Undulator Parameters

The normalized, dimensionless rms undulator parameter, defined by AW0 = (e/mc)(B_u/k_u), where e is the electron charge, m is electron mass, c is speed of light, k_u=2/_u is the undulator wave number, _u is the undulator period. B_u is the rms undulator field with B_u = B_p/2 for a planar undulator and B_u = B_p for a helical undulator, where B_p is the on-axis peak field.

Flag indicating the undulator type. A value of zero indicates a planar undulator, any other value a helical one.

Normalized natural focusing of the undulator in x. Common values are XKX = 0.0, XKY = 1.0 for a planar undulator or XKX, XKY = 0.5 for a helical undulator, but might vary if focusing by curved pole faces is simulated. The values should fulfill the constraint XKX + XKY = 1.0.

Normalized natural focusing of the undulator in x. See XKX for more information.

The coupling factor of the electron beam to the radiation field due to the longitudinal wiggle motion of the electrons. It is 1.0 for a helical undulator and J₀(x) - J₁(x) for a planar undulator where J₀(x), J₁(x) are Bessel functions and x = AW0²/2(1+AW0²). If FBESS0 is set to 0.0 GENESIS 1.3 calculates the value.

The undulator period length.

The number of periods within a single undulator module. The product of NWIG and XLAMD defines the length of the undulator module.

The number of sections of the undulator. Note that a section length in not automatically identical with the undulator module length. GENESIS 1.3 aligns modules to the FODO-lattice. If a module ends within a FODO cell the next module starts with the beginning of the next cell. Sometimes this results in a longitudinal gap between adjacent undulator modules.

A virtual undulator parameter for the gap between undulator modules. The only purpose of this parameter is to delay the longitudinal motion of the electrons in the same manner as AW0 does within the undulator modules. It is used to keep the electron and radiation phases synchronize up to the point when the interaction at the next undulator module starts again. AWD has typically the same value as AW0, but might vary for optimum matching between the modules.

Start of undulator tapering. Note that tapering is applied, even the magnetic lattice is defined by an external file.

The relative change of the undulator field over the entire taper length (AW(exit) = (1 - WCOEFZ(2)) AW(entrance)). In the case of a multi section undulator GENESIS 1.3 tapers the magnetic field over the gaps as well, resulting in a jump of the magnetic field AW(z) between two modules.

The taper model:
= 1 for linear taper,
= 2 for quadratic taper,
or no taper otherwise.

Type of undulator field errors. Either a uniform (+/-1) or Gaussian (+/- 2) distribution can be chosen. If IERTYP is negative the errors are correlated to minimize the first and second field integral. IERTYP =0 disables field errors. Field errors requires a integration step size of half an undulator period (DELZ = 0.5). Note that field errors are applied even if the magnetic lattice is defined by an external file.

RMS value of the undulator field error distribution. A value of zero disables field errors.

The initial seeding of the random number generator for field errors.

Maximum offset in x for undulator module misalignment. The error for each individual module follows a uniform distribution

Maximum offset in y for undulator module misalignment. The error for each individual module follows a uniform distribution