Synchrotron Radiation from the ATC Tokamak Plasma

Abstract

then it is found that N -1.2 for the south beam and 2.4 for the north beam. In 11 534 the correlation is not as good but a value of N ~ 1.2 is obtained.In conclusion it can be said that the time and spatially resolved 2co 0 and |co 0 measurements have begun to provide the data necessary for an understanding of the laser-beam-plasma interactions occurring in the region of the critical surface. The spatial resolution of the 2u> 0 and f u) 0 streaked results provides critical and quarter-critical surface trajectories. This gives information on the hydrodynamics of the ablation region. Time-resolved scale lengths provide information for absorption studies. Intensity histories of the plasma emissions should yield information on the processes that lead to the plasma emissions.This work is supported by the Laser FusionCostley and co-workers 1 * 2 recently reported on measurements of the spectral distribution and the polarization of the synchrotron radiation emitted by the CLEO and TRF tokamak plasmas (parallel and perpendicular to the major radius) over a frequency band (30 GHz </<450 GHz) that included the electron cyclotron frequency (co c = eB/ m) and its first few harmonics. They found, contrary to expectation based on theoretical analysis of simple plasma models, 3 " 5 that (1) the intensity was greater than would be expected for plasmas with the electron temperatures produced by these devices, (2) the intensity was spatially isotropic, and (3) the radiation was unpolarized. Their apparatus consisted of a scanning Michelson interferometer and Putley 6 detector combined to make a Fourier-transform spectrometer. This system, which has the advantage of excellent frequency resolution 10 msec to scan the frequency range of interest and produce a Fourier transform of the spectral distribution of the observed radiation. This meant that they were able to obtain valid spectra only for those stable tokamak discharges for which the plasma parameters were nearly constant over a 10-msec interval. This Letter reports measurements of the synchrotron radiation emitted by the adiabatic toroidal compressor 1 (ATC) tokamak plasma over the same band of frequencies, with an apparatus that had a worse frequency resolution (//A/~ 1-2), but much better time resolution (<10 /isec) than that used by Costley and co-workers. 1 * 2 Consequently, we concentrated on effects occurring on a time scale shorter than 10 msec and obtained a number of results not discussed in the present theory of synchrotron radiation in tokamas. We hope they will act as a stimulus to new theoreti-The synchrotron radiation emitted from the adiabatic toroidal compressor (ATC) tokamak plasma along a major radius was measured over a band of frequencies (35 GHz</ <450 GHz with resolution //A/~2 and rise time r< 10 /xsec) that included the electron cyclotron frequency and its first few harmonics. The radiation is at least 50% polarized (E* wave ± B). Radiation due to runaway electrons increases sharply and coincidentally with the appearance of positive spikes in the loop v...

Geometric properties of commutative subalgebras of partial differential operators

“…Under such conditions cyclotron emission is cut off. This is in contrast to the recently observed nonthermal emission from tokamaks (BOYD et al, 1976) where runaway electrons also give rise to nonthermal emission in plasmas with a , , 2 ope. The lack of harmonic structure in the spectrum is further evidence that the emission is not due to cyclotron emission.…”

Physics of runaway electrons in tokamaks

“…Kinetic instabilities are observed frequently in startup REs, often manifesting as periodic relaxation oscillations, with rises in loop voltage correlated to HXR spikes [151,219].…”

Nonlinear Evolution of Runaway-Electron Distribution and Time-Dependent Synchrotron Emission from Tokamaks

“…Recent measurements of cyclotron radiation from low-density tokamak plasmas have shown significantly nonthermal properties 1 " 3 : The radiation intensity is more than an order of magnitude above the thermal level expected from the measured temperature, with a broad frequency spectrum having minima at the gyroharmonics 4 ; the radiation level is nonsteady with sudden (% 10 jusec) increases in intensity, correlated with loop-voltage spikes, 4 with bursts of x rays and of radiation from oo pe to oo pi9 and with the ion heating. 5 In this Letter, we attempt to interpret this enhanced radiation as synchrotron emission by the runaway electrons.…”