A flame sensor with uniform sensitivity over a large field of view

The sensor is a gas-filled tube of the Geiger-Mueller type, in which an electron emitted from a photocathode is accelerated by an applied electric field to cause ionization of the fill gas. Although the operating principle is not new, this tube differs from others in that the cathode consists of a semitransparent layer of metal on the inside of the cylindrical tube envelope, which is applied by sputtering after filling and sealing. Used as a cathode during sputtering, the anode consists of a pin along the axis of the tube, providing the cylindrical symmetry for uniform wide-angle viewing. The performance of the tube is compared with that of a tube of the same external dimensions, but with more conventional parallel wire electrodes. The counting rate for the sputtered tube was a factor of 10 higher than the conventional tube, due to the larger sensitive cathode area, and uniform over 360° in a plane perpendicular to the tube axis, due to cylindrical symmetry. The counting rate for the sputtered tube was 2000/min in response to a flame 7 ft away burning natural gas at the rate of 138 cm³/min.     

刑侦日盲紫外折衍混合变焦光学系统设计

为了满足刑侦过程中紫外光学系统远距离搜索、近距离拍照的需求,采用二元衍射元件和非球面元件,设计了一种日盲紫外机械补偿变焦光学系统,其中焦距为40mm~80mm,F数为4,工作波段为0.24μm~ 0.28μm。选用S8844-0909型2.54cm紫外CCD,像元尺寸为24μm×24μm,对应视场角为6°~12°。系统由7块透镜组成,结构简单、体积小巧。结果表明,在整个变焦范围内,后截距10mm处,截止空间频率21cycles/mm时,各视场的光学调制传递函数均在0.7以上,接近衍射受限曲线,畸变小于5%,像质优良,像面稳定。该设计能满足光学系统的总体设计要求。     

一种提高光电倍增器光电阴极量子效率的方法

提出了一种可以提高光电倍增管光电阴极量子效率的方法。通过分析光电阴极的光电发射过程,从提高光子吸收率Pa和光电子迁移至真空一侧材料表面的几率Pe出发,确定可以在光电阴极膜层结构设计上增加合适的膜层,该膜层具有高带隙和减反射的作用。由于光电倍增管的外壳通常为细长的玻璃管,而常规的溅射设备为50mm的大靶,直接使用大靶对细管内部镀膜,效率低下且均匀性差。在常规大靶的基础上进行改造,成功实现了在细管内部快速均匀镀膜。使用分光设备测试光电阴极的光谱响应,结果表明,改进产品的光电阴极量子效率从常规的25%提高至35%。     

Glass envelope UV-sensitive flame detectors

The need for fast-response low-voltage flame sensors, able to operate for long periods in ambients presenting a wide range of temperatures, prompted the construction and testing of gas amplification UV-photosensitive detectors utilizing 9741 glass envelopes and a variety of gas fills and electrode and getter materials. Addition of 1 mole percent H2to a He gas fill reduced the required minimum time between counts for a given sensor operating voltage without significantly changing the threshold voltage. All sensors with H2additive ultimately became solar sensitive. Sensors performed well at temperatures as high as 350°C.     

A precision low-power analog front end in 180 nm CMOS for wireless implantable capacitive pressure sensors

This paper presents a new capacitance to voltage analog-front end (AFE) designed in 180 nm CMOS technology for wireless implantable applications. This AFE consists of a Low-dropout regulator (LDO), bandgap reference (BGR), switched-capacitor (SC) sampler, SC op-amp and oscillator. The LDO regulates the wireless power supply coming from an off-chip rectifier and provides a stable and accurate DC voltage. Capacitance is converted to a discrete voltage by a SC sampling circuit and then amplified by a SC op-amp. Both of SC sampling and SC op amp circuits form a correlated double sampling scheme. This AFE is designed to sense a capacitance range from 6 pF to 7 pF (300–1000 mmHg) corresponding to a 0.68 V–1.07 V discrete output voltage with a sampling frequency of 1.63 KHz. This AFE has a sensitivity of 0.39 mV/fF, average power consumption of 201 μW and 3.25% accuracy operating over a 2.1 V–3.3 V rectified wireless supply voltage and −40 °C ~125 °C temperature range.     

