Miniature quad-channel spin-exchange relaxation-free magnetometer for magnetoencephalography

A miniature quad-channel optically pumped atomic magnetometer(OPM) has been developed based on the spinexchange relaxation-free(SERF) mechanism. With a vapor cell of size 8 mm×8 mm×8 mm, we have incorporated four SERF magnetometer channels, which provides sufficient spatial resolution for magnetoencephalography(MEG). The four channels share the same laser beam for the best cancellation of common mode noise due to laser fluctuations. With gradient measurement, the sensitivities of the four sensors are better than 6 fT/Hz^(1/2), which is also good enough for MEG measurement. The vapor cell is heated to 160℃ by a novel nonmagnetic current-heating structure. Our sensor with high spatial resolution and compact size is particularly suitable for MEG systems.

Transverse relaxation determination based on light polarization modulation for spin-exchange relaxation free atomic magnetometer

A transverse relaxation determination of spin-exchange relaxation free （SERF） magnetometer based on polarization modulation technique is proposed. Compared with the radio-frequency （RF） excitation and light intensity excitation meth- ods used in SERF magnetometer, the light polarization modulation method has a high stability in low-frequency range, which indicates a more accurate transverse relaxation measurement.

Spin dynamics of the potassium magnetometer in spin-exchange relaxation free regime

The laser-pumped potassium spin-exchange relaxation free （SERF） magnetometer is the most sensitive detector of magnetic field and has many important applications. We present the experimental results of our potassium SERF magne- tometer. A pump-probe approach is used to identify the unique spin dynamics of the atomic ensemble in the SERF regime. A single channel sensitivity of 8 f.THz-1/2 is achieved with our SERF magnetometer.

A Calculation Method of Rolling Characteristics of Canard Missile with Free-Spinning Tails

The steady flow field of a canard missile on different angles of attack and Mach numbers were studied. Based on analysis, a method was proposed to reduce the calculation for the rolling characteristics of the canard missile with free-spinning tails, and was tested to obtain the relations between rolling moment coefficient, Mach number, and angle of attack. All the computed rolling moment coefficients obtained from the proposed method greatly agreed with the experimental results of FD-06 wind tunnel in CAAA, which proved that the method can not only reduce the calculation cost but also keep precision in calculating the rolling characteristics of canard missiles.

Rolling Control Characteristic Experimental Investigation of a Canard Missile with Free-Spinning Tail

To study the rolling control characteristics of a canard-controlled missile, a series of wind tunnel experiment is conducted. The experimental method, the structure features of wind tunnel model and the experimental results are introduced in this paper. The experimental data show that the canard is an inefficient rolling control device for canard-controlled missile with fixed tail fins; but for the free-spinning tail fin configuration, the canard can conduct rolling control of the missile, and even have higher controlling efficiency under larger canard deflection angle.

Zero-Magnetic-Field Oscillation of Spin Transfer Nano-Oscillator with a Second-Order-Perpendicular-Anisotropy Free Layer

The zero-magnetic-field oscillation behavior of spin torque nano-oscillator （STNO） with a perpendicularly mag- netized free layer with second-order uniaxial anisotropy is studied theoretically based on the Landau-Lifshitz- Cilbert-Slonczewski equation. It is demonstrated numerically that the second-order uniaxial anisotropy plays a significant role in the occurrence of a zero-magnetic-field steady-state precession, which can be understood in terms of the energy balance between the energy accumulation due to the spin torque and the energy dissipation due to the Gilbert damping. In particular, a relatively large zero-magnetic-field-oscillation current region, in which the corresponding microwave frequency is increased while the threshold current still maintains an almost constant value, can be obtained by modulating the second-order uniaxial anisotropy of the free layer. These results suggest a tunable zero-magnetic-field STNO, and it may be a promising configuration for STNO＇s applications in future wireless communications.

Election Spin Resonance Studies of Free Radical Formation and Oxygen Consumption of Lens Epithelium During Ultraviolet Exposure

A long life election spin resonance (ESR) signal at g=2.0006 was observed in the normal lens epithelium and cortical fibers. During ultraviolet (UV) exposure, a new ESR signal at g = 2.0060 was found in the lens epithelium. But this specific signal was not detected in the lens cortical fibers. This suggested that lens epithelial cells were more susceptible to the free radical formation which was induced by UV light. By means of ESR spin probe oxymetry, the oxygen uptake of lens epithelial cells was meas...

