prospect of high gradient cavity
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Tohoku Forum for Creativity 2013. Prospect of High Gradient Cavity. H. H ayano , 10222013. Remarks of Rongli Geng at IWLC2010 . >60MV/m by Thin-Film coated Cavity. Look review lecture by T. Tajima(LANL) f or “Thin Film coated Cavity”. Nb 3 Sn : tri-niobium tin. - PowerPoint PPT PresentationTRANSCRIPT
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Prospect of High Gradient Cavity
H. Hayano, 10222013
Tohoku Forum for Creativity 2013
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Remarks of Rongli Geng at IWLC2010
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>60MV/m by Thin-Film coated Cavity
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Look review lecture by T. Tajima(LANL)for
“Thin Film coated Cavity”
Nb3Sn : tri-niobium tin
MgB2 : magnesium di-boride
Multi-layer thin film concept
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T. Tajima
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T. Tajima
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T. Tajima
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T. Tajima
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T. Tajima
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T. Tajima
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T. Tajima
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T. Tajima
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T. Tajima
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T. Tajima
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T. Tajima
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How to make thin-film on Nb?
Look presentation by Chaoyue Cao (IIT)for
“Point Contact Tunneling as a Surface Superconductivity Probe of bulk Nb and (Nb1-xTix )N Thin Films”
@ 5th Thin Film workshop 2012(Jlab)
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• A thin film synthesis process based on sequential, self-limiting surface reactions between vapors of chemical precursors and a solid surface to deposit films in an atomic layer-by-layer manner.
Atomic layer deposition (ALD)C. Cao
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ALD thin film materialsC. Cao
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Advantages:
Atomic-level control of thickness and composition Smooth, continuous, pinhole-free coatings on large area substrates No line-of-sight limits → excellent conformality over complex
shaped surfacesCoat inside Nb SRF cavity with precise, layered structure → ALD
1 μm
200 nmZnOSi
ALD is very good at coating non-planar surfaces
C. Cao
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Multilayer thin films for SRF• Superconductor-Insulator multilayer [Gurevich, Appl. Phys. Lett. 88, 012511 (2006)]
Potential path to high Eacc and high Q0
d
B0
Bi=B0exp(-Nd/lL)
C. Cao
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Nb1-xTixN Thin Films made by ALD
TEM
Chemistry: (NbCl5:TiCl4) + Zn + NH3 at 450°C, 500°C
Can vary Ti content with NbCl5:TiCl4 ratio (1:2 ~ 20% TiN)
Impurity content: 0.05 atom % Cl
21 sec/cycle 2-7-1-5-1-5 ("NH3 dose"-"purge"-"MClx dose"-"purge"-"Zn dose"-"purge ")
C. Cao
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Nb1-xTixN-based superconductor-insulator structuresAluminum nitride: AlN Oxygen-free insulator, stable interface with Nb(Ti)N Good thermal conductivity (285 W/m-K) Similar structure to Nb(Ti)N
– 0.27% mismatch between in-plane spacing of (001)-oriented AlN and (111)-oriented NbN Can be grown with AlCl3 and NH3 at same temperature as Nb(Ti)N
C. Cao
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49nm Nb0.8Ti0.2N on AlN Tc= 12.8Kby SQUID
2Δ/kTc = 3.4 - 3.6(BCS limit)
Δ(meV)
Γ(meV)
C. Cao
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28nm Nb0.8Ti0.2N (without AlN layer)Tc= 8.3Kby SQUID
Δ(meV)
Γ(meV)
C. Cao
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• Point contact tunneling (PCT) technique is ideal for measuring the local surface superconducting energy gap and density of states (DOS) of samples with a natural barrier.
• Nb1-xTixN on AlN gives Tc = 12.8K, Δ = 1.8-2.2 meV, 2Δ/kTc = 3.4-3.6(BCS limit).
• Nb1-xTixN (without AlN) Tc = 8.3K. High quality gap region DOS, low zero bias conductance. Δ = 1.8-2.2 meV.
Conclusion
Substrate
Strained layer, low Tc
12.8 K
C. Cao
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Application of “thin-film on Nb” to ILC?
Technology of;(1) nm-level Smooth Nb cavity surface,
(2) Well controlled thin-film formation on Nb cavity, will be required.
Then, we can reach >100MV/m with TESLA cavity shape.
Tumbling, electro-polish, etc.
Hydroforming without welding.
Atomic Layer Deposition (ALD)
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