How X-rays Work" X-rays are basically the same thing as visible light rays. Both are wavelike forms of electromagnetic energy carried by particles called photons (see How Light Works for details). The difference between X-rays and visible light rays is the energy level of the individual photons. This is also expressed as the wavelength of the rays. Our eyes are sensitive to the particular wavelength of visible light, but not to the shorter wavelength of higher energy X-ray waves or the longer wavelength of the lower energy radio waves.
Visible light photons and X-ray photons are both produced by the movement of electrons in atoms. When a photon collides with another atom, the atom may absorb the photon's energy by boosting an electron to a higher level. The atoms that make up your body tissue absorb visible light photons very well. They can, however, knock an electron away from an atom altogether. In the next section, we'll see how X-ray machines put this effect to work. Ablation. Ablation is removal of material from the surface of an object by vaporization, chipping, or other erosive processes. Examples of ablative materials are described below, and include spacecraft material for ascent and atmospheric reentry, ice and snow in glaciology, biological tissues in medicine, and passive fire protection materials. Ablation near the electrode in a flashtube. The high energy electrical arc slowly erodes the glass, leaving a frosted appearance.
Biology Biological ablation is the removal of a biological structure or functionality. Genetic ablation is another term for gene silencing, in which gene expression is abolished through the alteration or deletion of genetic sequence information. Glaciology Ablation can refer either to the processes removing ice and snow or to the quantity of ice and snow removed.
Laser ablation while the peak power is Marine surface coatings Medicine Passive fire protection Spaceflight See also References Nuclear Fission Basics. The debate over nuclear power plants has been going on for some time, with nuclear physicists and lawmakers alike throwing around terms like nuclear fission, critical mass, and chain reaction. But how does nuclear fission work, exactly? In the 1930s, scientists discovered that some nuclear reactions can be initiated and controlled. Scientists usually accomplished this task by bombarding a large isotope with a second, smaller one — commonly a neutron. The collision caused the larger isotope to break apart into two or more elements, which is called nuclear fission. Figure 1 shows the equation for the nuclear fission of uranium-235. Figure 1: The equation for nuclear fission. Reactions of this type also release a lot of energy. You can actually calculate the amount of energy produced during a nuclear reaction with a fairly simple equation developed by Einstein: E = mc2.
Take another look at the equation for the fission of U-235. Figure 2: Chain reaction. How does fission work? Ryan, It's not so much the kinetic energy of the neutron - but the fact that it is falling into a nuclear potential well. Imagine you had an old well - the type people used to haul water up from in a bucket. Except this well is dry - it's just a very deep hole in the ground lined with stones. Now suppose you have a rock sitting on the side of the well - and you lightly push it off into the well. You didn't put much energy into the rock. Obviously, there's energy in the sound given off as the rock bounces around. When a neutron is absorbed by a nucleus, it is also falling into a well - it's just a nuclear potential well and not a gravity potential well. Dr. How do nuclear fusion and nuclear fission work. Compton Scattering. In Compton scattering, an incoming photon of energy E (shown in black) undergoes an elastic collision with a weakly bound (assumed free) outer-shell electron (shown in blue).
The electron is scattered with kinetic energy K at an angle j with respect to the x-axis (direction of incoming photon) while the scattered photon of energy E' (shown in green) makes an angle q with respect to the x-axis. Because energy has been given to the scattered electron, the scattered photon will have a lower energy and therefore a longer wavelength than the incident photon.
At photon energies (> 200 keV) where Compton scattering because important, the kinetic energy transferred to the scattered electron is a significant portion of its rest energy. Thus, the electron is traveling at relativistic speeds and Special Relativity must be used in analyzing the experiment. As in any elastic scattering event, linear momentum and energy of the system must be conserved.
Where E 0 is the rest energy of the electron. Electrons, photons, and the photo-electric effect. We're now starting to talk about quantum mechanics, the physics of the very small.
Planck's constant At the end of the 19th century one of the most intriguing puzzles in physics involved the spectrum of radiation emitted by a hot object. Specifically, the emitter was assumed to be a blackbody, a perfect radiator. The hotter a blackbody is, the more the peak in the spectrum of emitted radiation shifts to shorter wavelength. Nobody could explain why there was a peak in the distribution at all, however; the theory at the time predicted that for a blackbody, the intensity of radiation just kept increasing as the wavelength decreased.
Clearly, this prediction was in conflict with the idea of conservation of energy, not to mention being in serious disagreement with experimental observation. Planck's prediction of the energy of an oscillating atom : E = nhf (n = 0, 1, 2, 3 ...) where f is the frequency, n is an integer, and h is a constant known as Planck's constant.
The photoelectric effect. Plasmas. Plasmas exist in a wide range of settings and varieties.
Most stars are made up of plasma. The Aurora Borealis is a plasma light show in our upper atmosphere caused by the bombardment from space of the solar wind - another kind of plasma. Lightning bolts are visible plasma trails left by the passage of the electric current that formed it. As stated in the definition, plasma is a gaseous type of state where the matter making the plasma consists of electrically neutral and charged particles. Overall, plasma is electrically neutral having as many positive ions as free electrons distributed through it.
