COMPASS all

hands meeting 9/17

18/2007
Robert Ryne
Beam Dynamics Overview
Robert D. Ryne
COMPASS all

hands meeting
Sept 17

18, 2007
Fermilab
COMPASS all

hands meeting 9/17

18/2007
Robert Ryne
Overall Goals
•
Develop advanced beam dynamics capability
to meet the mission needs of DOE/SC HEP,
NP, and BES accelerator projects
•
Develop reusable software components to
produce a comprehensive, scalable (to
petascale), lasting accelerator modeling
capability for present and future
accelerator projects
COMPASS all

hands meeting 9/17

18/2007
Robert Ryne
COMPASS Beam Dynamics physics areas fall mainly in
7 categories
1.
Space

charge
2.
Beam

beam
3.
Multi

species
4.
Beam

environment
5.
Optics, errors, feedback
6.
High brightness e

beams, radiation
7.
IBS
COMPASS all

hands meeting 9/17

18/2007
Robert Ryne
Space Charge
•
Maintain SciDAC1 solvers, port/optimize
for SciDAC2 platforms
•
Develop/incorporate new solvers, working
math math/cs partners, to meet new
requirements (boundary conditions, etc)
—
See math/cs talks Tuesday
COMPASS all

hands meeting 9/17

18/2007
Robert Ryne
Beam

beam effects
•
Codes used
—
BeamBeam3D
—
Lifetime,Nimzovitch
COMPASS all

hands meeting 9/17

18/2007
Robert Ryne
BeamBeam3D
•
Developed by Ji Qiang
•
Multiple models (strong

strong, weak

strong)
•
Multi

slice (finite bunch length effects)
•
New algorithm

Shifted Green function

efficiently
treats long

range parasitic collisions
•
Particle

based decomp (perfect load balance)
•
Lorentz boost handles crossing angle collisions
•
Multi

IP collisions, varying phase advance,…
•
Arbitrary closed orbit sep (static or time

dep)
•
Applied to Tevatron, LHC, PEP

II, KEK

B, RHIC, RHIC/LARP
RHIC B

B

growth vs
x
,
y
•
Strong collaboration, code development by Stern et al at FNAL
—
Fourier 3D solver validated with observed synchro

betatron modes
—
Resistive

wall impedance model growth rate matches predictions
—
Chromaticity with coupled

motion maps and impedance matches predictions
—
Arbitrary bunch collision patterns w/ measured Tevatron optics & helix incorporated
COMPASS all

hands meeting 9/17

18/2007
Robert Ryne
BeamBeam3D code validation comparing with VEPP

II
data (E. Stern, A. Valisev, FNAL; J. Qiang, LBNL)
Beam

beam code validation comparing
with VEPP

II data
COMPASS all

hands meeting 9/17

18/2007
Robert Ryne
Sequence of frames from a BeamBeam3D simulation of a collision
at the Tevatron @ 200x nominal intensity (E. Stern, FNAL)
COMPASS all

hands meeting 9/17

18/2007
Robert Ryne
Lifetime, Nimzovitch
•
Developed by Andreas Kabel
•
LIFETIME application
—
Uses PLIBB to calculate lifetimes in storage
rings; applied to Tevatron, RHIC current wire
experiment, LHC
•
NIMZOVITCH
—
Strong

strong beam

beam code optimized for large
number of bunches/IP’s/parasitic crossings
COMPASS all

hands meeting 9/17

18/2007
Robert Ryne
Beam

beam plans
•
BeamBeam3D:
—
Implement wire compensation model
—
Implement rotating beam colliding w/crossing angle, test
on LHC luminosity monitor
—
Implement full nonlinear symplectic tracking
—
Implement quantum effects, test and perform high

resolution simulation of ILC beam

beam interactions
—
Incorporate solver into multi

physics framework
—
Use
to investigate antiproton intensity limits in the
Tevatron and the growth of multi

bunch modes and
electron cooling beam

beam compensation operation
COMPASS all

hands meeting 9/17

18/2007
Robert Ryne
Beam

beam plans, cont.
•
Nimzovitch:
—
Make Nimzovitch go away by reformulating under
enhanced PLIBB:
•
more physics (IBS, noise, imperfections)
•
low noise PIC
•
enforce symplectic correctness in 3D
•
beamline parallelization for multi

bunch calculations
•
Lifetime:
—
Apply PLIBB w/ IBS module to RHIC, experimental
validation
—
Strong

strong module: apply to LHC multi

bunch effects
COMPASS all

hands meeting 9/17

18/2007
Robert Ryne
Multi

species effects
•
Main emphasis on electron

cloud
•
2 approaches:
—
Full 3D using WARP/POSINST (A. Friedman, D. Grote, J.L.

