you cant stop ETRD from creating plasma in the first plase. however, you could fill all the space with stuff like VOID.

logic gates perform logical operations like "IF A=1 AND B=1; THEN C=1; ELSE C=0". you can control currents with logic gates and you can build stuff like calculators, displays etc only by using 1logic gates and input channels with only 1 or 0.
maybe wikipedia can explain it in a better way: http://en.wikipedia.org/wiki/Logic_gate
or look at powder toy examples:

logic gates:
http://powder.hardwired.org.uk/View.html?ID=1691
http://powder.hardwired.org.uk/View.html?ID=2754
http://powder.hardwired.org.uk/View.html?ID=2893

in action:
http://powder.hardwired.org.uk/View.html?ID=2333
http://powder.hardwired.org.uk/View.html?ID=2891
http://powder.hardwired.org.uk/View.html?ID=2563
http://powder.hardwired.org.uk/View.html?ID=3295

But you might need to give up your whole life for it...

If I may add some of my stuff:
http://powder.hardwired.org.uk/View.html?ID=4111

http://powder.hardwired.org.uk/View.html?ID=3989
http://powder.hardwired.org.uk/View.html?ID=4109

singularity
Have you ever tried programming? Logic gates are basically the same thing, but in physical form.