A 0.003-mm2, 0.35-V, 82-pJ/conversion ultra-low power CMOS all digital temperature sensor for on-die thermal management

In this paper, a 0.35 V, 82 pJ/conversion ring oscillator based ultra-low power CMOS all digital temperature sensor is presented for on-die thermal management. We utilize subthreshold circuit operation to reduce power and adopt an all-digital architecture, consisting of only standard digital gates. Additionally, a linearization technique is proposed to correct the nonlinear characteristics of subthreshold MOSFETs. A bulk-driven 1-bit gated digitally controlled oscillator is designed for the temperature sensing node. Also, a 1-bit time-to-digital converter is employed in order to double the fine effective resolution of the sensor. The proposed digital temperature sensor has been designed in a 90-nm regular V _T CMOS process. After a two-point calibration, the sensor has a maximum error of ?0.68 to +0.61 °C over the operating temperature range from 0 to 100 °C, while the effective resolution reaches 0.069 °C/LSB. Under a supply voltage of 0.35 V, the power dissipation is only 820 nW with the conversion rate of 10K samples/s at room temperature. Also, the sensor occupies a small area of 0.003 mm².     

Design and implementation of micro-power temperature to duty cycle converter using differential temperature sensing

The CMOS based temperature detection circuit has been developed in a standard 180 nm CMOS technology. The proposed temperature sensor senses the temperature in terms of the duty cycle in the temperature range of −30 °C to +70 °C. The circuit is divided into three parts, the sensor core, the subtractor and the pulse width modulator. The sensor core consists of two individual circuits which generates voltages proportional (PTAT) and complementary (CTAT) to the absolute temperature. The mean temperature inaccuracy (°C) of PTAT generator is −0.15 °C to +0.35 °C. Similarly, CTAT generator has mean temperature accuracy of ±1 °C. To increase thermal responsivity, the CTAT voltage is subtracted from the PTAT voltage. The resultant voltage has the thermal responsivity of 6.18 mV/°C with the temperature inaccuracy of ±1.3 °C. A simple pulse width modulator (PWM) has been used to express the temperature in terms of the duty cycle. The measured temperature inaccuracy in the duty cycle is less than ±1.5 °C obtained after performing a single point calibration. The operating voltage of the proposed architecture is 1.80±10% V, with the maximum power consumption of 7.2 μW.     

Integrated optical high-voltage sensor using a Z-cut LiNbO3 cutoff modulator

An integrated optical AC high-voltage sensor based on a Z-cut LiNbO₃ cutoff modulator is fabricated by the proton diffusion method. It is a passive sensor that does not require any electrical bias or any voltage divider. Its sensing voltage range is extended by using the following method. First, its inherent linear range is extended, both by utilizing a novel electrode structure with dummy electrodes and by shortening the electrode length. The dummy electrodes reduce the magnitude of the Z-component electric field applied to the cutoff modulator. Second, a sensor configuration is designed to adjust its operating bias point optically by annealing and thus to utilize the whole extended linear range. The sensing voltage range of the cutoff modulator sensor exceeds AC 1000 V peak to peak     

A Temperature Sensor With an Inaccuracy of ${-}{hbox{1}}/{+}{hbox{0.8}} ^{circ}$ C Using 90-nm 1-V CMOS for Online Thermal Monitoring of VLSI Circuits

This paper proposes an accurate four-transistor temperature sensor designed, and developed, for thermal testing and monitoring circuits in deep submicron technologies. A previous three-transistor temperature sensor, which utilizes the temperature characteristic of the threshold voltage, shows highly linear characteristics at a power supply voltage of 1.8 V or more; however, the supply voltage is reduced to 1 V in a 90-nm CMOS process. Since the temperature coefficient of the operating point's current at a 1-V supply voltage is steeper than the coefficient at a 1.8-V supply voltage, the operating point's current at high temperature becomes quite small and the output voltage goes into the subthreshold region or the cutoff region. Therefore, the operating condition of the conventional temperature sensor cannot be satisfied at 1-V supply and this causes degradation of linearity. To improve linearity at a 1-V supply voltage, one transistor is added to the conventional sensor. This additional transistor, which works in the saturation region, changes the temperature coefficient gradient of the operating point's current and moves the operating points at each temperature to appropriate positions within the targeted temperature range.      

