# I Question about making a coaxial magnetic field in a pipe

1. Jun 14, 2017

### ItsGameTime

Hi, for a particular project, I would like to create a 1~2 Tesla magnetic field in a stainless steel pipe along the z axis. I was wondering if my concept would work, or if anyone had better ideas.

Here's my concept.

Fig1. So I got a few pipes about 1 inch in diameter. I would like to have a 1T magnetic field through it along the vertical direction (z axis)

Fig2. My idea was to get a 2 cylinder blocks of iron, drill some holes in it to allow the pipes to fit in as shown in the diagram.

Fig3. Then attach some wire coils to the iron cylinders like as shown in the diagram.

My question is, if I actually create a device like this, how would the magnetic field be.....

....directly above the cylinder (region A)
....in the pipe space area inside the cylinder (region B)
...in the pipe area between the two cylinders (region C)
....in the pipe space area inside the bottom cylinder (region D)
....directly below the bottom cylinder (region E)

2. Jun 14, 2017

### CWatters

If you wind a coil around an iron pipe I think most of the field will stay in the iron with the field in the hole being small.

3. Jun 14, 2017

Staff Emeritus
I think you need more thought on the coil design than just "attach some coils".

4. Jun 14, 2017

### Staff: Mentor

I agree with @CWatters -- winding a coil around a ferrous metal pipe is not the right approach.

@ItsGameTime -- What is your project? What are you trying to do? If the pipe has to be metal, can it be a non-ferrous metal (like Al)?

5. Jun 14, 2017

### Staff: Mentor

BTW, that's a pretty strong magnetic field that will take quite a bit of power to produce. Why do you need such a strong field filling a long volume?

6. Jun 14, 2017

### davenn

sounds like a coil gun

7. Jun 15, 2017

### ItsGameTime

Thanks for all the replies so far. I guess I should explain a bit more.

I am trying to collimate an ion beam. I need gas ions to go straight through one end of the pipe and out the other. The pipes can be non magnetic. The pipes don't need to be that long, I think actually several centimeters should be fine. The diameter of the pipes hasn't been confirmed, but shouldn't exceed 3 or 4 cm.

I redrew the picture again. The upper half is the side view, the bottom half is the top view. I hope ions can go through the holes and that the magnetic field will help it "straighten out."

The giant helmholtz coil can extent out any size.

I said 1T for planning purposes. Realistically I am hoping this can be accomplished with around 50 to 100 mT.

Or is my physics completely out of whack here?