J.-L. Vay, ECLOUD 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 31 st ICFA Advanced Beam Dynamics Workshop on Electron-Cloud Effects Napa, California April 19-23, 2004 J.-L. Vay, M. A. Furman, A. W. Azevedo Lawrence Berkeley National Laboratory R. H. Cohen, A. Friedman, D. P. Grote Lawrence Livermore National Laboratory P. H. Stoltz, S. A. Veitzer Tech X Corp.

J.-L. Vay, ECLOUD 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, ECLOUD 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 N k 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, ECLOUD 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 (~ m, C~1.1 km), intense (N~5x10 10 ), high-energy (E~7 GeV,  ~14,000) PSR: single-proton long bunch (~60 m, C=90 m), intense (N~5x10 13 ), low-energy (E~1.7 GeV,  =1.85)

PSR

J.-L. Vay, ECLOUD The Heavy Ion Fusion Virtual National Laboratory POSINST simulation

J.-L. Vay, ECLOUD The Heavy Ion Fusion Virtual National Laboratory WARP: Time-dependent/s-dependent PIC plus Lattice Particles –q, m, w, x, y, z, u x, u y, u z (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 (  t fieldsolve =  t particles ) Quasi-time-dependent mode (  t fieldsolve >  t particles ) “steady-state” mode (converge to steady-flow solution iteratively)

J.-L. Vay, ECLOUD 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, ECLOUD 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, 30  s-10ns HCX: 1 Pt + beam, 180mA, 1.8MeV, 4  s IBX: 1 Pt + beam, 500mA, 1.7MeV, 250ns

J.-L. Vay, ECLOUD The Heavy Ion Fusion Virtual National Laboratory Artist’s Conception of an HIF Power Plant on a few km 2 site 120 beams Multibeam Accelerator E= 1.6MeV I= 0.63A/beam T= 30  s E= 4.0GeV I= 94.A/beam T= 0.2  s A= 209amu (Bi) q= +1 L= 2.9km E = 4.0GeV I = 1.9kA/beam T = 10 ns

J.-L. Vay, ECLOUD The Heavy Ion Fusion Virtual National Laboratory Electron production missing in simulation of a HIF experiment Beam head hit the structure

J.-L. Vay, ECLOUD 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, ECLOUD 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  f beam, , geom. electron dynamics (full orbit; drift) wall electron source volumetric (ionization) electron source gas module penetration from walls ambient charge exch. ioniz. n b, v b f b,wall  sinks nene ions Reflected ions f b,wall

J.-L. Vay, ECLOUD 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, u x, u y and u z 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, ECLOUD 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, ECLOUD 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