How to focus a beam of charged particles?

[NERV]

I was discovering a way to focus a number of charged particles which has been accelerated by Van de Graff generator into a beam.I do tried to find ideas in uniform magnetic field,but it seems I can only focus the particles onto a point rather than a beam.So here I was asking whether there had been any means discovered before?

Thanks.

[ZapperZ]

For many particle accelerators, one "focuses" a beam of charge particles using quadrupole magnets.

Zz.

[NERV]

Thanks for your reply.Would you mind if you describe it in details?

[malawi_glenn]

Use google, there are plenty of good resorces out there. Then you can ask more specific questions if you enounter any problems.

If you don't find anything, I can give you a bunch of links to lecture notes.

[NERV]

I've purchased two books on electromagnetic field designing.Thanks for your information.