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Topic: Thomson Scattering


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In the News (Tue 1 Dec 09)

  
  Scattering - Wikipedia, the free encyclopedia
Scattering, also called scatter, is the process by which small particles suspended in a medium of a different index of refraction diffuse a portion of the incident radiation in all directions.
Scattering varies as a function of the ratio of the particle diameter to the wavelength of the radiation.
In scattering experiments, a target of some material is bombarded with a beam of particles (typically electrons, protons, or neutrons) and the number of particles emerging in various directions is measured.
en.wikipedia.org /wiki/Scattering   (678 words)

  
 Thomson scattering - Wikipedia, the free encyclopedia
In physics, Thomson scattering is the scattering of electromagnetic radiation by a charged particle.
Thomson scattering is an important phenomenon in plasma physics and was first explained by the physicist J.J. Thomson.
The scattering is best described by an emission coefficient which is defined as ε where ε dt dV dΩ dλ is the energy scattered by a volume element dV in time dt into solid angle dΩ between wavelengths λ and λ+dλ.
en.wikipedia.org /wiki/Thomson_scattering   (545 words)

  
 Scattering: Tutte le informazioni su Scattering su Encyclopedia.it   (Site not responding. Last check: 2007-10-09)
Un semplice esempio di scattering può essere l'urto contro una sfera rigida.
Lo scattering Raman (dal nome del suo scopritore C.V. Raman che nel 1928 lo osservò per primo) è un esempio di scattering anelastico, ovvero di un urto fra particelle dove l'energia cinetica complessiva del sistema non si conserva (l'energia totale del sistema si conserva in tutti i tipi di urti).
Si definiscono fenomeni di scattering multiplo quei casi dove le particelle (o la luce) subiscono, all'interno del mezzo, un numero molto alto di eventi di scattering.
www.encyclopedia.it /s/sc/scattering.html   (2728 words)

  
 Scattering   (Site not responding. Last check: 2007-10-09)
In astronomy and optics scattering is deflection of photons that by macroscopic surfaces suchas an asteroid or by small particles as in the rings of Saturn.
Scattering, also called scatter, is the process by which small particles suspended in a medium of a different index ofrefraction diffuse a portion of the incident radiation in all directions.
Scattering varies as a function of the ratio of the particle diameter to thewavelength of the radiation.
www.therfcc.org /scattering-20793.html   (416 words)

  
 Observation of nonlinear relativistic Thomson scattering
Classical Thomson scattering-the scattering of low-intensity light by electrons-is a linear process, in that it does not change the frequency of the radiation; moreover, the magnetic-field component of light is not involved
Although the above two observations are consistent with nonlinear Thomson scattering as the source of the harmonic signal, the observation of the unique angular patterns is necessary in order to prove that the detailed dynamics of nonlinear Thomson scattering are indeed the same as the theoretical prediction.
The red-shifted broader peaks are believed to be part of the harmonic spectra generated by nonlinear Thomson scattering, because they vary in amplitude proportionally with the corresponding unshifted harmonic signals when the gas density and laser power are changed.
www.eecs.umich.edu /USL-HFS/nltsaps/nltsaps.html   (1917 words)

  
 Thomson scattering goes relativistic (December 1998) - News - PhysicsWeb
The magnetic field of the light is not involved and the scattered photon has the same wavelength as the incident photon.
Theory predicts that scattered photons should be radiated at multiple harmonics of the incident frequency, and that each harmonic should have its own unique angular distribution.
This change causes the scattered light to be emitted as harmonics of the incident light.
physicsweb.org /article/news/2/12/7   (306 words)

