Highlights of What’s New in Version 2019.4.0

Here is a summary of what’s changed since release 2019.3.0. Historical change logs are collected in Section 16.

The ILMATRIX element lacked path-length terms related to the betatron amplitude, and also did not properly handle non-zero α_x,y and η_x,y^′, as pointed out by forum user Teresia.
A bug was fixed in back-tracking for SBEN elements with nonzero values for HGAP and FINT. This was reported by Y. Park (UCLA).

The bunched_beam command was not generating particle ID values when use_moments_output_values=1, as reported by Z. Duan (IHEP).

Added SPARSE_INTERVAL parameter to the WATCH element, to allow sparsing coordinate output with regular spacing. This supplements the FRACTION parameter, which provides random sampling, and the START_PID and END_PID parameters, which provide sampling of a subset defined by particle ID.
Added RPN_PARAMETERS parameter to the SCRIPT element, which directs the program to load SDDS parameter values from the script output file into rpn variables, where they may be used for optimization. This provides the user the ability to perform script-based analysis of particle distributions and then optimize the results of that analysis.
The N_BINS parameter of the WAKE and TRWAKE elements now defaults to zero, which prevents some undesirable behavior when warnings are overlooked. This was requested by R. Lindberg (ANL).
The EDRIFT, EHVCOR, EHCOR, EVCOR, CSBEND, KQUAD, KSEXT, KOCT, and UKICKMAP elements can now be used with back-tracking (see run_setup).

The chaos_map command is now available. As the name suggests, it is similar to a frequency map, but provides other measures of chaotic motion. This includes a promising new approach outlined by Y. Li et al. [56].
The optimization_variable command has a new parameter differential_limits, which permits specifying that the lower and upper limits are being given relative to the initial value, rather than in absolute terms.
The tune_footprint command has a new parameter separate_xy_for_delta, which permits specifying that tracking for the x and y momentum-dependent tunes should be done either in a combined fashion (default) or separately. The latter might be helpful if nonlinear coupling of y motion into the x plane causes the x tune to be poorly determined for small x amplitudes.
Added egaussian mode to the ion_effects command. This mode results in computation of the fields from the electrons assuming a gaussian distribution, as normal, but determines the kick to the ions based purely on momentum conservation. This was inspired by the work of M. Blasciewicz (BNL) and implemented with J. Calvey (ANL).
Added multiple_ionization_energy_peak and multiple_ionization_energy_rms parameters to the ion_effects command, allowing control of the peak and rms energy of ions produced by multiple ionization. This was done by J. Calvey (ANL).