1. Advanced Study of Multilayer Films: A Proposed Research at LANL
Alberto Canabal & Tsuyoshi Tajima
Accelerator Operations and Technology Division
Los Alamos National Laboratory
The International Workshop on: THIN FILMS AND NEW IDEAS FOR PUSHING THE LIMITS OF RF SUPERCONDUCTIVITY
Padua, Italy, October 10th, 2006
Presentation Title Slide Notes
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2. Motivation
Cavities for accelerators are mostly made of Cu (NC) or Nb (SC).
Performance of superconductors whose Tc is higher than that of Nb (9.2 K) still to be determined.
Cu and Nb based technology have reached almost their theoretical limit. As to Nb cavities, the reproducibility of high-quality cavities remains to be an issue.
Multi-layer films with HTS might be able to enhance the capability of SRF cavities
Content Slide Notes
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3. Goals
Improve the performance of RF cavities (NC & SC) by using multilayer-coated normal or superconductors of different type and thicknesses.
Achieve overall values of δ, λL, Rs, k, etc. better than with a single material.
Solve the different scenarios (NC & SC) with both local and non-local electromagnetics for arbitrary orientation of the incident fields and including He and SF He.
Development of a thermal-electromagnetic coupled 2D FDTD code and optimization of parameters.
Predict Q vs Eacc graphs.

4. Goals
Background
A. Gurevich, Appl. Phys. Lett. 88, (2006)

5. Goals
Big picture…

6. Normal Conductors local electromagnetics ε, μ are tensors in general
Local relation:
Given
and that

7. Normal Conductors
local electromagnetics
Local relation:

8. Normal Conductors
local electromagnetics

9. Normal Conductors H E non-local electromagnetics
Wave equation in terms of … H E
Simpler!

10. Normal Conductors non-local electromagnetics Issues
Still a rather complicated expression
Need only to keep track of E but at the end H needs to be calculated through a numerical curl, adding unnecessary errors
Better alternative: Leap Frog interleave scheme
k-2
k-1 k
k+1
k+2
K-1-1/2
K-1/2
K+1/2
K+1+1/2
K+2+1/2
K-2
K-1
K+2

11. Normal Conductors non-local electromagnetics where
Only first order derivatives in both time and space!

12. Superconductors local electromagnetics London equation
Rewrite London equation
vector potential
choose
Local relation

13. Superconductors
non-local electromagnetics
In BCS theory

14. Summary Normal Conductors Superconductors Local Non-local Local

15. Perfect Matched Layer (PML)
For 1D not necessary
For lossless local relation
for non-local relation
PML still has to be formulated!

16. Electromagnetic Analysis
Ultimate goal
Program flowchart
Electromagnetic Analysis
RF Heating
Optimization
Heat Transfer

17. Backup Slides
Comments/Suggestions