Vay, M.
Furman, et al)
—
Quasi

static using QuickPIC (W. Mori, V. Decyk, T. Katsouleas et al)
e

i
+
halo
e

i
+
= ion
e

= electron
g
= gas
= photon
= instability
Positive
Ion Beam
Pipe
e

i
+
g
g
e

e

e

e

e

•
Ionization of

background gas

desorbed gas
•
ion induced emission from

expelled ions hitting vacuum wall

beam halo scraping
•
photo

emission from synchrotron radiation (HEP)
•
secondary emission
from electron

wall
collisions
COMPASS all

hands meeting 9/17

18/2007
Robert Ryne
Calculating the e

cloud effects in the ILC DR
wiggler is an
immense
numerical challenge
•
3D

fields and dynamics
•
Self

consistent (beam
electrons)
•
Large range of spatial scales (sets resolution,
memory req’t)
transverse:
longitudinal:
Must resolve beam
, but 3000 x 3000 x 6000 ~ 10
10

cell mesh!
•
Huge number of timesteps required
t =
(e

traverse <1 cell in 1 timestep)
COMPASS all

hands meeting 9/17

18/2007
Robert Ryne
E

cloud modeling using WARP

POSINST
•
3D field dynamics and dynamics
•
Fully self

consistent
•
Realistic boundary conditions
•
Detailed electron generation models
(POSINST, including energy
spectrum)
•
Drift Lorentz electron “mover”
(correct space charge w/out
resolving
cyclic orbit)
•
Mesh refinement
(spatial resolution only where needed

essential!)
•
Velocity sub

cycling
(small
t only for particles that need it)
•
Parallelized
QuickPIC uses a quasi

static model; under certain circumstances,
agrees well with self

consistent but is orders of magnitude faster
A 2

D slab of electrons
(macroparticles) is stepped backward
(with small time steps) through the
beam field and 2

D electron fields are
stacked in a 3

D array, that is used to
push the 3

D beam ions (with large
time steps) using maps (as in
HEADTAIL

CERN) or Leap

Frog (as in
QUICKPIC

UCLA/USC).
2

D slab of electrons
3

D beam
bend
drift
drift
quad
s
s
0
lattice
100x improvement with “no” loss in accuracy
QuickPIC: Pipelining
COMPASS all

hands meeting 9/17

18/2007
Robert Ryne
Calculation in boosted frame provides x10
n
speedup*

proton bunch through a given e
–
cloud

hose instability of a
proton bunch
Proton energy:
=
500 in Lab
•
L= 5 km, continuous
focusing
Code: WARP (Particle

In

Cell)
electron
streamlines
beam
proton bunch radius vs. z
CPU time:
•
lab frame:
>2 weeks
•
frame with
2
=512:
<30 min
Speedup x1000
*J.

L. Vay, PRL 98, 130405 (2007)
COMPASS all

hands meeting 9/17

18/2007
Robert Ryne
WARP

POSINST plans
•
Code needs development to perform run in boosted frame
and complete set of e

cloud related physics
—
Implementation of magnetoinductive (“Darwin”) model, or
reduce version of it if sufficient,
—
implement an interface linking zones of 3

D PIC
simulations to zones of MAPS transport in beween,
—
upgrade diagnostics to allow for results given in frame
different from the one of calculation,
—
implement self

consistent generation and tracking of
photo

electrons, based on Monte

Carlo methods,
—
implement adaptive macro

particle management
(reduction/coalescence),
—
upgrade parallel decomposition from 1

D to 2

D/3

D.
COMPASS all

hands meeting 9/17

18/2007
Robert Ryne
Beam

environment interactions
•
Maintain SciDAC1 wakefield modules,
port/optimize for SciDAC2 platforms
•
Implement circuit model for time

dep
beam loading effects
•
Fully self

consistent calculation using
VORPAL
COMPASS all

hands meeting 9/17

18/2007
Robert Ryne
Optics, errors, feedback
•
Maintain existing optics libraries that are
used in the BD framework, port/optimize
for SciDAC2 platforms
•
Extend multi

bunch capabilities
•
Implement models for dynamically changing
quantities (e.g. jitter), machine errors, and
feedback systems
COMPASS all

hands meeting 9/17

18/2007
Robert Ryne
High brightness electron beam dynamics
•
Codes used:
—
Elegant
—
IMPACT (collaboration with synergistic high
brightness e

beam activities at LBNL funded by
other sources)
•
Essential goal of this work is to support LCLS
commissioning, operation, and optimization with
fast, high

fidelity modeling tools
•
Large scale computing essential for detailed study
of the microbunching instability
COMPASS all

hands meeting 9/17

18/2007
Robert Ryne
Elegant: status and limitations
•
CSR and longitudinal space charge parallelized in elegant
•
Limited to ~60 million particles presently
•
With ~1.5 billion particles we could look at modulations on the 1 mm
level relevant to proposed laser/undulator beam heaters
•
Addressing I/O and memory management issues related to this
•
Present fast CSR algorithms are 1

d simplifications
•
Existing 3

d algorithms are coarse

grained, time

consuming
•
No standardized, accepted tools exist for transferring information
between various accelerator codes (elegant, IMPACT) and radiation
modeling codes (GINGER, GENESIS, SPUR)
•
No way to take a snapshot of an existing FEL, simulate it, then
compare simulated and real diagnostics
•
LCLS is already reporting [Frisch, PAC07] unexplained effects with
very short bunches in the first compressor
•
Must be able to optimize to match a selection of diagnostics, then
extrapolate to other diagnostics
FERMI FEL Microbunching Instability Simulated with elegant
BLS
BC1
BC2
Tiny initial density modulations
build up in bunch compression
systems due to CSR and space
charge. Gain increases
to ~2000

