13.12 Highlights of What’s New in Version 2020.3

Here is a summary of what’s changed since release 2020.2.

13.12.1 Bug Fixes for Elements

• The KQUAD and KSEXT elements had a bug when computing beam moments with moments_output if the XKICK or YKICK values were nonzero. This was reported by G. Penn (LBNL).
• The MALIGN was affecting floor coordinates, which actually doesn’t make much sense. This was changed, but the prior behavior can be restored by setting FLOOR=1.
• Lost particle coordinates inside CSBEND elements were recording the wrong value of the longitudinal coordinate. The reported coordinate was a mixture of the central path length and the individual particle’s path length, whereas the correct coordinate should be just the central path length.
• The FRFMODE and TFRFMODE elements had a bug that caused them to use up all the available file descriptors on a system when many such elements were inserted. This was reported by J. England (SLAC).

13.12.2 Bug Fixes for Commands

• Issues were resolved with the computation of the s coordinate for sigma and centroid output files when invoking backtracking mode from run_setup.
• The ion_effects command had a bug in the automatic bin size selection code that could result in pathological changes in the bin size over several bunches. This was found and fixed by J. Calvey (APS).
• When saving a lattice with output_seq=1, RFCA and other elements with the PHASE_REFERENCE parameter would have this parameter set to very large values. This bug was reported by Z. Duan (IHEP).

13.12.3 New and Modified Elements

• The SCRIPT element can now be used in backtracking mode. See the manual page for details. This was requested by Y. Park (UCLA).
• The MATTER element now accepts PRESSURE and TEMPERATURE values, which are used to compute the density according to the ideal gas law, allowing easier simulation of scattering from gasses.
• The CSBEND element now supports steering fields via the XKICK and YKICK parameters. The FSE and FSE_DIPOLE parameters can also be used for horizontal steering.
• The CCBEND element now supports horizontal steering via the XKICK parameter. One can also use the FSE and FSE_DIPOLE parameters.
• The CSBEND element now supports a new symplectic nonlinear edge model, developed by R. Lindberg (APS).
• The BRAT and BMXYZ elements, which propagate particles through 3D field maps for bending and non-bending elements, respectively, now offer higher-order 2D interpolation as an alternative to the detail multi-linear interpolation. The also support storing the field data in single-precision arrays to reduce memory requirements.
• The BRAT and BMXYZ elements now supports testing of particle locations against the global-coordinate obstruction contours specified by the obstruction_data command.
• The BRAT element now supports floor coordinate transformations.
• The TFBDRIVER element now supports individual gain factors for each bunch. This was requested by M. Venturini (LBNL).
• The BOFFAXE element now supports a high-order off-axis expansion for z-dependent sextupole fields.

13.12.4 New and Modified Commands

• The twiss_output command can now compute lattice functions for a half periodic cell, i.e., a cell with mirror symmetry, by setting matched=-1. This was inspired by a forum question from mcarla.
• The obstruction_data command now supports periodic replication of the obstructions for rings, as well as a global cap on the minimum and maximum vertical coordinates.
• The tune_shift_with_amplitude command now uses an improved 2D polynomial fitting routine in all the tracking-based modes. Discussions with Y.P. Sun (APS) motivated this change.
• The corrector-pegging feature of the trajectory/orbit correction command correct now works better. In particular, when a corrector is pegged, the iteration stops until the response matrix can be recomputed. Printouts and other output now reflect this.

13.12.5 Changes Specific to the MPI Parallel Version

• None.

13.12.6 Changes Specific to the GPU Version

The GPU version continues to be an alpha release and contains bugs. Users are encouraged to check results against the serial or parallel versions and report issues to the developers.

• None.

13.12.7 Changes to Related Programs and Files

• None.