一种火焰传感器高压驱动电路的研究

针对紫外火焰传感器设计了一种高压驱动电路,并对其工作原理进行了研究和说明, 最后介绍了所设计的原理样机的相关实验结果。该电路按照定占空比、跳周期的“打嗝”方式工作,具有结构简单和 升压比高等特点,满足火焰传感器所需的高工作电压条件,因而对多种小功率光电传感器具有广泛的适用性。     

Prospects of using rare-earth hexaborides in thermoelectric single-photon detectors

The results of the numerical simulation of heat propagation processes occurring after the absorption of single photons with energies of 1 eV–1 keV in a three-layer sensor of a thermoelectric detector are analyzed. Different configurations of the sensor with a tungsten absorber, a thermoelectric layer of cerium hexaboride, and a tungsten heat sink are considered. It is shown that sensors for detecting photons of a specific spectral range with the required energy resolution and counting rate can be developed by varying the geometric sizes of the sensor layers. It is concluded that a three-layer sensor has a number of advantages in comparison with a single-layer sensor and has characteristics allowing consideration of the thermoelectric detector as a realistic alternative to superconducting single-photon detectors.     

Microchannel plate inverter image intensifiers

The characteristics of microchannel plate/inverter image intensifiers (MCP/III) are described. This type of image tube is shown to be well suited to some night vision applications. The 25 mm MCP/III developed by the authors has a minimum magnification of 0.96, a maximum distortion of 5 percent, and a limiting resolution of 10 cycles/mm. Its luminance gain is about 10⁵at input levels up to 2 × 10^-3fc when an S20 photocathode and a P20 phosphor screen are employed. The operational life of a MCP/III is generally a few thousand hours. Accurate life data can be determined, for a given application, after the operating input light level value, the applied MCP potential, and the duty cycle are established. The unique bulb design allows the tube high voltage power supply to be placed around the tube envelope within a 50 mm diameter and reduces the total interelectrode capacitance of the gating/focus electrode to 7 pF.     

A Shape Memory High‐Voltage Supercapacitor with Asymmetric Organic Electrolytes for Driving an Integrated NO2 Gas Sensor

A high‐voltage supercapacitor with shape memory for driving an integrated NO₂ gas sensor is fabricated using a Norland Optical Adhesive 63 polymer substrate, which can recover the original shape after deformation by short‐time heating. The supercapacitor consists of multiwalled carbon nanotube electrodes and organic electrolyte. By using organic electrolyte consisting of adiponitrile, acetonitrile, and dimethyl carbonate in an optimized volume ratio of 1:1:1, a high operation voltage of 2 V is obtained. Furthermore, asymmetric electrolytes with different redox additives of hydroquinone and 1,4‐dihydroxyanthraquinone to the anode and cathode, respectively, enhance both capacitance and energy density by ≈40 times compared to those of supercapacitor without redox additives. The fabricated supercapacitor on the Norland Optical Adhesive 63 polymer substrate retains 95.8% of its initial capacitance after 1000 repetitive bending cycles at a bending radius of 3.8 mm. Furthermore, the folded supercapacitor recovers its shape upon heating at 70 °C for 20 s. In addition, 90% of the initial capacitance is retained even after the 20th shape recovery from folding. The fabricated supercapacitor is used to drive integrated NO₂ gas sensor on the same Norland Optical Adhesive 63 substrate attached onto skin to detect NO₂ gas, regardless of deformation due to elbow movement.     

Mg fluctuation in p-GaN layers and its effects on InGaN/GaN blue light-emitting diodes dependent on p-GaN growth temperature

Correlation between material properties of bulk p-GaN layers grown on undoped GaN and device performance of InGaN/GaN blue light-emitting diodes (LEDs) as a function of p-GaN growth temperature were investigated. The p-GaN layers of both structures grown by metal-organic chemical-vapor deposition were heavily doped with Mg. As the growth temperature of the bulk p-GaN layer increased up to 1,080°C, N_A-N_D increased. However, above 1,110°C, N_A-N_D sharply decreased, while the fluctuation of Mg concentration ([Mg]) increased. At this time, a peculiar surface, which originated from inversion domain boundaries (IDBs), was clearly observed in the bulk p-GaN layer. The IDBs were not found in all LEDs because the p-GaN contact layer was relatively thin. The change in photoluminescence emission from the ultraviolet band to blue band is found to be associated with the fluctuation of [Mg] and IDBs in bulk p-GaN layers. The LED operating voltage and reverse voltage improved gradually up to the p-GaN contact-layer growth temperature of 1,080°C. However, the high growth temperature of 1,110°C, which could favor the formation of IDBs in the bulk p-GaN layer, yielded poorer reverse voltage and saturated output power of the LEDs.     

