The Study On Photostimulated Discharge And Measuring System

The conception of dielectric was defined by Faraday early in the 1830s, which stood for a kind of materials different from metals and having internal electric field. In doing the research of charge storage and decay procedure, many researching methods, such as Thermally Stimulated Current, Thermally Stimulated Conductivity, Thermoluminescence and so on, appeared. During more than one hundred years, dielectric materials, a necessary part in our daily lives, developed rapidly with the theory becoming more mature. In the past ten years, space charge dielectrics are widely used in industry, commerce and military fields. Recently, the capability to store space charge for long periods of time of polymer dielectric attracts researchers'attentions. With their special properties, polymer dielectrics are applied in variety of sensors, detectors, switches, radiation detectors, air filters, artificial organs as well as other functional devices. Despite the widespread applications of space charge dielectrics, the microscopic mechanisms of charge storage are still poorly understood.In order to grope for the puzzle talking above, the author of this paper design the Photosimulated Discharge measuring system. For illumination can effectively release the charges in the impurity traps, it can be considered as a kind of trap diagnosing tools. With the PSD measuring system, the mechanism of space charge in typical polymer can be studied. The action of electrode injection and environmental induction injection, the types of space charge, the type of traps and the type of combination center, and their actions can also be studied. The affection for breakdown and electric aging of space charge can be studied from the polymer configuration, molecule structure, inter traps and the electric contact of polymer/electrode. The characterization technique of space charge distribution and their dielectric characteristics measurements can also be studied. The basic principle of PSD is that the sample is irradiated by the wavelength-assignment monochromatic light, whose charges are stimulated to form detrapping current. Then the current are measured and a final wavelength-current curve will be got. In a certain range of wavelength, the current increases and some peaks will be formed, whose shape and position can show the values and distributions of the energy levels. The PSD method, compared with others, can stimulate the charges in deeper energy levels as well as offer a direct observation of detrapping phenomenon.The design and realization procedure of the PSD measuring system, including wavelength-assignment light source, lens team, electrodes, sample chamber, electrometer control and data acquirement, are introduced in this paper in details. Based on Visual Stadio.NET program developing environment, using Visual C++.NET, the OCXs of the electrometer and monochromator are successfully utilized to develop the automatic control program of the whole system. The manufacture of lens system, electrodes and sample chamber are showed in this paper in details. Finally, the performances of the system, including wavelength output properties and systematic stationary characters, are tested. The maximum wavelength output divergence is less than 5nm and the average value of the stationary current is about 0. The two technical indexes talking above can well satisfy the PSD system. Using this system, a PET sample is tested in the end.