Helium discharges have been produced in the ST Tokamak with electron densities exceeding 1014 cm−3, with less than 1% oxygen (and other light impurities) and less than 0.05% metallic impurities. In such discharges, the effect of the impurities on the plasma resistivity is relatively unimportant, and, consequently, the usual ambiguities about the radial current distribution are unusually small. We find, consistently with previous experiments and in spite of various quantitative differences, that the plasma resistance is determined by Spitzer resistivity, that the rise of electron temperature is limited by the development of the q = 1 surface and that the electron kinetic energy confinement time is equal to the average particle confinement time. Energy loss by electrons constitutes about three quarters of the total and is roughly divided between line radiation and kinetic energy transport.
ヘリウム放電がSTトカマクにおいて生成され、電子密度は1014 cm−3を超え、酸素（およびその他の軽不純物）は1%未満、金属不純物は0.05%未満であった。このような放電では、プラズマ抵抗率に対する不純物の影響は比較的重要ではなく、その結果、径方向電流分布に関する通常の曖昧さは異常に小さい。我々は、以前の実験と一致し、様々な定量的差異にもかかわらず、プラズマ抵抗がSpitzer抵抗率によって決定され、電子温度の上昇がq = 1表面の形成によって制限され、電子運動エネルギー閉じ込め時間が平均粒子閉じ込め時間に等しいことを見いだす。電子によるエネルギー損失は全体の約4分の3を占め、ほぼ線放射と運動エネルギー輸送に分けられる。