Cornell models cavity for next generation light source
Contact: Paul Redfern
Cell: (607) 227-1865
FOR RELEASE: March 29, 2011
ITHACA, N.Y. – Cornell University is competing with other institutions for grants to build a coherent X-ray source. Cornell’s design is based on an extension of the existing Cornell Electron Storage Ring accelerator to an Energy Recovery Linac (ERL). Under a recent grant from the National Science Foundation, the Cornell ERL research team is developing an ultra-bright electron injector and linear accelerator, both based on superconducting technology. The ERL would be the most capable X-ray source in the world, with steady-state beams up to 1,000 times brighter than any in existence, creating a revolutionary tool for biology, medicine, and many basic science areas.
Central to the intended operation of the Energy Recovery Linac is the proper design and functioning of the superconducting RF cavities comprising its main accelerating structure. Nicholas Valles, a graduate student in the Department of Physics, is working on complex optimization routines for the design of these cavities using a high performance computing cluster and parallel software at the Cornell Center for Advanced Computing (CAC).
Cornell chose to implement superconducting Niobium seven-cell accelerating structures into the main linac design enabling a high current, very low emittance beam capable of producing short pulses of hard x-rays with a high repetition rate. There were physical considerations that had to be implemented into the cavity design and methods had to be developed to optimize cavities under these constraints. New features of the current cavity design, including a new higher-order-mode (HOM) absorber design and introduction of a Carbon Nanotube (CNT) absorber, required end-cell optimization.
The ERL team carried out the optimizations in parallel on a Linux cluster located at the CAC, and the electro-magnetic fields were solved using 2D finite element codes.“We began with a parallel optimization routine which generated cavity geometries and then used field solvers to compute the electro-magnetic properties of the cavity,” explains Valles. “We then used these parameters to damp higher-order modes that can deteriorate beam quality.” After obtaining an optimized geometry, the researchers introduced small perturbations to the design to model machining perturbations, and then used these new cavities to simulate several hundred ERLs, and calculate the threshold current that the linac can support. The researchers were able to successfully optimize the cells of the 7-cell cavity for the Cornell Energy Recovery Linac with a realistic HOM absorber geometry and material.
The ability to deploy several different types of cavities in the linac will enable the ERL to run high currents at an extremely stable level. “The design of multiple cavities would not be possible without parallel high performance computing,” noted Valles. “Further study will include power coupler design, 3D modeling of the cavity, and design of several classes of cavities to introduce frequency spread to the main linac.”
Valles’ research is supported by an ERL grant provided, in part, by the NSF to the Cornell Laboratory for Accelerator-based ScienceS and Education (CLASSE). Details on the cavity design and modeling are available in "Cavity Design for Cornell's Energy Recovery Linac," published in the Proceedings of the first International Particle Accelerator Conference with Matthias Liepe, Assistant Professor of Physics, Cornell University.
The Cornell University Center for Advanced Computing (CAC) is a leader in high-performance computing systems, applications, and data solutions that enable research success. For more information on CAC, visit http://www.cac.cornell.edu.