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FSU Sets 7 World Records In High Magnetics Research
spence calder writes "FSU's High Magnetic Field Lab, more specifically my Kenpo teacher, just broke 7 world records, and brought the record for a superconducting magnet to 25 Tesla. Check it out at FSView and a more detailed article here. Now if only our football team was that cool." And if you'd like your magnetic toys to shoot metal bits,
Jason Rollette points to his
railgun project, which looks like good, clean, high-voltage fun.
That'll keep those damn Americans off my base.
FP
Anti-social? My code is just platform-specific.
Yep, Alfred Nobel probably said a similar thing when inventing dynamite.
Now if only our football team was that cool Are you sure you're a geek?
Everything seemed to be going so nice
'till the end of all beings punched right through the ice
No one knows the effects of an 25 Tesla magnet on biological tissues. In addition, in order to get useable information out of an MRI system, one must hit it with radiofrequency (RF) waves. The higher the static field is, the higher these frequencies are going to be. A 7-tesla magnet uses frequences around 300 MHz. Therefore, by extrapolation (which I believe is right, since I know that a 9T system uses about 383 MHz), a 25 Hz system would need about 1.1 GHz. This might very well be extremely detrimental to biological tissue. In other words, to do MRI, you'd have to cook your sample.
Finally, to truly achieve a resolution advantage, you will need very powerful gradients. The gradients one would need to take advantage of such a system would be gigantic, at least tens if not hundreds of Tesla per meter. This would be very difficult to design for samples as large as a human body, if not impossible with today's technology, and at the very least extremely expensive.
Personally, I can see a 25 Tesla magnet being useful, just not for MRI. Perhaps for NMR being using not for imaging purposes, but in the study of non-soft condensed matter systems (i.e. not biological or organic, but solid state). It would be useful for examining superconductivity also.
One electron has a charge of 1.6E-19 Coloumbs, so you are talking about the equivalent of 6.7E18 electrons moving at 1m/s. One coulomb is the amount of charge that passes through a point in a wire in one second which is carrying one Amp of current.
The instantaneous force being described would be perpendicular to both the motion of the particle and that of the magnetic field. Make a gun with your right hand, let your index finger point in the direction of the charge, let the field point in the direction of your thumb. Stick out your middle finger so it makes a right angle with both digits, and that is the direction of the force.
It is a bit more tricky than just 'add more coils' or 'use more current'.
Back at university we had a 14T He cooled magnet. Reaching 12T was standard. No issues. But having 2 more Teslas out of that thing took many tricks: pumping off the Helium to make it even colder, increasing current near the limit. The thick copper cables got pretty warm. And heat and superconducting coils and Helium don't mix well, so for us, 15T was unreachable.
It's not unsimilar to the 10s/100m in athletics: Everyone get's close, but it took some time until someone finally was faster than 10s.
20T was the limit for 'usual' magnets. Getting more needed a new trick. But I admit that for people not using this stuff, it looks very much like no particular breakthrough. Like I never cared if I can run 100m in 10.1 or 9.9s. It's just 2% difference after all, isn't it?
BTW, at smaller scales, things work a bit differently- it is much easier to make powerful gradients over a small distance (say a few millimeters, or hundreds of microns) than it is over larger ones (say a human torso, or even a forearm). I wish I could be more specific about this, but my theory background on MRI is still a work in progress- I hope I didn't screw anything up in my post above. Any MRI geeks out there, feel free to correct or add anything I missed.
http://www.fsunews.com/vnews/display.v?TARGET=sho
Thats one hell of a soldering iron.
Speaking at Defcon 12 - Credit Card Networks Revisted: Pen
Just curiously, if these fields are being generated as 500,000 times stronger than tha earth's own... are they detectable from space?
None of my credit cards seem to be working anymore...
The problem is that you cant levitate your object because you need it touching the rail to conduct the drive current.
Thats the main problem. Else you could just throw a bagload of teflon on the slug and fire away.
The main problem is not physical abrasion, but the fact that even if the projectile fits perfectly, the current density creates arc discharges between rail and slug, vaporizing the top layers
HI O WISE PRINCE. WHT TOOK U SO DAM LONG?
In that case, the equivalent of Coulomb's Law becomes
F=q(E+v x B)
Here, F is force, q is the charge that is moving, E is the electric field (if present, you may remember something like E=kq/|r|, which is basically the force law you listed divided by a charge, giving units of Newtons/Coulomb), v is the velocity of the moving particle. All quantities in bold refer to vectors, so they not only have magnitude, but direction. In the case of the weber definition above, there is no electric field, so that part has no contribution. We are then left with:
F=q(v x B)
Here, the x does not just mean normal scalar multiplication but vector multiplication. All this means is to take into account the angles between the directions of the velocity and the magnetic field. Either way, the force will be perpendicular to both, so if you can imagine drawing lines indicating the velocity and magnetic field lying in a plane, the force the particle experiences points straight out of that plane. The more in line the velocity and field are (i.e. the smaller the angle they make relative to one another in that plane) than the smaller the force will be. If the particle is moving in the direction that the magnetic field points in, then it will experience no force- again, this is a result of the vector multiplication (better known as the cross product, where A x B=|A||B|Cos[theta], where theta is the angle between A and B.
Make sense? If you have questions, post them here.
Perhaps, after the recent power outages in the US, the most important application of supercoducting magnets could be power storage. There seem to be 2 ways they are used - either to make friction-free magnetic bearings for traditional flywheel systems, or (more interesting) direct short-term storage of power. For situations where you need to temporarily store a *lot* of power this is an interesting technology alternative to batteries/hydro/etc.. Current devices seem to cover mainly very short term variations, but what about covering longer term regulation (hours/days) of variable power from a wind-farm, or solar, for example?
Anyone got more gen on this?
Try Superconducting Magnetic Energy Storage (SMES) Systems
This link describes a commercial device that stores 3 megawatt-seconds..
"You lied to me! There is a Swansea!"