fold down to 25
m
modulation. Can't presently
go shorter than this!
COMPASS all

hands meeting 9/17

18/2007
Robert Ryne
IMPACT: status and limitations
•
Successfully used to perform 1B macroparticle
simulations of Fermi FEL linac
•
Limitations: 1D CSR model, difficult to use for
design optimization, simple matrix description of
RF elements, not fully integrated with FEL codes
COMPASS all

hands meeting 9/17

18/2007
Robert Ryne
1B particle simulation of microbunching in FERMI FEL
linac using IMPACT
Final Longitudinal Phase Space Distribution Using
10M
and
1B
particles (init. 15 keV energy spread, 2BCs)
COMPASS all

hands meeting 9/17

18/2007
Robert Ryne
Summary of ANL’s tasks/plans
•
Finish parallelization of
elegant
•
Develop accepted, robust interfaces among suite of
codes involved in FEL modeling
—
IMPACT (gun and linac modeling)
—
elegant (accelerator modeling and optimization)
—
GENESIS and GINGER (FEL modeling)
•
Develop integrated graphical user interface to provide
on

demand, high

fidelity modeling of data and experients
—
Selection of codes, algorithms, detail level
—
Utilizes data drawn from the control system
—
Utilizes high

performance computing resources
•
Develop optimizer based on genetic algorithm to provide
guidance on FEL performance improvement.
COMPASS all

hands meeting 9/17

18/2007
Robert Ryne
IMPACT development plans for high brightness e

beam
(funded by LDRD and other non

SciDAC projects)
•
Develop and implement interfaces for start

to

undulator parallel simulation
•
Fully self

consistent CSR (difficult!)
•
Automatic beam steering
•
Integration with optimization tool
•
Incorporate nonlinear model of RF beamline
elements
COMPASS all

hands meeting 9/17

18/2007
Robert Ryne
Frameworks
•
Synergia/SciDAC1
•
IMPACT suite
•
MaryLie/IMPACT
•
UPIC
•
PLIBB
COMPASS all

hands meeting 9/17

18/2007
Robert Ryne
Synergia/SciDAC1
•
See next talk
COMPASS all

hands meeting 9/17

18/2007
Robert Ryne
IMPACT
•
A code suite (linac design, 3D rms code, 2 parallel PIC tracking
codes) developed under SciDAC1
•
Includes IMPACT

Z and IMPACT

T 3D parallel PIC codes
•
Applicable to electron and ion accelerators
•
Recent enhancements
—
Cathode emission model; cathode image effects
—
Energy binning for large
E
—
Multi

charge state capability (RIA)
—
SW and TW structures
—
wakefields
—
1D CSR
•
IMPACT

T now widely used for
photoinjector modeling
—
BNL e

cooling project, Cornell ERL,
FNAL/A0, LBNL/APEX, ANL, JLAB,
SLAC/LCLS, Fermi@elettra
Emission from nano

needle tip
COMPASS all

hands meeting 9/17

18/2007
Robert Ryne
MaryLie/IMPACT (ML/I)
•
Hybrid code combining MaryLie beam optics
with IMPACT parallel PIC + new capabilities
—
Embeds operator splitting for all thick
elements
—
Allows mixed MaryLie and MAD input
—
New software modules (wakefields, soft

edge magnet models, …) add functionality
—
Performance optimization (R. Gerber,
NERSC staff)
•
Multiple uses all within in the same code
—
Particle tracking, envelope tracking, map
production, map analysis, lattice
functions, fitting.
•
User manual and example suite
•
Contributions from many people from many
disciplines (follows the SciDAC model)
damping ring simulation with MLI
COMPASS all

hands meeting 9/17

18/2007
Robert Ryne
PLIBB particle dynamics framework
•
Developed at SLAC (A. Kabel)
•
a general

purpose C++ framework for high

speed,
parallel tracking studies
•
fast and easily extensible through compile

time
polymorphism
•
easily applied: MAD{X,8} beamline parsers &
manipulators
•
physics: magnetic elements, cavities, wakefields,
beam

beam
•
analysis: statistics, differential algebra, collective
quantities
COMPASS all

hands meeting 9/17

18/2007
Robert Ryne
UPIC Framework for Parallel PIC
•
Developed by V. Decyk
•
Layered, Fortran based, but could be called from C/C++
•
Goals:
—
Rapid construction of new parallel PIC codes from trused components
—
High accuracy testbed for evaluating and verifying PIC algorithms
•
Supports
—
Multiple plasma models: electrostatic, Darwin, electromagnetic
—
Multiple boundary conditions: periodic, dirichlet, neumann, open3.
Multiple levels of accuracy: linear, quadratic, gridless4. Multiple
programming paradigms: procedural, object

oriented5. Multiple
parallel models: threads, message

passing.
•
Used in QuickPIC and other applications
COMPASS all

hands meeting 9/17

18/2007
Robert Ryne
Frameworks: Plans
•
See next talk
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