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.

As a new device, plasma window has been designed to use plasma discharge to separate atmosphere from vacuum with high difference of pressure. It has many excellent properties, being able to be used as available passage for ion beam with negligible energy loss, also impervious to radiation damage and thermal damage. Normally beam focusing by accelerators is not that easy to achieve within channel of small cross section. 10 mm diameter plasma window's experimental realization could contribute to its further application in accelerator system. In this paper, 10 mm diameter 60 mm long plasma window has first been designed and managed to generate arc discharge with argon gas experimentally. The result proves that it has ability to separate at least 28.8 KPa (not the upper limit) from 360 Pa with 50 A direct current and 2.5 KW power supplied.Current increase leads to linear inlet pressure increase obviously, while it has less impact on outlet pressure and voltage, coming to the conclusion that the higher current of plasma discharge, the larger pressure difference it creates. Theoretical analysis of 10 mm diameter plasma window in axis symmetrical configuration using argon also has been provided, in which a numerical 2D FLUENT-based magneto-hydrodynamic simulation model is settled. It has a good agreement with experimental result on voltage and mass flow rate when inlet pressure is increased.

We have fabricated (110) epitaxy YBa 2 Cu 3 O 7−δ (YBCO), PrBa 2 Cu 0.8 Al 0.2 O 7 (PB-CAO), PrBa 2 Cu 0.8 Ga 0.2 O 7−δ (PBCGO) nanometer-thin films and YBCO/PBCAO, YBCO/PBCGO multilayers of a variety of film thicknesses. Electrical resistivities measured from these systems were plotted against temperatures and film thicknesses and are presented in this paper. Superconducting onset temperature Tc of the YBCO films was estimated and plotted against YBCO film thickness. Superconducting coupling length was deduced. Finite size effect and 2D to 3D transition are also discussed.