I'm gonna expose myself and say that I don't recall watching or reading of stuff that shut off circuits in Fate (unless we count a certain Shroud in HF), but I've mostly stuck to the original VN, ataraxia and extra. The idea was to have a key component to explain the potency of the Jokers (and explain why they are so 'irreplaceable'), but I didn't have anything specific to this series in mind for the second one. 

I was originally working off the idea of Otataral, an ore in a different setting, and the explanation I had planned for that one if asked IC was mostly to reference that as a nod to that series, the use of a rare, poorly understood mineral that had the strange property of negating magic. It is implied that it did this by eating it, as though magical energy just suddenly slipped into a black hole when activated under its area of influence. In that particular setting that ore could have long-term, sometimes permanent effects on people who were exposed to it (such as by rubbing Otataral dust over their bodies), the most typical of which was the person acquiring the same magic-deadening properties as the ore. 

Now, because I don't want to permanently cripple all the mages in a setting by blowing dust on them, let's assume this is a made-up version for convenience and say any effects of a device taking advantage of this are only temporary.