Yonglin Bai

Properties and performance of two wide field of view Cherenkov/fluorescence telescope array prototypes

A wide field of view Cherenkov/fluorescence telescope array is one of the main components of the Large High Altitude Air Shower Observatory project. To serve as Cherenkov and fluorescence detectors, a flexible and mobile design is adopted for easy reconfiguring of the telescope array. Two prototype telescopes have been constructed and successfully run at the site of the ARGO-YBJ experiment in Tibet. The features and performance of the telescopes are presented

Experimental verification of the HERD prototype at CERN SPS

The High Energy cosmic-Radiation Detection (HERD) facility is one of several space astronomy payloads of the cosmic light house program onboard Chinas Space Station, which is planned for operation starting around 2020 for about 10 years. Beam test with a HERD prototype, to verify the HERD specifications and the reading out method of wavelength shifting fiber and image intensified CCD, was taken at CERN SPS in November, 2015. The prototype is composed of an array of 5*5*10 LYSO crystals, which is 1/40th of the scale of HERD calorimeter. Experimental results on the performances of the calorimeter are discussed.

A new designed impedance matching circuit used for gated framing camera

Framing camera based on gated Micro-channel plate (MCP) was widely used in inertial confinement fusion (ICF) and Z-pinch because of its ultrafast time-resolve. Electrons with imaging information are multiplied when the HV pulse propagating through the MCP strip line. Obviously, the HV pulse was used as a shutter here, then the exposure time of the imagine will be determined by the width of the pulse. Theoretical analysis indicates that thegating pulse(200ps) has a bandwidth of 5GHz, thus, impedance match in the propagating path of the pulse will be very important. Impedance mismatch will cause reflecting of the pulse and decrease the transmission efficiency. This will cause un-uniformity of the dynamic gain of the MCP, and finally resulting in imagedistortion. A new designed impedance matching circuit is developed in this paper. Simulated results showedthatthe newdesignedimpedance matching circuit couldreduce the reflection of thegating pulse significantly, and dynamicgain uniformity of the MCP was increased simultaneously

A Prototype X-ray Framing Camera With Variable Exposure Time Based on Double-Gated Micro-Channel Plates

We present a novel X-ray frame camera with variable exposure time that is based on double-gated micro-channel plates (MCP). Two MCPs are connected so that their channels form a Chevron-MCP structure, and four parallel micro-strip lines (MSLs) are deposited on each surface of the Chevron-MCP. The MSLs on opposing surfaces of the Chevron-MCP are oriented normal to each other and subjected to high voltage. The MSLs on the input and output surfaces are fed high voltage pulses to form a gating action. In forming two-dimensional images, modifying the width of the gating pulse serves to set exposure times (ranging from ps to ms) and modifying the delay between each gating pulse serves to set capture times. This prototype provides a new tool for high-speed X-ray imaging, and this paper presents both simulations and experimental results obtained with the camera.

A novel 3-D calorimeter for the high energy cosmic-radiation detection (HERD) facility onboard China's future space station

The High Energy cosmic-Radiation Detection (HERD) facility is a flagship and landmark scientific experiment onboard Chinas Space Station, planned for operation starting around 2025 for about 10 years. The main instrument of HERD is a 3-D calorimeter (CALO) sensitive to incident gamma-rays and particles from five sides. With this design, the effective geometric factor of HERD is more than one order of magnitude larger than that of previous missions. CALO is made of about 7,500 cubes of LYSO crystals, corresponding to about 55 radiation lengths and 3 nuclear interaction lengths, respectively. The crystal signals are transferred by wavelength shifting fibers and read out by ISCMOS devices. Energy deposition in each crystal is then derived by summing up about 400 CMOS pixels and with necessary correction for light saturation. Both a low range ISCMOS and a high range one are required to meet the requirement of a large dynamic range of at least 10 million. The prototype of CALO has been tested successfully in November 2015 at CERN, which leads to an improved design of CALO.

