Ultraviolet Photon Counting Research Articles

An Ultraviolet Photon Counting Imaging System Based on a SiC SPAD Array

This letter presents a novel ultraviolet photon counting system based on a SiC SPAD array. The detector is made of 4H-SiC with a fairly low dark current in pA level and the array size is $1\times 128$ . In order to reduce the influence of dark count on image quality, this letter proposes an adaptive sampling readout circuit system, which can automatically adjust the SPAD hold-off time according to the photon density of the applications. Aiming at the nonuniform breakdown voltage of SPADs in a linear array, an adjustable bias voltage circuit is adopted to realize the accurate adjustment of pixel SPAD’s bias voltage. The ROIC is taped out in TSMC 0.18 $\mu {\mathrm{ m}}$ standard CMOS process and connected to the SPAD array by a gold bonding package. Based on the self-developed imaging system, UV photon counting imaging and deep violet- visible light fusion imaging are realized for the first time.

Experimental Study of Ultraviolet Corona Photon Counting Based on Image Features of Substation Electrical Equipment

When ultraviolet (UV) spectral light is used to detect corona, the photon counting is used to judge the intensity of the corona discharges. However, there are many factors that would affect the photon counting, such as detection distance, instrument gain and weather, etc. In this paper, we studied the shape features of the electrical equipment, and proved that the image width of the electrical equipment is in square and proportional relation to the photon counting. Finally, the method of calculating the ultraviolet corona photon counting was also discussed to remove the distance effect, which could improve the judgment of the intensity of corona discharges.

Design of High-speed Readout Circuit for Far Ultraviolet Photon-counting Imaging Detector

摘要: 远紫外光子计数成像探测技术通过探测微弱的单光子信息,记录每个单光子位置,在一定时间累积之后达到总体成像的目的.单光子的计数率限制着信息的获取,在分析影响计数率因素的基础上,需要设计前端模拟电路对探测器信号进行放大和整形,具体实现采用A225芯片作为前置放大器,并设计相应的整形电路.仿真和实验结果表明,电路设计合理,计数率可达到200kHz. 关键词: 远紫外 / 单光子成像 / 楔条形阳极 / 计数率

极紫外光子计数成像探测器采集电路的研制

极紫外光子计数成像探测器采集电路的研制

EUV成像仪极间串扰和伪信号触发计数修正

In order to improve the resolution of an Extreme Ultraviolet(EUV) photon counting imager,this paper analyzed the influence of the crosstalk between Wedge Strip Zigzag(WSZ) anodes and the false trigger resulted from out-range signals on image quality.First,the reasons which caused the crosstalk were analyzed,and the range of crosstalk coefficient and its optimum value were determined by measuring interelectrode capacitance.Then,the crosstalk coefficient was used to process photons and determine a proper energy interval(upper and lower limit).Finally,the image obtained in the setting energy interval was compared with an original image.The comparison shows that the image quality has been improved obviously.The results demonstrate that the image edge becomes stronger further and image resolution is improved by eliminating the crosstalk between WSZ anodes and removing fake data from real data.

Imaging properties of a tetra wedge readout

The decoding principle of a tetra wedge anode, which is a development of the wedge and strip anode, is described. The influence of charge cloud size on decoding accuracy is studied using the Monte Carlo method. Simulation results show that the decoding error is large when the size of charge clouds collected by the anode is small. Thus, the charge clouds collected by the tetra wedge anode should reach a necessary size to ensure accurate decoding. Finally, using the ultraviolet photon counting imaging system, the linearity and the spatial resolution of the system are tested. Experimental results show that the system has a good linearity and the spatial resolution is better than 100 μm.

A near ultraviolet photon counting imaging detector

Photon counting imaging detector is classified to direct collection mode and induction mode, based on the readout mode of microchannel plate (MCP) output charge. Previously, we discussed the detector with direct collection mode. A near ultraviolet (NUV) photon counting imaging detector with induction readout mode is presented here. The detector consists of a cesium telluride (Cs 2Te) photocathode, a v-stack MCP, a semiconductor germanium layer on ceramic substrate, and wedge and strip anode (WSA). Quantum efficiency of the detector photocathode is 12% at (230 nm), dark count rate is 10.7 counts/(s cm 2) and spatial resolution is 110 μm.

