Magnetic Flux Concentrator

This topic has been discussed many times in different forums. Yet I have not seen any worthwhile result. In some cases I found magnetic lens meant concentrating an electron beam using But here our intention is to focus a magnetic flux. There is no electron beam / magnetic field interaction..

I found from Wilkipedia that industrial lasers are about 5 to 15 % efficient and laser beam size may be about 0.1 mm. Laser power will be about 1Kw to 3 KW depending on material to be cut. Iron requires lower power where as aluminum requires higher power for same metal thickness.

Given that suppose we employ induction cutting using magnetic lens (WISH LIST r TARGET TO BE ACHIEVED) - we need to focus say about 150 w inductive energy- emanating from a ferrite rod with 0.3 T – down to about 0.1 mm.

Energy stored in an inductor is

E= ½ L I^2. Also same as = ½ Al B^2/µi given that µr = 1 for air.

Hence for B = 0.3, one could still reduce Area of cross section A and L= magnetic path length (air gap length)

Have I missed some thing in my specification? I do find practical difficulties of getting high LI^2 over say 0.1 mm dia magnetic area and hence one will need to use magnetic flux concentrators as much as possible. I do not see any difficulty ANY DOUBTS ????