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Advancing Accelerator Projects Through Electromagnetic Modeling

This project showcases the impact of SciDAC on accelerator projects, using advanced computing and electromagnetic modeling to improve existing accelerators and design future facilities. Collaboration with ISICs and SAPP has enabled large-scale computation and high-resolution modeling for better performance and optimization. Achievements include IR heating in PEP-II, DDS cell design in NLC, RF gun design in LCLS, and more.

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Advancing Accelerator Projects Through Electromagnetic Modeling

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  1. Impact of SciDAC on Accelerator Projects Across SC through Electromagnetic Modeling DOE/HEP SciDAC AST Project: “Advanced Computing for 21st Century Accelerator Science and Technology” Kwok Ko Stanford Linear Accelerator Center Rich Lee - Achievements in ISIC/SAPP Collaborations for Electromagnetic Modeling of Accelerators (Poster) * Work supported by U.S. DOE ASCR & HEP Divisions under contract DE-AC02-76SF00515

  2. DOE Office of Science Accelerators HEP NP Accelerators are essential tools for doing science in SC - close to 50% of the Facilities for the Future of Science involve accelerators ILC LCLS RIA PEP-II BES ILC LCLS PEP II CEBAF

  3. Electromagnetic Structures in Accelerators FEL • High resolution modeling and end-to-end simulation are being used to improve existing accelerators (e.g. PEP-II) and design future facilities (e.g. ILC). • Due to the large complex geometry and required accuracy Large-scale computation is absolutely essential LCLS ILC

  4. Partitioning Solvers Analysis CAD/Meshing Refinement Optimization Visualization Performance Electromagnetic Modeling NLC Cell Design SciDAChas enabled collaborations with the ISICs andSAPP toadvance the computational scienceneeded for Large-scale electromagnetic modeling .

  5. H High Performance Computing (NERSC, ORNL) Parallel Code Development ComputationalScience Simulation and Modeling Accelerators SLAC DESY KEK Jlab ANL MIT PSI SLAC Accelerator Modeling Computational Mathematics Computing Technologies ISICs/SAPP LBNL LLNL SNL Stanford, UCD RPI, CMU Columbia UWisconsin SciDAC AST- Electromagnetics Project

  6. Stanford G. Golub AST Electromagnetics Team SLAC/ACD Computing Technologies N. Folwell, G. Schussman, R. Uplenchwar, A. Guetz (Stanford) Computational Mathematics L. Lee, L. Ge, E. Prudencio, S. Chen (Stanford), Accelerator Modeling K. Ko, V. Ivanov, A. Kabel, Z. Li, C. Ng,, L. Xiao, A. Candel (PSI) ISICs (TSTT, TOPS, PERC) and SAPP LLNL L. Diachin, D. Brown, D. Quinlan, R. Vuduc LBNL E. Ng, W. Gao, X. Li, C, Yang P. Husbands, A. Pinar, D. Bailey, D. Gunter SNL P. Knupp, K. Devine. L. Fisk, J. Kraftcheck UWisconsin T. Tautges, H. Kim, RPI M. Shephard, A. Brewer, E. Seol UCD K. Ma, H. Yu Z. Bai Columbia D. Keyes CMU O. Ghattas V. Akcelik

  7. Generalized Yee Grid Finite-Element Discretization S3P Omega3P Tau3P/T3P Frequency Domain Mode Calculation Time Domain Simulation With Excitations Scattering Matrix Evaluation Track3P – Particle Tracking with Surface Physics V3D – Visualization/Animation of Meshes, Particles & Fields Parallel EM Code Development Solve Maxwell’s equations in time & frequency domains using unstructured grid and parallel computing

  8. Achievements in Accelerator Science/Design • PEP-II - IR Heating • - Vertex Bellows Heating • NLC – DDS Cell Design • - DDS Wakefields • - Dark Current Pulse • RIA - RFQ Design and AMR • LCLS - RF Gun Design

  9. PEP-II IR Omega3P/Tau3P calculated heat power distribution to help in the IR upgrade design to reduce beam heating TSTT generated good quality hexahedral meshes to enable Tau3P simulation with beam Power Distribution 15% higher beam current since upgrade led to higher luminosity/physics discovery Total power = 17.2 kW for 3A (330 Modes) HEP PEP-II- IR Heating

  10. Omega3Pwas used to evaluate the damping of localized modes by mounting ceramic tiles on the bellows convolution. Bellows modes were found to be damped to very low Qs Bellows Modes HEP PEP-II– Vertex Bellows Heating Bellows mode Ceramic tile absorber Dielectric loss

  11. +1MHz -1MHz HEP NLC - DDS Cell Design Omega3P provided the dimensions for 206 NLC Damped Detuned Structure cells. Microwave QC of cells verified frequency accuracy of 1 part in 10,000 as targeted. SLAC/Stanford/LBL (SAPP/TOPS) developed faster and more scalable eigensolvers (ISIL & ESIL) • Potential savings of $100 million+ in NLC machine cost since DDS is 14% more efficient than standard cell design • New core accelerator design capability

  12. HEP NLC- DDS Wakefields Omega3P/Tau3Pcomputed the long-range wakefields in the entire 55-cell DDS to assess the NLC baseline design in wakefield suppression. SLAC/SNL/LBL (SAPP) improved Tau3P speedup with alternate partitioning tools from Zoltan Omega3P: Sum over eigenmodes Tau3P: Direct beam excitation