Detection efficiency for an ultraviolet photon counting imaging system based on the Ge induction readout

The detection efficiency, assumed proportional to the count rate, of an ultraviolet photon counting imaging system based on the Ge induction readout is studied. For the Ge induction readout, the system count rate with different Ge layer resistances, Ge layer thicknesses and ceramic thicknesses are tested under different light intensities. The test results show that the system count rate with a high resistance in the Ge layer is lower than that with a low resistance in the Ge layer; further, the imaging area decreases as the Ge layer resistance increases under high photon flux. Moreover the system count rate with a thick Ge layer is lower than that with a thin Ge layer. In addition, the system count rate with 2-mm ceramic is higher than that with 1.5- and 3-mm ceramic. The above observation should be considered when designing an ultraviolet photon counting imaging detector based on the Ge induction readout.

One-dimensional photon counting detector with vernier position sensitive anode

One-dimensional photon counting detector with vernier position sensitive anode is reported. The decode principle and design of vernier position sensitive anode are described in detail. An ultraviolet photon counting system was built based on one-dimensional photon counting detector with vernier position sensitive anode. One-dimensional coordinates of single-photon events can be simultaneously measured when the detection system works in photon counting mode. The spatial distribution of pulse counts, which corresponds to one-dimensional spatial distribution of incident light intensity, was obtained. The resolution of this system is better than 100 mμ according to the resolution test. The detector can detect one-dimensional spatial distribution of the intensity of very weak particle flow such as high-energy photons, electrons and ions flow, so it can be used for deep space exploration, spectral measurement, high-energy physics and bio-luminescence detection.

Study of ultraviolet photon counting imaging technology based on induction readout

An ultraviolet photon counting imaging system based on charge induction readout was built and its structure, working principle and spatial resolution are reported. The single photon stream can be obtained via atmospheric dispersion, some weakeners, and narrow-band optical filters. A photo-electron produced in microchannel plate is multiplied, forming a charge cloud, which is collected on the Ge film and then detected through capacitive coupling by a PSA located a few millimeters behind the Ge film. The signal data from the anode is acquired and processed with software after being transformed, filtered and shaped by a charge-sensitive preamplifier and a main amplifier in sequence. Finally, a 30-minute counting image is obtained. The resolution of this system can reach 150 micrometers as tested with the resolution board, and the influence of Ge film resistivity and its substrate thickness on the performance of this system is also analyzed. The system is beneficial in good imaging properties and time resolution to bioluminescence, astronomy and nuclear radiant detection.

An ultraviolet photon counting imaging detector system based on Ge induction readout mode

Photon counting imaging technology has been widely used in nuclear radiation detection, space environment detection, astronomy observation, nuclear physics and ultraweak bioluminescence. The structure and operating principles of ultraviolet photon counting imaging systems based on direct electron collection mode and induction readout mode are introduced, but there are more advantages with the induction readout mode. The gain characteristic, resolution, linearity and count rate of a system based on induction mode are evaluated. The dark count pulse height distribution curves shift towards higher pulse height, and the dark count rate increases as the voltage increases. The pulse height distribution curves with light incidence also indicate that the count rate with higher pulse height increases as the voltage increases. The resolution test results show that the system resolution is better than 100 μm along the Y direction and better than 80 μm in some areas. The nonlinearity in both directions is less than 5% in a Φ35 mm area. The system resolution at a low count rate is better than that at a high count rate.

The estimation of charge footprint size of ultraviolet photon counting imaging detector with induction readout

The structure and work principle of an ultraviolet photon counting imaging detector based on wedge and strip anode with induction readout mode are introduced. Two methods of estimating the charge footprint size are presented. One way is theoretical calculation and simulation. The physical course of electrons is simulated from the microchannel plate output side to the readout anode. The calculated results show that the final charge footprint size is sensitive to the thickness of ceramic and not sensitive to the charge footprint size on the Ge layer. The other way is experimental image estimation. The final charge footprint size can be estimated according to the position where the light line of resolution board image begins to bend. Both methods show that the charge footprint size is sensitive to the ceramic substrate. The two methods are simple and effective for estimation of charge footprint size of photon counting imaging detector with induction readout.

Ultraviolet photon counting with GaN avalanche photodiodes

Photon counting, utilizing Geiger-mode avalanche response, has been demonstrated at 300 K in avalanche photodiodes fabricated in GaN grown by hydride vapor-phase epitaxy. Measurements have been made using both passive-quench and time-gated modes of operation. The two important figures of merit for photon-counting applications, photon detection efficiency (PDE) and dark count rate, were measured. A maximum PDE of 13% was measured at 325 nm with a dark count rate of 400 kHz. Typical mesa-etched devices exhibit a parasitic shunt leakage current of less than 20 nA at 90% of breakdown voltage.

Ultraviolet photon counting with an electron multiplier.

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