Update documentation.

docs/source/usage/examples.rst

@@ -28,6 +28,7 @@ This section allows you to **download input files** that correspond to different
    examples/cfbend/README.rst
    examples/compression/README.rst
    examples/kicker/README.rst
+   examples/thin_dipole/README.rst
 
 
 Unit tests

docs/source/usage/parameters.rst

@@ -509,6 +509,13 @@ Lattice Elements
 
             * ``<element_name>.units`` (``string``) specification of units: ``dimensionless`` (default, in units of the magnetic rigidity of the reference particle) or ``T-m``
 
+        * ``thin_dipole`` for a thin dipole element.
+          This requires these additional parameters:
+
+            * ``<element_name>.theta`` (``float``, in degrees) dipole bend angle
+
+            * ``<element_name>.rc`` (``float``, in meters) effective radius of curvature
+
         * ``beam_monitor`` a beam monitor, writing all beam particles at fixed ``s`` to openPMD files.
           If the same element name is used multiple times, then an output series is created with multiple outputs.
 

docs/source/usage/python.rst

@@ -725,6 +725,15 @@ References:
    :param mapsteps: number of integration steps per slice used for map and reference particle push in applied fields
    :param nslice: number of slices used for the application of space charge
 
+.. py:class:: impactx.elements.ThinDipole(theta, rc)
+
+   A general thin dipole element.
+
+   :param theta: Bend angle (degrees)
+   :param rc: Effective curvature radius (meters)
+
+Reference:
+   * G. Ripken and F. Schmidt, Thin-Lens Formalism for Tracking, CERN/SL/95-12 (AP), 1995.
 
 Coordinate Transformation
 -------------------------

examples/thin_dipole/run_thin_dipole.py

@@ -0,0 +1,70 @@
+#!/usr/bin/env python3
+#
+# Copyright 2022-2023 ImpactX contributors
+# Authors: Axel Huebl, Chad Mitchell
+# License: BSD-3-Clause-LBNL
+#
+# -*- coding: utf-8 -*-
+
+import amrex.space3d as amr
+from impactx import ImpactX, RefPart, distribution, elements
+
+sim = ImpactX()
+
+# set numerical parameters and IO control
+sim.particle_shape = 2  # B-spline order
+sim.space_charge = False
+# sim.diagnostics = False  # benchmarking
+sim.slice_step_diagnostics = True
+
+# domain decomposition & space charge mesh
+sim.init_grids()
+
+# load initial beam
+kin_energy_MeV = 5.0  # reference energy
+bunch_charge_C = 1.0e-9  # used with space charge
+npart = 10000  # number of macro particles
+
+#   reference particle
+ref = sim.particle_container().ref_particle()
+ref.set_charge_qe(1.0).set_mass_MeV(938.27208816).set_kin_energy_MeV(kin_energy_MeV)
+
+#   particle bunch
+distr = distribution.Waterbag(
+    sigmaX=1.0e-3,
+    sigmaY=1.0e-3,
+    sigmaT=0.3,
+    sigmaPx=2.0e-4,
+    sigmaPy=2.0e-4,
+    sigmaPt=2.0e-4,
+    muxpx=-0.0,
+    muypy=0.0,
+    mutpt=0.0,
+)
+sim.add_particles(bunch_charge_C, distr, npart)
+
+# add beam diagnostics
+monitor = elements.BeamMonitor("monitor", backend="h5")
+
+# design the accelerator lattice)
+ns = 1  # number of slices per ds in the element
+segment = [
+    elements.Drift(ds=0.003926990816987, nslice=ns),
+    elements.ThinDipole(theta=0.45, rc=1.0),
+    elements.Drift(ds=0.003926990816987, nslice=ns),
+]
+bend = 200*segment
+
+inverse_bend = elements.ExactSbend(ds=-1.570796326794897,phi=-90.0)
+
+sim.lattice.append(monitor)
+sim.lattice.extend(bend)
+sim.lattice.extend(inverse_bend)
+sim.lattice.append(monitor)
+
+# run simulation
+sim.evolve()
+
+# clean shutdown
+del sim
+amr.finalize()

src/python/elements.cpp

@@ -471,6 +471,18 @@ void init_elements(py::module& m)
     ;
     register_beamoptics_push(py_SoftQuadrupole);
 
+    py::class_<ThinDipole, elements::Thin> py_ThinDipole(me, "ThinDipole");
+    py_ThinDipole
+        .def(py::init<
+                amrex::ParticleReal const,
+                amrex::ParticleReal const>(),
+             py::arg("theta"), py::arg("rc"),
+             "A thin kick model of a dipole bend."
+        )
+    ;
+    register_beamoptics_push(py_ThinDipole);
+
+
     // free-standing push function
     m.def("push", &Push,
         py::arg("pc"), py::arg("element"), py::arg("step")=0,