A photomultiplier tube for a NT-200 deep-underwater neutrino telescope

A fast, high-sensitive photomultiplier tube (PMT) with a 25-mm diameter bialkali photocathode is being developed to be used as part of a KBA3AP-370 hybrid photodetector. Its linearity is ∼ 150 mA. The rise time of an anode current pulse is ∼ 2 ns. The transit time difference of photoelectrons originating from different points of the photocathode does not exceed 1 ns. Deceased.     

A controlled stabilized high-voltage power supply for a photomultiplier tube

A small-size stabilized high-voltage power supply for a photomultiplier tube with remote digital and analog regulation of the output voltage is designed. The output voltage is smoothly regulated from 0.5 to 3 kV, the load current is 0–2 mA, and the ripple factor is 0.008%. The supply voltage is 12–16 V.     

Development of a compact tomography camera system using a multianode photomultiplier tube for compact torus experiments

A compact tomography camera system consisting of a photomultiplier tube, a multislit optical system, and a band-pass interference filter has been developed. The viewing area and spatial resolution can be configured by the arrangement of the slit system. The camera system has been specially designed for self-organized compact torus experiments having strong magnetohydrodynamics events with a submicrosecond time-scale. The developed system has been tested on a field-reversed configuration formed by the field-reversed theta-pinch. Performance evaluation of the system has been performed by comparison to the former optical system.     

High-temperature superconducting quantum interference device with cooled LC resonant circuit for measuring alternating magnetic fields with improved signal-to-noise ratio

Certain applications of superconducting quantum interference devices (SQUIDs) require a magnetic field measurement only in a very narrow frequency range. In order to selectively improve the alternating-current (ac) magnetic field sensitivity of a high-temperature superconductor SQUID for a distinct frequency, a single-coil LC resonant circuit has been used. Within the liquid nitrogen bath, the coil surrounds the SQUID and couples to it inductively. Copper coils with different numbers of windings were used to cover the frequency range from <1 to nearly 100 kHz. A superconducting coil made of YBa(2)Cu(3)O(7-delta) tape conductor was also tested. With the LC circuit, the signal-to-noise ratio of measurements could be improved typically by one order of magnitude or more in a narrow frequency band around the resonance frequency exceeding a few kilohertz. The best attained equivalent magnetic field resolution was 2.5 fT/radicalHz at 88 kHz. The experimental findings are in good agreement with mathematical analysis of the circuit with copper coil.     

A dilution microcryostat cooled by a refrigerator with an impulse tube

A dilution microcryostat is described, which is designed for conducting physical measurements at temperatures down to 0.1 K or lower. A refrigerator with an impulse tube is used to provide its operation. Owing to the use of a passive stabilization system, which is based on helium condensation, the temperature can be maintained at a level of 0.1 K for 5 h at the disabled refrigerator. The microcryostat is used to investigate low-temperature radiation detectors.     

航磁补偿系统延迟偏差补偿方法研究

航空磁法勘探是一种重要的地球物理勘探方法,由于飞机磁干扰会对光泵磁力仪测量的数据产生严重的影响,因此有效的补偿飞机磁干扰具有重要的意义。提出了一种非线性航磁补偿方法,通过对信号时间序列的加权,实现对当前时刻输出信号的预测,通过L-M(Levenberg-Marquardt)算法求解修正同步误差后的非线性航磁补偿模型。仿真结果表明,该非线性航磁补偿方法可有效的解决传统航磁补偿方法无法补偿通道间延迟的问题,有效地降低各类信号延迟导致的补偿偏差,补偿后信号的标准差降低至10-4n T/m量级,该剩余残差水平与光泵磁力仪的本底噪声处于同一量级,符合高精度航磁勘探的要求。通过野外模拟飞行实验对理论分析和仿真结果进行了验证。     

Miniature ceramic-anvil high-pressure cell for magnetic measurements in a commercial superconducting quantum interference device magnetometer

A miniature opposed-anvil high-pressure cell has been developed for magnetic measurement in a commercial superconducting quantum interference device magnetometer. Non-magnetic anvils made of composite ceramic material were used to generate high-pressure with a Cu-Be gasket. We have examined anvils with different culet sizes (1.8, 1.6, 1.4, 1.2, 1.0, 0.8, and 0.6 mm). The pressure generated at low temperature was determined by the pressure dependence of the superconducting transition of lead (Pb). The maximum pressure P(max) depends on the culet size of the anvil: the values of P(max) are 2.4 and 7.6 GPa for 1.8 and 0.6 mm culet anvils, respectively. We revealed that the composite ceramic anvil has potential to generate high-pressure above 5 GPa. The background magnetization of the Cu-Be gasket is generally two orders of magnitude smaller than the Ni-Cr-Al gasket for the indenter cell. The present cell can be used not only with ferromagnetic and superconducting materials with large magnetization but also with antiferromagnetic compounds with smaller magnetization. The production cost of the present pressure cell is about one tenth of that of a diamond anvil cell. The anvil alignment mechanism is not necessary in the present pressure cell because of the strong fracture toughness (6.5 MPa?m(1∕2)) of the composite ceramic anvil. The simplified pressure cell is easy-to-use for researchers who are not familiar with high-pressure technology. Representative results on the magnetization of superconducting MgB(2) and antiferromagnet CePd(5)Al(2) are reported.     

