Qin Junjun

High-speed, high-voltage pulse generation using avalanche transistor

In this work, the conduction mechanism of avalanche transistors was demonstrated and the operation condition for generating high-speed pulse using avalanche transistors was illustrated. Based on the above analysis, a high-speed and high-voltage pulse (HHP) generating circuit using avalanche transistors was designed, and its working principle and process were studied. To improve the speed of the output pulse, an approach of reducing the rise time of the leading edge is proposed. Methods for selecting avalanche transistor and reducing the parasitic inductance and capacitance of printed circuit board (PCB) were demonstrated. With these instructions, a PCB with a tapered transmission line was carefully designed and manufactured. Output pulse with amplitude of 2 kV and rise time of about 200 ps was realized with this PCB mounted with avalanche transistors FMMT417, indicating the effectiveness of the HHP generating circuit design.

SG diagnostic equipment:Gating pinhole framing camera

In order to install an X-ray Pinhole Framing Camera(X-PFC) conveniently and run smoothly in the SG3 prototype system(SG3-PS) of Inertial Confinement Fusion(ICF),a novel type X-PFC was developed on the basis of original models and a conical barrel pinhole imaging system was desined to eliminate the stray light and to obtain the pinhole imaging in the SG3-PS.The matching parameters were evidently improved by designing a long micro-strip in new tube,which could keep the number of imagings to be still 16 frames in the limited space by using new type fluorescent screen,steady clamp method and the way of sealing up with two optics fiber plates.The save quality of new tube was improved greatly by gating pulse voltage on the screen.Furthermore,the high-voltage pulse generators and all of monitoring facilities were assembled in the cylinder barrel type vacuum seal configuration by PC104.Experiments show that all kinds of technical indexes have been upgraded when some parts of the new camera structure are redesigned and experimental results are received better.

An Intelligent Control System for X-ray Framing Camera

An intelligent system of X-ray framing camera is designed and realized to fulfill the demand of being intelligent and automotive in the diagnosis system for Inertial Confinement Fusion (ICF). Being controlled by PC104 embedded host computer and combining with Interface Card, the camera system can achieve human-computer interface interactive, networking, camera working point setting, mode switching and working condition monitoring. The system has characterization of self-diagnosing, self-adjusting, and self-protection, which can not only satisfy the requirements of the automotive networking test, but also realize the consistent and accurate of the measurement results, and the stability and dependability of the framing camera are improved. The experimental results show that the gate pulse jitter is confined to 10 ps, screen voltage keeps a very small variation less than 2%, rising and falling edge are shorter than 200 ns, the flat-topped time lasts for 10 us. The new system makes great significance on improving the physical diagnosis on ICF studies.

Spectrum acquisition of detonation based on CMOS

The detection of high-speed dynamic spectrum is the main method to acquire transient information. In order to obtain the large amount spectral data in real-time during the process of detonation, a CMOS-based system with high-speed spectrum data acquisition is designed. The hardware platform of the system is based on FPGA, and the unique characteristic of CMOS image sensors in the rolling shutter model is used simultaneously. Using FPGA as the master control chip of the system, not only provides the time sequence for CIS, but also controls the storage and transmission of the spectral data. In the experiment of spectral data acquisition, the acquired information is transmitted to the host computer through the CameraLink bus. The dynamic spectral curve is obtained after the subsequent processing. The experimental results demonstrate that this system is feasible in the acquisition and storage of high-speed dynamic spectrum information during the process of detonation.