Research of an oxide cathode as a cathode-neutralizer for EPSPS

2019 ◽  
Author(s):  
A.S. Benklyan ◽  
A.A. Lyapin ◽  
G.K. Klimenko
Keyword(s):  
Vacuum Chamber ◽  
Theoretical Explanation ◽  
Emission Current ◽  
Laboratory Model ◽  
Activation Process ◽  
Emitter Temperature ◽  
Temperature Range ◽  
Thermionic Cathodes ◽  
Oxide Cathode ◽  
Temperature Time

In this research, a laboratory model of a thermionic oxide cathode was tested as part of a diode circuit. The ultimate goal of this work was to obtain the thermionic characteristics of the emitter of the laboratory model and to study the processes of emitter activation. The relevance of the study is due to the increased interest in the possibility of using thermionic cathodes as cathode-neutralizers for electrically-powered spacecraft propulsion system (EPSPS). During the experiment, the following parameters were recorded: the pressure in the vacuum chamber and the emission current to the anode-collector. The current of the emitter and the voltage applied between the anode-collector and the emitter were regulated. The gap between the emitter and the anode-collector was set before the beginning of the experiment and was 2 mm. The emission current was measured in the emitter temperature range from 600 °C to 1260 °C. The temperature of the emitter was controlled by infrared and optical pyrometers. In the course of the work, three emitter activation processes were identified: temperature, time and voltage. The processes of activation by temperature and time are widely known, in contrast to the activation process by voltage, for which there is currently no unambiguous theoretical explanation.

Kinetic Characteristics of Si3N4 CVD

1991 ◽  
Vol 250 ◽  
Author(s):  
W. Y. Lee ◽  
J. R. Strife ◽  
R. D. Veltri
Keyword(s):  
Deposition Rate ◽  
Mass Spectroscopy ◽  
Flow Rate ◽  
Molar Ratio ◽  
Kinetic Characteristics ◽  
Temperature Range ◽  
Time Flow ◽  
Effects Of Temperature ◽  
Temperature Time

AbstractThe CVD of Si3N4 from SiF4 and NH3 gaseous precursors was studied using a hotwall reactor in the temperature range of 1340 to 1490°C. The effects of temperature, time, flow rate, and SiF4/NH3 molar ratio on deposition rate and axial and radial deposition profiles were identified. The decomposition characteristics of pure NH3 and SiF4 were studied utilizing mass spectroscopy and compared to thermodynamic predictions.

100 A/cm2 high emission current density oxide cathode

IVESC 2012 ◽  
2012 ◽  
Author(s):  
Xiaoxia Wang ◽  
Min Zhang ◽  
Xianheng Liao ◽  
JirRun Luo ◽  
Qinglan Zhao ◽  
...  
Keyword(s):  
Current Density ◽  
Emission Current Density ◽  
Emission Current ◽  
Oxide Cathode ◽  
High Emission

Experimental Investigation of Radiative Transfer Between Metallic Surfaces at Cryogenic Temperatures

1970 ◽  
Vol 92 (3) ◽  
pp. 412-416 ◽  
Author(s):  
G. A. Domoto ◽  
R. F. Boehm ◽  
C. L. Tien
Keyword(s):  
Radiative Transfer ◽  
Liquid Helium ◽  
Liquid Helium Temperature ◽  
Helium Temperature ◽  
Metallic Surfaces ◽  
Emitter Temperature ◽  
Temperature Range ◽  
Order Of Magnitude ◽  
Temperature Levels ◽  
Lower Temperature

Experimental measurements of the radiative heat flux between two parallel copper disks in the liquid-helium temperature range are presented. The temperature levels investigated were primarily for the higher temperature disk (emitter) at 10.0 deg K and 15.1 deg K and the lower temperature disk (receiver) at approximately 4.5 deg K. For the 15.1 deg K emitter temperature, the spacing was varied from 0.201 cm to 0.001 cm. For the 10 deg K emitter case, the spacing was varied from 0.044 cm to 0.005 cm. Experimental data at small spacings show a definite spacing dependence of radiative transfer which agree qualitatively with the predicted result. Based on the measurements at large spacings, an estimate of the total hemispherical emissivity for the copper surfaces in the liquid-helium temperature range indicates a value of 0.015, which is approximately one order of magnitude higher than predicted. The possible causes for the discrepancies are discussed.

