# Will it be easier to separate a low or high density plasma into negative electrons and positive ions

I know separating plasmas into positive ions and negative particles requires energy. Now, I was wondering whether it would be easy to separate a low or high density plasma. The first thing I thought about was: When we have a high density plasma, there is a lot of positive charge attracting the electron.... but there is also a lot of negative charge that repel it. But as we pick out electrons one by one, there would be an extremely large positive charge to oppose.(which requires a lot of energy). Since I need a lot of energy, I thought maybe I could just turn it into a low density plasma instead. .. Now as we pick electrons one by one, there is less positive charge to oppose. Hence it requires less energy. But since we just converted the high density plasma into a low density one, we have a lot of low density plasma to separate. Now, I was wondering if in the low density case, will we need the same total energy to separate the plasma or will it be less than or greater than the energy required to separate the plasma in the high density case??

--To sum it all up, I am asking whether it would be energy efficient to convert the high density plasma into a lower one to separate it into negative electrons and positive ions & Is there any general formula for the energy required to separate a plasma

• Most plasmas I'm familiar with (of the astrophysical variety) are quasineutral; that is the electrons are separated from the atoms. I'm not sure what the point would be in doing what you ask. – Kyle Kanos Feb 1 '17 at 12:14
• Yeah, electrons are separated from the atoms, but what I am trying to do is pull the electron from the plasma off to infinity. I was wondering about this for a project. But anyway, its more like a thought experiment. – Chandrahas Feb 1 '17 at 12:29
• Just use an electric potential and a collecting plate for the ions but not the electrons. First accelerate the electrons (e.g., cathode ray tube) along the "horizontal" then apply an electric field transverse (i.e., along the "vertical") and watch the two species separate. You can then use a grounded collecting plate for the ions and send the electrons off to infinity if you like. Though I should mention that you could just use something like a cathode ray tube and generate only an electron beam from the beginning. – honeste_vivere Feb 2 '17 at 14:39