Minimizing the RF Fields on the Surface of an SRF Cavity by Optimizing its Shape David Stark Advisor: Valery Shemelin Cornell University Cornell Laboratory for Accelerator-based Sciences and Education (CLASSE)

June 18, 2009 Cornell CLASSE REU 2 SRF Cavities RF power through superconductor produces electric fields that accelerate particles

June 18, 2009 Cornell CLASSE REU 3 Limitations Magnetic field cannot exceed critical field High electric fields can cause field emission For TESLA: Useful parameters: –e and h are each 1 for TESLA

June 18, 2009 Cornell CLASSE REU 4 Minimizing h and e Flatten maxima of e and h curves to lower peak values Looking at e≤1.2 case in particular L E H

June 18, 2009 Cornell CLASSE REU 5 SuperLANS Calculates electric and magnetic fields in cavity Program performs a numerical analysis using a mesh of points Input cavity shape via geometry file Sample Geometry file: Mesh:

June 18, 2009 Cornell CLASSE REU 6 Initial Testing 2 Conjugate Ellipses 2 Overlapping Ellipses 2 Separated Ellipses

June 18, 2009 Cornell CLASSE REU 7 6-elliptic Arc Upper and lower arcs each broken into 3 conjugate ellipses Shifting intersection points allows us to flatten fields R(mm) Z(mm)

June 18, 2009 Cornell CLASSE REU 8 Testing each Variable Systematically change each variable, one at a time, and see how e and h change

June 18, 2009 Cornell CLASSE REU 9 Progress and Goals Want to minimize h for e ≤ 1.2 Starting point: Current best: Goal:

Sources Graber,J. “Superconducting RF Cavities: A Primer.” Cornell University June 18, 2009 Cornell CLASSE REU 10