I am a plasma scientist so I work closely with this. This would not work, it's not that your idea isn't a good one, I have often thought about isolation of particles like such, but you fail to realize that particles aren't compressed as such, they will follow the magnetic fields generated. Also the protons could never align, even if you removed all forms of instabilities and completely eliminated the inherent quality of randomness, there could be no electron bonds to keep the protons locked, and if you tried increasing the force to the point where they would be you would force fusion, which just transfers the kinetic energy of the particle. There is no way to lock these particles in space, as well as the fact that if you didn't keep it high energy it would rip electrons from the shells of any wall you would be using for the vacuum. Cold plasma is a tricky situation, and there is no way of controlling it, even under perfect situations. Also you seem to have flawed ideas on the basic principles of the conservation of energy. The protons wouldn't get cold even if you managed the impossible task of locking a plasma which is inherently high energy the kinetic energy of the particles wouldn't go anywhere, as there is no place for that energy to dissipate. In fact we use density to keep plasma high energy because there is less energy loss through motion and more high frequency interaction. Finally it is not the Bose-Einstein effect but rather the Bose-Einstein state of matter which inherently cannot be a plasma. I hope this helps.