Hydrogen outgassing and permeation in stainless steel and its reduction for UHV applications

Stainless steel, grade 304L and 316L are widely used structural steel in most of the Ultra High Vacuum (UHV) systems in present-day research. Large size vacuum chambers and beam lines are used in much scientific applications, few examples are CERN accelerators, ITER, LIGO, Neutrino observatory, FAIR, Space research, etc. The selection and operation of the large size vacuum pumping system and the material to be used for UHV application is one of the crucial tasks for the vacuum system engineers as it relates the capital and operational cost linked to it. Any failure in operation has a direct impact on the project execution timeline and the huge refurbishment cost. Hydrogen in structural steel and its reduction for ultra-high vacuum systems is one of the major challenges for the present day. Therefore, prior understanding is required for knowing hydrogen content and its permeation and outgassing behaviour in vacuum system establishment and operation. Based on the available literature, a theoretical model for estimating permeation and outgassing rate is discussed. Relating the permeation and outgassing, the theoretical model contains first and second-order Fick?s law and their solutions. Permeation and outgassing rate of 3 mm thick stainless steel is calculated for different thermal bake-out conditions and are discussed. A brief discussion (after going through various references) is mentioned for lowering the outgassing rate for hydrogen in steel. (c)& nbsp;2021 Elsevier Ltd. All rights reserved. Selection and peer-review under responsibility of the scientific committee of the International Conference on Materials, Processing & Characterization.