The prototype for the series production of the 400 modules to be built by C
NIM is first shortly described after the surface cleaning and 400 degreesC
air firing. The system for the 160 degreesC bake out, the pumping and measu
ring bench installed in the CNIM premises are then presented. The results o
n leak tightness, hydrogen outgassing and residual hydrocarbon contaminatio
n are reported and compared to the 20 degreesC VIRGO specifications. An add
itional test on hydrogen diffusion at 400 degreesC performed at CERN on a s
tainless-steel sample is reported. Our measurement of the hydrogen outgassi
ng rate is discussed in relation with this test and also with regard to the
oxide layer resulting from the air firing. (C) 2001 Elsevier Science Ltd.
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