metal or ceramic foam

>
> >Can anyone give a rough estimate of the mass of a lunar mass driver?
> I presume
>
> [...]
> Electrical component total mass 53 tons

When I last looked at it the worst problem seemed to be for the
energy storage component - capacitors being a common choice,
but to store that much energy for quick release you need a lot of them...
Is that what this "electrical component" mass consisted of here?

Arthur