[BANANA] Berkeley Lab - Scientific Computing Seminar - Wednesday, 08/27/2008, 1:00pm

[Esmond G. Ng]

Berkeley Lab - Scientific Computing Seminar

Date:   Wednesday, August 27, 2008
Time:   1:00pm-2:00pm  
Location:   Building 50F, 1647 Conference Room

Seminar Speaker:
    Braxton Osting
    Department of Applied Physics & Applied Mathematics
    Columbia University

Title:   Particle Accelerator Cavity Design with PDE Constrained 
Optimization

Abstract:
In the design of particle accelerators, one wishes to find the shape of 
a cavity that produces the optimal electromagnetic field distribution -- 
one with maximal quality factor for the accelerating mode and minimal 
quality factor for higher-order modes. Unfortunately, these are often 
competing goals and the lengthy procedure of manually attempting to find 
the optimal shape is undesirable. We formulate the design procedure as a 
constrained optimization problem for a parameterization of the shape 
where the constraint is a quadratic eigenvalue problem resulting from 
the discretization of the time-harmonic Maxwell equations with radiating 
boundary conditions. The resulting nonlinear optimization problem may be 
solved using a line-search based reduced-space quasi-Newton method where 
the shape sensitivities are computed using the adjoint method. Using a 
simple one-dimensional model arising in the design of the index of 
refraction for photonic crystals, we demonstrate the effectiveness of 
this method. We conclude with the results of a massively parallel 
computation for the optimal shape of a choke cavity.

Sponsor of Seminar:   Esmond G. Ng