Hee Myung Shin

Conductivity and ion density of a plasma channel induced by a mildly relativistic electron beam from a gas-filled diode

Conductivity and ion density of a plasma channel induced by a mildly relativistic electron beam (300 kV, ∼2 kA, 10–50 ns) have been experimentally investigated under various gas pressures. Pressures of filling gas (air) in this experiment ranged from 10 mTorr to 100 mTorr. The net currents of the beam-induced plasma channel were measured by four Rogowski coils located along the propagating region, while the electron beam currents were measured by a Faraday cup. The inductive plasma currents observed at the above pressure regimes have been characterized by magnetic decay time. Plasma-channel conductivity and ion density induced by the beam are measured along the propagating axial positions under various gas pressures. The numerical result of the ion density is also obtained at the charge neutralization time when the ion density is just the same as the electron beam density, and the digitizing experimental data of the beam current Ib(t) and voltage Vd(t) have been used. As expected, in both numerical and ex...

Pulsewidth and rising time of relativistic electron beam in gas-filled diode

The pulsewidth and rising time of a mildly relativistic electron beam (300 kV, 1-3 kA) passing through a gas-filled diode region are investigated experimentally under various gas pressures P. The pulsewidth and rising time of a relativistic electron beam (REB) were controlled by adjusting the gas pressures P of the diode region. The pulsewidth and rising time of the relativistic electron beam are experimentally found to scale as P/sup -0.807/spl plusmn/0.054/ and P/sup -0.770/spl plusmn/0.058/, respectively. The REB pulsewidth and rising time are shown to have the same scaling law, within the experimental error range as a function of pressure. In particular, the empirical scaling law of the REB pulsewidth is in remarkably good agreement with the numerical scaling law P/sup -0.809/spl plusmn/0.059/ of the full-space charge neutralization time t/sub n/ at which the ion density n/sub i/ is just equal to the electron beam density n/sub b/ at the diode region under a given gas pressure P. It also is found that ion density n/sub i/ at the full space-charge neutralization time t/sub n/ has quite a similar profile in terms of pressure P to that of the REB peak current detected by a Faraday cup.

Influence of Insulator Length on the Downstream Electron Temperature and Density in the Coaxial Plasma Focus Device

We have generated the Ar plasma in the diode chamber based on the established coaxial electrode type and investigated the emitted visible light for emission spectroscopy. The optical emission spectrum data have been obtained for the focused plasma in the cylindrical diode chamber under the input voltage of 4.5 kV and pressure of 40 mtorr. We observed the nine emission lines of Ar II: 407.3, 410.6, 422.4, 426.8, 427.9, 435.0, 438.1, 444.5, and 488.0 nm. The downstream electron temperature and density have been measured by the Boltzmann plot and Stark broadening, respectively, from the assumption of local thermodynamic equilibrium. The length of the acrylic insulator has been changed to 30, 40, and 45 mm, respectively, which is covered on the inner cathode surface, to investigate the influence of insulator length on the downstream electron temperature and density in this experiment. Our results show that the downstream electron temperature and density of focused plasma are 2.5 eV and 1.6times1016 cm-3, respectively, for the coaxial plasma focus with cylindrical electrodes at the insulator length of 40 mm.

Corrections to “Influence of Insulator Length on the Downstream Electron Temperature and Density in the Coaxial Plasma Focus Device” [Jan 09 184-189]

In the above titled paper (ibid., vol. 37, no. 1, pp. 184-189, Jan 09), the superscript 6 in (3) is incorrect. The correct equation is presented here.

Influence of insulator length on the electron temperature in the coaxial electrode of Plasma focus device

Summary form only given. We have generated the argon plasma in the diode chamber based on the established coaxial electrode type and investigated the emitted visible light for emission spectroscopy. We applied various voltages 2-3.5 kV to the device by 0.5 kV. and obtained the emission spectrum data for the focused plasma in the diode chamber on the diverse argon pressure. The Ar I and Ar Il emission line are observed. The electron temperature and ion density have been measured by the Boltzmann plot and Stark broadening from assumption of local thermodynamic equilibrium (LTE). We changed the length of insulator which is covered with the anode and cathode and measured the electron temperature on the its diverse insulator type. It can be shown that the electron temperature will be influenced by the insulator length in argon plasma with coaxial electrode.

Influence of insulator length on the downstream electron temperature and electron density in the coaxial electrode of plasma focus device

We have generated the Ar plasma in the diode chamber based on the established coaxial electrode type and investigated the emitted visible light for emission spectroscopy. It is applied to the input voltage 4.5 kV, and obtained the emission spectrum data for the focused plasma in the diode chamber on the argon pressure 40 mTorr. We observed the nine emission lines of Ar II ; 407.3 nm, 410.6 nm, 422.4 nm, 426.8 nm, 427.9 nm, 435.0 nm, 438.1 nm, 444.5 nm and 488.0 nm. The downstream electron temperature and electron density have been measured by the Boltzmann plot and Stark broadening from assumption of local thermodynamic equilibrium (LTE). The length of Acrylic insulator had been changed, which is covered in the cathode by the 30 mm, 40 mm and 45 mm, respectively, to measure the downstream electron temperature and electron density in the experience. The centered wavelength of Stark broadening was 444.58 nm. This experiment can be shown that the downstream electron temperature will be influenced by the insulator length in argon plasma with coaxial electrode. Our results show that the maximum downstream electron temperature and electron density are 2.5 eV and 1.6×1016 cm−3, respectively for the Our result have been appeared the maximum electron temperature of 2.50 eV and density of 1.6×1016 cm−3 for the plasma focus in coaxial electrode under the insulator length of 40 mm.

Propagation characteristics of a mildly relativistic electron beam in sub-Torr pressure

Summary form only given, as follows. Using a mildly relativistic electron beam (300 kV, 40 kA, 60 ns) with a foilless diode in a beam-induced plasma channel, the effect of return current has been investigated experimentally. The pressure of filling gas (air) in this experiment ranged from 10 mTorr to 100 mTorr. The net current and beam current variation were measured by a Rogowski coil and a Faraday cup. The peak return current observed at a propagation window has been characterized in terms of the beam current and the charge neutralization factor. The beam instability attributed to the return current resulted from an inductive phenomena of a beam-induced plasma channel has been observed.