Petascale self-consistent electromagnetic computations using scalable and accurate algorithms for complex structures

Presenter: John R. Cary
Tech-X/University of Colorado-Boulder

Authors: John R. Cary,^1,2 D. Abell,¹ J. Amundson,³ D. L. Bruhwiler,¹ R. Busby,¹ J. Carlsson,¹ D. A. Dimitrov,¹ E. Kashdan,⁴² P. Messmer,¹ C. Nieter,¹ D. N. Smithe,¹ P. Spentzouris,³ P. Stoltz,¹ R. M. Trines,⁵ H. Wang,⁶ G. Werner²

High-performance computational accelerator physics continues a long tradition of the use of computation in the design and operation of accelerators. Early computations relied heavily on approximation methods, such as expansions in distance from the design orbit (used extensively in the field of beam optics), and at times were unable to supply detailed accurate results, such as in the computation of wake fields in complex cavities. However, with the advent of message passing supercomputers composed of 1000’s of processors or more, many of the earlier approximations need no longer be made, and it is now possible to compute wake fields, the effects of dampers, and self-consistent dynamics in cavities accurately. In this environment, the focus has shifted towards the development and implementation of algorithms that scale to large numbers of processors. Such include so-called charge-conserving algorithms that eliminate the need for any global solves. This can now be carried out in complex cavities through use of cut-cell (or embedded) boundaries. Inclusion of emission processes enables the computation of multipactoring and similar effects. New implicit algorithms that conserve charge are stable for any time step. These allow one to compute systems with structures small compared with the characteristic wavelength of the system in reasonable time. This presentation will discuss these algorithmic and computational advances and their implementation in and addition to VORPAL? Framework, a flexible, object-oriented, massively parallel modeling framework. VORPAL allows one to assemble algorithms and objects at run time, thus composing an application on the fly. In addition we will discuss the application to beam physics. Example computations for cavities, photoinjectors, and compact acceleration will be presented.

¹ Tech-X Corporation
² University of Colorado, Boulder
³ Fermi National Accelerator Laboratory
⁴ Brown University
⁵ Rutherford Appleton Laboratory
⁶ Thomas Jefferson National Accelerator Facility
* C. Nieter and J. R. Cary, "VORPAL: a versatile plasma simulation code", J. Comp. Phys. 196, 448-472 (2004).