Quantitative characterization of arc discharge as vacuum interface

Abstract

An arc discharge with channel diameters of 3 mm and 6 mm and lengths between 30 mm and 60 mm was experimentally investigated for its potential to function as plasma window, i.e., interface vacuum regions of different pressures. Electron temperature of the plasma channel measured spectroscopically varied in the range of 7000 K to 15 000 K, increasing with discharge current while decreasing with gas flow rate. That plasma window had a slightly positive I-V characteristics over the whole range of investigated current 30 A-70 A. Measurements of pressure separation capability, which were determined by input current, gas flow rate, discharge channel diameter, and length, were well explained by viscosity effect and "thermal-block" effect. The experimental results of global parameters including temperature, gas flow rate, and voltage had a good agreement with the simulation results calculated by an axis-symmetry Fluent-based magneto-hydrodynamic model. V C 2014 AIP Publishing LLC. [http://dx.

Theoretical and experimental investigation on magneto-hydrodynamics of plasma window

“…When pumping efficiency is improved, 10 -5 Pa vacuum separation from atmosphere is believed to be achieved. From the experimental result of 3 mm plasma window discharge U-I plot in Reference of S. Huang [10], we can conclude that temperature has a linear correlation with current. As we know, electrical conductivity has such relation:…”

“…The accuracy of temperature simulation compared with experimental result can be traced from the previous research in Reference [10]. So the temperature of plasma discharge under such condition must be located between 5000 K and 17000 K, When it comes to variation trend of outlet pressure showed in Fig.…”

“…Previous research shows that the plasma arc could be used to separate high pressure at 2.85 bar [4] from vacuum (0.6 mbar) across a 2.36-mm diameter 40-mm long arc by three chamber differentially pumped system, and up to 9 atm [5] from 2 mbar with 2 mm channel in diameter. The diameter of plasma channel in record reaches from 2 mm to 6 mm [1][2][3][4][5][6][7][8][9][10]. As the result says, the electron beam with 175 KeV could successfully pass through from vacuum to atmosphere [7].…”

“…Obviously it shows sealing effect, keeping pressure difference between inlet and outlet side. Compared with 3 mm and 6 mm diameter plasma window[10], 10 mm sealing effect is relatively weak as the result of enlarged diameter of plasma channel. But it can be compensated by cascade plasma window configuration.…”

Demonstration of Plasma Window with 20 mm Diameter and Pressure Separation for Accelerator Applications

“…Since the viscosity of Ar plasma is proportional to temperatures up to 12,000 K [8], the high temperature plasma causes large pressure differ- ence. These equations give a prediction of the upstream pressure (i.e., the confinement pressure) P 1 [6,7].…”