LASER-PLASMA INTARECTION
With the development of the technology of laser enabled the experiments using laser pulse with a high intensity of the order 〖10〗^22 W/〖cm〗^2. So now it brings the possibility of study the parameters of plasma as well as the atoms. The study related to the laser-plasma interaction involves the self-focusing, which is a very important factor to consider. Because the intensity of such a huge order came from it and high power laser and its applications, harmonic generation, X-ray generation, various laser plasma accelerator are depend upon it. Laser will not diverge up to the Rayleigh length, after this range the beam expands due to the natural diffraction. So laser need a channel for guiding the beam and prevent the diffraction. All phenomena like harmonic generation, relativistic self focusing can be studied in the relativistic nonlinear optical effect.
Propagation of laser beam in plasma
When a laser pulse interacts with plasma, the free electrons and ions that are inside the plasma will respond to, a very small scale deviation of their orientation and will be displaced slightly in an electromagnetic wave of frequency . Subsequently to a distortion of the charge neutrality, the particles which are in plasma tend to oscillate with a frequency known as electron plasma frequency. The resonance frequency of the resulting oscillations is known as the plasma frequency . Depending on their mass , charge and density .
, =
Where is the electron plasma frequency, is the ion plasma frequency. Plasma is considered as an electron clouds having the background of heavy ion and collisions are nearly neglected according to the drude model. That’s why dielectric constant of electron can be ...
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...ration of proton is not possible with available laser intensity. Because of its heavy mass, acceleration up to MeV need more laser intensity to overcome relativistic threshold. Energetic ions observed in the laser-solid interaction have been accelerated not directly by the laser fields but by the plasma fields which are formed by the laser heated electrons formed from solid or gas. However, these plasma electrons can inter-mediate the forces of laser fields on ions by generating strong quasi-static electric fields which arises from the charge separation due to the laser propagation. To accelerate the ion or proton need strong enough static electric field which can be explained best in two scenarios. These scenarios are
I. Radiation Pressure Acceleration ( RPA ) ii. Target Normal Sheath Acceleration ( TNSA ).
...been initiated. Plans call for 12-18 months of field testing both in the U.S. and Israel. The THEL demonstrator will provide the first opportunity to assess the utility of high energy lasers in an operational scenario.
In this experiment a Thomson tube can be used to measure the deflection of electrons in magnetic and electric fields. A Thomson tube is a cathode ray tube which contains an electron gun and a florescent screen. The florescent screen illuminated when the electron gun was turned on and from this the trajectory of the electrons can be measured. By applying a known voltage for both the electric and magnetic fields the charge of the electron c...
The method to use protons such as medical treatment of cancer was proposed by Robert Whilson, who was fade American physicist, in 1946 (McDonald and Fitzek 2010, 257). He argued that the unique physical properties of protons are relevant to utilize this radiation techology in medicine. The principle of the proton beam therapy consists in the appreciable mass of protons than other particles; as a result, the beam slightly broaden and stays focused on the c...
on the primary beam is that it limits the x-ray beam field size. The beam restricting device alters
Research on application of laser in dentistry began when Ralph H Stern & Reider F Sognnaes1(1963) of Los Angeles School of Dentistry, University of California studied thermal effect of ruby laser on dental hard tissues & restorative materials. Since then there had been attempts to utilize the benefits of laser in each and every field of dentistry. Laser may be used in dentistry effectively for their ability to incise, cut and ablate soft and hard tissues. In 1965, Leon Goldman first reported the case of laser exposure to a vital human tooth2.
Ionization: When an orbiting electron is ejected from its shell in an electrically stable (neutral)
This optical amplification is started from some emission but it is not exposed yet until Albert Einstein proposed in 1916. After that, the things became more seriously after 1954 when Townes and Arthur Schawlow also with Gordon Gould proposed laser action, then not long after 4 years, in 1960, first laser was build by Theodore Maiman. Besides that, Gordon also derived the word laser from “light amplification by the stimulated emission of radiation”. The laser developer look amplification is very important as a step to build a laser, so these people make one advance to develop amplifiers from semiconductor laser to be used as light sources. This is because of semiconductor have high gain. Laser made up with high gain and low noise is categorized as the best laser.
Based on the type of IORT being used, the desired products of these reaction will be focused into a beam directed at the treatment site during surgery. The ionizing radiation beam will then interact with the soft tissue based on the energy of the beam. While the photoelectric effect and pair production do occur during radiation therapy, Compton effect is the most significant interaction. Compton effect (or Compton scattering) is the inelastic scattering of X-Ray photons by loosely bound outer electrons. The photon transfers some of its energy to the electron, which ionizes the
The plasma consists of electronically excited atoms and ions, which can then be analyzed by the spectrometer. When the laser pulse terminates, the plasma begins to cool [11]. It is during this cooling process, where the electrons of the atoms and ions at the excited states decay back into their natural ground states, causing the plasma to emit characteristic wavelengths of light. The atomic emissions can be detected approximately 1 μs after the initial pulse. The emitted light from the plasma is collected by the spectrometer coupled with either a CCD or ICCD spectrograph detector module for the LIBS spectral analysis [11]. Each element correlates to a unique LIBS spectral peaks. Thus, by identifying the different peaks of the analyzed sample, its chemical composition can be rapidly
Rapid generation of large area polished optical surfaces by high-power CO2 laser irradiation is shown. Results focus on glasses with high expansion coefficients (a>1025/°C) conventionally used in the optical industry. The technique involves active beam integration to obtain an intensity irradiation profile with a good uniformity over large spot sizes and is applied to preheated glass samples with initial rms roughness up to 500 nm. To find out the conditions for successful and reliable use of the proposed laser polishing method, the laser-driven heating process was monitored by means of the surface and depth temperature
At Lebedev Institute, Prokhorov studied the propagation of radio waves in ionosphere. But then he join the red army after that he goes back and start on with his research. In 1946, he defended his PhD thesis on ‘Theory of Stabilization of Frequency of a Tube Oscillator in the Theory of a Small Parameter’. The following year, he started working on coherent radiation emitted by electrons orbiting in a cyclic particle accelerator called synchrotron. He demonstrated that the emission is mostly concentrated in the microwave spectral range.“ Stimulated emission means that a light packet, a photon, coming in contact with an atom can cause an electron to descend to a lower energy level so that an additional photon with the same amount of energy is emitted. If electrons are elevated to higher energy levels with the help of heat or light, an avalanche-like effect occurs when they fall to lower levels” . In the 1950s Alexandra Prokhorov, Nicolay Basov, and Charles Townes contributed to putting this phenomenon into practical use in masers and lasers, which produce concentrated and coherent beams of microwaves and light,
Most people don't know where the idea of the laser came from. The idea for the laser came from a machine called a maser. The maser was a tool that was able to strengthen, or amplify radio and light waves. The first laser was made in California in 1960. It was built by Theodore Maiman along with a group of American scientists. The material they used for a concentrator was a man- made ruby. This was done by, coiling a simple flash tube around a rod, and beaming powerful flashes of light at it. The result was pulses of red laser light. Once they made the device they had to name it. They had think of some word or words to described it. They came up with Light Amplification by Stimulated Emission of Radiation. Using the first letter of each main word they named it laser. The laser had everyone excited.
Schultz, James. "Force Fields and 'Plasma' Shields Get Closer to Reality." Technology 25 July 2000: 20 pars. Web. 25 Oct. 2010. .
For nuclear fusion to occur, nuclei must have very high kinetic energies that will exceed the electrostatic repulsion between the nuclei. The extremely high temperature of the sun causes electrons to be stripped o...
As you can see lasers are a very useful and important tool which is why I have