In order to know the distribution of magnetic field in a novel flow control of mold (NFC Mold) and to provide the experimental data for the electromagnetic structure design and the analysis of flow control in continuo...In order to know the distribution of magnetic field in a novel flow control of mold (NFC Mold) and to provide the experimental data for the electromagnetic structure design and the analysis of flow control in continuous casting mold, the magnetic field in a NFC Mold were measured by Tesla meter of Model CT-3. The method of vector synthesis was adopted in the measurement of magnetic fields. The results showed that the magnetic field in the NFC Mold was composed of two main magnetic areas that were symmetrical. Although there was leaking magnetic flux between the lower surface of the upper pole and the upper surface of the lower pole on the sides, it was restrained by the main magnetic fields effectively. Therefore the NFC Mold was more preferably satisfied to be used in controlling the molten steel flow in continuous casting mold.展开更多
The maximum entangled number state (NOON state) can improve the sensitivity of physical quantity measure- ment to the Heisenberg limit 1/N. In this work, the magnetic field measurement based on the individual solid ...The maximum entangled number state (NOON state) can improve the sensitivity of physical quantity measure- ment to the Heisenberg limit 1/N. In this work, the magnetic field measurement based on the individual solid spin NOON state is investigated. Based on the tunable effective coupling coefficient, we propose a generation scheme of the three-spin NOON state, i.e, the Creenberger-Horne-Zeilinger (CHZ) state, and discussed the mea- surement resolution reduction due to decoherence. It is unnecessary to entangle spins as many as possible when decoherence exists. In practice, defect spins in diamond and alp donors with long coherence time can be applied with current techniques in the nano-scaled high resolution magnetic measurement.展开更多
The article designs a new type of bridge circuit with a controlled source—when the resistance on the bridge arm of the controlled source bridge circuit meets the bridge balance condition, and the bridge branch contai...The article designs a new type of bridge circuit with a controlled source—when the resistance on the bridge arm of the controlled source bridge circuit meets the bridge balance condition, and the bridge branch contains only one Current-Controlled Current Source (CCCS), a Voltage-Controlled Current Source (VCCS), a Current-Controlled Voltage Source (CCVS), or a Voltage-Controlled Voltage Source (VCVS), the circuit is called a controlled bridge circuit, which has the characteristics of bridge balance. Due to the relationship between the controlled source and the bridge arm, the sensitivity of the components on the bridge is higher mathematically and logically. When applied to measurement, engineering, automatic control, and other fields, the controlled bridge circuit has higher control ac-curacy. Mathematical derivation and simulation results prove the correctness of the bridge balance conclusion and the special properties of this bridge when applied to the measurement field.展开更多
The magnetization behavior of a CuFeO2 single crystal grown by the floating zone technique is investigated with a pulsed high magnetic field. We observe a series of field-induced multi-step-like transitions with hyste...The magnetization behavior of a CuFeO2 single crystal grown by the floating zone technique is investigated with a pulsed high magnetic field. We observe a series of field-induced multi-step-like transitions with hysteresis, of which the critical magnetic fields are temperature-dependent and show anisotropy. By using a pulsed high magnetic field up to 75 T, the magnetization behavior shows that the critical transition magnetic fields of spin- flip/flop shift to lower field regions with an increase in temperature. According to the magnetization curves, a complete magnetic phase diagram is depicted.展开更多
Most triaxial-vectorial magnetic field measurements with spin-exchange relaxation free(SERF)atomic magnetometer(AM)are based on the quasi-steady-state solution of the Bloch equation.However,the responding speed of the...Most triaxial-vectorial magnetic field measurements with spin-exchange relaxation free(SERF)atomic magnetometer(AM)are based on the quasi-steady-state solution of the Bloch equation.However,the responding speed of these methods is greatly limited because the frequency of the modulation signal should be slow enough to ensure the validity of the quasi-steady-state solution.In this work,a new model to describe the response of the three-axis sensitive SERF AM with high modulation frequency is presented and verified.The response of alkali-atomic spin to high-frequency modulation field is further investigated by solving the Bloch equation in a modulation-frequency-dependence manner.This solution is well verified by our experiments and can offer a reference for selection of modulation frequencies.The result shows a potential to achieve a SERF AM operating in a geomagnetic field without heavy aluminum shielding when the modulation frequencies are selected properly.展开更多
