Physics Department Lancaster University Cavity development Rebecca Seviour

Physics Department Lancaster University Operating Cavities in an Magnetic field

Physics Department Lancaster University Where do the electrons go μ 6 μ Initial Particle Data Input (X,Y,Z) (Vx,Vy,Vz) Use Comsol to Extract (E, B) Field Parameters Compute New Particle Data by Integration Extraction of Particle Data at Point of Impact FEA Analyses at the Point of Impact Secondar y Electron Emission

Physics Department Lancaster University

Physics Department Lancaster University As received Ra(nm)101 Rq(nm)136 Electropolished Ra(nm)89 Rq(nm)118

Physics Department Lancaster University Before As receivedElectropolished

Physics Department Lancaster University Need to do the experiment to prove

Physics Department Lancaster University R.L.Geng, PAC 2003 Q E Field (Mv/m) Generic Problem

Physics Department Lancaster University FP7 – EuCard Thin Films Examining phenomena limit current performance and investigating alternative coating techniques Several mechanisms for the thin film Q-drop [i]ii],[iii] ; [i]ii][iii] Nb High R interface Low 200 MHz,  ~ 40 nm Layer thickness ~ 10  m

Physics Department Lancaster University

Physics Department Lancaster University CERN, Nb on Cu Nb High R interface

Physics Department Lancaster University Renormalisation of N by induced condensate (Proximity Effect) Quasiparticle current Contribution from conversion of low energy quasiparticle current into condensate current (Andreev Reflection) Superconductor Normal Conductor Nb High R interface

Physics Department Lancaster University Nb (850 nm) on Si AFM photodetector Tip piezo Sample piezotransducer Microfabricated cantilever AFM tip laser Sample Such elasticity variations are linked with –Local surface and subsurface material composition –Subsurface strain variations (they affect local elastic moduli via third order elastic constants) UFM allows surface topography to be mapped simultaneously with the material composition and strain Ultrasonic Force Microscope: Measuring Strain and Elasticity

Physics Department Lancaster University

Physics Department Lancaster University

Physics Department Lancaster University Towards a High Temperature SC RF Cavity ? Conventional SCRF (Nb) – Require He Cryosats (< 4 K) HTc SC - Operate >30 K HTc SC RF - Minehara (1990) considered HTc RF Cavity resonator made from isostaticaly pressed YBCO & BSCCO. Achieving Q > 10^6 at 30K. - Others considering the use of HTC Thin Film

Physics Department Lancaster University Bulk HTS Cavity limited by several factors, HTS have high residual resistance ratios,  f Transport properties very sensitive to imperfections. This gives rise to low current in the superconductor. HTS are extremely sensitive to the right stoichiometry and oxygen content.

Physics Department Lancaster University Some experimental RF work has been done on Proximity effect - Sputtered Cu on Nb - R s of Cu reduced > 50% - SC is shielded from magnetic field

Physics Department Lancaster University Experiment Detachable wall Coaxial coupler Hybrid wall Normal Metal HTS 2 Hybrid walls Working at 10 GHz (small sizes for ALD), create a number of hybrid proximity effect walls for evaluation ( Q, Rs, λ, ξ, , surface properties: stress, strain, elasticity) repeat Cu /Nb experiments asses various HTC (Magnisium Diboride, BaKBiO) asses various N metals (silver, lead, Cu) Try various coating techniques