In order to decrease mechanical resonance, the cylindrical external shell which is connected the annular enclosure null annular ended

摘要

A hollow cylindrical vessel comprising a cylindrical outer shell (12) and a cylindrical inner shell (14) joined by annular end caps (16), wherein at least one of: an end cap, or the cylindrical outer shell (12), or the cylindrical inner shell (14), is provided with an arrangement of recesses or protrusions (18). Preferably, the arrangement of recesses or protrusions is asymmetrical in all axes.