Nitrogen-vacancy color centers can perform highly sensitive and spatially resolved quantum measurements of physical quantities such as magnetic field,temperature,and pressure.Meanwhile,sensing so many variables at the...Nitrogen-vacancy color centers can perform highly sensitive and spatially resolved quantum measurements of physical quantities such as magnetic field,temperature,and pressure.Meanwhile,sensing so many variables at the same time often introduces additional noise,causing a reduced accuracy.Here,a dual-microwave time-division multiplexing protocol is used in conjunction with a lock-in amplifier in order to decouple temperature from the magnetic field and vice versa.In this protocol,dual-frequency driving and frequency modulation are used to measure the magnetic and temperature field simultaneously in real time.The sensitivity of our system is about 3.4 nT=√Hz p and 1.3 mK=√Hz p,respectively.Our detection protocol not only enables multifunctional quantum sensing,but also extends more practical applications.展开更多
We demonstrate a method for quickly and automatically detecting all three components of a remanent magnetic field around a shielded spin-exchange relaxation-free(SERF)atomic magnetometer(AM)using the trisection algori...We demonstrate a method for quickly and automatically detecting all three components of a remanent magnetic field around a shielded spin-exchange relaxation-free(SERF)atomic magnetometer(AM)using the trisection algorithm(TSA)for zero-field resonance(ZFR).To satisfy the measurement of AMs,a resonance light of the ^(87)Rb D1 line with a spectral width of less than 1 MHz is converted to circular polarization by a linear polarizer and a quarter-wave plate.After the light beam has passed through the alkali metal vapor cell,the residual magnetic field can be measured by searching for triaxial ZFR optical peaks.The TSA stably reduces the measurement time to 2.41 s on average and improves the measurement accuracy,significantly outpacing existing methods.The weighted averages of all measurements with corresponding uncertainties are(–15.437±0.022)nT,(6.062±0.021)nT,and(–14.158±0.052)nT on the x-,y-,and z-axes,respectively.These improvements could facilitate more extremely weak magnetic studies in real time,such as magnetoencephalography(MEG)and magnetocardiography(MCG)measurements.展开更多
A 16-pole superconducting multipole wiggler with a large gap of 68 mm was designed and fabricated to serve as a multipole wiggler for HEPS-TF.The wiggler consists of 16 pairs of NbTi superconducting coils with a perio...A 16-pole superconducting multipole wiggler with a large gap of 68 mm was designed and fabricated to serve as a multipole wiggler for HEPS-TF.The wiggler consists of 16 pairs of NbTi superconducting coils with a period length of 170 mm,and its maximum peak field is 2.6 Tesla.In magnet design,magnet poles were optimized.Furthermore,the Lorentz force on the coils and electromagnetic force between the upper and lower halves were computed and analyzed along with the stored energy and inductance at different currents.To enhance the critical current of the magnet coil,all the pole coils selected for the magnet exhibited excellent performance,and appropriate prestress derived from the coil force analysis was applied to the pole coils during magnet assembly.The entire magnet structure was immersed in 4.2-K liquid helium in the cryostat cooled solely by four two-stage cryocoolers,and the performance test of the superconducting wiggler was appropriately completed.Based on the measured results,the first and second field integrals on the axis of the superconducting wiggler were significantly improved at different field levels after the compensation of the corrector coils.Subsequently,the wiggler was successfully installed in the storage ring of BEPCII operation with beams.展开更多
This paper presents a study on the effects of radiation from electronic equipment in hospitals. This study was performed in Argentinean, Colombian and Spanish hospitals. The work consists of two parts: a survey to det...This paper presents a study on the effects of radiation from electronic equipment in hospitals. This study was performed in Argentinean, Colombian and Spanish hospitals. The work consists of two parts: a survey to determine the hospital personnel’s knowledge of the problem and a technical part consisting of a measurements campaign to determine the levels of radiated electrical and magnetic fields in several hospitals due to the presence of electromagnetic interferences, such as the use of mobile phones. The study of this problem has been of special interest in countries such as the USA and Canada, and this paper attempts to convey the necessity of creating regulations that can be applied to the hospitals of the countries analyzed. More than fifty hospitals were studied in these three countries, considering the following aspects: the hospital personnel’s awareness of the problem, whether the hospitals have performed previous studies of this type, the appearance of problems in medical equipment due to this interference, the origin of the interference, and the failures that have appeared in computers due to electromagnetic interference. The results show that, most hospitals have a lack of knowledge regarding this issue and that field levels above those allowed by international regulations are present. Therefore, a regulation must be established to avoid the problem.展开更多
An experiment on measuring the magnetic field in Ramsey interaction region of the atomic fountain clock by detecting the Zeeman frequency shift of 87Rb hyperfine transition is presented.By mu-metal shielding and coils...An experiment on measuring the magnetic field in Ramsey interaction region of the atomic fountain clock by detecting the Zeeman frequency shift of 87Rb hyperfine transition is presented.By mu-metal shielding and coils compensating,the magnetic fluctuations resulting from asymmetry and instability are less than 10 and 0.025 nT,respectively.The relative frequency uncertainty of atomic fountain clock caused by the magnetic field is less than 5.4×10-16.展开更多
