[en] Tandem mirror GAMMA 10, a large scale mirror equipment of Plasma Research Center, University of Tsukuba is one of the leading (mirror type) machines in the world. Three computers are used for controlling, monitoring, and data acquisition. Integrated operation of GAMMA 10 is performed by these three computers which are interconnected by computer communication links. This report describes the computer system for GAMMA 10 system. (author). 2 refs.; 4 figs

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[en] Physics issues relevant to minimum B mirror configuration that are studied on the GAMMA 10 tandem mirror are examined. The ion beta created in minimum Bmirror cells (anchors) by heating at ICRF (Ion Cyclotron Range of Frequency) provides the interchange-stability of the whole plasma. The anisotropic velocity distribution created by RF heating bears an advantage in terms of the macrostability while it can be a source of microscopic instabilities. The anistoropy also affects the fusion reaction rate as evaluated absolutely in terms of deuterium-deuterium (D-D) neutron yield. The 3-dimensional distribution of the hot-ion anchor plasma is determined with a soft X-ray pinhole camera. The anchor beta has been increased to 30% with hot electrons that show different spatial distribution depending on heating configurations. Relevance of the high beta hot electrons is discussed with reference to previous experiments and theories

[en] After the attainment of the density doubling due to the potential confinement, GAMMA 10 experiments have been directed to obtain a high-density plasma with potential confinement and also to study the dependence of the confining potential and confinement time on the plasma density. These problems are important to understand the physics of potential formation in tandem mirrors and also for the development of a tandem mirror reactor. GAMMA 10 experiments have advanced greatly after the Sorrento IAEA Conference, where high-density plasma production by using an ICRF heating at a higher harmonic frequency was reported. Recently, a high-density plasma was attained and the reproducibility of high-density plasma production was much improved by adjusting the spacing of the conducting plates installed in the anchor transition regions. In this paper, we report the production of a high-density plasma and the dependence of the confining potential and confinement time on the density up to a density of 4 x 10¹² cm^-3

[en] Radio frequency waves in the ion cyclotron range of frequency (ICRF) are mainly used for the plasma production and heating in the central cell of the GAMMA 10 tandem mirror. The GAMMA 10 has minimum-B anchor cells with a non-axisymmetric magnetic field configuration. The ICRF heating system in the central cell has been improved to create a more axisymmetric plasma. A high ion temperature is attained with the system and high energy ions more than 50 keV are detected in both parallel and perpendicular directions to the magnetic field line. Strong temperature anisotropy is observed and strong Alfven ion cyclotron (AIC) modes are excited due to the anisotropy. With the AIC modes, high energy ions detected at the end increase and high energy ions with nearly 90 degrees pitch angle in the central cell decrease. (author)

[en] Basic experimental results obtained in TMX, TMX-U, and GAMMA-10 tandem mirror devices are described and analyzed. The problem of the longitudinal confinement of electron energy is discussed. Secondary electron emission from the plasma collectors is taken into account. The problem of removal of ions trapped in the thermal barrier is considered. An analytical review of papers on the MHD stabilization of high-pressure plasma with β∼1 in the axisymmetric tandem mirror device is presented. Attention is drawn to the key problems that must be solved for developing the conception of tandem mirror DT reactor

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[en] In the hot ion mode experiments of the tandem mirror GAMMA 10/PDX plasma, suppression of the flute-like fluctuation, for which the rotation direction is the same as the ion diamagnetic rotation direction, was observed during the axially confined potential formation while electron cyclotron heating (ECH) was applied at the barrier and plug cells for the first time. In the previous experiments, the electron diamagnetic rotation type fluctuations were clearly suppressed with the application of both barrier (B) and plug (P) ECH. We show that the flute-like fluctuation of ion diamagnetic rotation is also suppressed with the application of P/B-ECH. (paper)

[en] Radiofrequency waves in the ion cyclotron range of frequency (ICRF) are mainly used for plasma production and heating in the central cell of the GAMMA 10 tandem mirror. GAMMA 10 has minimum-B anchor cells with a non-axisymmetric magnetic field configuration. The ICRF heating system in the central cell has been improved to create a more axisymmetric plasma. A high ion temperature is attained with the system, and high energy ions with energies of more than 50 keV are detected both parallel and perpendicular to the magnetic field lines. Strong temperature anisotropy is observed and strong Alfven ion cyclotron (AIC) modes are excited due to the anisotropy. With the AIC modes, the number of high energy ions detected at the end of the mirror increase and the number of high energy ions with a pitch angle in the central cell of nearly 90 deg. decrease. (author)