Study on antireflective coatings of PbTe/PbSnTe heterojunction infrared detectors

ZnS antireflective coatings and passivation layer are developed on self-made PbTe/PbSnTe heterojunction infrared detectors and following experiments have been finished: WaterProof properties of ZnS coatings; Anti-reflective properties of PbSnTe materials and their detectors with ZnS coatings, respectively; ageing and stability tests of the PbSnTe detectors with ZnS coatings.All experimental results are excellent: The typical detectivity (D^*) of PbSnTe detector is 2.83×10¹⁰ cmHz^1/2W^–1. (with peak wavelength p=9.8 m and cut-off wavelength c=11.7 m). Average detectivity of the PbSnTe detector with ZnS anti-reflective coatings is increased by 45%. Ageing tests indicated that the PbSnTe detectors with ZnS coatings have still high stabilities after several years. They are used successfully in medical infrared imaging systems and other applications.     

Profile characterization and biological activities of cold pressed Garden Cress (Lepidium sativum) seed oil

Lepidium sativum is cultivated mainly for the edible oil from its seeds, and considered as an unutilized and neglected crop despite its important properties. Its oil fraction is used to produce soap and stabilize linseed oil when it is mixed with wild mustard seed oil. Once converted into fatty acid methyl esters, it represents a good substitute for imported petroleum diesel after alkaline transesterification reaction. In the current study, Lepidium sativum seeds cultivated in Tunisia and the physicochemical properties and nutrient profile of its cold pressed seed oil were investigated. The antioxidant, antibacterial, and anti-inflammatory activities of the above oil were also assessed. Lepidium sativum seed oil was abundant in both linolenic (35.59 ± 1.9%) and oleic (21.14 ± 0.63%) acids, and high amounts of β-sitosterol (42.57 ± 2.96 mg/100 g), campesterol (20.04 ± 1.4 mg/100 g) and Δ 5,24 stigmastadienol (11.82 ± 0.45 mg/100 g) were detected. The total tocopherol content of Lepidium sativum seed oil reached 136.83 ± 7.6 mg/100 g with a predominance of γ-tocopherol (86.23%). Its seed oil exhibited an IC₅₀ of 10.33 ± 0.05 mg/mL and a radical scavenging activity of 415.6 ± 40 Trolox Equivalent Antioxidant Capacity (TEAC) for the DPPH and the ABTS assays, respectively. While the thermal analysis proved a high thermal stability of Lepidium sativum seed oil, that of eight bacteria and one fungal strain showed no noticeable bacterial or antifungal effects. It was also revealed that Lepidium sativum seed oil held a remarkable anti-inflammatory activity. Hence, the obtained results evidenced remarkable chemical, antioxidant and anti-inflammatory properties of Lepidium sativum seed oil, which might potentially be promising for enhancing human health and preventing age-related diseases.     

MBE-grown MCT hetero- and nanostructures for IR and THz detectors

We present an overview of our technological achievements in the implementation of detector structures based on mercury cadmium telluride (MCT) heterostructures and nanostructures for IR and THz spectral ranges. We use a special MBE design set for the epitaxial layer growth on (013) GaAs substrates with ZnTe and CdTe buffer layers up to 3” in diameter with the precise ellipsometric monitoring in situ. The growth of MCT alloy heterostructures with the optimal composition distribution throughout the thickness allows for the realization of different types of many-layered heterostructures and quantum wells to prepare the material for fabricating single- or dual-band IR and THz detectors.We also present the two-color broad-band bolometric detectors based on the epitaxial MCT layers that are sensitive in 150–300-GHz subterahertz and infrared ranges from 3 to 10 μm, which operate at the ambient or liquid nitrogen temperatures as photoconductors, as well as the detectors based on planar HgTe quantum wells. The design and dimensions of THz detector antennas are optimized for reasonable detector sensitivity values. A special diffraction limited optical system for the detector testing was designed and manufactured. We represent here the THz images of objects hidden behind a plasterboard or foam plastic packaging, obtained at the radiation frequencies of 70, 140, and 275 GHz, respectively.     

