|WikiProject Physics||(Rated Start-class, Mid-importance)|
Go on, clean it up !
But the scientific true, remains.. the truth : the thermonuclear plasma could be a good amplification medium for the LASER and photonic emissions ; like the Free ELectrons Laser, the Gudzenko-Shelepin laser-photonic rocket engine, uses high energy particles for extracting the photons ; the FEL uses the high speed electron fascicles and the Gudzenko-Shelepin uses the thermonuclear plasma, mores precisely the bremsstrahlung (intenses emissions of photons) of the hot plasma. See some informastions about this method :
(extract from the papers published by http://laserstars.org)
" The cited texts are from : http://laserstars.org/ see the papers cited in this text AMPLIFICATION IN RECOMBINING PLASMAS (PLASMA LASERS) Gudzenko, L.I., Shelepin,L.A., Yakovlenko,S.I.: 1975, Sov.Phys.Usp., 17, 848. A review is given of the investigations of lasers in which the amplifying medium is a rapidly recombining (supercooled in respect to free electrons) dense plasma. Efficient amplification of visible and ultraviolet radiation is possible in a plasma with free-electron density Ne = 10^13 - 10^18 cm^-3 and an electron temperature Te = 0.05 - 2 eV. At short wavelengths and high energies, the plasma lasers have important advantages over the conventional gas lasers in which the active medium is a gas-discharge overheated plasma which is being ionized. The purpose of the review is to identify the developing trends in the investigations of plasma lasers. An analysis is made of the recombination mechanisms of population inversion of atomic, ionic and molecular levels, of the methods of producing a supercooled plasma, and of the characteristics of different variants of plasma lasers. The general theoretical ideas are illustrated by numerical calculations and experimental results. INTRODUCTION The amplification of laser radiation in plasmas is attractive for two reasons. First, in contrast to a solid, liquid or gas, the aggregate state of a plasma does not change at high densities of the pump energy and, therefore, it should be possible to build plasma lasers with a considerably higher energy output than the output of lasers using other media. (Berger et al.) Secondly, plasmas provide provide means for efficient population of electron-excited atomic, ionic, and molecular levels which can be used to generate short-wavelength radiation. In this way, it should be possible to generate coherent radiation not only in the visible or ultraviolet range but also in the x-ray range. Gudzenko and Shelepin drew attention in 1963 to a recombining plasma as a potential active medium. In that paper and in several later communications they showed that the recombination flux between excited states of atoms and molecules in a dense plasma can ensure a population inversion and a fairly high gain; lasers utilizing recombining plasmas have since been called plasma lasers. The development of plasma lasers was also stimulated by the appearance of lasers utilizing various forms of gas discharges. In these lasers, the amplification occurs due to the ionization of a gas and it is usual to call them gas lasers. (Mir, 1968) We shall retain the terminology in spite of the fact that the degree of ionization of the amplifying medium in high power gas lasers is now considerable. Thus we may distinguish between two types of lasers utilizing ionized gases: 1. Gas lasers in which the active medium amplifies the radiation because of ionization. 2. Plasma lasers in which the amplifying medium is a recombining plasma. The current terminology reflect, in particular, the fact that a gas is transformed into plasma in the gas lasers and a plasma is transformed into a gas in the plasma lasers. Moreover, under recombination conditions, the plasma properties of an 'overionized' medium are manifested more strongly than in the case of ionization. The qualitative differences between the the plasma and gas lasers is the deviation of the active medium from thermodynamic equilibrium in opposite directions. In a gas laser, the electrons are overheated and the temperature of the free electrons Te is higher than the equilibrium temperature Ti at which the degree of ionization is equal to that actually observed, whereas, in a plasma laser, the electrons are supercooled: Te is less than Ti. This qualitative difference determines in each specific case the method used to produce an amplifying medium. For example, the pulsed gas laser use the leading edges of heating-field pulses, whereas the plasma lasers utilize the afterglow (Sec.5); in the case of gas laser, an electron beam enters a rarefied medium, whereas, in the case of a plasma laser, a beam enters a dense medium (Sec.6 and 8), and so on. The problem of building an efficient plasma laser can be reduced to two tasks: 1. The establishment of a sufficiently rapid depopulation of the lower lasing level. 