J.-L. Vay, ECLOUD04 -1-

The Heavy Ion Fusion Virtual National Laboratory

Status report on the merging of the electron-cloud code POSINST with the 3-D accelerator PIC code WARP

31st ICFA Advanced Beam Dynamics Workshop on Electron-Cloud EffectsNapa, California

April 19-23, 2004

J.-L. Vay, M. A. Furman, A. W. AzevedoLawrence Berkeley National Laboratory

R. H. Cohen, A. Friedman, D. P. GroteLawrence Livermore National Laboratory

P. H. Stoltz, S. A. VeitzerTech X Corp.

J.-L. Vay, ECLOUD04 -2-

The Heavy Ion Fusion Virtual National Laboratory

OUTLINE

• Descriptions of POSINST and WARP

• Motivations for the “merge”

• “Merging” process and status

• Conclusion

J.-L. Vay, ECLOUD04 -3-

The Heavy Ion Fusion Virtual National Laboratory

POSINST: Time-dependent PIC plus ECE

• Particles– electrons, x, y, x, y, z v/c

• Self-Fields– Electrostatics on regular cartesian grid

• 2-D XY, 1-D R– perfect-conductor BCs (surface charges included)

• elliptical or rectangular vacuum chamber geometry, with a possible antechamber

• External Fields (beam bunches)– multi-bunch passages

– bunch divided longitudinally into Nk kicks (2D, purely transverse)

• Independent variable– t: evolution of thin slice at fixed station

• Particles generation– photoelectron emission (very simplified input model)– secondary electron yield (SEY) (detailed model included) – residual gas ionization– lost protons hitting the vacuum chamber walls

J.-L. Vay, ECLOUD04 -4-

The Heavy Ion Fusion Virtual National Laboratory

POSINST: Time-dependent PIC plus ECE (2)

• Diagnostics– histories of electron density, energy, % loss, energy loss, angle loss,

ionization, SEY, …– post-processing with third party software

• Cross-platform– ~ 9000 lines of FORTRAN 77 (and a few in F 90)– uses IMSL

• Application– E-cloud studies in High Energy accelerators or storage rings such as:

• APS: e+ (e–) short bunches (~1 cm), well-separated (~0.85-100 m,

C~1.1 km), intense (N~5x1010), high-energy (E~7 GeV, ~14,000)• PSR: single-proton long bunch (~60 m, C=90 m), intense

(N~5x1013), low-energy (E~1.7 GeV, =1.85)

11/17/00 RJM_ICANS-XV.ppt4

PSR Layout

Skew Quad

Merging Dipole Stripper Foil

C Magnets

Bump Magnets

Matching Section

Skew SectionSkew Quad

H- Beam

Final Bend

Extraction Line

H-/H0 Dump Line

ED42

ED52

ED02ED92

ROED1

Circumference = 90m

Beam energy = 798 MeV

Revolution frequency =2.8 MHz

Bunch length ~ 250 ns (~63 m)

Accumulation time ~ 750 ms

~2000 turns

PSR

J.-L. Vay, ECLOUD04 -6-

The Heavy Ion Fusion Virtual National Laboratory

POSINST simulation

1.2x104

1.0

0.8

0.6

0.4

0.2

0.01.1x10

-6 1.00.90.80.70.60.50.40.30.20.10.0

time [s]

beam current signal (arb. units) PSR test, WC41a_1001,ispch=4, macrop=1000,plossrate=4e-6, plelyield=100,pressure=1e-10

WCsignal nex_4

PSR

time-developmentof the electron cloud

J.-L. Vay, ECLOUD04 -7-

The Heavy Ion Fusion Virtual National Laboratory

WARP: Time-dependent/s-dependent PIC plus Lattice

• Particles– q, m, w, x, y, z, ux, uy, uz (u=v), + user- or pre- defined attributes

• Self-Fields – Electrostatic in moving window on regular cartesian grids

• 3-D XYZ warped coordinates, 2-D XY, 2-D RZ, 1-D R, 1-D Z – AMR available for RZ, in development for 3D with CHOMBO– Images from embedded conductors through “cut-cell” method

• External fields (lattice elements)– Sharp-edged, multipole expansion, data or first-principles on 3-D grid– MAD-like description of lattice (MAD to WARP translator available)

• pre-defined elements: dipoles, accelerating gaps, quads, sextupoles,…• box, sphere, cylinder, cone, torus,… primitives for user-defined elements

• Independent variables– s: progression of thin slice along propagation axis of steady flow– t: evolution of window or thin slice at fixed or moving station

• Pure time-dependent mode (tfieldsolve

= tparticles

)

• Quasi-time-dependent mode (tfieldsolve

> tparticles

)• “steady-state” mode (converge to steady-flow solution iteratively)

J.-L. Vay, ECLOUD04 -8-

The Heavy Ion Fusion Virtual National Laboratory

WARP: Time-dependent/s-dependent PIC plus Lattice (2)

• Envelope/fluid equation solvers• Particle loading

– predefined KV, semi-gaussian, user-defined function,…– list from previous run or data (can be time-dependent)

• Beam injection– Child-Langmuir– Gauss pill-box– Flat or curve with specialized mesh refinement patch for fast rise time

• Diagnostics– Fields, particles, lattice, moments, histories, user defined, dumps. – 2-D line, contours, scatter, 3-D surface through Gist/OpenDX

