sics Department caster University Cavity development Rebecca Seviour
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......
7 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
Secondary 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 received Electropolished
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 techniquesSeveral mechanisms for the thin film Q-drop[i]ii],[iii];
mfp
NbHigh Rinterface
Low
200 MHz , ~ 40 nmLayer thickness ~ 10 m
Physics Department
Lancaster University
Physics Department
Lancaster University
CERN, Nb on Cu
Nb
High Rinterface
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 ConductorNb
High Rinterface
Physics Department
Lancaster University
0 100 200 300 400 500 600 700012345678
AFM profile
position along the path / nm
Heig
ht /
nm
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
mfp
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 UniversitySome experimental RF work has been done on Proximity effect
- Sputtered Cu on Nb
- Rs of Cu reduced > 50% - SC is shielded from magnetic field
Physics Department
Lancaster UniversityExperiment
Detachable wall
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