Measurement of Electron Cyclotron Emission from the Tandem Mirror GAMMA 10

Abstract

Electron cyclotron emission (ECE) measurements on the tandem mirror GAMMA 10 are reported. The fifth-harmonic ECE in the thermal barrier region was measured in order to obtain the temporal and spatial evolution of hot electrons produced by electron cyclotron resonance heating for the formation of a thermal barrier potential well. The electron temperatures in the central and plug cells were determined using the second-harmonic ECE which was corrected for the hot-electron emission by considering a relativistic shift of resonance layers. The results, thus obtained, show strong evidence for the existence of a thermal barrier.

Millimeter-wave two-dimensional imaging array for the GAMMA 10 tandem mirror

“…In the plug/barrier cells, the warm and hot electrons are produced by ECRH-P and ECRH-B, respectively, for the formation of plug/barrier potentials. 6 It is often seen that the synchrotron emission due to the hot electrons dominates the ECE signal. We have measured 2D and 3D profiles of the ECE as well as the density during the ECRH operation.…”

Enhancement of the thermal barrier depth and two-dimensional potential profiles in GAMMA 10

“…Figure 3 is a plot of the time evolution of the onaxis potentials in the central cell and the barrier cells. The plug potential, which is higher than the central potential, is observed by means of end-loss analysers, and the temperature difference between bulk electrons in the central cell and bulk electrons in the plug cell is measured during first harmonic ECRH [20]. However, we do not give details of the plug potential in this paper since the confining potential is discussed in Ref.…”

“…The hot electron density in the barrier is estimated from X-ray and diamagnetism measurements [18]. The electron temperatures in the central cell and the plug/barrier cells are determined from electron cyclotron emission (ECE) [19,20]. The ECE measurements are carried out by using three standard heterodyne receiver systems, one at 42-48 GHz for the central cell and two at 68-72 GHz for the plug/barrier cells.…”

Observation of scaling laws of ion confining potential versus thermal barrier depth and of axial particle confinement time in the tandem mirror GAMMA 10

“…Here, we use the expansion from r° to r 10 for minimizing the fitting errors, where r is a normalized plasma radius. The electron temperatures in the central cell and the plug region are measured by soft X-ray diagnostics using silicon surface barrier detectors [12] combined with absorbers of polypropylene, polyester and aluminium [25] of various thicknesses, and also by electron cyclotron emission (ECE) diagnostics using standard heterodyne receiver systems (42-48 GHz for the central cell and 68-72 GHz for the plug region), having an intermediate frequency of 100 MHz and a bandwidth of 10 MHz with a voltage gain of 80 dB [26]. These data on T_.…”

“…The theoretical basis for this scaling law is set forth in the above-mentioned papers by Cohen et al; we can derive this scaling by using the experimental results yielding the plug electron temperature, T , versus 0 b , and the central cell NUCLEAR FUSION, Vol.28, No. 12 (1988) temperature, T ec , versus 0 b [25][26][27]. Therefore, in this paper, we carry out the first comparison of the experimental results on the 0 C versus 0 b scaling law and the Cohen theories in a broader potential range (from 0 to about 1 kV) than was done in our preliminary report [28].…”