相干斑噪声抑制技术研究

本文研究了一种新的合成孔径雷达相干斑噪声抑制的算法.传统的噪声抑制和近年来的小波变换方法都有其不足之处.本文结合增强Lee算法中的思想与小波算法用于抑制SAR图像中相干斑噪声,能够获得良好的效果,通过对比试验,本文算法具有较好的相干斑噪声抑制能力和边缘保持能力.     

刚架变形的简单计算方法

将2端固定梁的转角位移方程和改进的力矩一面积法相结合，用于刚架结构的转角和位移的计算。这种方法简单实用，在刚架结构设计中有一定应用价值。     

Scanning superconducting quantum interference device on a tip for magnetic imaging of nanoscale phenomena

We describe a new type of scanning probe microscope based on a superconducting quantum interference device (SQUID) that resides on the apex of a sharp tip. The SQUID-on-tip is glued to a quartz tuning fork which allows scanning at a tip-sample separation of a few nm. The magnetic flux sensitivity of the SQUID is 1.8 μΦ(0)/Hz and the spatial resolution is about 200 nm, which can be further improved. This combination of high sensitivity, spatial resolution, bandwidth, and the very close proximity to the sample provides a powerful tool for study of dynamic magnetic phenomena on the nanoscale. The potential of the SQUID-on-tip microscope is demonstrated by imaging of the vortex lattice and of the local ac magnetic response in superconductors.     

Unbalance vibratory displacement compensation for active magnetic bearings

As the dynamic stiffness of radial magnetic bearings is not big enough,when the rotor spins at high speed,unbalance displacement vibration phenomenon will be produced.The most effective way for reducing the displacement vibration is to enhance the radial magnetic bearing stiffness through increasing the control currents,but the suitable control currents are not easy to be provided,especially,to be provided in real time.To implement real time unbalance displacement vibration compensation,through analyzing active magnetic bearings(AMB) mathematical model,the existence of radial displacement runout is demonstrated.To restrain the runout,a new control scheme-adaptive iterative learning control(AILC) is proposed in view of rotor frequency periodic uncertainties during the startup process.The previous error signal is added into AILC learning law to enhance the convergence speed,and an impacting factor influenced by the rotor rotating frequency is introduced as learning output coefficient to improve the rotor control effects.As a feed-forward compensation controller,AILC can provide one unknown and perfect compensatory signal to make the rotor rotate around its geometric axis through power amplifier and radial magnetic bearings.To improve AMB closed-loop control system robust stability,one kind of incomplete differential PID feedback controller is adopted.The correctness of the AILC algorithm is validated by the simulation of AMB mathematical model adding AILC compensation algorithm through MATLAB soft.And the compensation for fixed rotational frequency is implemented in the actual AMB system.The simulation and experiment results show that the compensation scheme based on AILC algorithm as feed-forward compensation and PID algorithm as close-loop control can realize AMB system displacement minimum compensation at one fixed frequency,and improve the stability of the control system.The proposed research provides a new adaptive iterative learning control algorithm and control strategy for AMB displacement minimum compensation,and provides some references for time-varied displacement minimum compensation.     

测色仪中光电倍增管的电源设计

光电倍增管对电压的稳定性要求比较高。论述了电源设计的三种方案并详细地论述了采用 SG35 2 4脉宽调制器的方案 ,最后给出了由 SG35 2 4构成的电路原理图并得出了实验调试的结果     

磁悬浮电主轴单元径向轴承的磁场分析

介绍了磁悬浮电主轴单元的工作原理,以5.5kW电主轴单元为例,利用ANSYS软件对其径向磁轴承磁场进行了有限元分析.找出其系统磁场分布的变化规律和影响因素.分析表明:在主轴正常悬浮且单边气隙值取0.3±0.004mm,主轴支承处轴颈圆度取0.003mm,径向磁轴承磁极内圈圆度取0.007mm时,磁路磁漏不影响控制系统的性能,主轴实际中心线距理想位置的最大偏移量为0.0025mm,可满足精密机床主轴径向旋转精度性能要求.研究结果为磁悬浮电主轴单元的径向支承结构的优化设计提供了理论依据.     

Anomalous gain changes in photomultiplier tubes for use in scintillation counting

Abrupt pulse height changes and different steady state pulse heights exhibited at particular count rates are observed reproducibly in RCA 8850 and 8575 tubes. These phenomena are shown to be identical in nature with the hysteresis effect observed previously in a different type of tube. The implications for a standard count rate stability test and precision scintillation counting experiments are briefly discussed.     

