The influence of the vacuum environment on the growth of electron irradiation induced voids

The variability of the void swelling in nimonic alloy P.E.16 produced by electron irradiation in the high voltage electron microscope has indicated some influence of the vacuum environment on the nucleation and growth of voids.Specimens of double vacuum remelted nimonic alloy P.E.16 prepared under controlled conditions were preheated at 550°C for 1 hour in the microscope and then irradiated at temperature with 1 Mev electrons at a displacement rate of 2 x 10-3 per sec to a total dose of 10 - 20 displacements per atom.Measurement of the vacuum environment around the specimen was made with a Vacuum Generators Micromass 2A mass spectrometer fitted with a long sampling tube extending to within 10cm of the specimen position. Control of the specimen environment was achieved by bleeding in a chosen gas by way of a Leybold leak valve fixed into the side of the specimen chamber so as to introduce the gas to a point within 5cm of the specimen position and on the same plane.