Microwave plasmas were excited and studied in cylindrical chambers with inner diameters of 5–15 cm in the presence of the static axial magnetic fields of 800–1200 G. Rectangular (TE10) and circular (TM01) modes of electromagnetic waves at a frequency of 2.45 GHz were introduced into the plasma chamber via a dielectric vacuum window. It was found that a transition to the high level of microwave power absorption occurred when the plasma density reached a value of Ncr =7.4×1010 cm−3 and magnetic field was about 875 G. Hysteresis in the dependences of reflected microwave power, Pr, versus incident microwave power, Pi, and gas pressure were observed. Two ‘‘resonant’’ magnetic fields which provided the highest plasma densities in electron cyclotron resonance (ECR) plasma were found: 875 and 920–930 G. Both column- and donut-type high density (Ne ∼1012 cm−3) ECR plasmas were achieved in 15 cm diam chamber utilizing rectangular TE10 and circular TM01 modes.
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Oleg A. Popov (1990) studied this question.