Based on cosmic ray events without a magnetic field taken with the BESIII detector during the summer shutdown of BEPCII in 2012 and di-muon events from a data sample taken at center-of-mass energy of 3.686 GeV in 2009...Based on cosmic ray events without a magnetic field taken with the BESIII detector during the summer shutdown of BEPCII in 2012 and di-muon events from a data sample taken at center-of-mass energy of 3.686 GeV in 2009, we compare the coordinates of hits registered in the BESIII muon counter with the expected interaction point extrapolated from reconstructed tracks from the inner tracking system in the absence of a magnetic field. By minimizing the difference, we align the muon counter with the inner tracking system. Moreover, the strength of the magnetic field in the muon counter is measured for the first time with di-muon events from data taken at a center- of-mass energy of 3.686 GeV. After the Mignment and the magnetic field strength measurement, the offsets in the reconstructed hit positions for muon tracks are reduced, which improves the muon identification. The alignment and magnetic field strength measurement have been adopted in the latest version of the BESIII offiine software system. This addition to the software reduces the systematic uncertainty for the physics analysis in cases where the muon counter information is used.展开更多
Background High Energy Photon Source(HEPS)is the fourth-generation synchrotron radiation source to be established in China.HEPS is a high-performance and high-energy synchrotron radiation light source with a beam ener...Background High Energy Photon Source(HEPS)is the fourth-generation synchrotron radiation source to be established in China.HEPS is a high-performance and high-energy synchrotron radiation light source with a beam energy of 6 GeV and an ultra-low emittance of better than 0.06 nm×rad(http://english.ihep.cas.cn/heps/index.html).Superconducting 3W1 wiggler magnet is one of the insertion devices in High Energy Photon Source Test Facility project(HEPS-TF).And it is also the key component to obtain higher brightness in high photon energy range.Purpose In the development process of superconducting wiggler,in order to ensure the magnetic field quality of each processing,it is necessary to monitor the magnetic field performance of before and after the full length bare magnet installed with cryostat.Therefore,different magnetic field measuring devices are being developed for different develop stages.Methods The magnetic field performance of the full length bare magnet should be tested in vertical at low temperature.After the magnetic structure is installed in the horizontal cryostat,the horizontal test is carried out.In view of these two processes,the vertical magnetic field measurement system and the horizontal magnetic field measurement system have been developed,respectively.Results The magnetic performances of the full length bare magnet and assembled with the horizontal cryostat were measured by the vertical and horizontal magnetic field measurement system.The first and second field integrals are corrected to better than the Physical requirements according to the magnetic field measurement results.Detailed magnetic field performances are described in this paper.Conclusion After more than a year operation of 3W1-SCW on the BII line station,the characteristic energy and photon flux of synchrotron radiation have been greatly improved,and the performance is excellent.It indicates that the measurement results of the magnetic field measurement system are reliable and credible.展开更多
A novel distributed feedback(DFB) fiber laser sensor, which can measure acoustic and magnetic fields simultaneously, is proposed. The magnetic field can be measured by detecting the change of resonant frequency of t...A novel distributed feedback(DFB) fiber laser sensor, which can measure acoustic and magnetic fields simultaneously, is proposed. The magnetic field can be measured by detecting the change of resonant frequency of the fiber laser, and the acoustic pressure can be measured by detecting the phase shift of the fiber laser. Both of the signals can be simultaneously demodulated in the frequency domain without affecting each other. Experimental studies show that the acoustic pressure sensitivity of this sensor is about-130 d B(0 dB re 1 pm∕μPa) and the sensor has a good linearity with a magnetic field sensitivity of 0.57 Hz∕mT.展开更多
A novel fiber-optic magnetic field sensor with high interrogation speed and resolution by using an etched fiber Bragg grating(FBG)in conjunction with a dual-loop optoelectronic oscillator(OEO)is proposed and experimen...A novel fiber-optic magnetic field sensor with high interrogation speed and resolution by using an etched fiber Bragg grating(FBG)in conjunction with a dual-loop optoelectronic oscillator(OEO)is proposed and experimentally demonstrated.A commercial FBG is firstly dipped into mixed hydrofluoric acid solution to remove the cladding layer and then is embedded with the magnetic fluid(MF)as a sensing element.The central wavelength reflected from the FBG is related to the overall time delay of the dual-loop OEO,which determines the oscillating frequency of the OEO.Therefore,the magnetic field can be estimated by measuring the oscillating frequency shift of OEO.The experimental results show that the oscillating frequency linearly increases with the increment of the magnetic field,achieving the sensitivity of 16.3 Hz/Oe with a R-square of 0.991 in the range of 5 mT-10 mT.In addition,the maximum error is within±0.05 mT in the range of 7 mT-8 mT,which offers potentials in many fields where the high-precision magnetic field measurement is required.展开更多
