High Current Properties Research Articles

Effect of nanostructure building formation on high current field emission properties in individual molybdenum nanocones.

The building formation of a one-dimensional nanostructure greatly affects its physical properties. By controlling the supersaturation of deposited molybdenum (Mo) vapor, two kinds of nanostructure building formations can be synthesized in Mo nanocones (spiral- and stacking-type) through a thermal evaporation process. The field emission performances of these two formations are vastly different, particularly with respect to their high current properties. The maximum current of a spiral-type individual Mo nanocone is five times that of the stacking-type nanocone. Electrical transport may not be the decisive factor for this difference because both types of individual Mo nanocones have similar excellent conductivities. Heat conduction during the high current emission process has been considered a primary factor, and it strongly depends on the number of internal nanostructure boundaries in the Mo nanocone. These results indicate that nanostructure building formations with fewer inner boundaries in Mo nanocones contribute to a higher current field emission performance when applied to vacuum electron devices.

Development of Pulsed Ion Beam Source by Washer Gun

A new type pulsed ion beam source was developed by use of washer gun plasma source. It will provide low-cost and maintenance-free ion beam for the neutral beam injector (NBI), eliminating the conventional filament and water cooling systems. Its low-voltage and high-current properties are suitable for the present spherical tokamak experiment.

Recent progress of low temperature superconducting materials at Bochvar Institute

According to requirements of the applications (fusion reactors, accelerators or superconducting switches), different NbTi and Nb 3Sn strands have been developed and manufactured at Bochvar Institute (VNIINM) for several last years. Design of the fusion and accelerator strands is dependent on the required performance and function of the conductor to be used. Good performance superconducting persistent switches called for the use of high electrical resistivity matrix together with high current properties. The characteristics of the strands manufactured for toroidal (Nb 3Sn) and poloidal (NbTi) field coils of experimental fusion reactor ITER are presented as well as the accelerator strands based on NbTiTa alloys and Nb 3Sn and also the wires with CuNi and CuMn matrices for superconducting persistent current switches.