procedure for the testing of surfaces of components and in
particular of welds.In contrast to this desire for widespread penetrant testing, how-
ever,there is the general fear that components or welds tested with the dye penetrant and which are used in the environment of cryo-vacuum and particularly in the ultra-high vacuum conditions are contaminated by the dye in such a way that they do not fulfill the cleanliness requirements for vacuum components. This fear is mainly based on the high penetrating property of the dye and its particular creeping characteristics, which just is the property required for the test procedure. After the penetration test, however,the penetrant dye may remain in cavities like porosities or in
cracks and might cause virtual leaks during the evacuation and in
the vacuum, due to extended outgassing. As the penetrant dye primarily consists of hydrocarbons, which are considered critical for outgassing in fusion devices, penetrant test of such vacuum components is usually considered problematic. In this investigation we