In-situ measurement of magnetic field gradient in a magnetic shield by a spin-exchange relaxation-free magnetometer

A method of measuring in-situ magnetic field gradient is proposed in this paper. The magnetic shield is widely used in the atomic magnetometer. However, there is magnetic field gradient in the magnetic shield, which would lead to additional gradient broadening. It is impossible to use an ex-situ magnetometer to measure magnetic field gradient in the region of a cell, whose length of side is several centimeters. The method demonstrated in this paper can realize the in-situ measurement of the magnetic field gradient inside the cell, which is significant for the spin relaxation study. The magnetic field gradients along the longitudinal axis of the magnetic shield are measured by a spin-exchange relaxation-free （SERF） magnetometer by adding a magnetic field modulation in the probe beam＇s direction. The transmissivity of the cell for the probe beam is always inhomogeneous along the pump beam direction, and the method proposed in this paper is independent of the intensity of the probe beam, which means that the method is independent of the cell＇s transmissivity. This feature makes the method more practical experimentally. Moreover, the AC-Stark shift can seriously degrade and affect the precision of the magnetic field gradient measurement. The AC-Stark shift is suppressed by locking the pump beam to the resonance of potassium＇s D1 line. Furthermore, the residual magnetic fields are measured with σ＋- and σ--polarized pump beams, which can further suppress the effect of the AC-Stark shift. The method of measuring in-situ magnetic field gradient has achieved a magnetic field gradient precision of better than 30 pT/mm.

Decoherence-free spin entanglement generation and purification in nanowire double quantum dots

We propose a deterministic generation and purification of decoherence-free spin entangled states with singlet-triplet spins in nanowire double quantum dots via resonator-assisted charge manipulation and measurement techniques. Each spin qubit corresponds to two electrons in a double quantum dot in the nanowire, with the singlet and one of the triplets as the decoherence-free qubit states. The logical qubits are immunized against the dominant source of decoherence- dephasing--while the influences of additional errors are shown by numerical simulations. We analyse the performance and stability of all required operations and emphasize that all techniques are feasible in current experimental conditions.

Proposal for a Loophole-Free Bell Test with Electron Spins of Donors in Silicon

So far, all experimental tests of Bell inequalities which must be satisfied by all local realistic hidden-variable theories and are violated by quantum mechanical predictions have left at least one loophole open. We propose a feasible setup allowing for a loophole-free test of the Bell inequalities. Two electron spin qubits of donors31P in a nanoscale silicon host in different cavities 300 m apart are entangled through a bright coherent light and postselections using homodyne measurements. The electron spins are then read out randomly and independently by Alice and Bob, respectively, with unity efficiency in less than 0.7 μs by using optically induced spin to charge transduction detected by radio-frequency single electron transistor. A violation of Bell inequality larger than 37% and 18% is achievable provided that the detection accuracy is 0.99 and 0.95, respectively.

基于白噪声分析理论的Spin Glasses能量模型

使用白噪声分析理论研究Spin Glasses随机能量模型,对Derrida极限定理进行了推广;在白噪声分析框架下,给出了基于指数映射的极限定理,并提出了白噪声分析框架下的随机模型.

Low drift nuclear spin gyroscope with probe light intensity error suppression

A nuclear spin gyroscope based on an alkali-metal–noble-gas co-magnetometer operated in spin-exchange relaxationfree(SERF) regime is a promising atomic rotation sensor for its ultra-high fundamental sensitivity. However, the fluctuation of probe light intensity is one of the main technical error sources that limits the bias stability of the gyroscope. Here we propose a novel method to suppress the bias error induced by probe light intensity fluctuations. This method is based on the inherent magnetic field response characteristics of the gyroscope. By the application of a bias magnetic field, the gyroscope can be tuned to a working point where the output signal is insensitive to probe light intensity variation, referred to herein as ‘zero point’, thus the bias error induced by intensity fluctuations can be completely suppressed. The superiority of the method was verified on a K–Rb–21 Ne co-magnetometer, and a bias stability of approximately 0.01°/h was obtained. In addition, the method proposed here can remove the requirement of the closed-loop control of probe light intensity, thereby facilitating miniaturization of the gyroscope volume and improvement of reliability.

Design and Numerical Simulation of Low-Fiber Hollow Spindle in Air-Jet Vortex Spinning

Based on the mechanical system of free-end fibers and the analysis of pulling free-end fibers out of the spun yarn during spinning,a low-fiber hollow spindle is designed and the air distribution of fluent field is simulated numerically. The negative pressure effect is much bigger at the top of low-fiber hollow spindle than that in Murata No.861,which is more conducive for single fiber to get into the channel of hollow spindle. The tangential velocity in 0-3 mm at the top of hollow spindle increases and the fluctuation of radial velocity is much stronger,which enhance the wrapping effect. In the addition,the distribution of axial velocity remains the same.

Consumption of Mercury-contaminated Rice Induces Oxidative Stress and Free Radical Aggravation in Rats

Objective To study the oxidative stress induced by consumption of mercury-contaminated rice in rats, and to assess the possible public health risk of mercury contamination in Wanshan mining area. Methods Sprague Dawley rats were fed the mercury-contaminated rice produced from Wanshan area for 90 days. The antioxidant status and the free radicals in rat serum were evaluated. Results High mercury accumulation in organs of rats fed the mercury-contaminated rice confirmed the server pollution of mercury in Wanshan mining area. The intensity of electron spin resonance （ESR） signal increased by 87.38% in rats fed the rice from Wanshan compared with that in the control rats fed the rice from Shanghai, suggesting that chronic dietary consumption of rice from mercury mining area could induce an aggravation of free radicals. Feeding the mercury-contaminated rice was associated with significant decreases in the antioxidant enzymatic activities of superoxide dismutase （SOD） and glutathione peroxidase （GSH-Px） and concentration of serum nitric oxide （NO）, but it had no effect on serum nitric oxide synthase （NOS） activity. Feeding the mercury-contaminated rice raised the level of serum malonyldialdehyde （MDA）, indicating the occurrence of oxidative stress. Conclusion The long-term dietary consumption of mercury-contaminated rice induces the aggravation of free radicals and exerts oxidative stress.

