(iv) The presentation equipment which was made up of a pointer and a Graphtec Plotter. During testing, signals from the diode thermocouples, the pyrometer and the load circuit were fed to the HP system. These signals were processed by the HP-3852A and accessed by the Z-248 using ASYST software. This data was then converted to the appropriate format necessary for use with the Graphtec plotter. These files were then used to produce the required plots to analyze and characterize the diode. Testing Procedure The vacuum level was brought down to 10~7 torr or better before firing up the filament and the bombardment power supply to heat the emitter. The bombardment power was adjusted till the required emitter temperature was obtained. The collector and cesium reservoir temperatures were then adjusted with the heating and cooling mechanisms. The data acquisition and processing system were then activated using the ASYST program. Once the temperatures had stabilized the diode was biased with a positive bias voltage corresponding to a diode output voltage of +2 V. The bias voltage was then changed to a lower value and the temperatures adjusted once again and the output data such as current and voltage were recorded. This was repeated till a full cycle of biasing was completed. The data was then transferred to the Graphtec plotter to get the output J-V characteristics for those temperatures. Keeping the emitter and collector temperatures unchanged the cesium reservoir temperature was changed and the corresponding J-V characteristics generated. This was repeated for several cesium reservoir temperatures in the temperature range of 350 to 550 K at 30°C intervals. The first stage optimized cesium reservoir temperature was determined using all the J-V characteristics generated. Keeping the emitter and optimum cesium reservoir temperature constant, the tests were repeated for several collector temperatures in the range of 750-1050 K in
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