metal or ceramic foam

Can anyone give a rough estimate of the mass of a lunar mass driver? I presume
that SSI must have conducted a great many studies, but I have found it extremely
difficult locating any mass estimates. I started to citehttp://lifesci3.arc.nasa.gov/SpaceSettlement/75SummerStudy/Design.htmlas a source, but I see that this study assumes a 30 G acceleration of the payload. Working models later achieved 1,800 Gs, and a mass driver operating at this level of acceleration would be much shorter and hence weigh less. Seems like I heard someone say that the components for the mass driver itself could fit into a single Shuttle payload, but that its PV panel power supply would be several times this.