Add documentation.

docs/source/usage/parameters.rst

@@ -409,7 +409,7 @@ Lattice Elements
 
             * ``<element_name>.nslice`` (``integer``) number of slices used for the application of space charge (default: ``1``)
 
-        * ``shortrf`` for a short RF (bunching) cavity element.
+        * ``buncher`` for a short RF cavity (linear) bunching element.
           This requires these additional parameters:
 
             * ``<element_name>.V`` (``float``, dimensionless) normalized voltage drop across the cavity
@@ -420,6 +420,23 @@ Lattice Elements
 
                 = 2*pi/(RF wavelength in m)
 
+        * ``shortrf`` for a short RF cavity element.
+          This requires these additional parameters:
+
+            * ``<element_name>.V`` (``float``, dimensionless) normalized voltage drop across the cavity
+
+                = (maximum energy gain in MeV) / (particle rest energy in MeV)
+
+            * ``<element_name>.freq`` (``float``, in Hz) the RF frequency
+
+            * ``<element_name>.phase`` (``float``, in degrees) the synchronous RF phase
+
+                phase = 0: maximum energy gain (on-crest)
+
+                phase = -90 deg:  zero energy gain for bunching
+
+                phase = 90 deg:  zero energy gain for debunching
+
         * ``uniform_acc_chromatic`` for a region of uniform acceleration, with chromatic effects included.
            The Hamiltonian is expanded through second order in the transverse variables (x,px,y,py), with the exact pt dependence retained.
            This requires these additional parameters:

docs/source/usage/python.rst

@@ -602,13 +602,21 @@ References:
    :param B: Magnetic field in Tesla; when B = 0 (default), the reference bending radius is defined by r0 = length / (angle in rad),   corresponding to a magnetic field of B = rigidity / r0; otherwise the reference bending radius is defined by r0 = rigidity / B.
    :param nslice: number of slices used for the application of space charge
 
-.. py:class:: impactx.elements.ShortRF(V, k)
+.. py:class:: impactx.elements.Buncher(V, k)
 
-   A short RF cavity element at zero crossing for bunching.
+   A short RF cavity element at zero crossing for bunching (MaryLie model).
 
    :param V: Normalized RF voltage drop V = Emax*L/(c*Brho)
    :param k: Wavenumber of RF in 1/m
 
+.. py:class:: impactx.elements.ShortRF(V, freq, phase)
+
+   A short RF cavity element (MAD-X model). 
+
+   :param V: Normalized RF voltage V = maximum energy gain/(m*c^2)
+   :param freq: RF frequency in Hz
+   :param phase: RF synchronous phase in degrees (phase = 0 corresponds to maximum energy gain, phase = -90 corresponds go zero energy gain for bunching)
+
 .. py:class:: impactx.elements.ChrUniformAcc(ds, k, nslice=1)
 
    A region of constant Ez and Bz for uniform acceleration, with chromatic effects included.