Development and synchronization of semiconductors excitation sources for active elements on self-terminatint transitions in metal vapors

Abstract

The paper is devoted to development of atypical excitation approaches of bistatic laser monitor active elements for the imaging of high-speed processes at a powerful background radiation. The practical significance is increasing the temporal resolution of the bistatic laser monitor, as well as improving the imaging parameters by minimizing the jitter of radiation pulses. To achieve this goal, semiconductor excitation sources of active media based on copper bromide vapor were developed, and their synchronization was performed in a pulse-repetition mode. The developed pump sources are set of identical commutation cells. Each cell contains storage capacitor, commutator and transformer. Powerful HGTG27N120BN insulated-gate bipolar transistors (IGBT) were chosen as commutators. Their switching storage capacitors are discharged through the primary winding of the transformer and as result the voltage pulse is induced in the secondary winding. The transformer load was the gas discharge tube (GDT) of the small-size brightness amplifier with the specified geometric parameters (l=40 cm, d=2.5 cm, V=196 cm3). The simultaneous switching of 10 identical cells provided GDT breakdown. The radiation power of the active element in oscillator mode was 665 mW. The developed brightness amplifier with semiconductor pump source was used in the bistatic scheme of the laser monitor for the imaging of the test object. The pumping of the second active element, the illumination source (l=90 cm, d=5 cm, V=1767 cm3), was performed by means of thyratron TGI1-1000-25. The pulse repetition frequency of the illumination source and the brightness amplifier was 10,5 and 21 kHz respectively. As result each second image was formed with increased brightness and contrast. The maximal jitter of radiation pulses in this case was 16 ns. The average jitter was 6 ns. Two identical semiconductor pump sources were tested simultaneously. The resulting array of waveforms (GDT current and GDT voltage) show that in most cases the jitter was completely absent, and when it appeared, it did not exceed 4 ns. The imaging at this configuration of the pump sources was not performed due to semiconductor source power (465 W) turned out to be insufficient for the excitation of the illumination source, and therefore options for increasing it were proposed.