Theoretical Advance in Magnetism

7 01 2013

PDF of  research paper.

phys.org reports on a theoretical advance in magnetism:

A general property of magnetic fields is that they decay with the distance from their magnetic source. But in a new study, physicists have shown that surrounding a magnetic source with a magnetic shell can enhance the magnetic field as it moves away from the source, allowing magnetic energy to be transferred to a distant location through empty space.

The basis of the technique lies in transformation optics, a field that deals with the control of electromagnetic waves and involves metamaterials and invisibility cloaks. While researchers have usually focused on using transformation optics ideas to control light, here the researchers applied the same ideas to control magnetic fields by designing a magnetic shell with specific electromagnetic properties.

Although no material exists that can perfectly meet the requirements for the magnetic shell’s properties, the physicists showed that they could closely approximate these properties by using wedges of alternating superconducting and ferromagnetic materials.

The Polywell depends greatly on advances in magnet technology. This approach may be applicable, I don’t know.

A practical realization of a magnetic metamaterial still requires all the inconvenience of superconductors which tempers my enthusiasm. Still, this idea glimmers with potential.

Also, I bet I could build and test one. In fact I have almost all the materials on hand. Submit your ideas for an experiment in the comments.

magnetic_metamaterial

FIG. 4: Enhanced magnetic coupling of two dipoles through free space. In (a), magnetic energy density of two identical cylindrical dipoles separated a given gap. When separating and enclosing them with two of our shells with R2=R1 = 4 [(b)], the magnetic energy density in the middle free space is similar to that in (a). When the inner radii of the shells are reduced to R2=R1 = 10 [(c)], the magnetic energy is concentrated in the free space between the enclosed dipoles, enhancing the magnetic coupling.





Inconclusive Symmetry Test

14 08 2012

The symmetry test was an experiment we ran to determine if our potential well was symmetrical across its x-axis. It featured three langmuir probes, one in the center, on at the extreme left, and one at the extreme right. more details are in this post.

While there were a few interesting results few interesting results, on the whole the experiment was inconclusive, and totaled our electron gun assembly.

The first problem we encountered was the vacuum level. We barely got into the 10^-4 Torr range, and when we turned on the electron beam, the pressure went up into the 10^-3 Torr range. High pressures like these don’t render the experiment impossible, but they certainly don’t help. Ideally, the only particles in the chamber would be electrons, and so everything else just adds to the list of unknown factors.

The e-gun was running normally, giving us readings of about -50VDC on the oscilloscope.

The glow from the hot cathode

For the first shot we did a control. We hooked up one probe to the center langmuir, and one the the shunt resistor on the on power supply, and we got a small well.

 

So everything was working as expected, despite the unusually high pressure. This is good, but also strange in light of the last test results, in which the charge at charge at the center of the core became less negative when we fired the coils.

Then we switched the oscilloscope probe on the coil power supply to the left langmuir probe, and fired.

Top: Left langmuir probe
Bottom: center langmuir probe

Nothing on the left langmuir. We tried again with more power going into the coils.

Here’s what we got

The charge at the leftmost extreme of the well is about -3VDC, and the charge at the center is about -10VDC. Not surprisingly, electron density has some relationship to distance from the center of the core. We intend to eventually define this relationship precisely, but to do so would require much more data.

Notice how even before the coils were fired, the top line is a slightly below its zero point (indicated by the crosses at the left of the screen). This means that for some reason, the left langmuir is brought to a slightly negative potential by the electron gun, even though it’s not pointed anywhere near the probe

We then switched the oscilloscope probe on the left langmuir to the right langmuir, and fired the core again. The moment we did, we heard a metallic noise from inside the chamber, like a coin dropping onto a metal surface. Can’t be good. This was the readout on the oscilloscope

Not especially meaningful to us.

We rightly assumed that the noise meant our trial was over, so we opened up the chamber.

We found the accelerator anode laying in the bottom of the chamber. The heat from the filament melted the plastic enough for the screw mounted in it to come loose. Everything around it was coated in a thin film of blue plastic, and much of the wire insulation was burnt as well.

 

Obviously, ABS plastic and rubber insulated wires just aren’t right for this experiment. They can’t take the heat of the cathode, and they out-gas so much that they ruin the vacuum.

Back to the drawing board.

Domenick Bauer





Neodymium Magnet

2 11 2010

All photos.

I received a neodymium ring magnet today with an eye towards a permanent magnet magrid.

This thing is wicked strong!





Superconducting Magnet

15 10 2009

Gearing up for a second superconducting magnet test. This time computer controlled. Here is the new bobbin with 133 turns:

IMG_4262

Read the rest of this entry »





Hacking the DC Magnetometer

21 09 2009

Today I hacked the Alpha Labs magnetometer to add an interface for the DAQ. Here is the finished product:

IMG_4072

Here is how:

First I got some info from the manufacturer:

DCM output instructions

Easy! Now we cut a shape out of prototype PCB by scoring and snapping:

IMG_4052

I used a small circle file to remove the corners we cannot score and snap:

IMG_4054

Here is the finished PCB fragment:

IMG_4058

Next we solder in some jumpers, mount the piece and solder the cable tie-downs to secure the assembly:

IMG_4062

And wire it all up:

IMG_4070

I plugged it into a differential channel on the DAQ and…

SUCCESS!

We have a DC magnetometer sending data to the computer. Regarding interpreting the results, Andrew from Alpha Labs says:

The Gauss conversion to output voltage is 200mV at full scale. So if you are in the 20,000 range and you are reading 5000 Gauss, your output should be 50mV. If you are in the 2000 Gauss range reading 1500 Gauss, your output should be 150mV. So the output jack gains by 10 WITH the range control switch.





Superconducting Levitation

22 04 2009

Finally got a good photo of superconducting levitation produced by the Meissner effect (the white disk is a tiny magnet):

levitation





Mad Magnets

20 02 2009

I had no idea permanent magnets could be so strong… then I saw this insane magnet accident.








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