can anyone explain howz x-ray been produced.
Photoelectric emission occurs when e.m radiation of a certain frequency falls on a metal, each photon gives a single electron energy which causes it to be ejected from the surface of the metal. Now think what happens when the reverse occurs?
Electrons, using a high voltage are slammed into a piece of metal and x-rays are produced. The incoming electrons can knock an electron out of the K-shell (lowest energy level in an atom) and then an electron can fall from a higher energy level into the lower one with the release of energy which is seen as x-rays.
Here is a nice link:
Just for completeness sake, I would like to point out that this isn't the only means of producing X-rays. In fact, the "inverse photoemission" process is quite inefficient in generating X-rays and most users now are moving towards other methods.
One of the most widely-used technique is that obtained from synchrotrons. Using insertion devices such as a wiggler or an undulator, a beam of high energy electrons are made to "oscillate" as it passes through such a device. The x-rays generated by this technique is not only intense, but one can also, in principle, dial in the exact wavelength required. It can also be highly polarized of needed. At most synchrotron centers throughout the world, x-rays are the major "product". Its wide use ranges from material science studies to biomedical imaging.
One can also generate x-rays using linear accelerators. This is getting to be more common in medical applications because it produces very little, if any, radioactive waste to be disposed of, and produces a more intense beam. Varian Medical systems have been producing a lot of these for various hospitals. There's a good chance that a large hospital near you is using such a technique to generate x-rays for both diagnostics and treatment.
That last bit isn't entirely accurate. You don't generate x-rays with a linear accelerator, you accelerate them. The principle for x-ray generation remains the same; electrons hitting a target and undergoing bremsstrahlung (sp?). Linacs are in use all over the world, and have been for some time.
Also, linacs are only used for treatment; a normal x-ray tube suffices for diagnostic x-rays.
You're correct in the sense that I didn't explain myself on how linacs generate x-rays. In medical linacs, x-rays are generated either via similar insertion devices as used in synchrotron beamlines, or via bending magnets at the end of the linac, or, as you've said, via direct collision with a target. The linac by itself doesn't produce any x-rays.
Examples of such devices can be found at the Varian homepage
How do you accelerate X-rays ?
In short, with a combination of something known as a "waveguide" and resonant microwaves supplied by a syncrhotron.
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