4H-SiC肖特基二极管γ射线探测器的模型与分析

 在研究反偏压4H-SiC肖特基二极管作为g射线探测器工作机理的基础上建立了数值模型,模拟了不同偏压和辐照剂量率下探测器的暗电流、工作电流和灵敏度。模拟结果表明:探测器的灵敏度随反向偏压的增加而上升;对于Au/SiC肖特基二极管,有源区掺杂数密度为2.2×10¹⁵ cm^-3时,0 V偏压下探测器的灵敏度为13.9×10^-9 C/Gy,100 V偏压下为24.5×10^-9 C/Gy。计算结果与实验数据符合得较好。     

Design and implementation of the detector control system for the BESⅢ drift chamber cosmic ray test

After the construction of the BESⅢ drift chamber, a long period of cosmic rays test is necessary to verify its performance. This also provides a good opportunity to integrate the detector readout electronics and Detector Control System (DCS) into a unified working system. The goal of the DCS is to guarantee reliable physics data quality and the safe operation of the detector. It monitors and controls the HV, gas, VME crates and the nvironmental variables. The upper-level system is mainly developed from LabVIEW and the lower-level system mainly uses MCU and PLC technology. The system is designed to be highly flexible and scalable so that it can be applied to other detectors with little or no change. In the immediate future, it will be integrated into the entire BESⅢ Slow Control System.     

L-C耦合电路对散粒噪声探测器电子学噪声的影响

通过分析基于L-C耦合跨阻运放电路的散粒噪声探测器噪声来源,提出了电感的寄生电容对电子学噪声影响的分析模型,并进行了实验验证.研究表明,电感的寄生电容会增大跨阻运放的输入电压噪声增益,从而增加探测器的电子学噪声.当总电感值为1mH时,选用两个0.5mH的电感串联结构相比选用单个1mH的电感,探测器电子学噪声明显降低.由于电感的自共振频率越低,寄生电容越大,选用高自共振频率的电感有助于进一步降低电子学噪声.实验测量得到,在2.5 MHz分析频率处,选用两个0.5mH、自共振频率为6 MHz的电感串联相比选用单个1mH、自共振频率为1.6 MHz的电感,电子学噪声的降低了3dB.在相同入射激光条件下,该改进模型可以有效提高探测器的信噪比.     

基于近红外漫反射测量的便携式土壤有机质测定仪的开发

开发了一款基于近红外漫反射测量的便携式土壤有机质测定仪。测定仪主要由光学单元和电路单元组成。光学单元包括光源、入射和反射光信号传导光纤、光电转换器件等。电路单元包括光源驱动电路,放大电路、A/D转换电路、液晶显示和U盘存储电路等。工作时探头部分插入土壤形成密闭空间,光源发出的光通过入射光纤传送到探头的顶端,并照射顶端周围的土壤;来自土壤的漫反射光沿反射光纤被传送到光电转换器件,产生的电流再被送至电路单元进行放大、滤波、A/D转换、显示和存储。分别针对自然土样和烘干土样的性能试验结果表明,反射率和SOM含量之间具有很高的相关性,在土壤有机质实际含量大于2%时,平均相对误差率低于5%。开发的仪器能够满足农业生产需要。     

基于FPGA 的超导动态电感探测器频梳读出信号产生

超导动态电感探测器(Kinetic Inductance Detectors, KIDs) 作为一种新型的超导探测器, 在天文学等领域得到了广泛应用, 具有高灵敏度、 高能量分辨率等优点, 并且可以通过频域复用直接扩展到大型阵列. 然而, 为了支持上千像素的探测,KIDs 阵列需要产生复杂的频梳信号, 占用较大的信号带宽. 因此, 数模转换器件(Digital-to Analog Converter, DAC) 的采样率对于 KIDs 阵列的读出电路实现至关重要. 基于JESD204B 传输协议的高速 DAC相较于传统低电压差分信号(Low-Voltage Differential Signaling, LVDS) 协议的转换器具有更高的采样率和传输速率, 可用于频梳信号波形的产生. 为此, 本文提出了一种基于现场可编程门阵列(Field Programmable Gate Array, FPGA) 的设计, 以 Xilinx 公司 Kintex-7 系列 FPGA 为主控芯片, 通过高速串行接口JESD204B 和高速 DAC 芯片AD9136 实现高速数据传输,DAC 采样率为2 GSPS, 能生成带宽为1 GHz 的基带信号. 实验结果表明, 该设计能够有效地生成复杂的频梳信号, 具有较高的信号质量和灵活性, 解决了传统 DAC 及直接数字频率合成(Direct Digital Synthesizer, DDS) 器件难以产生复杂多变波形的难题, 有助于拓展 KIDs 阵列的工程应用.