Battery-powered pulsed high density inductively coupled plasma source for pre-ionization in laboratory astrophysics experiments

Abstract

Articles you may be interested inReduction of plasma density in the Helicity Injected Torus with Steady Inductance experiment by using a helicon pre-ionization source Rev. Sci. Instrum. 84, 103506 (2013) An electrically floating radiofrequency (RF) pre-ionization plasma source has been developed to enable neutral gas breakdown at lower pressures and to access new experimental regimes in the Caltech laboratory astrophysics experiments. The source uses a customized 13.56 MHz class D RF power amplifier that is powered by AA batteries, allowing it to safely float at 3-6 kV with the electrodes of the high voltage pulsed power experiments. The amplifier, which is capable of 3 kW output power in pulsed (<1 ms) operation, couples electrical energy to the plasma through an antenna external to the 1.1 cm radius discharge tube. By comparing the predictions of a global equilibrium discharge model with the measured scalings of plasma density with RF power input and axial magnetic field strength, we demonstrate that inductive coupling (rather than capacitive coupling or wave damping) is the dominant energy transfer mechanism. Peak ion densities exceeding 5 × 10 19 m −3 in argon gas at 30 mTorr have been achieved with and without a background field. Installation of the pre-ionization source on a magnetohydrodynamically driven jet experiment reduced the breakdown time and jitter and allowed for the creation of hotter, faster argon plasma jets than was previously possible. C 2015 AIP Publishing LLC. [http://dx

One-dimensional time-dependent fluid model of a very high density low-pressure inductively coupled plasma

“…Details of the experiment setup and motivation have been described previously, 10 and only a brief overview of the portion of the apparatus relevant to the modeling work will be given here. A custom battery-powered 3 kW 13.56 MHz RF amplifier was used to drive a 10.5 cm long half-turn helical antenna 13 surrounding the R ¼ 1:1 cm inner radius quartz tube shown in Fig.…”

Emission and afterglow properties of an expanding RF plasma with nonuniform neutral gas density

“…Details of the experiment setup and motivation have been described previously, 14 and only a brief overview of the apparatus will be given here. A custom battery-powered 3 kW 13.56 MHz RF amplifier was used to drive a 10.5 cm long half-turn helical antenna 20 surrounding the R ¼ 1:1 cm inner radius quartz tube shown in Fig.…”

“…The high density of RF power input (>2 kW into a 2.2 cm inner diameter discharge tube) led to an unusually high plasma density for an inductively coupled discharge in this pressure range; as a result, stepwise ionization dominated over direct ionization from the ground state. 6,14 The high population densities of ground state and excited neutral atoms made the plasma optically thick at the wavelengths of a number of important emission lines. Additionally, axial nonuniformity of the neutral gas density played an important role in regulating the time-dependent discharge evolution.…”