# Accelerator Modelling and Advanced Computing

## AMAC Codes

AMAC staff members have developed or participated in the development of several state-of-the-art beam dynamics modeling packages. The most important of these is the IMPACT suite of codes, which is widely used throughout the accelerator community. The IMPACT suite was originally developed for modeling high intensity, high brightness beams in rf proton linacs, and has been greatly enhanced to include electron linacs, photoinjectors, and other types of accelerators. It consists of an rf linac lattice design code, a 3D rms envelope matching code, the 3D parallel PIC codes IMPACT-Z and IMPACT-T, and a number of pre- and post-processing utilities. Both PIC codes use a quasi-static model of the beam and calculate space-charge effects self-consistently at each step together with the external acceleration and focusing fields. There are several parallel Poisson solvers in the IMPACT suite that use different algorithms and that corresponding to various types of boundary conditions. These include convolution-based Greens function solvers, spectral solvers, and a wavelet-based solver. The parallel implementation of the PIC codes is based on a 2D domain decomposition. Besides 3D parallel space-charge, key features include a choice of particle advance algorithms, energy binning to treat large energy spread beams, tracking through detailed 3D external field distributions, wakefield effects, and a 1D Coherent Synchrotron Radiation (CSR) model.

In addition to the IMPACT suite, AMAC staff develop and maintain two other codes, BeamBeam3D and MaryLie/IMPACT. All these codes are described below.

**IMPACT-T:** IMPACT-T
is part of the IMPACT code suite. It uses time as the independent variable and
is used for modeling beam dynamics in photoinjectors and other types of
accelerators where a time-based model is needed. IMPACT-T has been used by
researchers at ANL, BNL, SLAC/LCLS, NIU/Fermilab, LANL, LBNL, UCLA, Cornell,
UW-Madison, PSI, INFN-Frascati, and Trieste/Elettra. Applications include ALS
streak camera studies, APS upgrade, BNL photoinjector, LCLS injector, Fermilab
A0 experiment, UCLA photoinjector, Cornell photoinjector, UW-Madison FEL photoinjector,
PSI FEL photoinjector, SPARC/X photoinjector, and the Fermi/Eletrra
photoinjector. IMPACT-T was developed by Ji Qiang.

**IMPACT-Z:** IMPACT-Z
is part of the IMPACT code suite. It uses arc length as independent variable.
IMPACT-Z was the first beam dynamics code in the USA used for performing
regular production runs with 1 billion macroparticles. IMPACT-Z has been used
by researchers at Fermilab, NIU, ORNL, LBNL, MSU, KEK, RIKEN, GSI, CERN, and
IHEP. Applications include Berkeley FEL studies, the LEDA Halo experiment, the
Fermilab booster, ILC, SNS, the RIA driver linac, the JPARC linac, the RIKEN
cyclotron injector, the GSI linac, the CERN SPL, and the CSNS linac. IMPACT-Z
was developed by Ji Qiang and Robert D. Ryne.

**BeamBeam3D:** BeamBeam3D
is a comprehensive PIC code for modeling beam-beam interactions in colliders.
It includes multi-bunch, multi-interaction point, and multi-slice modeling. It
is able to treat weak-strong and strong-strong collisions, head-on collisions,
long-range collisions, and crossing angle collisions. It is capable of
high-fidelity, realistic simulations of a large number of beam revolutions.
During the development of the strong-strong capability special attention was
given to the parallelization strategy, and three different approaches were
implemented and assessed: domain decomposition, particle decomposition with
field replication, and hybrid particle/field decomposition. Due to the extreme
particle movement between collisions, the conventional approach of domain
decomposition does not have the best performance. Instead, the hybrid
decomposition performs best and is used in the production code. BeamBeam3d has
been used by researchers at LBNL, Fermilab, and the Jefferson Laboratory.
Applications include the LHC, RHIC, Tevatron, and KEKB colliders. BeamBeam3D
was developed by Ji Qiang.

**MaryLie/IMPACT:** The MaryLie/IMPACT (ML/I) code is a 3D parallel PIC code that combines the
nonlinear optics capabilities of MaryLie 5.0 (the Maryland Lie Algebraic beam optics code developed by Prof. Alex
Dragt) with the parallel PIC space-charge capability of IMPACT-Z. In addition
to combining the capabilities of these codes, ML/I has a number of powerful new
features including a fifth-order rf cavity model (developed by Dan Abell of
Tech-X Corporation), an embedded envelope package, and multiple reference
particles for rf cavities. Several of
the code features are the result of a LANL collaboration on MaryLie, including
a library of soft-edge magnet models (developed by P. Walstrom), representation
of magnet systems in terms of coil stacks with possibly overlapping fields
(developed by F. Neri), and a fitting/optimization package (developed by C.T.
Mottershead). The combination of soft-edge magnet models, high-order
capability, and fitting plus optimization, makes it possible to simultaneously
remove third-order aberrations while minimizing fifth-order, in systems with
overlapping, realistic magnetic fields. The ML/I code allows for map
production, map analysis, particle tracking, and 3D envelope tracking, all
within a single, coherent user environment. ML/I has a front-end that can read
both MaryLie input and lattice descriptions in the Standard Input Format widely used in the accelerator community. The code can model beams with or
without acceleration, and with or without space charge. ML/I has been used by
researchers at LBNL, U. Maryland, Tech-X Corporation, and BNL. The main application currently is for modeling related to the RHIC luminosity upgrade. ML/I
has been developed by a team led by Robert D. Ryne involving LBNL, U. Maryland,
LANL, and Tech-X Corporation.