Simple, high current LaB_6 cathode

A cathode constructed of a thin, directly heated strip of LaB_6 is described. The cathode is simple to construct, requires modest heating power, has high current emission capability and is quite rugged. Construction details will be given and cathode performance data presented. The cathode has been used in tokamak dc current injection experiments

Hydrogen hollow cathode ion source

A source of hydrogen ions is disclosed and includes a chamber having at one end a cathode which provides electrons and through which hydrogen gas flows into the chamber. Screen and accelerator grids are provided at the other end of the chamber. A baffle plate is disposed between the cathode and the grids and a cylindrical baffle is disposed coaxially with the cathode at the one end of the chamber. The cylindrical baffle is of greater diameter than the baffle plate to provide discharge impedance and also to protect the cathode from ion flux. An anode electrode draws the electrons away from the cathode. The hollow cathode includes a tubular insert of tungsten impregnated with a low work function material to provide ample electrons. A heater is provided around the hollow cathode to initiate electron emission from the low work function material

Chromium poisoning effects on performance of (La, Sr) MnO3-based cathode in anode-supported solid oxide fuel cells

Chromium (Cr) vapor species from chromia-forming alloy interconnects are known to cause cathode performance degradation in solid oxide fuel cells (SOFCs). To understand the impact of Cr-poisoning on cathode performance, it is important to determine its effects on different cathode polarization losses. In this study, anode-supported SOFCs, with a (La,Sr)MnO3 (LSM) + yttria-stabilized zirconia (YSZ) cathode active layer and a LSM cathode current collector layer were fabricated. At 800°C, cells were electrochemically tested in direct contact with Crofer22H meshes, under different cathode atmospheres (dry air or humidified air) and current conditions (open-circuit or galvanostatic). Significant performance degradation was observed when cell was tested under galvanostatic condition (0.5 A/cm2), which was not the case under open-circuit condition. Humidity was found to accelerate the performance degradation. By curve-fitting the experimentally measured current-voltage traces to a polarization model, the effects of Cr-poisoning on different cathodic polarization losses were estimated. It is found that, under normal operating conditions, increase of activation polarization dominates the cathode performance degradation. Microstructures of the cathodes were characterized and Cr-containing deposits were identified. Higher concentrations of Cr-containing deposits were found at the cathode/electrolyte interface and the amounts directly correlated with the cell performance degradations.http://jes.ecsdl.org/content/164/7/F740.fullPublished versio

Titanium diaphragm makes excellent amplitron cathode support

Cathode support structure designed around a titanium diaphragm prevents radial misalignment between the cathode and anode in amplitrons. The titanium exhibits low thermal conductivity, tolerates lateral thermal expansion of the cathode, and is a poor primary and secondary emission medium

Advances in electrometer vacuum tube design

Single-ended, miniature-cathode tube with a relatively low grid current level is constructed. Adequate cathode temperature at relatively low heater power drain is provided by designing the supporting spacers to provide a square cathode hole. Method of assembling the mount and bonding the elements is discussed

High speed electrostatic photomultiplier tube for the 1.06 micrometer wavelength. Cup and slat dynode chain combined with flat cathode and coax output produces 0.25 nsec rise time

The Varian cup and slat dynode chain was modified to have a flat cathode. These modifications were incorporated in an all-electrostatic photomultiplier tube having a rise time of 0.25 n sec. The tube delivered under the contract had a flat S-20 opaque cathode with a useful diameter of 5 mm. The design of the tube is such that a III to V cathode support is mounted in place of the existing cathode substrate. This cathode support is designed to accept a transferred III to V cathode and maintain the cathode surface in the same position as the S-20 photocathode