Problem understanding Paul traps

[chandrahas]

Paul traps have been confusing me a lot recently. So sorry if there are too many questions

• I know that paul traps confine ions with the help of rapidly switching quadruple electric fields, I've heard that paul traps actually force the particle to move to the center where the electric field is zero. But I see no reason behind this. Wouldn't the particle just oscillate about a mean position? Why would they drift to the center?
• For paul traps to work, the electric fields must switch faster than of which the particle reaches the wall. So, does any frequency above this value work fine? Just to make my point clear, would a paul trap operating at 1 Thz work just as well as a one at 1 or 2 Mhz?
• If my assumption above is accurate, then can a paul trap trap more than one type of species? Say electrons and protons? I understand that in order to confine electrons, we would need the switching of electric fields to be much higher than that needed to confine ions.
• Then can't we confine plasmas just as well? Debye shielding would hardly be a problem as the particles lack time for screening to occur?
  

Thanks

 

[nbryan5]

a lot for your help!Paul traps use rapidly switching electric fields to trap ions by accelerating them towards the center of the trap where the electric field is zero and then confining them there. The frequency of the electric fields needs to be higher than the particle's transit time, which is the time it takes for the particle to reach the wall of the trap, otherwise the particle will not be able to be confined.Yes, higher frequencies above the transit time will work fine. Paul traps can be used to confine multiple species of particles as long as the frequency of the electric fields is high enough to be faster than each particle's transit time. Paul traps cannot be used to effectively confine plasmas, as the particles in plasmas move too quickly for the electric fields to be able to keep up with them.