• Journal of Korean Ophthalmic Optics Society
• /
• v.13 no.3
• /
• pp.57-60
• /
• 2008

Purpose: The radial speed of plasma current sheath was measured at the plasma focus apparatus. Methods: The measurement was used to time-resolved spectroscopic method and Rogowski coils. Results: Radial current sheath speed was measured with $10^5$ cm/s at Helium and Argon pressure between 5 to 100 torr and discharging voltage of 15 kV. When the gas pressure was increased, the current sheath speeds were decreased. Conclusions: At the optimum condition of plasma focus apparatus, the radial speed is guessed $10^7$ cm/s as a results of the measurement of current sheath speed.

• Journal of Korean Ophthalmic Optics Society
• /
• v.12 no.1
• /
• pp.69-74
• /
• 2007

The axial speed of plasma current sheath was measured with Rogowski coils and compared with the theory of snowplow model. Current sheath speed is measured with $10^6cm/s$. The speed of light gas, $H_2$ and He were similar to the theory of model, but the heavy gas, Ar was not similar to the theory. The disagreement of the heavy gas was guessed as a results of the instability of the current sheath.

• The Transactions of The Korean Institute of Electrical Engineers
• /
• v.56 no.12
• /
• pp.2173-2178
• /
• 2007

Dynamics of plasma sheath was analyzed using simple ion fluid model with poison equation. Incident ion current, energy, potential distribution and space charge density profile were calculated as a function of time. The effects of initial floating sheath on the evolution of biased sheath were compared with ideal matrix sheath. The effects of finite rising time of pulse bias voltage on the ion current and energy was studied. The influence of surface charging on the evolution of sheath was also investigated

• Proceedings of the Korean Vacuum Society Conference
• /
• 2010.02a
• /
• pp.470-470
• /
• 2010

Negative ions are generated in fusion edge plasmas, material processing plasmas, ionospheric plasmas. Analytic formulas for the deduction of the absolute density of negative ions was given by using the current-voltage(IV) characteristics of two electric probes at two different pressures [1], and negative ion density has been measured by one electric probe using the current-voltage characteristics of three different pressures [2]. Ratios of ion and electron saturation currents and electron temperatures and sheath areas of different pressures are usually incorporated into two equations with two unknowns for the negative ion density. In the previous publications, the sheath factor(sheath area, sheath density, sheath velocity) and effective masses of background ions with different pressures are qualitatively incorporated for the deduction of negative density. In this presentation, the quantitative and detailed relation of negative ion density with sheath factor and effective masses are going to be given. The effect of these parameters on the change of IV characteristics will be addressed.

• Proceedings of the Optical Society of Korea Conference
• /
• 1989.02a
• /
• pp.65-69
• /
• 1989

Mather type dense plasma focus device was develooped for the feasibili쇼 study in its application to the x-ray lithography. To etermine the electrical characteristics,the temporal begavior of the discharge current and the voltage was measured by using the Rogowski coil and the high voltage probe respectively. The results are 9 $\mu\textrm{s}$ of the period, 18m$\Omega$ of resistance and 0.16$\mu$Η of inductance. The average current sheath velocity was measured by the light signal emitted at the moving plasma sheath. The light signal was detected through two fiber bundles. When the applied voltage was 13 kV and the initial jpressure of argon was 21.8 Pa, the best plasma focus was occurred. The x-ray emission characteristics from the plasma focus was determined by the x-ray pictures taken by pinhole camera. It is focus that the plasma was focused at 1.4 cm distant position above the center electrode and its diameter was about 1.0 m.

• Journal of Astronomy and Space Sciences
• /
• v.17 no.1
• /
• pp.99-106
• /
• 2000

When a deployed probe is biased by a high positive potential during a space experiment, the payload is induced to a negative voltage in order to balance the total current in the whole system. The return currents are due to the responding ions and secondary electrons on the payload surface. In order to understand the current collection mechanism, the process was simulated with a combination of resistor, inductor, and capacitor in SPICE program which was equivalent to the background plasma sheath. The simulation results were compared with experimental results from SPEAR-3 (Space Power Experiment Aboard Rocket-3). The return current curve in the simulation was compatible to the experimental result, and the simulation helped to predict the transient plasma response to a high voltage during the plasma sheath formation.

• Journal of the Korean Vacuum Society
• /
• v.7 no.4
• /
• pp.381-389
• /
• 1998

The time variation of an ion current density has been analyzed based on the plasma particle dynamic model for the plasma immersion ion implantation. The implanted ion current density has its maximum value at a particular time after sheath formation, and decays. The influence of the particle collisions, the capacitive time of the substrate, and the pulse formula has been represented on the implanted ion current.

• Proceedings of the Korean Society of Propulsion Engineers Conference
• /
• 2008.03a
• /
• pp.602-605
• /
• 2008

The anode sheath structure in the hollow anode of an anode-layer type Hall thruster was numerically computed using a fully kinetic 2D3V Particle-in-Cell and Direct Simulation Monte Carlo(PIC-DSMC) code. By treating both ions and electrons as particles, anode surface region, which is electrically non-neutral, was analyzed. In order to analyze in detail, the calculation code was parallelized using Message Passing Interface (MPI). The code successfully simulated the discharge current oscillation. In the low magnetic induction case, ion sheath appears in the anode surface because ionization is enough to maintain the plasma occurs in the anode hollow. As the magnetic induction increases, main ionization region move to outside of the anode. At the same time, anode sheath voltage decreases. In the high magnetic induction case, electron sheath appears on the anode surface periodically because the ionization occurs mainly in the discharge channel. This anode sheath condition shift can be explained using the simple sheath model.

• Journal of the Korean Vacuum Society
• /
• v.15 no.3
• /
• pp.246-258
• /
• 2006

A circuit model has been developed to analyze characteristics of the PSII(plasma source ion implantation) pulse system with dynamic plasma load. The plasma sheath in front of the immersed planar target biased with a negative-high voltage pulse is assumed to be governed by the dynamic Child-Langmuir sheath model. Target current is self-consistently varied with the applied voltage by using the voltage-controlled current source in the circuit model. Circuit simulations are conducted with Pspice circuit simulator, and simulated pulse currents and voltages on the target are compared and confirmed with experimental results for various voltage pulses and plasma conditions.

• Korean Journal of Optics and Photonics
• /
• v.1 no.1
• /
• pp.65-72
• /
• 1990

Mather type plasma focus system is designed and fabricated, and its electrical behaviors and the ,~haracteristics of the plasma are investigated. The discharge CUlTent is measured with a Rogowski coil, and the external resistance and inductance of the system are found to be $20m\Omega, 0.2{\mu}H respectively from the measured voltage signals and current signals, and discharge inductance, magnetic, and mechanical energy are calculated. 'i'he speed of the plasma current sheath in the acceleration phase is found to vary as $P^{-0.25}\timesV^{0.38}$ and its value is about is 106 cm/sec. The electron temperature in the plasma is determined from the measurement of the X-ray transmittance with the number of X-ray filters and its value is found to be about I keY. The size of plasma, measured using X-ray pin-hole camera, is about 17 (dia.) x 30 (length)mm2. h)mm2.