光阴极电压对微光像增强器性能影响研究

文章基于阴极半导体电子发射理论和微通道板(MCP)电子倍增基本物理过程,分析阴极背景噪声和信噪比与阴极电压的关系,分析指出:像增强器背景噪声会随着阴极电压的增大而增长;像增强器系统噪声因子随着阴极电压的增大而减小,并趋于饱和。通过实验证明:增大阴极电压的幅度,像增强器背景噪声随之呈指数增长;输出信噪比随之呈单调增长,并趋于饱和。由此得出阴极最佳工作电压在-160V左右。     

基于光电倍增管单光子脉冲幅度分布的多比特光量子随机源

提出并验证了一种基于光电倍增管单光子脉冲高 度分布的多比特光量子随机源。将紫外LED发出 的光衰减成离散的单光子序列,光电倍增管探测到的单光子后,输出脉冲幅度随机分布的单 光子脉冲,通 过数字化单光子脉冲的峰值作为熵源来提取随机数,实现了一个单光子事件产生多个随机比 特位。为减小 所提取原始随机数存在的偏差,提出并实现了基于FPGA的SHA-256后 处理方法。光量子随机源工作在 500kc/s时,平均每个探测光子可提取7bit随机位,获得了3.5Mbit/s的随机位产生速率。运用随机性 测试程序ENT和STS对所获的随机位序列进行测试,测试结果表明,序列的随机性满足真随机 数的标准。     

基于MPPC阵列的三维单光子成像技术研究

三维成像技术在自动驾驶、航空任务、军事领域等都有着广泛的应用,不同技术体制的成像系统有不同的优点,其中基于多像素光子计数器(Multi-Pixel Photon Counter, MPPC)的三维成像技术由于其成像速度快、对极弱光敏感等优势具有广阔的发展潜力。然而,由于MPPC阵列发展不成熟,基于MPPC阵列的弱光三维成像探测水平受到限制。利用日本滨松公司研发的具有32×32规模的MPPC阵列S15013系列二维光子计数图像传感器,开发了一套三维成像系统,传感器的每个像素由12个单光子雪崩二极管并联而成,其总探测像素达到1 K以上。基于该系统,分析了阈值电压、镜头光阑等参数条件对三维成像探测结果的影响,对系统探测灵敏度和精度进行了测试,并针对37 m远模拟目标开展了三维成像探测试验。试验结果表明:在回波光子数约1.98 (光子/像素)的暗弱条件下,目标区域测距精度达到0.268 m,三维结构特征明显,达到了接近单光子成像的探测水平。     

Development and testing of a fire-resistant optical cable

A new type of fire-resistant optical cable has been developed. It is based on the loose tube concept employing special mica and glass tape wrappings together with a new type of buffer jacket material to provide the desired properties. With this design, ordinary acrylate-coated fibers are used. The cable has the unique property that during fire it converts from a cable, which mostly consists of organic materials, to a ceramic loose-tube structure that gives the fiber sufficient protection to prevent damage during fire. The cable has been tested according to IEC 331 which specifies a 750°C flame exposure for 3 h, and passed that test with negligible loss increase even at temperatures up to 900°C.     

Soft Mechanical Sensors Through Reverse Actuation in Polypyrrole

The phenomenon of voltage generated from a soft sensor using polypyrrole in response to mechanical deformation is described and investigated. The sensor consists of two polypyrrole layers in contact with an electrolyte and operates in bending mode in air. The magnitude and sign of the induced voltage was found to depend on the type of dopant counter‐ions and the nature of the surrounding electrolyte. The mechanical sensor response is shown to be a “reverse actuation”, generating millivolt signals for millimeter sized deflections or ～ 1000 C m^–3 charge for 1 % strain in the polypyrrole layer. A model based on ‘Deformation Induced Ion Flux' has been proposed whereby the strain induced volume change in the polymer produces a shift in the Donnan equilibrium between mobile dopant ions inside the polymer and in the external electrolyte. A simple thermodynamic model provides reasonable estimates of the size of the voltage and charge produced.     

A technique for aging the phosphor of high-resolution cathode-ray tubes with particular application to P-16

An accelerated aging technique--restricted to P-16 phosphor--that measures a cathode-ray tube screen degradation with use is described. A small area of the screen is aged at high excitation densities and the light output from this area is plotted as a function of deposited charge per unit area. A pre-aged part of the screen is used as a reference level for measuring these light output levels. Measurements made to determine phosphor aging with cathode-ray tube operating modes are described. Aging is found invariant with spot focus, beam voltage, beam current, power density per unit area, and sweep speed over normal operating ranges. Deposited charge per unit area is confirmed as the dominant stress factor. Under restricted operating conditions, the data is reproducible within ±4 percent at the 95 percent confidence level. Aging rates accelerated by a factor of more than a thousand as compared to normal usage have been obtained.