Simulating the spatial resolution of the framing camera

The structural models of micro-channel plate (MCP) and fluorescent screen of the framing camera were established. By combining the finite element integration and Monte Carlo method, software Simion and Lorenz were respectively used to simulate the effects of different voltages loaded on the fluorescent screen, different closed distance between fluorescent screen and MCP, and electrode immersion depth at MCP output on the spatial resolution, in order to obtain an axisymmetric distribution curve. Results showed that the closed distance between MCP and fluorescent screen had the largest impact on the framing camera’s spatial resolution. In addition, higher fluorescent screen voltage did not necessarily result in better spatial resolution, as it was influenced by the light-emitting mechanism of the fluorescent screen. At the framing camera’s current closed distance of 0.8mm, a fluorescent screen voltage of 5000V could achieve the best spatial resolution.

Two-dimensional photon counting imaging detector based on PCB delay line anode

Delay line anode detector has high spatial resolution and high count rate. It has been an important technical means for single photon imaging from near earth space to deep space. A two dimensional delay line anode is designed using multilayer circuit board technology. A complete set of PCB delay line anode single photon detection system is established. The spatial resolution of the detector is theoretically analyzed. Moreover, the signal transmission characteristic of PCB delay line and the dark count rate of the detector are tested. Theoretical analysis and experimental results show that the detector spatial resolution is about 100um and the overall dark count rate is 4counts/cm2 at 2.3KV.

Design and research of moving objects dimension measurement system based on linear array CCD

A novel moving objects dimension measurement system based on the linear array CCD is designed. The light source is a pulsed laser with pulse width 200ns. Single point of light passes through lens converted to parallel light which will illuminate to the CCD through the moving object to be tested. CCD pixels which are blocked by the object while light is on are low, and the remaining pixels are high conversely. The distance of the tested objects while light is on can be ignored since the light pulse width is much smaller than the integration time of CCD (generally). The size of the tested object can be achieved by the number of dark pixels of CCD while light is on. This paper introduces the principle and composition of the dimension measurement system. The results show that this system can measure the size of moving objects and measuring accuracy is better than 50 microns. Accuracy and stability of the system can achieve actual production requirements when the object’s moving speed is smaller than 50mm/s. Optimizing the parallelism of the parallel light, the measurement accuracy can be further improved.

The New High-speed Switching Study of Ultra-short Laser Pulse Technology

Ultrafast phenomenon has presented widely in natural phenomenon and scientific and technological research. Therefore, study on ultrafast phenomenon is of great important in many research and technology fields. In recent years, the development and application of ultra-short laser pulse has been covered many areas. It has been developed into a powerful tool used to research ultrafast phenomena. In the implementation process of the ultra-short laser pulses, high-speed switching plays a vital role. The difficulty of high-speed switching design is to make the ultrafast electric pulse load on the both ends of the crystal with minimum distortion and delay. It is very difficult to switch electro-optic crystal at a high frequency in traditional method. In this paper, a new method is designed, which combined the electro-optic crystal and micro-strip line. The crystal is a part of the transmission path and the signal path of the micro-strip line is broadened or narrowed continuously to make the impedance matching to 50 ohm. The good match between pulse signal and the crystal make sure the high frequency switches of the crystal. The amplitude loss is less than 11%, and the delay is less than 1 nanosecond.

Transmission loss in x-ray framing cameras

We present evidence that transmission loss in gated x-ray framing cameras can affect relative gains. Transmission loss is caused by a variety of factors including: incident voltage waveform, matched load, width of Au electrode gap, and so on. The transition electrode in MCP (Micro-channel Plate) is continuous gradual change line, and it has good capability of compensation. When continuous gradual change micro-strip line is designed, dielectric loss tangent is one of transmission loss factors too. The model structure is designed based on the analysis of modeling and simulation techniques and experiment data as well as forecast target. The transmission loss is reduced from 50% to 25%, the transmission efficiency is greatly improved.