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Abstract

Noise diagnostics has been performed on the cold field-emission cathode in high-vacuum. The tested cold field-emission cathode, based on tungsten wire with ultra-sharp tip coated by epoxy was designed to meet the requirements of transmission electron microscopy, which uses a small and stable source of electrons. Current fluctuations are reduced by improving the structure and fabrication technology. Noise was measured both in time and frequency domains, which gives information about current fluctuations and also about charge transport. Mutual correlation between the noise spectral density, extractor voltage and beam brightness was analyzed.
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Abstract

Samples of CdTe single crystals which are used as radiation detectors were periodically measured during a long time interval with different values of an applied voltage. The samples were also periodically exposed during long time periods to high temperatures of 390 K and to rapid changes of temperature from 300 K to 390 K. After 1.5 years of measurements we observed ageing of the samples which resulted in deterioration of their transport characteristics. The resistance of the samples increased significantly and current-voltage characteristics were unstable in time. Noise spectroscopy showed that low frequency noise can be used for detection of CdTe sample ageing as its spectral density increases significantly comparing to the 1/f noise of a high quality sample
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