Low Temperature Attachment For X-Ray Powder Diffractometry

1993 ◽  
Vol 37 ◽  
pp. 457-463 ◽  
Author(s):  
H.W. King ◽  
M.A. Peters ◽  
E.A. Payzant ◽  
M.B. Stanley
Keyword(s):  
High Temperature ◽  
Barium Titanate ◽  
Low Temperature ◽  
Phase Transformations ◽  
Vacuum Chamber ◽  
X Ray ◽  
Temperature Range ◽  
Beryllium Window ◽  
Open Cycle

AbstractA low temperature attachment based on a miniature open-cycle Joule-Thomson refrigerator has been developed for x-ray diffractometry measurements over the temperature range from 65 - 400 K, By use of a special mounting plate, the device can be substituted for the heater assembly of a high temperature attachment and thereby utilize the available vacuum chamber and x-ray transparent beryllium window. The device is demonstrated by investigating the polymorphic phase transformations that occur in barium titanate.

Studies of the Effect of Heat Treatment on Hardness and Creep Behavior of a Modified 9Cr-1Mo Steel

2011 ◽  
Author(s):  
Z. Wuthrich ◽  
T. Shrestha ◽  
I. Charit ◽  
K. Rink ◽  
M. Basirat ◽  
...  
Keyword(s):  
Heat Treatment ◽  
Microstructural Evolution ◽  
Creep Deformation ◽  
Microstructural Analysis ◽  
Time Range ◽  
Creep Tests ◽  
Tempering Temperature ◽  
Temperature Range ◽  
Before And After ◽  
Temperature Time

In this study, heat treatment was carried out on modified 9Cr-1Mo steel specimens to determine the microstructural evolution for various normalizing temperature/time and tempering temperature/time combinations. Normalization was carried out in the temperature range of 1020–1100°C and time range of 2–8 hours, while tempering was performed in the temperature range of 690–790°C and time range of 2–20 hours. Optical microscopy was then used to visualize and chronicle the microstructural characteristics at varying levels of heat treatment. Vickers micro-hardness measurements were performed on each sample to obtain hardness values as a function of normalizing and tempering temperature/time. Creep tests have also been performed on as-received and welded specimens of modified 9Cr-1Mo steel, in the temperature range of 500–700°C and stress range of 50–200 MPa. Microstructural analysis was carried out on the specimens before and after creep deformation using both scanning and transmission electron microscopy. The microstructural evolution during the heat treatment and creep tests provided useful information to understand and characterize the creep deformation mechanisms of modified 9Cr-1Mo steel.

scholarly journals Modelling Contaminant Formation during Thermal Processing of Sea Buckthorn Purée

Molecules ◽  
2019 ◽  
Vol 24 (8) ◽  
pp. 1571 ◽  
Author(s):  
Oana Emilia Constantin ◽  
Kristina Kukurová ◽  
Ľubomír Daško ◽  
Nicoleta Stănciuc ◽  
Zuzana Ciesarová ◽  
...  
Keyword(s):  
Thermal Treatment ◽  
Exposure Time ◽  
Thermal Processing ◽  
Sea Buckthorn ◽  
Temperature Range ◽  
Lower Quantity ◽  
The Impact ◽  
Found Model ◽  
Temperature Time ◽  
Thermally Treated

Background: The impact of thermal treatment on acrylamide (ACR) and hydroxymethylfurfural (HMF) formation was investigated for thermally treated sea buckthorn purée. Methods: An optimized procedure for minimizing ACR and HMF formation in thermally treated sea buckthorn purée was described. The precursors of ACR and HMF and their impact in heating of sea buckthorn purée to obtain jam-like products were also evaluated. Results: The contaminant content formed in samples was analyzed on thirteen running variants using a temperature range of 59.3–200.7 °C, and for heating durations between 5.9 and 34.1 min. The calculated equations of contaminant formation in sea buckthorn purée have established that the minimum content is formed at the lowest exposure time, between 10 and 20 min, for both ACR and HMF. The lowest ACR content was attained at 5.9-min exposure time and 130 °C temperature (0.3 µg/kg). For HMF the results revealed a lower quantity at 59.3 °C for 20-min exposure time (1.4 mg/kg). Conclusions: the found model is useful for the prediction of the best temperature/time conditions of the thermal treatment to obtain the lowest contaminates levels in the final product.

Phenomenological Model of Non-Evaporated Getter for Micro-electromechanical Systems (MEMS) Applications

2000 ◽  
Vol 657 ◽  
Author(s):  
Caroline A. Kondoleon ◽  
Thomas F. Marinis
Keyword(s):  
Depth Profiling ◽  
Activation Process ◽  
Ambient Conditions ◽  
Electromechanical Systems ◽  
Simple Diffusion ◽  
Efficient Operation ◽  
Absorbing Material ◽  
Simple Diffusion Model ◽  
Temperature Time ◽  
Process Constraints

