs(phase) must be < 2*pi"
 
         # check that initialising from y_min-plane only is sensible
@@ -110,36 +105,41 @@ def get_as_pypicongpu(self) -> laser.GaussianLaser:
         ), "laser propagation parallel to the y-plane or pointing outside \
             from the inside of the simulation box is not supported by this \
             laser in PIConGPU"
+
+        # propagation direction is normalized
         assert self.testRelativeError(
             1,
-            (
-                self.propagation_direction[0] ** 2
-                + self.propagation_direction[1] ** 2
-                + self.propagation_direction[2] ** 2
-            ),
+            self.scalarProduct(self.propagation_direction, self.propagation_direction),
             1e-9,
         ), "propagation vector must be normalized"
 
-        # check centroid outside box
+        # centroid outside box
         assert self.centroid_position[1] <= 0, "the laser maximum must be \
             outside of the \
             simulation box, otherwise it is impossible to correctly initialize\
             it using a huygens surface in the box, centroid_y <= 0"
+
         # @todo implement check that laser field strength sufficiently small
         # at simulation box boundary
+        # @todo extend this to other propagation directions than +y
 
-        # check polarization vector normalization
-
+        # polarization vector normalization
         assert self.testRelativeError(
             1,
-            (
-                self.propagation_direction[0] ** 2
-                + self.propagation_direction[1] ** 2
-                + self.propagation_direction[2] ** 2
-            ),
+            self.scalarProduct(self.propagation_direction, self.propagation_direction),
             1e-9,
         ), "polarization vector must be normalized"
 
+    def get_as_pypicongpu(self) -> laser.GaussianLaser:
+        util.unsupported("laser name", self.name)
+        util.unsupported("laser zeta", self.zeta)
+        util.unsupported("laser beta", self.beta)
+        util.unsupported("laser phi2", self.phi2)
+        # unsupported: fill_in (do not warn, b/c we don't know if it has been
+        # set explicitly, and always warning is bad)
+
+        self.check()
+
         pypicongpu_laser = laser.GaussianLaser()
         pypicongpu_laser.wavelength = self.wavelength
         pypicongpu_laser.waist = self.waist
@@ -148,11 +148,18 @@ def get_as_pypicongpu(self) -> laser.GaussianLaser:
         pypicongpu_laser.phase = self.picongpu_phase
         pypicongpu_laser.E0 = self.E0
 
-        pypicongpu_laser.pulse_init = max(
-            -2 * self.centroid_position[1] / (self.propagation_direction[1] * constants.c) / self.duration,
-            15,
+        # unit: multiple of laser pulse duration
+        pypicongpu_laser.pulse_init = (
+            -2.0 * self.centroid_position[1] / (self.propagation_direction[1] * constants.c) / self.duration
         )
-        # unit: duration
+
+        # @todo extend this to other propagation directions than +y
+        if pypicongpu_laser.pulse_init < 3.0:
+            logging.warning(
+                "set centroid_position and propagation_direction indicate that laser "
+                + "initalization might be too short.\n"
+                + f"Details: laser.pulse_init = {pypicongpu_laser.pulse_init} < 3"
+            )
 
         pypicongpu_laser.polarization_type = self.picongpu_polarization_type
         pypicongpu_laser.polarization_direction = self.polarization_direction

share/picongpu/pypicongpu/examples/laser_wakefield/main.py

@@ -1,7 +1,7 @@
 """
 This file is part of PIConGPU.
 Copyright 2024 PIConGPU contributors
-Authors: Masoud Afshari, Brian Edward Marre
+Authors: Masoud Afshari, Brian Edward Marre, Richard Pausch
 License: GPLv3+
 """
 
@@ -51,10 +51,12 @@
 
 solver = picmi.ElectromagneticSolver(grid=grid, method="Yee")
 
+laser_duration = 5.0e-15
+pulse_init = 15.0
 laser = picmi.GaussianLaser(
     wavelength=0.8e-6,
     waist=5.0e-6 / 1.17741,
-    duration=5.0e-15,
+    duration=laser_duration,
     propagation_direction=[0.0, 1.0, 0.0],
     polarization_direction=[1.0, 0.0, 0.0],
     focal_position=[
@@ -64,7 +66,7 @@
     ],
     centroid_position=[
         float(numberCells[0] * cellSize[0] / 2.0),
-        0.0,
+        -0.5 * pulse_init * laser_duration,
         float(numberCells[2] * cellSize[2] / 2.0),
     ],
     picongpu_polarization_type=pypicongpu.laser.GaussianLaser.PolarizationType.CIRCULAR,