A photo-counting imaging sealed detector has been fabricated for far-ultraviolet (FUV) radiation detection, including an MgF2 input window, CsI photocathode, V-stack MCPs, circular arc terminated (CAT) resistive anode, and detector tube. The CsI photocathode was prepared by vacuum thermal evaporation. The CAT resistive anode was fabricated using thick-film technology. The detector body is mainly made of Kovar alloys and ceramics and was sealed in a cathode-transfer and indium-sealed vacuum system. The detector performance was evaluated using an FUV parallel light system consisting of a deuterium lamp, a reflective condenser, a filter wheel, a monochromator, a collimation system, and a vacuum chamber. The test results show that the imaging RMS nonlinearity is less than 3%, the spatial resolution is about 235um, and the dark count rate is less than 2.74 counts·s-1.
KEYWORDS: Control systems, Ultraviolet radiation, Spectroscopy, Sensors, Process control, Signal processing, Telecommunications, Temperature metrology, Sun, Interfaces
The ultraviolet (UV) spectrometer installed on the balloon platform is a cost-effective instrument to observe the UV spectrum of near space, which can meet the needs of biological evolution and planetary material exchange research. A control system of an enhanced UV spectrometer is designed in this paper. Firstly, the framework of the control system is introduced, and the functions of each module are described. Then, the solar angle sensor and automatic air pressure balance device in the enhanced detector module are introduced, making the detector operate safely and reliably in solar radiation and low-pressure environments. Next, the temperature controller is introduced, which can automatically adjust the heating power through the PID algorithm in the embedded chip according to the data collected from the light body and the atmosphere. Finally, the automatic detection mode is described. Among them, the controller can automatically adjust the system gain and integration time according to the spatial ultraviolet radiation intensity information, thus maximizing the efficiency of data. The flight test results of Honghu HH-20-7, HH-20-9 and HH-19-7 show that the spectrometer works normally in the flight experiment. Compared with the ultraviolet radiation in the MODTRAN database, the ultraviolet spectrum data of adjacent space obtained by the spectrometer has the same consistency, but provides a lot of detailed information.
A Finite Element Method (FEM) to establish the model of CAT resistive anode and Square resistive anode is proposed. The characteristics of electrode charge signal are analyzed. The factors that affect the position reconstruction linearity of resistive anode are analyzed, including the geometric parameters and sheet resistance of the surface resistive layer, by calculating the amount of electrode charge from a simulated photon hit. It has been concluded that signal development time should be greater than 8R'C' ( R'C' =RC / μ2 ) seconds in order to ensure the root mean square (RMS) nonlinearity (%) of position reconstruction is less than 3% for these two resistive anodes, with capacitance C , and sheet resistance R of sensitive region.
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