Schematic diagram of the experimental system showing the axial magnetic field ( B 0) profiles for various coil currents in relation to the plasma chamber. Also shown are the locations of the two antenna loops used for launching the helicon waves. In the figure, mark “A” inside the circle on x-axis represents the centre of 2nd loop antenna.
(a) A typical I-V characteristic taken on axis, obtained by the RF compensated LP in Helicon discharges at 2 mTorr pressure of argon gas, 940 watts of RF power, and 215 Gauss magnetic field (plateau region).; (b) Plot of ln (I e) versus V for the plot in (a) after subtracting the ion saturation current. Figure shows the two linear regions corresponding to two electron populations with temperatures T w = 20 eV and T e = 2 eV. The other plasma parameters are n e = 1.2 × 1011 cm−3, n w = 2.6 × 108 cm−3, V f = 24 V, and V p = 43 V.
Block diagram of LP power supply used in the present experiment.
Axial profile of the plasma density (n 0), bulk electron temperature (T e), warm electron density (n w), warm electron temperature (T w), and plasma potential (Vp) measured at the operating conditions given in Fig. 2 . In the figure, z = 0 cm corresponds to mark “A” inside the circle on x-axis as shown in Fig. 1 .
Axial potential energy profiles for electrons (= U e) and ions (= U i) corresponding to the plasma potential profile in Fig. 4(d) . Figure also shows the different regions and the particle populations. The dashed lines represent the transition region. In the figure, z = 0 cm corresponds to mark “A” inside the circle on x-axis as shown in Fig. 1 .
Plasma potential profile in Fig. 4(d) associated with the expansion of high density plasma into the region with a low density. The figure shows the “knee” structure developed in a localized region of a few cm in expanding plasma.
Approximate plasma potential profile as in Fig. 4(d) showing two different plasmas and DL for ease on discussion.
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