Berlin 2012 – wissenschaftliches Programm

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VA: Fachverband Vakuumphysik und Vakuumtechnik

VA 2: Desorption

VA 2.1: Vortrag

Montag, 26. März 2012, 14:00–14:20, HFT-FT 131

Outgassing rate measurement by using the difference method — •Katharina Battes and Volker Hauer — Karlsruhe Institute of Technology (KIT), D-76344 Eggenstein-Leopoldshafen, Germany

Outgassing plays an important role in the field of vacuum technology, especially if ultrahigh vacuum conditions shall be reached. For example hydrogen desorption from stainless steel is a common problem. For building new vacuum systems the outgassing rates of the materials should be strongly considered.

Often, outgassing rates of different materials are reduced by a pre-treatment like electro-polishing, baking or vacuum-firing.

However, the theory of outgassing is quite complicated and not yet fully understood. Also, experimental results reported in the literature are often not consistent. This is why new experimental efforts are under way at KIT to provide a better understanding.

The two main methods to measure outgassing rates are the pressure-rise method and the throughput method.

The new outgassing measurement apparatus currently being built at KIT uses the difference method (a modified throughput method). With this method the pressure difference between two identical vacuum chambers, with one containing the sample and the other acting as a reference, is measured to achieve the outgassing rate of the sample. Like this, the outgassing of the vacuum chamber can be subtracted and also very low sample outgassing rates can be measured.

This paper introduces in the various outgassing measurement concepts and describes the current status of the new facility.