  
 Lidar Thomson Scattering Diagnostic   (Site not responding. Last check: 2007-10-09)
The monochromatic laser light is scattered and doppler shifted by the fast moving plasma electrons producing a broad spectrum of scattered light, figure 2.
The scattered spectrum is dispersed into the six detection channels using a set of dielectric edge filters which act together to make a high throughput spectrometer.
Thomson Scattering = the classical theory of the scattering of electromagnetic radiation by a charged particle was developed by Joseph John Thomson (1856-1940) - an English physicist generally credited as the discoverer of the electron
www.jet.efda.org /pages/focus/001lidar   (657 words)

  
 Example of WDS style article: MS WORD template   (Site not responding. Last check: 2007-10-09)
Thomson Scattering is a powerful diagnostic which is applied at almost every magnetic confinement device.
Physical principle of TS is based on the measurement of the spectrum of photons scattered by the free electrons in the plasma.
Scattering of the monochromatic electromagnetic radiation on hot electrons in plasma leads to a spectral broadening of the scattering spectrum due to the Doppler effect.
server.ipp.cas.cz /~brotance/Thomson/thomson.htm   (561 words)

  
 Thomson scattering -- Facts, Info, and Encyclopedia article   (Site not responding. Last check: 2007-10-09)
In (The science of matter and energy and their interactions) physics, Thomson scattering is the scattering of (Radiation consisting of waves of energy associated with electric and magnetic fields resulting from the acceleration of an electric charge) electromagnetic radiation by a
The (A car that is powered by electricity) electric and (additional info and facts about magnetic) magnetic (An artifact that is one of the individual parts of which a composite entity is made up; especially a part that can be separated from or attached to a system) components of the
The scattering is best described by an (additional info and facts about emission coefficient) emission coefficient which is defined
www.absoluteastronomy.com /encyclopedia/t/th/thomson_scattering.htm   (600 words)

  
 Instrument Description
The angular distribution of x-rays scattered from the lithium target depends on the polarization of the incident x-ray according to the Thomson scattering cross-section.
The IPCs are part of the scattering polarimeter subassembly of the SXRP and are used to detect x-rays which have passed through a polarization analyzer, either reflected from a graphite crystal or scattered in a metallic lithium target.
Since photons are scattered from the lithium over all angles, the detectors must intercept a large fraction of the solid angle; also, the distance from the target to the detector window must be at least 90 mm in order to reduce false polarization signatures due to spacecraft pointing errors.
hea-www.harvard.edu /SXG/obsguide/node50.html   (959 words)

  
 Width of Fraunhofer Lines - Bad Astronomy and Universe Today Forum
The Thomson scattering cross section is 6.7*10^-29 m^2 and if one multiplies these two numbers one gets an optical depth with regard to Thomson scattering of about 1.
The scattering should therefore be significant and the lines broadened to a half width of around 10 A. This seems to be in contradiction to observations which show a line width of less than 1 A. http://www.physicsmyths.org.uk
Thomson scattering by free electrons does broaden the spectral lines, but by too much and produces overlapping and a continuous spectrum as a result.
www.bautforum.com /showthread.php?t=27797   (1383 words)

  
 Astron. Astrophys. 340, 617-625 (1998)   (Site not responding. Last check: 2007-10-09)
This is quite a standard approximation, which assumes that the scattering of radiation on free electrons is a fully coherent event, in which the frequency of a photon is kept fixed before and after scattering.
Thomson scattering does not influence the equation of radiative equilibrium, because scattering terms there precisely cancel out (Mihalas 1978).
Compton scattering is the same physical photon-electron process which is described with a very precise mathematical formulation, in which both photon and electron change their energies and momenta as is required by the conservation principles.
aa.springer.de /papers/8340002/2300617/sc1.htm   (1280 words)

  
 Lecture 7 : Compton Scattering
Thomson scattering, or the scattering of a photon by an electron at rest, strictly only applies at low photon energy, i.e.
In Thomson scattering the incident photon and scatter photon have the same wavelength or energy, so this scattering is also called coherent or elastic.
In this case the scattering cross-section is independent of the photon energy and is approximately equal to the Thomson cross-section.
www.astro.utu.fi /~cflynn/astroII/l7.html   (1386 words)