Accelerating electrons through ordinary gas can create plasma, in just the way they create lightning. If you do it in a very low pressure gas - something like the interior of an incandescent light bulb - you usually just get a kind of diffuse glow. How does a Plasma Globe Work? We apply an electric voltage to the metal electrode in the center of the plasma globe. New Cold Fusion Evidence Reignites Hot Debate. 25 March 2009—On Monday, scientists at the American Chemical Society (ACS) meeting in Salt Lake City announced a series of experimental results that they argue confirms controversial ”cold fusion” claims.
Chief among the findings was new evidence presented by U.S. Navy researchers of high-energy neutrons in a now-standard cold fusion experimental setup—electrodes connected to a power source, immersed in a solution containing both palladium and ”heavy water.” If confirmed, the result would add support to the idea that reactions like the nuclear fire that lights up the sun might somehow be tamed for the tabletop. But even cold fusion’s proponents admit that they have no clear explanation why their nuclear infernos are so weak as to be scarcely noticeable in a beaker. The newest experiment, conducted by researchers at the U.S.
After the experiment, the group analyzed the CR-39 and found microscopic blossoms of ”triple tracks.” National Ignition Facility. The National Ignition Facility, located at Lawrence Livermore National Laboratory.
The target assembly for NIF's first integrated ignition experiment is mounted in the cryogenic target positioning system, or cryoTARPOS. The two triangle-shaped arms form a shroud around the cold target to protect it until they open five seconds before a shot. The National Ignition Facility, or NIF, is a powerful laser-based inertial confinement fusion (ICF) research device, located at the Lawrence Livermore National Laboratory in Livermore, California.
NIF uses powerful lasers to heat and compress a small amount of hydrogen fuel to the point where nuclear fusion reactions take place. NIF's mission is to achieve fusion ignition with high energy gain, and to support nuclear weapon maintenance and design by studying the behavior of matter under the conditions found within nuclear weapons. NIF is the largest and most energetic ICF device built to date, and the largest laser in the world. ICF basics National Ignition Facility & Photon Science - Bringing Star Power to Earth. Scientists plan to ignite tiny man-made star. How scientists brought the power of the Sun to Earth « Goodheart's Extreme Science. How scientists brought the power of the Sun to Earth Posted by Steven Goodheart on February 1, 2010 · 6 Comments The super-amplified light impacts the target area with an intensity and ferocity only found in the hottest places in the universe.
Imagine 500 times the energy of the entire United States being used at any given moment focused on a target smaller than a pinhead! In a few billionths of a second, the target reaches temperatures well over 100 million degrees and pressures billions of time greater than Earth’s atmosphere. There’s only one other place in our solar system this extreme, and that’s at the very core of our own Sun. This last Thursday, Jan. 28th, 2010, for the briefest of moments, “the Sun” came to the Earth in Livermore, California. Well, almost! The star-making process in a nutshell So, what exactly happened? Whew, OK! But actually, what scientists do is way more cool than popular imagination. Fusion—that’s what it’s all about! “In order to demonstrate fusion…” Like this: Fusion power. The Sun is a natural fusion reactor.
Fusion power is the energy generated by nuclear fusion processes. In fusion reactions, two light atomic nuclei fuse to form a heavier nucleus (in contrast with fission power). In doing so they release a comparatively large amount of energy arising from the binding energy due to the strong nuclear force which is manifested as an increase in temperature of the reactants. Fusion power is a primary area of research in plasma physics.
Background Binding energy for different atoms. Mechanism Fusion happens when two (or more) nuclei come close enough for the strong nuclear force to exceed the electrostatic force and pull them together. Theoretically, any atom could be fused, if enough pressure and temperature was applied. Mankind has studied many high energy fusion reactions, using particles beams. These are fired at a target. Cross Section where: Lawson criterion η, is the efficiency with which the plant captures energy Other 106, 085004 (2011): Demonstration of Ignition Radiation Temperatures in Indirect-Drive Inertial Confinement Fusion Hohlraums. Big science in a small space.
The National Ignition Facility (NIF) at Lawrence Livermore in California was designed with a specific goal: to use high-powered lasers to ignite a fusion reaction that releases more energy than the one million joules needed to start it.
Now, in a pair of papers appearing in Physical Review Letters (Kline et al. and Glenzer et al.), scientists at NIF are reporting some of the first tests at the new facility. In experiments that simulate “real” conditions more closely than any previous attempt, the team shows they are able to successfully generate the almost sunlike levels of heat needed for laser-driven fusion. The planned target of NIF’s lasers is a pill-sized hollow gold target, called a hohlraum, that encases a “fusion capsule”—about micrograms of solid deuterium-tritium mix, surrounded by a light material.
As a test, the NIF team used plastic capsules filled with helium instead of nuclear fuel. Nuclear Fusion : WNA. (Updated February 2014) Fusion power offers the prospect of an almost inexhaustible source of energy for future generations, but it also presents so far insurmountable scientific and engineering challenges.
The main hope is centred on tokamak reactors which confine a deuterium-tritium plasma magnetically. Today, many countries take part in fusion research to some extent, led by the European Union, the USA, Russia and Japan, with vigorous programs also underway in China, Brazil, Canada, and Korea. Initially, fusion research in the USA and USSR was linked to atomic weapons development, and it remained classified until the 1958 Atoms for Peace conference in Geneva. Following a breakthrough at the Soviet tokamak, fusion research became 'big science' in the 1970s. Fusion technology Fusion powers the Sun and stars as hydrogen atoms fuse together to form helium, and matter is converted into energy.
In any case, the challenge is to apply the heat to human needs, primarily generating electricity.