2. The generation of a rapidly recombining dense plasma. RECOMBINATION MECHANISMS OF POPULATION INVERSION OF ATOMIC AND IONIC LEVELS 1.Relaxation of population. Simplest plasma laser In this section, we shall consider briefly the approximations which are frequently used in discussing the population inversion between the atomic and ionic levels. A general discussion of the relaxation processes in plasmas can be found in the review of Biberman et al. (26) and in several monographs. (27-29) Unfortunately, the problem of the population kinetics in a strongly supercooled plasma is not treated sufficiently fully (for the purposes of plasma lasers) in these works. Populations at a given moment can be represented by the rate equations
N __ \ dNm/dt = / Kmn Nn + Dm = Gm (1.1) -- n=1
The matrix Kmn will be called the relaxation matrix. Its elements give the average number of transitions from state n to state m in an atom in a unit time interval; the diagonal term Kmn governs the total loss of particles (per unit time) from the state m. The quantity Dm represents the arrival of particles from the continuum. In the case pf a plasma of simple chemical composition, it is usual to allow only for the spontaneous radiative transitions (3) and for collisions with electrons; (4)
Kmn = Vmn Ne + Amn(m not equal to n),
N __ \ -Kmm = / Knm + Vem Ne = Ne Vm + Am (1.2) -- n=1 -Kmm = Km =
here, Amn is the rate at which the radiative transition n to m takes place (this quantity is known as the Einstein coefficient), and Vmn=(sigmamn v) is the rate of this transition as a result of inelastic collisions with electrons. In the case of a low-temperature dense plasma with
Ne cm^-3 > 3 X 10^13 [Te eV]^3.75 (1.3)
we can ignore the radiative recombination compared with the three-particle process (28) and can assume that Dm = Vem Ne^2 N+. The effective limit of the continuous spectrum N is selected in such a way that its position does not affect significantly the results of the calculations of the populations. a) General calculation methods ………………………………………………………….. NEGATIVE ABSORPTION IN A NONEQUILIBRIUM HYDROGEN PLASMA Gudzenko, L.I., Shelepin,L.A.: 1964, Sov.Phys.JETP., 18, 998. Conditions are examined for which a nonequilibrium hydrogen plasma can be regarded as a medium with a negative absorption sufficient for the creation of a generator operating close to the frequencies of ionization of hydrogen from the ground or low-lying levels.
CONCLUSIONS This review is necessarily partial. The shortage of space does not allow us to consider the processes of recombination in dense low-temperature plasmas which are of particular relevance to the laser action. For the same reason, we have ignored completely problems which may be encountered in x-ray lasers. We must stress once again that the use of the plasma (recombination) principle is most promising in two situations: (a) in the development of high power high-energy lasers; (b) in the generation of shorter wavelengths (vacuum ultraviolet and x-ray region). These two directions of the development of laser physics are currently of greatest interest but the experiments are still being carried out on the basis of the theory of gas lasers rather that plasma lasers. It seems to us that the adoption of recombination ideas will help in many ways. The theory of plasma lasers is currently held up by the absence of information on the cross sections of elementary events. Even in the case of electron collisions with excited atoms of simple electronic structure (H, He, Li, Na), there are practically no experimental data and it is not clear how reliable are the theoretical calculations. The situation is even worse in the case of parameters of chemical reactions in which excited atoms and molecules participate. This lack of information is holding up progress in many aspects of the theory of plasma lasers. Therefore, it is desirable not only to try to build high-power lasers and lasers emitting shorter wavelengths but also to extend considerably systematic studies of the rates of elementary events occurring in such lasers. Recombination Laser Research An author index is available or you can access all of the abstracts together. (about 20 kbytes) boldface emphasis is placed on papers available in HTML format. ________________________________________ SUBJECT INDEX 1. Negative absorption in a nonequilibriun hydrogen plasma 2. Radiation enhancement in a recombining plasma 3. Rapid recombination of plasma jets 4. Relaxation processes and amplification of radiation in a dense plasma 5. Collisional-radiative coefficients and population coefficients of hydrogen plasma 6. Theory of short-wavelength lasers from recombining plasma 7. Plasma dynamic lasers 8. Amplification in recombining plasmas (plasma lasers) 9. A recombination laser from cooled hydrogen plasma (plasma dynamic laser) 10. Recombination lasers from cooled hydrogenlike plasma 