Results 1 - 10 of 19935
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[en] A Thomson scattering system has been designed and constructed for probing a relativistic electron beam heated plasma. Ruby laser light scattered through 900 is resolved by a polychromator and detected by one of six photomultipliers. The system is capable of resolving electron temperatures of 150 eV at densities of n/sub e/<1013 cm-3 with a 4-J ruby laser and an f/9 throughput collection system. Scaling to a 10-J, f/5 system would allow resolving densities of approximately 1012 cm-3. System design, calibration, alignment, and data reduction are discussed. At elevated temperatures (T/sub e/approx. =600 eV) evidence of the relativistic blue shift was observed
[en] Thomson scattering was used to measure the Langmuir wave spectrum generated by stimulated Raman scattering. This experiment detected Langmuir waves with components both parallel and antiparallel to the incident laser close-quote s wave vector k searrow 0. The parallel component was attributed to stimulated Raman scattering. However, the Langmuir waves moving antiparallel to k searrow 0, which cannot be explained by stimulated Raman scattering, were attributed to the Langmuir decay instability. copyright 1996 The American Physical Society
[en] Electron temperature and electron density in a dc plasma jet at atmospheric pressure have been obtained using Thomson laser scattering. Measurements performed at various scattering angles have revealed effects that are not accounted for by the standard scattering theory. Differences between the predicted and experimental results suggest that higher order corrections to the theory may be required, and that corrections to the form of the spectral density function may play an important role. copyright 1999 The American Physical Society
[en] A collective Thomson scattering diagnostic is being developed for the measurement of confined fast ions in hot, dense plasmas. This includes such measurements as the ion tail in JT-60U and the alphas produced in a burning reactor or the upgraded Joint European Torus device. The diagnostic also has the capability of measuring the isotopic ratio of the core ions such as the D/T ratio (required in optimizing a burning plasma experiment). The advances under development for this diagnostic include improvements in the high power source laser, increased bandwidth and reduced noise in the receiver, and the development of an intermediate frequency electronic filter bank. Such improvements are designed to permit the temporal measurement of the fast ions and improve the accuracy in determining their velocity distribution. Modeling of the expected scattered signals produced by these improvements and the diagnostics capability to measure the velocity distribution and isotopic ratio are presented
[en] In this paper, collective Thomson scattering (CTS) is proposed for measuring the ion temperature and axial/rotational velocity of a plasma jet in the linear plasma generator Magnum-PSI, where ITER-relevant plasma conditions will be simulated. CTS is feasible at Magnum-PSI, because high electron densities (ne) can be obtained at low electron temperatures, which means that small Debye lengths are achievable. Calculations show that CTS is possible at the fundamental wavelength (1064 nm) of a Nd : YAG laser. At this wavelength, a scattering angle of 17-35 deg. is sufficiently small to achieve a scattering parameter 1 < α < 3. The estimated observational error in the ion temperature Ti is expected to be below 10% at ne = 5.0 x 1020 m-3 and Ti = 2.5 eV, for a scattering volume with a length of 2.4 mm using an accumulated scattering energy of 12 J (10 pulses of 1.2 J at 10 Hz). The accuracy in the determination of axial velocity is expected to be about 15%. Setting the required accuracy for ion temperature measurements at 15%, single pulse CTS is expected to be feasible for ne > 1.5 x 1021 m-3. The design considerations of the CTS diagnostic are described in this paper.
[en] The channeled particles undergo quasiperiodic transverse bound motion along main crystallographic directions at either 1D planar or 2D axial channeling. This motion is accompanied by spontaneous radiation known as channeling radiation due to projectile’s transmission between discrete quantum states. In this work we have presented preliminary evaluation of the processes of resonance scattering of external electromagnetic field when the external frequency becomes close to the channeled particle transition energies that might be of the source for induced radiation at channeling.
[en] In the context of one-dimensional nonlinear waves in plasmas, we derive an integrable model of coupled nonlinear equations for the description of the interaction of the Langmuir waves with the acoustic waves through the ponderomotive force. Our model includes nonlinearity and dispersion of the acoustic wave and accounts for a resonant scattering of the electrostatic wave. The integrability of the model allows us to understand the instability of the Langmuir wave as (i) a mutual trapping of the acoustic wave and the scattered Langmuir wave, (ii) an asymptotic time evolution of the solution towards the formation of a local singularity of the Langmuir wave (collapsing). (orig.)
[en] The lifetime formula Τ=h/Σ for Breit-Wigner resonances, which is conventionally derived from the assumption of exponential decay, is obtained rigorously from a general formulation of decay and unstable states is exactly exponential and that the scattering time delay for these states is identical to the lifetime itself. (Auth.)