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Prospect of High Gradient Cavity

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.

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Prospect of High Gradient Cavity

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  1. Tohoku Forum for Creativity 2013 Prospect of High Gradient Cavity H. Hayano, 10222013

  2. Remarks of RongliGeng at IWLC2010

  3. >60MV/m by Thin-Film coated Cavity

  4. 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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  28. 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)

  29. C. Cao Atomic layer deposition (ALD) • 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.

  30. C. Cao ALD thin film materials

  31. ZnO Si 200 nm 1 μm C. Cao 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 surfaces Coat inside Nb SRF cavity with precise, layered structure → ALD • ALD is very good at coating non-planar surfaces

  32. B0 Bi=B0exp(-Nd/lL) d C. Cao Multilayer thin films for SRF • Superconductor-Insulator multilayer [Gurevich, Appl. Phys. Lett.88, 012511 (2006)] • Potential path to high Eacc and high Q0

  33. C. Cao Nb1-xTixN Thin Films made by ALD • 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 ") TEM

  34. C. Cao Nb1-xTixN-based superconductor-insulator structures Aluminum 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

  35. C. Cao 49nm Nb0.8Ti0.2N on AlN Tc= 12.8K by SQUID 2Δ/kTc = 3.4 - 3.6 (BCS limit) Δ(meV) Γ(meV)

  36. C. Cao 28nm Nb0.8Ti0.2N (without AlN layer) Tc= 8.3K by SQUID Δ(meV) Γ(meV)

  37. C. Cao Conclusion • 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. 12.8 K Strained layer, low Tc Substrate

  38. Application of “thin-film on Nb” to ILC? Technology of; 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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