  
 Thomson scattering
It is clear that the differential scattering cross section is independent of the frequency of the incident wave, and is also symmetric with respect to forward and backward scattering.
The frequency of the scattered radiation is the same as that of the incident radiation.
The scattering of a photon by a charged particle is called Compton scattering, and the quantum mechanical version of the Compton scattering cross section is known as the Klein-Nishina formula.
farside.ph.utexas.edu /teaching/jk1/lectures/node85.html   (722 words)

  
 OhioLINK ETD: Lee, Wonchul
Laser light scattering diagnostic techniques, for characterization of weakly ionized molecular plasmas, are developed and demonstrated in high pressure, low temperature air-like molecular plasmas sustained by a continuous wave CO laser.
When the wavelength of the laser is precisely tuned to the strong absorption line of rubidium at 780nm, the Rayleigh/stray light signal is absorbed essentially completely by the filter, placed in the detection path, while the Doppler broadened/wavelength shifted signal is transmitted.
Electron temperature and number density are measured by filtered Thomson scattering in an argon constricted dc glow discharge.
rave.ohiolink.edu /etdc/view?acc_num=osu1054652829   (383 words)

  
 Temporal and spatial characterization of harmonics structures of relativistic nonlinear Thomson scattering
Temporal and spatial characterization of harmonics structures of relativistic nonlinear Thomson scattering
The harmonics of the scattering of a femtosecond intense laser pulse by an electron has been numerically investigated.
The backward scattering has its own distinct pattern: line-shaped nodes perpendicular to the laser electric field, the number of which is the harmonic order number minus one.
www.opticsexpress.org /abstract.cfm?URI=OPEX-11-4-309   (616 words)

  
 ScatteringProcess   (Site not responding. Last check: 2007-10-09)
Up to about 2 keV, the scattering factor is approximately independent of scattering angle, with a real part that represents the effective number of electrons that participate in the scattering.
In relativistic quantum mechanics, the scattering of x-rays by a free electron is given by the Klein-Nishina formula.
In that case, if the scattering leaves the atom in the ground state, we deal with coherent scattering (see above), whereas if the electron is ejected from the atoms, the scattering is (incoherent) Compton scattering.
xdb.lbl.gov /Section3/Sec_3-1.html   (427 words)

  
 OSU Department of Chemistry Faculty Member
In a broad sense, current research topics can be divided into three areas; development of new laser/optical technology, studies of the influence of vibrational nonequilibrium on gas phase chemical reaction rates, and application of ultra high frame rate (~MHz) planar imaging diagnostics to problems in fluid mechanics.
A second example is shown on the right which is a filtered Thomson scattering spectrum.
Thomson scattering refers to the scattering from free electrons.
www.chemistry.ohio-state.edu /cgi/brochure?Faculty=lempert   (639 words)

  
 UCLA Electric Tokamak Homepage   (Site not responding. Last check: 2007-10-09)
The laser is being fired through hydrogen in the tokamak vacuum chamber at a pressure of 300 torr (approximately half atmospheric pressure, made possible by backfilling the chamber).
The Thomson trace in the bottom of image is reduced compared to that of Figure 3.
The measured light due to Thomson scattering must be extracted from a bright background due to the plasma and other stray light sources.
et.ucla.edu /diag/thomson/thomson.htm   (730 words)

  
 Thomson Scattering Made Relative - March, 1999   (Site not responding. Last check: 2007-10-09)
Thomson dismissed the idea that light's magnetic field was potent enough to influence electron motion.
The researchers then were able to make two observations based on what they termed "relativistic Thomson scattering." The intense electromagnetic fields from the laser beam sent electrons oscillating in figure-eight patterns, scattering radiation with wavelengths that were harmonically related to the original beam.
To isolate the scattering from the prodigious background noise, the team ionized the plasma with a 10- to 18-W prepulse for a few picoseconds before the main pulse.
www.photonics.com /spectra/tech/XQ/ASP/techid.522/QX/read.htm   (506 words)