  13. Omega3P Tau3P HEP NLC- Wakefields Comparison Wakefields behind leading bunch Mode Spectrum • 1st ever wakefield analysis of an actual DDS prototype • Provided benchmarking of Omega3P and Tau3P

  14. HEP NLC– Dark Current Pulse Dark current pulses were simulated for the 1st time in a 30-cell X-band structure with Track3P and compared with data. Simulation shows increase in dark current during pulse risetime due to field enhancement from dispersive effects. Track3P: Dark current simulation Track3P: Dark current simulation Red – Primary particles, Green – Secondary particles Red – Primary particles, Green – Secondary particles Dark current @ 3 pulse risetimes -- 10 nsec -- 15 nsec -- 20 nsec Data Track3P

  15. RFQ Qo Convergence Frequency Convergence Wall Loss on AMR Mesh NP RIA- RFQ Design Omega3Pwas used to model RIA’s low energy RFQ. With Adaptive Meshing Refinement accuracy in frequency and wall loss calculations improved by a factor of 10 and 2 respectively while using a fraction of CPU time required for no AMR case. SLAC\RPI (TSTT) developed AMR in Omega3P to speed up convergence, improve accuracy and reduce computing time. More accurate f and Q predictions reduce the number of tuners and tuning range, and allow for better cooling design

  16. Quad (βr)/mm BES LCLS– RF Gun Cavity Omega3P/S3Pprovided the dimensions for the LCLS RF Gun cavity that meet two important requirements: • minimized dipole and quadrupole fields via a racetrack dual-feed coupler design, • reduced pulse heating by rounding of the z coupling iris. A new parallel Particle-In-Cell (PIC) capability is being developed in T3P for self-consistent modeling of RF guns needed for the LCLS upgrade, future light sources and FELs. Quad

  17. Projects in Progress • ILC – Cavity Design • Eigensolvers • Visualization • Shape Optimization • Parallel Meshing • Performance

  18. HEP ILC – Accelerating Cavity The ILC, highest priority of future HEP projects, will be the most costly accelerator (many billion $) and is being designed by an international team Europe, Asia and North America. An international collaboration (KEK, DESY, SLAC, FNAL and Jlab) is assessing a Low-Loss (LL) design as a viable option for the ILC superconducting RF accelerating cavity.

  19. HEP ILC – Low-Loss Cavity Design The LL Cavity uses a cavity shape that has 23% less cryogenic loss. The design challenge is to ensure damping of the HOMs over a broad band of frequencies via the two HOM couplers while maintaining the efficiency of the fundamental mode. Two variants of the LL cavity are being considered, the DESY LL design and the KEK Ichiro design. SLAC is simulating both designs.

  20. KEK DESY HEP ILC – HOM Damping Partitioned Mesh of LL Cavity With new advances in eigensolvers under SciDAC, Omega3P can now compute the complex frequency or Qe = r / i of HOMs as a result of damping by the HOM couplers Qext Qe Qe

  21. Omega3P Lossless Lossy Material Periodic Structure External Coupling ISIL w/ refinement ESIL Implicit Restarted Arnoldi SOAR Self-Consistent Loop i WSMP MUMPS SuperLU Krylov Subspace Methods Domain-specific preconditioners Advances inEigensolvers (SLAC, TOPS/SAPP - LBL, Stanford, UC Davis) Cavity designs with coupling to external waveguides require solutions to a nonlinear eigenvalue problem as the boundary conditions also depend on the eigenvalue. Two solvers, SOAR and SCL have been applied successfully to the ILC cavities.

  22. Advances in Visualization (SLAC, SAPP - UC Davis) Rendering of LARGE, 3D multi-stream, unstructured data is essential to the analysis of accelerators, such as mode rotation exhibited by the two polarizations of a damped mode in the ILC cavity as they are coupled through resonance overlap. New graphics tools for rendering LARGE, multi-stream, 3D unstructured data have been developed, to be supported by a dedicated visualization cluster to help in analyzing cavity design, such as mode rotation in the ILC cavity.

  23. a1 b2 b1 a2 R L b Geometric model Omega3P Sensitivity Optimizer Meshing Omega3P Advances in Shape Optimization (SLAC, TOPS – CMU, LBL, Columbia, TSTT – SNL, LLNL) A parallel shape optimization capability is under development in Omega3Pfor optimizing the ILC cavity end cells to damp trapped HOMs so the cavity can meet beam stability requirements.

  24. Processor: 1 2 3 4 Advances in Meshing (SLAC, TSTT – U Wisconsin, SNL) 4 cavity cryomodule at STF (KEK) To model a chain of cavities within a cryomodule a parallel meshing capability has been developed to overcome the single CPU memory limitation of standard meshing software. CAD-based Partitioning for Parallel Meshing

  25. Latest communication pattern study on NERSC Breakdown of Solve & Postprocess Speedup after code optimization LBL Advances in Omega3P Performance (SLAC, PERC – LBL, LLNL) LLNL

  26. AST- ESS under SciDAC • Support Accelerator Science/Design across SC • Advance Computational Sciencethrough ISICs and SAPP ILC BPM & Wakefields in LCLS Undulator ILC LL Cavity & Cryomodule XFEL SC RF Gun MIT PBG Cavity for Jlab 12 GeV Upgrade

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