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Titanium Nitride Coating by Reactive DC Magnetron Sputtering as a Multipactor Suppressor on Coupler RF Ceramic Windows Walid KAABI Anti e - Cloud Coatings-

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Presentation on theme: "Titanium Nitride Coating by Reactive DC Magnetron Sputtering as a Multipactor Suppressor on Coupler RF Ceramic Windows Walid KAABI Anti e - Cloud Coatings-"— Presentation transcript:

1 Titanium Nitride Coating by Reactive DC Magnetron Sputtering as a Multipactor Suppressor on Coupler RF Ceramic Windows Walid KAABI Anti e - Cloud Coatings- AEC’09 Laboratoire de l’Accélérateur Linéaire

2 CERN- Octobre 12th 2009 2 Power coupler for superconductive cavities Power coupler have 3 functions to fulfil:  Electromagnetic role  Vacuum barrier  Thermal interface Principle and Functions

3 CERN- Octobre 12th 2009 3 Power coupler for superconductive cavities Coupler Design: example of TTF-III Model RF Source Cavities Cryogenic module TTF-III is the baseline solution for the future XFEL linac in DESY. In this framework, our laboratory is responsible of the RF conditioning task of 800 TTF-III couplers.

4 CERN- Octobre 12th 2009 4 Power coupler for superconductive cavities Coupler Ceramic Windows Cold windows (Ø = 47 mm, h= 48 mm) Warm windows (Ø = 75 mm, h= 57 mm) Windows made of Alumina ceramic (97.6% Al 2 O 3 ):  Mechanical and dielectric strength  High thermal stability  Low out-gazing rate  High Secondary Electron Emission Yield (SEY)

5 CERN- Octobre 12th 2009 5 Multipactor phenomenon RF Field + Best conditions for Multipactor phenomenon occurring: Electron-avalanche discharge + High vacuum Conditions of occurring

6 CERN- Octobre 12th 2009 6 Multipactor phenomenon Multipactor phenomenon may cause damages in ceramic windows:  Creation of damaging arcs,  Surface overheating that may lead to surface evaporation,  Load mismatch causing dangerous power reflection to the RF source. Necessity of suppression, or at least limitation of this effect Solution: decrease Alumina’s SEY by surface coating with multipactor suppressor thin layer: Titanium Nitride Damages caused in ceramic windows

7 CERN- Octobre 12th 2009 7 Multipactor suppressor thin film TiN is characterised by a low SEY that remain stable on RF operational conditions

8 CERN- Octobre 12th 2009 8 Multipactor suppressor thin film DC Reactive Magnetron Sputtering of TiN

9 CERN- Octobre 12th 2009 9 TiN sputtering system Titanium target Rotating magnet pack Shield Rotating magnet shape = Plasma shape Rotating sample holder Sputtering machine overview

10 CERN- Octobre 12th 2009 10 TiN sputtering system Sample holder motion

11 CERN- Octobre 12th 2009 11 Practical guidances Ceramic window exposure to RF field induce some additional constraints:  Stoichiometry control: the layer can get the multipactor suppressor property (XRD analyses ),  Thickness control: deposit should be thick enough to reduce multipactor, but not so much to prevent increasing RF power reflection in ceramic surface (X-Ray reflectivity Analyses, in addition to Quartz Crystal Microbalance monitoring).  Deposits made on 10x10mm quartz substrates,  Use of multi-sample holder.


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