13.9 Highlights of What’s New in Version 2021.2

Here is a summary of what’s changed since release 2021.1. Historical change logs are collected in Section 13.

13.9.1 Bug Fixes for Elements

• Beam moments calculations with the moments_output command now work correctly for CSBEND, CSRCSBEND, KQUAD, KSEXT, QUAD, SBEND, and SEXT elements in the presence of misalignments. Previously, if the misalignments were large the results would be unreliable.
• Beam moments computations for BGGEXP have been improved to use a tracking-based method for determination of the diffusion matrix. This can be turned off by setting tracking_based_diffusion_matrix_particles to 0 in the moments_output command.
• Radiation calculations for BGGEXP have been changed to correct the dependence of energy loss and energy spread on energy offset, as well as to correctly model direct effects on transverse momenta when the symplectic integrator is used.
• The MAPSOLENOID element contained a global sign error in using the magnetic fields. To restore the previous (incorrect) behavior, multiply the FACTOR parameter by -1.

13.9.2 Bug Fixes for Commands

• The bunched_beam and bunched_beam_moments commands previously did not use the centroids from moments_output when use_moments_output_values=1. This was fixed.
• The -pipe commandline option was broken, as reported by V. Sajaev (APS). This was fixed.
• The correct command no longer complains about diverging orbits and no longer adjusts the iteration fraction if the orbit is smaller than the accuracy requirement.
• The matrix_output command now respects the full_matrix_only setting for SDDS output. Also, the Step parameter is now set correctly.

13.9.3 New and Modified Elements

• The BEAMBEAM element was added. At present, it provides beam-beam kicks from a rigid opposing beam with a defined charge, center, and sizes, using either a gaussian or uniform ellipsoidal charge distribution. This was requested by A. Blednykh and M. Blaskiewicz (BNL).
• The BGGEXP element has five new parameters, FACTOR0, FACTOR1, FACTOR2, FACTOR3, and FACTOR4 which permit scaling the solenoidal, dipolar, quadrupolar, sextupolar, and octupolar field components independently.
• The BGGEXP and BMXYZ elements have three new parameters, BXFACTOR, BYFACTOR, and BZFACTOR, which allow multiplying the indicated field components by the given factors. This may be unphysical, but can provide helpful diagnostics.

13.9.4 New and Modified Commands

• The global_settings command has a new parameter, allow_overwriting which controls whether elegant is allowed to overwrite existing files. By default, it is allowed.
• The moments_output command now provides control of how many tracking-based matrices can be stored for reuse, via the tracking_based_matrices_store_limit parameter.
• The closed_orbit command has a new parameter, immediate, which allows requesting immediate computation of the closed orbit rather than the default computation as part of the major action.

13.9.5 Changes to Related Programs and Files

The elegant distribution includes many programs and scripts that perform computations with elegant output data, provide interfaces with other programs, or prepare data for use with elegant. These are listed in Section 8.

Changes to these tools in this release include

• computeCBGGE can now compute the expansion for solenoidal fields if provided with B_z data on a cylinder. Ryan Lindber (APS) provided the theoretical basis and helped with debugging.