ABSTRACTThere has been increasing interest in the development and use of micro-electromechanical systems (MEMS) for various applications. Some MEM devices such as gyroscopes, accelerometers and bolometers, must be sealed under vacuum, at pressures below 10 millitorr, for efficient operation. A gas absorbing material (getter) is placed in the packages of these devices, to help maintain vacuum levels over service lives of many years. Heating under vacuum, just prior to sealing the package, activates getter, of this type. This study was undertaken to develop a model that could be used to estimate the quantity of getter needed as well as optimize the activation process subject to process constraints on time and temperature.The material studied was a titanium and zirconium-based alloy (7:3 by weight) non-evaporable getter in the form of strips produced by SAES Getters. The zirconium alloy consisted of zirconium (70.0%), vanadium (24.6%) and iron (5.4%) by weight. The getter was analyzed under different ambient conditions of temperature, time and atmospheric pressure. Auger electron spectroscopy (AES) depth profiling was used to analyze the diffusion depth of the contaminant gases absorbed by the getter material under each condition. The data acquired from the depth profiles were fit to a simple diffusion model. This model is currently being validated, by activating the getter material under various ambient conditions, and measuring pressures and gas compositions inside packages using a residual gas analyzer (RGA). The utility of this model for optimization of getter activation and estimating package vacuum levels over time will be discussed.

The Tensile Strength of Water as a Function of Temperature

2005 ◽  
Author(s):  
Rhodri L. Williams ◽  
P. Rhodri Williams ◽  
A. Al-Hussany
Keyword(s):  
Tensile Strength ◽  
Negative Pressure ◽  
Pressure Pulse ◽  
Theoretical Explanation ◽  
Temperature Range ◽  
Order Of Magnitude

This paper reports the results of measurements of the effective tensile strength Fc of water, in experiments involving a pulse of tension (‘negative pressure’) created by the reflection of a pressure pulse at a boundary, as a function of temperature. Using a modified ‘Bullet-Piston’ (B-P) pulse reflection apparatus, measurements presented herein show that degassed, deionised water is capable of sustaining tensions an order of magnitude greater than previously reported in B-P work. A theoretical explanation is developed indicating that the pressure records arising in B-P experiments are the result of cavitation due to a pulse of tension. Results are reported for measurements of Fc made over the temperature range 1°C ≤ T ≤ 95°C.

ABOUT THE CROSSOVER PHENOMENON FOR VRH-CONDUCTIVITY

1994 ◽  
Vol 08 (07) ◽  
pp. 891-896 ◽  
Author(s):  
I.S. Shlimak ◽  
M.J. Lea
Keyword(s):  
Low Temperature ◽  
Fermi Level ◽  
Alternative Explanation ◽  
Temperature Limit ◽  
Activation Process ◽  
The Real ◽  
Temperature Range ◽  
Lower Resistance ◽  
Straight Line ◽  
Increasing Temperature

In a number of recent publications observations of the phenomenon of crossover from the Efros-Shklovskii (ES)-law to the Mott-law in VRH-conductivity were reported. In some experiments, deviations were observed from a straight line in a lnR vs T−1/2 plot to lower resistance values with increasing temperature. However, deviations to higher resistance with increasing temperature should be observed. In other experiments deviations from the “T−1/2 law” to higher resistances with decreasing temperature were observed. This effect was considered as a transition to a simple activation process, “T−1 law”, caused by the appearance of a hard gap at the Fermi level. In the present work an alternative explanation is given, based on the idea that the temperature range showing the “T−1/2 behaviour” actually corresponds to the crossover regime, while the real ES-regime is only reached in the low-temperature limit.

Application of an additional electrode for improving the emission properties of the lossless cathode-neutralizer for EPSPS

2020 ◽  
Author(s):  
A.S. Benklyan ◽  
A.A. Lyapin ◽  
G.K. Klimenko
Keyword(s):  
Laboratory Tests ◽  
Activation Process ◽  
Emitter Surface ◽  
Propulsion Systems ◽  
Hall Effect Thrusters ◽  
Ion Thrusters ◽  
Thermionic Cathodes ◽  
Basic Concepts ◽  
Additional Stimulation ◽  
Stimulation Of

The article considers the advantages of application of an additional electrode — anode-collector in the design of a lossless cathode-neutralizer (LCN) for electrically powered spacecraft propulsion systems (EPSPS) (hall-effect thrusters and ion thrusters). The relevance of the work is due to the increased interest in the possibility of using lossless thermionic cathodes as cathodes-neutralizers (CN) of EPSPS. Based on the results of laboratory tests of the lossless cathode-neutralizer model conclusions are drawn about the effectiveness of the anode-collector in the design of the lossless cathode-neutralizer. The presence of the collector-anode allows for additional “stimulation” of the emitter by voltage intensifying the emitter activation process and increasing the emission current from the emitter surface by 2-2.3 times. The saved energy for emitter heating due to using an anode-collector is estimated. The basic concepts and recommendations for the development of the design of lossless cathode-neutralizer design are presented.

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