From: Axil Axil
I think that the direction of the current rings alternate down the length of the nanotube which would negate the axial magnetic field. Check if this is true. I did not word the description very well. Yes, the current rings would probably alternate down the length and around the circumference, so they would not provide an axial field themselves. They would however provide a very intense focusing field, just as do quadrupole and hexapole magnets on any large beam line. That need for an axial field is why an external field becomes important. A weak magnetic field must be provided from outside the system which will be the axial field in which weak field lines which are being focused by CNT would be highly compressed so that any charged particle seeing those lines would tend to take the opposite alignment, be attracted and thereafter be subject to acceleration forces when inside the tube. For Fran Roarty's amusement, this is where the Casimir force could enter the picture since the interior dimension of CNT is precisely the Casimir prime exclusion zone for virtual photons. There is no proof of any of this for now - but in the event that anyone should see photons in the keV range as a characteristic of any CNT device, then this provides a plausible explanation of how that finding is related back to the basic hexagonal bond-length of CNT, about 0.142 nm and how bremsstrahlung at low energy (around 1 keV) provides the feedback mechanism for the SPP. It all fits, proof or no. I am using the wording: field "lines" as an abstraction for simplicity and do not espouse the existence of physical lines.