Simple magnetic holders for critical point drying of microspecimen suspensions

Microspecimens can be critical point dried from suspension in holders consisting of three magnets and two filters. These holders are inexpensive, require no construction, and are easily assembled and disassembled.     

A self-sensing technology of active magnetic bearings using a phase modulation algorithm based on a high frequency voltage injection method

Conventional AMB(active magnetic bearings) systems consist of electromagnetic coils, position sensors, power amplifiers and a feedback controller. This hardware configuration can lead to a structural complexity, problems of space limitations for the installation, and position control difficulties due to the non-collocation of actuators and sensors. In this paper, a self-sensing mechanism is proposed to resolve such limitations of the general AMB system. The proposed self-sensing scheme uses a phase difference of the injected current of two opposite electromagnetic actuators while an object is levitating between the actuators. The relationship between the phase difference of injected currents and the position of a levitated object was theoretically derived and linearized. In order to realize the proposed self-sensing scheme, a signal processing algorithm was developed. The frequency response of the estimator was measured to verify the performance of the proposed self-sensing scheme. In addition, a magnetic levitation and a disturbance rejection response were experimentally obtained to verify the feasibility of the proposed self-sensing mechanism. Experimental results showed that the developed self-sensing technique has similar performance as a practical gap sensor.     

马赫-曾德尔干涉集成化的全光纤磁场与温度传感器

为了简化光纤磁场与温度传感器的结构并提高传感器灵敏度,设计并制作了马赫-曾德尔干涉集成化的全光纤磁场与温度传感器。将单根光纤的马赫-曾德尔模间干涉结构和双臂马赫-曾德尔干涉结构结合:将总长度为1.2m的单模光纤部分制备成长度为2.7cm、锥腰直径为30.1μm的锥形微纳光纤,并得到了拉锥时间与锥腰直径的关系。将锥形微纳光纤放置尼龙槽内并包覆磁凝胶构成传感头,实现模间干涉的马赫-曾德尔磁场传感器;将磁场传感器通过两耦合比为50%∶50%的耦合器并联带有可调谐光衰减器的单模光纤形成马赫-曾德尔干涉的温度传感器。从理论上分析了光谱漂移对磁场和温度传感的特性关系,实验测得室温下磁场强度在25~50mT时,磁场传感的灵敏度为0.301 14nm/mT;在磁场强度为0,温度由25℃升高到30℃时,温度传感的灵敏度为0.518 86nm/℃。该传感器可广泛应用于电力系统放电检测、材料加工、安全监控等领域。     

无缝钢管张力减径过程壁厚不均匀模拟分析

为研究无缝钢管张力减径过程中钢管壁厚不均现象,建立无缝钢管张力减径过程三维热力耦合模型。模拟所得壁厚与实测结果误差最大不超过5.2%。模拟结果直观显示钢管在轧制过程中内壁形状的变化过程,最终内壁形状为规则的正六方形。分析张力减径过程中摩擦力的分布,结果表明,摩擦力沿钢管圆周分布不均,使得在辊底处形成附加轴向压应力,辊缝处形成附加轴向拉应力,从而影响壁厚变化不均。进一步研究钢管初始温度对成品壁厚分布的影响,模拟结果表明,随着钢管初始温度的升高,钢管壁厚不均现象得到明显改善。     

双框架磁悬浮控制力矩陀螺磁轴承负载力矩复合补偿的控制

提出一种基于角速率前馈与力矩观测相结合的磁轴承负载力矩复合补偿控制方法来提高双框架磁悬浮控制力矩陀螺磁悬浮转子的悬浮精度。建立了双框架磁悬浮控制力矩陀螺磁悬浮转子动力学模型,分析了内外框架转动情况下的磁轴承负载力矩。分别基于框架角速率前馈和力矩观测设计了磁轴承负载力矩复合补偿控制方法,分析了补偿后系统的稳定性。最后,利用实验室研制的样机搭建试验平台对本文所提出的方法进行了实验验证。结果表明:在框架以角加速度120(°)/s2启动至10(°)/s时,该方法使转子Ax端位移跳动量减小为未补偿前的44.8%;内外框架以幅值频率10Hz正弦激励时,转子Ax、By端的位移跳动量分别减小为未补偿前的23.4%和35.5%。结果显示提出的方法有效地提高了磁悬浮转子在负载力矩扰动下的悬浮精度。     

Magnetic interference compensation method for geomagnetic field vector measurement

Ferromagnetic interferential field from platforms is one of the most dominating error sources for magnetometer. For magnetic vector and gradient tensor measurement, what is cared about most is the effect of compensating magnetic field vector. In this paper, a magnetic compensation method is proposed, which uses host platform’s attitude from inertial sensor as auxiliary information and sets up a vectorial compensation model. By introducing three intermediate parameters, the issue of parameter estimation is linearized and solved with least squares method. Simulations show that errors of magnetic field vector and magnitude can both be reduced to several nT after compensation. Experiment has been conducted with a geomagnetic vector measurement system and results suggest that the method is an effective way for compensating both magnetic field magnitude and vectors.