Experimental investigation of standing wave interactions with a magnetized plasma in a minimum-B field

Abstract

Standing waves in the microwave regime are generated by a superposition of forward and backward moving waves induced by reflections from geometrical transitions in the plasma vacuum boundary. The waves are preferentially damped in the weakly collisional (νen∕ω≅10−4) plasma near the launch region (∼3−15cm), where the electron temperature has a higher than average value (Te>Teavg∼12eV). Typical e-folding damping lengths are of the order of 10cm, and depend upon the wave power and plasma collisionality. Fourier spectrum of the standing waves indicates about 23% downshift in the vacuum wave-number due to plasma dispersion. Electron trapping is observed in the potential troughs of the waves.

Micron-focused ion beamlets

“…27 The ratio of the diameters of through aperture and the slot is optimized using the AXCEL-INP simulation code and found to be good when maintained at 1:6, which provides best focusing effect. The PE is in contact with the plasma and attains the plasma potential usually in the range 50-80 V. 9,28 In the simulation the interelectrode distance d as shown in the inset of Fig. 1, is normally kept fixed at 2 mm and the potential V 2 on the collector ͑C͒ is varied.…”

Penetration and screening of perpendicularly launched electromagnetic waves through bounded supercritical plasma confined in multicusp magnetic field

“…In a multicusp device, supercritical plasmas ͑ p Ͼ ͒ are generated in compact geometries, which interact self-consistently with the wave that generates the plasma. [9][10][11][12] Such wave assisted plasma sources are a major requirement in emerging applications such as high current focused ion beams, 13 miniplasma thrusters, 14 broadband wave sources, 15 and plasma wake field accelerators. 16 It is known that when an EM wave impinges on an infinitely long, unbounded, and uniform plasma, where ␣ p 2 Ͼ 1 ͑supercritical͒ and ␤ c 2 Ӷ 1 ͑minimally magnetized͒, most of the EM wave is reflected from the plasma.…”

“…The waves are launched primarily in the k Ќ B o mode. [9][10][11][12] A planar Langmuir probe having a 4 mm diameter stainless steel tip is swept between Ϫ90 and +60 V to obtain the I-V characteristics with the help of a National Instruments data acquisition system in association with a PC running LABVIEW 8.0. The total sweep time is set at 75 s in steps of 0.2 V, with 100 data points acquired and averaged at each point.…”

“…[1][2][3][4][5][6][7][8][9][10][11][12] In the presence of a static magnetic field in the plasma, the interaction becomes all the more interesting due to the generation of a variety of wave modes, cutoffs, and resonances. 1 Most of the earlier experiments have focused on launching waves parallel to a nearly uniform axial magnetostatic ͑B o ͒ field produced by current carrying coils ͑k ʈ B o case͒.…”

Electron energy probability function and L-p similarity in low pressure inductively coupled bounded plasma

“…The motivation further arises from the fact that, normally in most wave assisted plasma devices, the heating frequency is maintained constant (e.g., 13.56 MHz for rf discharges and 2.45 GHz in microwave discharges [11][12][13]), and two important parameters that may be varied are the system length (size) and the pressure, which can determine the dynamics of the particles (electrons and ions) present in the discharge. In many actual experiments, it may be inconvenient and quite cumbersome to vary the length of the system.…”