05 Dec 12
2 edits
I missed this bit of physics news that happened a few months back but I was interested to discover today that physicists managed to create a 100 Tesla magnetic field without blowing up the magnet:
http://www.gizmag.com/100-tesla-pulsed-magnet/21946/
I have some burning questions:
If such a 100 Tesla magnetic field was used for MRI, what would its maximum resolution be? I mean, what would be the distance across of the smallest feature it could image? are we talking here about just a few nanometers?
And, what is the mathematical formula for the maximum possible resolution of a MRI scanner given it uses a magnetic field that is X Tesla strong?
And, given unlimited strength of a magnetic field, is it theoretically possible to get an MRI image of single atoms? or even single electron orbitals? what is, if any, the fundamental limit to the maximum resolution to an image from MRI given unlimited magnetic field strength?
05 Dec 12
Originally posted by humyI work with 1 tesla magnets and even THEY are 3000 pound monsters.
Does anyone have a qualified opinion on the likelihood of 1,000 Tesla field ever being made without blowing up the magnet? What about 10,000 Tesla?
The work they do is for ion implanters, for steering the ion beam in one machine and in all ion implanters, there is one of them that picks out the right isotope of whatever you are using for the ion beam. For instance, one dopant is boron and it comes in two main isotopes, B10 and B11. B10 occurs in nature roughly 1/4th the amount of B11.
They both do the job of doping the bare silicon wafer into conduction but because B11 makes a beam about 4 times stronger simply because there is more of it in the arc chamber that makes the beam, you tune the magnetic field to cause B11 to bend at a 90 degree angle and B10 just hits a graphite stop barrier. That is an easy pick because B10 and B11 are relatively far apart mass wise about 10 percent difference. Harder is to discriminate between antimony 123 and 121, after sending one on a 90 degree bend, the other one is very close so other means is used to separate the two.
So that's what you can do with just 1 tesla. If we used 1000 tesla magnets or even 100 tesla magnets, even huge ions like antimony or arsenic would get bent around in a circle, which would do no good for an ion implanter.
I imagine 1000 T magnets will be built eventually but 10k Tesla, that is a real stretch. I wonder if they can ever make a floating magnetic field, that is to say where the magnetic field is in the center of a cylinder and there is no field or very small field in the windings. That would seem to me the only way they could make super strength 1000 tesla, 10,000 tesla magnets. 1000 tesla is 10 MILLION gauss.
Even my 1 tesla magnets are 10,000 gauss capable.
Safety becomes a big issue with 100 tesla fields, 1 million gauss.
You remember the story of the little 5 yo boy killed when he had an MRI and some idiot forgot to clear the room of magnetic material? There was an iron cased fire extinguisher on the other side of the room and when they fired up the magnet it was slammed across the room and hit the boy in the head, killing him instantly.
And that was just an MRI machine. Imagine the safety procedures they had to go through to contain a million gauss magnet.
One thing those monster fields will do is to way increase spectroscopy resolution.
They already know a 10 tesla magnet can make a frog levitate so I imagine a 100 tesla job could make humans levitate, maybe the ultimate elevator!
I imagine they are thinking of ways to weaponize it also, like a 100 tesla rail gun...
06 Dec 12
Originally posted by sonhouseI suppose my question is why would science find valuable a microscope using MRI technology able to distinguish individual atoms when the technology already exists, is mass-producible, and mature? Is there benefit to additional atomic-fineness technologies when STM/SEM can already do the job?
I work with 1 tesla magnets and even THEY are 3000 pound monsters.
The work they do is for ion implanters, for steering the ion beam in one machine and in all ion implanters, there is one of them that picks out the right isotope of whatever you are using for the ion beam. For instance, one dopant is boron and it comes in two main isotopes, B10 and B11. B10 ...[text shortened]... tor!
I imagine they are thinking of ways to weaponize it also, like a 100 tesla rail gun...
06 Dec 12
9 edits
Originally posted by sasquatch672
I suppose my question is why would science find valuable a microscope using MRI technology able to distinguish individual atoms when the technology already exists, is mass-producible, and mature? Is there benefit to additional atomic-fineness technologies when STM/SEM can already do the job?
I suppose my question is why would science find valuable a microscope using MRI technology able to distinguish individual atoms when the technology already exists
because the current methods for imaging and distinguish individual atoms are useless for seeing certain things that we want to see.
For example, if you want to distinguish individual atoms within an enzyme as it does its chemical reaction within its normal watery environment so that you can see how the molecules change shape and exactly how the enzyme molecule does its job, with current electron-microscopes and other current imaging techniques, you can almost forget! That is because an electron-microscope does not generally work directly on liquid samples ( although there is an ingenious albeit a very limited workaround that by adapting this technique: http://physicsworld.com/cws/article/news/2012/apr/10/graphene-capsule-reveals-nanocrystal-growth-in-action ) .
An MRI with a magnetic field that is powerful enough should, at least in theory ( I think ) , be able to directly image an enzyme at work in a watery environment which is something that has never been done before.