  
 New Page 4   (Site not responding. Last check: 2007-10-09)
The polarization anisotropy in the CMBR is due to Thomson scattering of quadrupole moments in the photon radiation intensity at the surface of last scattering.
The Thomson scattering cross section is sensitive to the polarization of the incoming photons, but the large number of scattering events in the early universe wiped out any polarized components of the CMBR.
Because photon scattering events after z = 1000 were rare, the CMBR photons kept the polarized anisotropies acquired at the surface of last scattering.
cfcp.uchicago.edu /~peterh/polarimetry/intro.html   (670 words)

  
 Rayleigh scattering
giving a scattering cross section which depends on the inverse fourth power of the wavelength of the incident radiation.
Equation (5.79) is known as the Rayleigh scattering cross section, and is appropriate to the scattering of visible radiation by gas molecules.
This is Rayleigh's famous explanation of the blue sky: the air molecules of the atmosphere preferentially scatter the shorter wavelength components out of ``white'' sunlight which grazes the atmosphere.
farside.ph.utexas.edu /teaching/jk1/lectures/node86.html   (249 words)

  
 CMB pol physical mechanism   (Site not responding. Last check: 2007-10-09)
Thomson scattering from a randomly polarized light source to the left of the electron.
Thomson scattering for randomly polarized light incident on an electron from all directions.
Now the previously seen linear polarization in the scattered wave is cancelled, as the linear polarizations from different angles average out.
cosmology.berkeley.edu /~mmyers/Ay228/mechanism.htm   (205 words)

  
 ScienceWeek
OBSERVATION OF RELATIVISTIC NONLINEAR THOMSON SCATTERING In general, the "scattering" of electromagnetic radiation is a process in which the radiation is deflected by particles in the matter through which the radiation passes.
Classical Thomson scattering is a linear process, i.e., the frequency of the radiation does not change.
*coherent generation of the harmonics: In general, coherent scattering is scattering for which there is a well- defined relationship between the phase of the incoming wave and the phase of the outgoing wave.
scienceweek.com /1999/sw990326.htm   (7940 words)

  
 A1.1 Fast ion collective Thomson scattering   (Site not responding. Last check: 2007-10-09)
CTS is based on the scattering of radiation by the wakes drawn by fast ions in the plasma.
The radiation is launched at the outer midplane and scattered radiation detected by one receiver, later two receivers.
The scattering geometry was set to resolve the velocity component near perpendicular to the magnetic field, with the measuring volume near the plasma centre.
www.rijnh.nl /n5/n7/n6/node6.html   (571 words)

  
 Kierein's Erroneous Compton Model for the Redshift   (Site not responding. Last check: 2007-10-09)
Kierein adds a nonstandard factor of (wavelength)/(Compton wavelength) to the Thomson scattering cross-section, and thus gets a wavelength shift that is proportional to wavelength as required by the observations of redshifted spectra.
The Thomson cross-section gives the correct scattering rate, and it is not increased by a factor of trillions for radio waves as proposed by Kierein.
The change in angle per scattering could be less if there were more electrons (but Kierein already needs 1000 times too many electrons), but this would lead to more scatterings, and with more scattering the variances of the angles would add up to the same smearing.
www.astro.ucla.edu /~wright/kierein.html   (1268 words)

  
 Thomson Scattering
In this case we have coherent or ``collective'' Thomson scattering and we are then probing the collective behavior of the plasma.
Unfortunately, it is rather rare for the results of a practical scattering experiment to be sufficiently accurate as to provide detailed information on the precise shape of the distribution function.
Actually, of course, the number of scattered photons observed is proportional to the total incident energy (regardless of pulse length) for a given frequency.
hutchinson.belmont.ma.us /tth/tth_example2.html   (3268 words)

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