• Python interpreter– provides interactivity, extensibility, “steering” of runs by user – access to a huge collection of freely available third party libraries and software

which can communicate with WARP with no or minor changes

• Expandable GUI– interactive plotting, Python-smart editor, step-by-step running– user-expandable at will -- can add specialized notebook pages

J.-L. Vay, ECLOUD04 -9-

The Heavy Ion Fusion Virtual National Laboratory

WARP: Time-dependent/s-dependent PIC plus Lattice (3)

• Parallel– MPI, 1-D decomposition in Z (different for particles and fields)

• Cross-platform– uses D.P. Grote F90-Python wrapper FORTHON

~5000 lines descr. files + ~70000 lines F90 + ~40000 lines Python– built on linux pc, Unix workstations, IBM-SP, MAC-OSX, Windows

• Dump/Restart capability– all or part of data can be dumped in portable data files (using LLNL PDB

library or HDF5)– dumps can be used to restore portion of data or to restart a run– overcome time limits in supercomputer queues through dump/restart(s)– extends collaborative capabilities: sequences of run can be done by

different researchers geographically distant on different computers

• Application– beam dynamics in Heavy Ion Fusion driver and experiments

• driver: 120 Bi+ beams, 1A-2kA, 1.6MeV-4GeV, 30s-10ns• HCX: 1 Pt+ beam, 180mA, 1.8MeV, 4s• IBX: 1 Pt + beam, 500mA, 1.7MeV, 250ns

J.-L. Vay, ECLOUD04 -10-

The Heavy Ion Fusion Virtual National Laboratory

Artist’s Conception of an HIF Power Plant on a few km2 site

120 beams Multibeam

Accelerator

E = 1.6MeV I = 0.63A/beamT = 30s

E = 4.0GeV I = 94.A/beamT = 0.2s

A = 209amu (Bi)q = +1L = 2.9km

E = 4.0GeV I = 1.9kA/beamT = 10 ns

J.-L. Vay, ECLOUD04 -11-

The Heavy Ion Fusion Virtual National Laboratory

Electron production missing in simulation of a HIF experiment

Beam head hit the structure

J.-L. Vay, ECLOUD04 -12-

The Heavy Ion Fusion Virtual National Laboratory

Motivations for the “merge”

• HEP: the ECE is a consequence of the strong coupling between the beam and its environment;– many ingredients: bunch charge and spacing, photoelectric yield, beam

energy, photon reflectivity, secondary emission yield, chamber size and geometry, particle loss rate, vacuum pressure, ...

3-D parallel particle code ultimately needed

• HIF: strong economic incentive to fill the pipe– ECE and gas desorption may be an issue Need for electron and gas modules

• Each code needs part from the other in order to reach self-consistency

J.-L. Vay, ECLOUD04 -13-

The Heavy Ion Fusion Virtual National Laboratory

Toward a self-consistent model of electron effects

• Plan for self-consistent electron physics modules for WARP

• Key: operational; implemented, testing; partially implemented; offline development

WARP ion PIC, I/O, field solve

fbeam, , geom.

electron dynamics(full orbit; drift)

wall electron source

volumetric (ionization)

electron source

gas module

penetration from walls ambient

charge exch.ioniz.

nb, vb

fb,wall

fb,wall

sinks

ne

ions

Reflectedions

fb,wall

J.-L. Vay, ECLOUD04 -14-

The Heavy Ion Fusion Virtual National Laboratory

“Merging” process

• SEY routines extracted from POSINST (collaboration Tech X)– packaged and distributed by Tech-X in library CMEE (see presentation from

P. Stoltz Wednesday morning)– IMSL routines replaced using free mathematical libraries (the routines

needed by SEY routines are included in CMEE)

• POSINST “Forthonized”– F77 Common blocks translated to description file– subroutines added to description file– main subroutines translated to Python– => POSINST and WARP can be started simultaneously through Python

• Particles data unified– u=v as alternative to =v/c in POSINST– x, y, z, ux, uy and uz declared twice (WARP,POSINST) point to same

memory locations (.i.e top.x=pos.x)

• Specialized GUI page added to WARP GUI– run POSINST– read output data and plot– use WARP diagnostics and plots on common data

J.-L. Vay, ECLOUD04 -15-

The Heavy Ion Fusion Virtual National Laboratory

“Merging” status

• WARP and POSINST cooperate– POSINST provides

• input deck,• main control loop,• initial sources of electrons, • beam bunches kicks, • particle mover, • diagnostics.

– WARP provides • field solvers (1-D R, 2-D XY, 2-D RZ, 3-D XYZ),• diagnostics

– Tech-X package CMEE provides• Secondary emission routines

• But are still independent– WARP and POSINST can still run independently

plan

lattice description

J.-L. Vay, ECLOUD04 -16-

The Heavy Ion Fusion Virtual National Laboratory

Conclusion

• Self-consistency essential to better understand EC-induced instabilities– Correlate instability signals with e– detector signals– Quantify emittance growth, particle losses, multibunch coupling,…

• 3rd dimension essential in many cases:– Fringe fields in quads, higher multipoles, solenoids, …– Any machine dominated by RF and focusing/defocusing

• In practice, the above two => parallel PIC codes• This work combines a vast body of existing:

– Multiparticle dynamics (space-charge, interaction geometry,…)– 3D PIC electrostatic solvers– Molecular and surface physics (SEY, gas desorption, ionization, …)– Parallel computational optimization techniques

• Ultimate goals:– Predict and optimize machine performance– Design future machines based on multiparticle dynamics ab initio rather

than perturbatively