Ultra High Vacuum Technology Section

Technology Development

DC Magnetron Sputter Coating System for Development of NEG Coated Vacuum Chamber

Non-evaporable getter (NEG) coating technology for stainless steel vacuum chambers was developed in UHV Section for its application in vacuum systems of particle accelerator and storage ring. Ti-Zr-V NEG coating is a novel room temperature sorption pump for achieving very low pressure down to extreme high vacuum (< 10-11 mbar). It pumps active gases by chemisorption and hydrogen by diffusion. Salient features of Ti-Zr-V NEG thin film coating are: (i) It is a passive pump which doesn’t require any power for its pumping action. (ii) It acts as a diffusion barrier & hence reduces the specific thermal outgassing rate (iii) It does not require any extra space hence very useful for conductance limited long vacuum chambers of particle accelerators (iv) It reducesphoto desorption yield (PID) and (v) It facilitates reduction of the Secondary Electron Yield (SEY) of a vacuum chamber surface.
A UHV compatible cylindrical DC magnetron sputtering system was developed for this purpose and the NEG coating parameters were optimized for stainless steel (SS) 316L vacuum chambers. Fig 1.shows the DC Magnetron Sputter Coating Set-up in UHV Lab. Many vacuum chambers (Size: 100mm diameter, 400mm length and material grade SS-316L) were coated with Ti-Zr-V NEG film at different coating parameters. Ti-Zr-V getter alloy with a well-defined composition ranges to provide low activation temperature. The vacuum performance and activation of coated chambers were studied by pumping speed measurement and ultimate vacuum testing of these chambers. Some of the important results achieved for coated SS chambers are as follows: The lowest ultimate vacuum achieved: 4x10-12 mbar, Thickness of coating: ~ 2.8 µm, Coating composition: Ti- 32%, Zr-23%& V-45%, Activation temperature & time: 250C for 24 hrs.
This development has paved the way for the indigenous development of NEG coating of conductance limited vacuum chambers to be used in particle accelerators and storage rings.

DC Magnetron Sputter Coating System

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