CoFe/NiFe复合自由层对自旋阀磁电阻变化率的影响

研究CoFe/NiFe复合自由层对自旋阀磁电阻变化率的影响。在实验中通过固定溅射功率、时间和气流,调节靶基距(TSD)得到不同厚度及均匀性的复合自由层CoFe/NiFe薄膜,进而达到优化自旋阀结构提高其磁电阻率的目的。实验结果表明:在TSD分别为8.382 cm、8.890 cm时,制备的CoFe和NiFe单层膜性能最优,电阻标准偏差分别为1.33%、0.98%。通过磁性能综合测试平台对优化后的CoFe/NiFe复合自由层的自旋阀结构进行了测试,磁电阻变化率(MR)较优化前提高了约0.84%。该研究可为高性能自旋阀结构的制备提供参考。

基于包缠结构羊毛腈纶纱的制备及性能分析

为了探索基于包缠结构羊毛混纺纱的性能,采用平行纺技术,以羊毛纤维须条为芯纱、腈纶长丝为外包纤维制备包缠结构纱线。通过优选包缠捻度,综合分析包缠结构纱线的强伸性能、毛羽、外观等质量指标。结果表明:当纺纱号数为44 tex,张力系数设置为1.1,锭速选择2000 r/min,设计牵伸为40倍时,优选出最佳包缠捻度为400捻/m。与同号数的常规环锭纺纯羊毛纱相比较,包缠结构羊毛纱不仅更柔软,条干等指标也有明显改善。

双旋尾控弹全周期自由旋振运动分析

目前,制导化改造的双旋构型成为了提升弹药打击精度的一种有效方法。研究一种新型双旋尾控弹的全周期扰动运动特性,基于理想轴承假设和非滚转坐标系,建立双旋尾控弹的7自由度弹道模型。采用系数冻结法和小扰动假设对弹道方程进行线性化,获得了全周期扰动运动方程,并将其表示为状态空间形式。选择理想弹道上的特征点,采用数值计算方法获得全周期自由扰动运动解的模态,双旋弹的自由扰动运动表现为一种衰减旋振运动,讨论不同初始偏差下旋振运动解的形式。分析数值计算结果表明:双旋尾控弹在纵侧向运动上表现出了强烈的耦合特征;扰动下的旋振运动可分为长周期和短周期两个阶段,攻角偏量收敛速度慢,且不同攻角偏量的模态幅值具有不同的分布规律,为角运动和制导率设计奠定了基础。

基于遗传算法的磁自抑制加热器的设计与优化

超低磁噪声(0~10 nT)的碱金属加热技术是无自旋交换弛豫原子磁力仪实现超高灵敏度的关键,文章提出一种基于遗传算法的磁自抑制加热器多目标优化设计方法。该方法基于毕奥-萨伐尔定律推导目标函数新模型,优化的目标包括加热丝的长度、宽度、厚度和电流方向4类(18个)参数,以此获取加热器最佳磁自抑制性能。利用有限元分析方法,仿真分析了目标区域的磁场分布和温度分布,结果表明:加热器在目标区域的中心区域产生0.02 nT/mA的平均磁场和180.34℃的平均温度。实验测试结果显示:目标区域的磁通密度取值在0.13 nT/mA和0.14 nT/mA范围内,这表明加热器的磁场自抑制性能较好。该研究有助于进一步提高原子磁力仪的性能。

A Novel Classical Model of the Free Electron

Previous models of the free electron using classical physics equations have predicted attributes that are inconsistent with the experimentally observed attributes. For example, the magnetic moment has been calculated for the observed spinning electric charge. For the calculated moment to equal the observed moment, the electron would either have to spin at two hundred times the speed of light or have a charge radius two hundred times greater than the classical radius. A similar inconsistency results when the mass derived from the spin angular momentum is compared with the observed mass. A classical model is herein proposed which eliminates the magnetic moment inconsistency and also predicts the radius of the electron. The novel feature of the model is the replacement of a single charge with two opposite charges, one on the outer surface of the electron and the other at the center.

电子顺磁共振技术应用及进展

电子顺磁共振(EPR)波谱技术是一种新的检测方法,用于检测顺磁性离子、自由基及顺磁性配合物分子的结构。近几年又发展成为一种操控自旋电子材料内部原子核外单电子自旋状态手段,用于单电子自旋相干态的制备,实现量子运算和信息传输。目前文献中报道EPR在化学、物理、生物和医药领域的应用很多。针对当前EPR在不同领域的应用,综述了EPR技术的应用原理和进展,为更好地将EPR技术应用在量子物理、配合物化学、自由基生物学、医学、药学等领域提供参考和借鉴。