Magnetic Field Record Set with a Bang: 1,200 Tesla
spectrum.ieee.org
spectrum.ieee.org
TNT aside, would one survive a MRI at 1200 T? I estimate the resolution would be around 1/10th of a nerve fiber - would that be small enough to _really_ scan a brain?
> For static magnetic fields, acute effects are only likely to occur when there is movement in the field, such as motion of a person or internal body movement, such as blood flow or heart beat. A person moving within a field above 2 T can experience sensations of vertigo and nausea, and sometimes a metallic taste in the mouth and perceptions of light flashes. Although only temporary, such effects may have a safety impact for workers executing delicate procedures (such as surgeons performing operations within MRI units).
> Static magnetic fields exert forces on moving charges in the blood, such as ions, generating electrical fields and currents around the heart and major blood vessels that can slightly impede the flow of blood. Possible effects range from minor changes in heartbeat to an increase in the risk of abnormal heart rhythms (arrhythmia) that might be life-threatening (such as ventricular fibrillation). However, these types of acute effects are only likely within fields in excess of 8 T.
Finding a likely target seems impossible. The way magnetism drops off with distance means it would only be useful when you were already there (or just starting out).
Also the magnetic field in this case is only lasting a tiny fraction of a second, which would be an issue for propulsion.
https://news.ycombinator.com/item?id=8178450
https://www.nextbigfuture.com/2013/11/john-slough-personally...
https://www.centauri-dreams.org/2014/08/28/thinking-about-ma...
https://en.wikipedia.org/wiki/Magnetic_sail
http://casa.colorado.edu/~danforth/science/magsail/magsail.h...
My understanding is that it's more useful as a "magnetic parachute", as it lets you brake without using reaction mass, just electrical power. That could let make an interstellar journey with less mass, as you only need reaction mass to accelerate on departure, and not to decelerate on arrival.
Could someone with more understanding of the material explain the above fragment?
Just like 60 mph isn't hugely fast, but we still quote 0 to 60 times.
Or take the power rating and divide that by 110.
So a 100 watt bulb is close to an amp.
As to the rate, you could use an oscilloscope or a high speed camera.
Household power is AC, I'm sure that will have an impact. For example, switching on the circuit when the voltage is instantaneous 0V would surely result in no change in the flow of current. All you'd have in that scenario would be the rate of change of AC, which would be 10A at 50Hz = 2000 A/s in Australia (1Hz = +240 to -240 and back in 1s).
I'm sure this is hopelessly simplistic though, nothing happens instantaneously - there will be some period of high-resistance arking, etc.
So instead of modeling your home wiring as wires, you should model them as wires plus capacitances, inductances and resistances. The loop from light switch to lamp and back is basically one "big" inductor. The challenge is to find adequate values for these parasitic elements.
You are right about AC though, didn't think of that.
Anyway, the typical MRI power supply is pretty beefy, a few KV and 100's of Amps. And that in a way says it all about how impressive those machines are, they get up to serious field strengths without breaking up.
For reference, a back-of-the-envelope calculation puts the current ramp rate for the LVDS data lines coming from your phone's camera around a few hundred thousand amps per second (-1 to 1 mA in a few nanoseconds).
The setup described in the article is different, with a secondary coil, so I was mistaken.
Is this due to resistive dissipation (heat)? I was under the impression they used superconductors, for which this problem does not exist, but I'm probably wrong.
No:
> The two currents produce magnetic fields that repel each other. However, the main coil is a relatively thick and heavily reinforced ring of copper-lined steel, and the liner is practically foil. You can guess which wins this fight. “Because of the difference in the mass inertia, the liner implodes inwards” at a rate of about 5 kilometers per second, explains Takeyama. As it does so, it compresses the 3.2 T field so that when the liner is at its smallest, the magnetic field inside it reaches 1,200 Tesla. Unable to be compressed any further, the liner rebounds at about the same rate it imploded, destroying itself and the main coil.
Coincidentally, it's the same technological challenge in building an EMP (plus or minus some explosives).
Direct real world applications? There are none, really. Where would you need 1000 T which basically makes everything metallic evaporate in it's vicinity?
There are lots of metallic big things on different types of battlefields, like tanks or even aircraft carriers, it would be really helpful for the opposing sides to be able to “evaporate” them. Not sure how close to implementing this as a weapon we are, though, probably not that much.
70 years ago
Seemly some fusion power reactor designs DO need a temporary very strong magnetic field.
Hmm, does that mean it would evaporate a Faraday cage?
One could argue, why not use superconducting electromagnets (used in fusion machines), but surprisingly the limit is lower there, something above 20T!
So, pulses are much stronger, but also very short. Continuously strong fields need insane machinery which might have thermodynamic limits of what is possible to achieve.
>How would you continuously crush hydrogen with that?
Why do you the crush to be continuous? I thought the idea of metallic hydrogen was that it is stable once you get it in a metallic state.
there are two main hypothetical uses for it: a solid rocket fuel (with a x4 increase in specific impulse) and a superconducting wire with zero transmission loss across long distances (making solar farms in remote places attractive). there may also be military applications eg. hypersonic thermobaric weapon delivery systems.
the other replies in this thread are more realistic. the experiment is likely to study what happens to atoms in high magnetic fields, electrons for example start to pool together in strange ways. as with most scientific research, useful applications are often beyond the horizon and emerge from serendipitous discovery.