Also, what if you wanted to see the arrangement of molecules deep inside a fossil ( say, 1cm deep ) without destroying the fossil? With electron microscopes, you couldn’t because you can only image with that much detail on or very near to the surface of a sample with electron microscopes although you could, at least in theory, image molecules deep inside the fossil with difficulty using X-rays or gamma-rays but this might significantly degrade the sample due to ionization and heating effects.
06 Dec 12
Originally posted by humyOn the same subject; I tried to see if a 'gamma ray laser' has ever been built that can probe the position of molecules or atoms within a sample.I suppose my question is why would science find valuable a microscope using MRI technology able to distinguish individual atoms when the technology already exists
because the current methods for imaging and distinguish individual atoms are useless for seeing certain things that we want to see.
For example, if you want to distinguish in ...[text shortened]... amma-rays but this might significantly degrade the sample due to ionization and heating effects.
From what I can gather from the net, no such devise has ever been built.
But, I have found this link to newscientist magazine of news published last year that shows research suggests it certainly should be possible to build such a devise:
http://www.newscientist.com/article/mg21228442.500-how-to-build-a-gammaray-laser-with-antimatter-hybrid.html
How to build a gamma-ray laser with antimatter hybrid
22 December 2011 by David Shiga
Magazine issue 2844. Subscribe and save
HALF matter, half antimatter, positronium atoms teeter on the brink of annihilation. Now there's a way to make these unstable atoms survive much longer, a key step towards making a powerful gamma-ray laser.
All the elements in the periodic table consist of atoms with a nucleus of positively charged protons, orbited by the same number of negatively charged electrons. Positronium, symbol Ps, is different. It consists of an electron and a positron orbiting each other (see diagram). A positron is the electron's antimatter counterpart. Though positively charged like the proton, it has just 0.0005 times its mass. Positronium "atoms" survive less than a millionth of a second before the electron and positron annihilate in a burst of gamma rays.
In principle, positronium could be used to make a gamma ray laser. It would produce a highly energetic beam of extremely short wavelength that could probe tiny structures including the atomic nucleus - the wavelength of visible light is much too long to be of any use for this.
The trouble is that this means assembling a dense cloud of positronium in a quantum state known as a Bose-Einstein condensate (BEC). How to do this without the positronium annihilating in the process was unclear.
Now a team led by Christoph Keitel of the Max Planck Institute for Nuclear Physics in Heidelberg, Germany, suggests that ordinary lasers could be used to slow the annihilation. The trick is to tune the lasers to exactly the energy needed to boost the positronium into a higher energy state, in which the electron and positron orbit farther from one another. That makes them much less likely to annihilate (arxiv.org/abs/1112.1621).
The positronium will eventually lose energy by emitting photons and return to the annihilation-prone state. But the team calculates that about half the excited positronium atoms can survive for 28 millionths of a second on average, 200 times as long as unexcited ones.
This may be long enough to assemble the BEC cloud. In a BEC, positronium atoms behave in lockstep, so when one annihilates itself, the rest follow suit, producing a burst of laser radiation made of gamma rays.
It may sound like a lot of work, but one thing makes the task easier. Ordinary atoms can only form a BEC when cooled gradually to within a fraction of a degree of absolute zero. By contrast, due to quantum effects, positronium will form a BEC at close to room temperature.
09 Dec 12
1 edit
Originally posted by humyI saw the video of the pulsed field. I wonder if they can go from 15 ms to full time? The 15 ms shot took a 1.2 gigawatt generator. If you assume 100 % use of that energy, then the power involved was 18 megajoules! I imagine they will be pushing for even higher field strength.
On the same subject; I tried to see if a 'gamma ray laser' has ever been built that can probe the position of molecules or atoms within a sample.
From what I can gather from the net, no such devise has ever been built.
But, I have found this link to newscientist magazine of news published last year that shows research suggests it certainly should be possible to quantum effects, positronium will form a BEC at close to room temperature.
[/quote]
BTW, did you look at that motor video in Spanish and the second video? The dude made a motor out of rotating magnet parts. Not sure what he was trying to show since something had to power the first spinning magnet. It looked like he was generating about 100 watts or so in the second video.
It looks more like a magnetic right angle gear than a motor but it seemed to generate enough energy to power a small fan and some kind of light, probably an LED. He didn't explain where the power came from to power the first spinner or how much energy it used.
18 Dec 12
1 edit
Originally posted by sasquatch672The main thing MRI's can do that SEM's and STM's can't is examine living tissue.
I suppose my question is why would science find valuable a microscope using MRI technology able to distinguish individual atoms when the technology already exists, is mass-producible, and mature? Is there benefit to additional atomic-fineness technologies when STM/SEM can already do the job?
The thing about electron microscopes is this: The subject being probed has to be put in a vacuum so the electron beam does not get diffracted away, blasting through a bunch of atmospheric gasses which would at the very least defocus the beam to unusability. Put a biological cell in a vacuum and you would just have a tiny smear of blown up cell in the microscope probe chamber.
MRI's have no need of vacuum so they can examine living tissue.