11. Population inversion in helium in supersonic plasma expansion 12. Observation of population inversions in freely expanding pure hydrogen plasmas 13. Quasi-steady laser oscillation in the recombining hydrogen plasma 14. Population inversion in a stationary recombining plasma 15. Population inversion in recombining weakly ionized hydrogen plasma 16. Quasi-steady population inversion of He+ in a freely expanding plasma 17. Population inversion between the ground and first excited states in a recombining hydrogen plasma 18. Population inversion in optically thick, recombining hydrogen plasmas 19. Numerical study of overpopulation density for laser oscillation in recombining hydrogen plasma 20. The behaviour of population in a plasma interacting with an atomic gas 21. The derivation of scaling laws for the lithium-like aluminum recombination laser 22. Detailed modeling of the hydrogenic carbon expansion cooled recombination laser 23. Microsphere-based short-wavelength recombination X-ray laser 24. Gas-contact cooling for quasi-stationary oscillation of the XUV laser recombining plasmas 25. Study of recombination lasing of C3+ "
The informations about new methods and new technical solutions are prohibited and erased in Wikipedia ? That is the specific policy of Wikipedia ? —Preceding unsigned comment added by 22.214.171.124 (talk) 08:48, 1 May 2009 (UTC)
Who is working Ablative Laser propulsion, now that Pakhomov is in the clink??? http://www.whnt.com/news/whnt-andrew-pakhomov-sentencing,0,5513440.story —Preceding unsigned comment added by 126.96.36.199 (talk) 19:29, 19 October 2009 (UTC)
Removed new section: "Fail-safe method to colonize other planets and moons"
- I've just removed this section. Was created by a single ip address at end of March. Gives no citations and makes several dubious comments, especially about capability of lasers to boost city sized spacecraft into orbit. If you are the author - do you have a citation for this? If you do, should be attributed to them also, as I don't think most physicists think such powerful lasers are a near future possibility. Even in space - a powerful laser could only accelerate a city sized spacecraft rather slowly - though it would build up perhaps to respectable velocities if you kept it up for months and years of continuous laser power from Earth. But to boost from the Earth's surface to orbit - as far as I know this has only been shown feasible for really lightweight craft and you still have the issue of dealing with the opacity and the tendency of the Earth's atmosphere to disperse laser beams even for those, they can be made to hover, but I don't think any have been boosted all the way to orbit from the Earth's surface by this method, or anything like that.
The author may have Lightcraft in mind. These are lightweight vehicles and so far in tests AFAIK have only risen as far as, perhaps 100 meters or so.
The main problem we have in regards to colonizing other planets and moons is getting out of the earths gravity well, this requires a lot of power, once we are in orbit it's plain sailing to get to other planets and moons. It's possible that lightcraft could be beamed into orbit, another alternative is for the spacecraft to have a photovoltaic array and when the laser beam or maser beam hits the photovoltaic array on the spacecraft electrical energy is produced to power a jet engine to get into orbit. If all of the potential renewable energy on planet earth is harnessed very powerful laser guns or maser guns could be constructed and it may be possible to beam city size spacecraft into orbit, the renewable energy infrastructure would require . . .
Biofuel, Biomass, Geothermal, Hydroelectricity, Solar energy, Tidal power, Wave power, Wind power, Osmotic power, Marine current power, Ocean thermal energy conversion.
In order to develop the renewable energy infrastructure and renewable energy technologies you will have to use robotics, this is called RREIC Robotic Renewable Energy Infrastructure Construction. City sized spacecraft can then be beamed into orbit by using laser beams or maser beams powered by renewable energy, once the city sized spacecraft are in orbit they can begin to travel to other planets and moons by using solar sails or other propulsion systems, its plain sailing once in orbit. Lasers can also simulate a magnetic field in a BEC, Bose–Einstein condensate, this is ideal for space fountain construction, this could even be a better option than building space elevators with carbon nanotubes all along the equator.
If you think it should be included - please discuss here, and before putting it back into the article - you should back up the more way out assertions with citations - and also the language needs to be changed. Especially calling it "fail safe" unless you have a citation that says it can't fail - is not encyclopedic. Robert Walker (talk) 11:46, 20 April 2014 (UTC)