A STUDY OF 3-HALF-TURN AND FRAME ANTENNAE FOR ION-CYCLOTRON RANGE OF FREQUENCY PLASMA-HEATING IN THE URAGAN-3M TORSATRON

Numerical and experimental results of Alfven wave heating of plasmas i n the frequency range below the ion cyclotron frequency (omega < omega (ci)) are presented. Two different types of antenna were used for plas ma production and heating: a frame type antenna (FTA) conventionally u sed in the URAGAN-3M device and a three-half-turn antenna (THTA) propo sed recently to avoid the deleterious effects of conversion of fast wa ve to slow wave in the plasma periphery and to perform plasma core hea ting more effectively. Numerical modeling of electromagnetic field exc itation in the URAGAN-3M plasma by the FTA and THTA was performed usin g a one-dimensional code. The results of calculations showed better pe rformance of the compact THTA compared with the FTA for the case of a high density plasma (approximately 10(13) cm(-3)). When using the THTA , the experiments performed showed the possibility of dense plasma pro duction (more than 2 x 10(13) cm(-3)) and heating, which had not been obtained earlier in the URAGAN-3M. Shifting the power deposition profi le deeper inside the plasma body with the THTA resulted in modificatio n of the plasma density profile and an improvement in plasma confineme nt.