Tiny X-rays of Tiny Animals 30
Johnny Vector writes: "Scientists at Cornell have taken X-rays of fruit flies, with enough detail to see the hairs on their wings. The AIP has more photos. They did it with an "X-Pinch" machine: vaporize a wire, the resulting plasma implodes, producing a tiny (1/1000 inch), fast (nanosecond) pulse of X-rays. I want one of those machines."
Re:I hope they don't ignite the atmosphere... (Score:3, Informative)
See, for example, this Scientific American article [sciam.com] about "Z-pinch fusion".
Re:"Pinches" (Score:3, Informative)
The pinch effect is created by the strong axial magnetic field created by the current flowing through the material in question. See here [electronicstheory.com] for illustrations of magnetic fields. In the case of the article they used two crossed wires which were vaporized to a plasma(therefore still conducting like a wire) by high current. You can picture the strong magnetic field wraping cylindrically around (and squeezing inward with increasing current) the vaporized wire/plasma's axis. At the intersection of the two wires there would then be a small bubble of highly compressed plasma which is heated to extremely high temperatures, as the plasma cools there is a fast plasma "recombination" where the electrons rejoin their nuclei and emit a fast burst of x-rays.
(IANAP so if someone here is, and there is a mistake anywhere feel free to correct me)
If you instead picture an annular array of wires(eg. 10-20 wires) rather than two crossed wires than you can see that the individual magnetic fields of the wires combine into one huge axial field. This is the so called Z-pinch (because the magnetic field is in the "z" axis). These are the pinches used to initiate thermonuclear fusion in machines like this [sandia.gov].
As an aside: Sandia used to use an X-Pinch to "backlight" implosion experiments on the Z-Machine with x-rays so that they may be imaged. Recently they upgraded this setup with a more reliable method of x-ray backlighting using ultrahigh power laser pulses to heat a metal foil target that then creates x-rays. The place where I work supplied the laser parts.
Re: Did you just guess that that would happen? (Score:2, Informative)
Yes you get RF emission and visible light and even a substantial amount of UV. But if you knew anything about the EM spectrum that you mentioned in your post, you would know that x-ray photons are a thousand times more energetic than UV photons and the puny spark in a blown fuse at household current could not possibly create x-rays.
The Z-machine [sandia.gov] at Sandia National Labs uses up to 20 Million amperes!! to pinch its plasma fusion experiments. In order to create x-rays from a pinch you need to heat the plasma in the pinch to millions of degrees celsius; the x-rays are produced by hot plasma radiating its energy through bremsstrahlung emission and the nuclei-electron recombination time during plasma cooling.
Re: X-rays from ordinary electrical fuses (Score:4, Informative)
What the previous poster says is completely wrong. You always get X-rays even from ordinary electrical sparks such as from fuses blowing. The ideas explaining this fact have been known since the theories of quantum mechanics were developed in the 20th century.
Planck's Law [egglescliffe.org.uk] states there are emissions of electromagnetic radiation at all wavelengths from zero to infinity, i.e. including visible light, infrared, ultraviolet, x-ray, gamma ray, etc.
Planck's Law of Energy Distribution:
L is the wavelength of emitted radiation [metres],
T is the temperature of the black-body emitter [Kelvin],
c is the speed of light (3x10^8 metres/second),
k is Boltzmann's constant (1.38x10E-23 Joules/Kelvin),
h is Planck's constant (6.62606891 x 10E-34 Joule seconds), and
PI is the mathematical constant (3.14159...)
The electromagnetic emissions are strongest at one wavelength given by
Wien's Law [egglescliffe.org.uk]
There is a simple experiment to give a visible indication that a wide range of wavelengths is emitted by electrical sparks. Wearing gloves and safety eye glasses, connect a short 2cm length of 1Amp fuse wire across the two terminals of a low voltage supply like a 12Volt car battery. The fuse wire will blow. Notice the color of the centre of the spark is roughly white. This is because the temperature of the vaporised metal from the fuse wire, created when the fuse blows, momentarily exceeds 5000K, giving a wavelength of peak emission by Wien's Law of 580nm (green light).
If you want to understand more about the electromagnetic spectrum, there is a great summary of the quantum mechanics of black body radiation here [egglescliffe.org.uk]