Dear Mark,

    I have simulated the 30-cm focus point setup. The large focus distance allows to place seven coils with spacing of 15 degrees. Please see the picture attached.

    I also constructed the plot Force/Weight for the 100 nm-particle. Please see the pdf-file attached.

    Gradually the flux density is decreasing and the force is directed towards the coil (in the air of higher magnetic flux density). But you may notice that there is a horizontal plateau at about 10 cm distance. The gradient is zero there so is the force.
    The interesting fact is that the force has maximum at the distance (22 cm) - shorter than the focus point (30 cm)
    
    Time spent 1.5 hours.
	
	
	


Dear Alex,

There are 2 requirements which are interesting. 
The radius of the circle is increased to 30 cm what will be the magnetic field distribution instead of 20 cm ( i.e. in the same set up increasing the radius to 30cm). I can understand it will not be of any use at the centre but it can be of help in other areas.


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Also the graph or paramedic  analysis I am looking for is attached below a similar graph (attached with this mail) in this location will make things clear.
Thereafter, if you can increase the diameter to 30cm, and if you can give a similar graph in that location it will make things easier to understand.


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      I guess you could get the graph in negative values. The force /wt could be in the negative values. However, this could mean a sucking force or the negative force on the magnetic nanoparticles which would be interesting.
If 30 cm is very large a radius you may change it as 25 cm.



with regards,
Mark