The response time and transmittivity of the magnetic fluid (MF) for different concentrations at room temperature were investigated in this letter. The volume fraction of the investigated sample ranged from 0.44% to ...The response time and transmittivity of the magnetic fluid (MF) for different concentrations at room temperature were investigated in this letter. The volume fraction of the investigated sample ranged from 0.44% to 6.47%. It was found that the transmittivity decreased with increasing concentration under a given magnetic field, and the evolution time was changed with different concentrations. Moreover the light intensity decreased rapidly at the beginning and then became stable when the magnetic field was applied.展开更多
In the present paper,a method for reliable estimation of defect profile in CK45 steel structures is presented using an eddy current testing based measurement system and post-processing system based on deep learning te...In the present paper,a method for reliable estimation of defect profile in CK45 steel structures is presented using an eddy current testing based measurement system and post-processing system based on deep learning technique.So a deep learning method is used to determine the defect characteristics in metallic structures by magnetic field C-scan images obtained by an anisotropic magneto-resistive sensor.Having designed and adjusting the deep convolution neural network and applied it to C-scan images obtained from the measurement system,the performance of deep learning method proposed is compared with conventional artificial neural network methods such as multilayer perceptron and radial basis function on a number of metallic specimens with different defects.The results confirm the superiority of the proposed method for characterizing defects compared to other classical training-oriented methods。展开更多
Examples of changes in the magnitude of the <b><span style="font-family:Verdana;">B</span></b><span style="font-family:Verdana;"><span style="font-family:Verda...Examples of changes in the magnitude of the <b><span style="font-family:Verdana;">B</span></b><span style="font-family:Verdana;"><span style="font-family:Verdana;"><b><span style="font-family:Verdana;">-</span></b></span></span><span><span><span style="font-family:;" "=""><span style="font-family:Verdana;">field after the heliosphere termination shock (TS) with both Voyager spacecraft (SC) are presented. The work focuses on similarities and differences in the observations at their </span><i><span style="font-family:Verdana;">in-situ</span></i><span style="font-family:Verdana;"> measurements along divergent paths. The presented results were collected where the accuracy of the magnetometer is the highest. These locations are those wherein, four to seven times during the year, the SC performs about 330 minutes of slow rotations identified in the SC language as MAGROLs. They are next reviewed, with the understanding that after the TS, at MAGROLs, the solar wind (SW) flows appear to be mostly sub-magnetosonic and compressional in this region, region named helio-sheath (HS). This is a preliminary survey that uses </span><span style="font-family:Verdana;">48 sec</span> <b><span style="font-family:Verdana;">B</span></b><span style="font-family:Verdana;">-field averages. The time-intervals in this work fill gaps in the currently available studies for longer time intervals. The present study reinforces the view that in the HS after the TS the SW is most likely strongly compressional. </span><span style="font-family:Verdana;">Further</span><span style="font-family:Verdana;"> we discuss the fact that observed fluctuation intensity-modes of the </span><b><span style="font-family:Verdana;">B</span></b><span style="font-family:Verdana;">-field in our time-ranges appear to be much more pronounced at the Voyager 2 path than at the Voyager 1 path.</span></span></span></span>展开更多
Purpose A new rotating coil measurement system based on the coordinate measurement machine(CMM)is developed for measuring high-gradient small-aperture quadrupole magnet in the Test Facility of High Energy Photon Sourc...Purpose A new rotating coil measurement system based on the coordinate measurement machine(CMM)is developed for measuring high-gradient small-aperture quadrupole magnet in the Test Facility of High Energy Photon Source(HEPS-TF).Methods The CMMand two groups of Newport translate stages are combined to align the rotating coil relative to the magnet mechanical center.A high precision ceramic skeleton with bucked coil is made as a measurement sensor.The integrated field gradient,harmonics,magnetic center offset and excitation curve of a high-gradient small-aperture quadrupole prototype magnet are measured.Results The rotating coil is aligned to the magnet mechanical center within 10μm.The reproducibility of higher harmonics is within 0.2×10–4.The repeatability of the magnet center in horizontal direction is under 1.5μm,while that in vertical direction is less than 2.5μm in different days.The architecture of the measurement system,the measuring procedure and some primary results of the quadrupole prototype magnet are illustrated in this paper.Conclusion A rotating coil measurement system based on CMM has been well developed,and the collimation efficiency and precision are improved.The harmonic changes caused by iron fingers are measured by the measurement system.The difference between the measurement result and the OPERA-3D simulation result is less than 0.5×10–4.The performance of this measurement system can meet the magnet measurement requirements of HEPS-TF.展开更多
Purpose More undulators are required of HEPS in future.The efficiency of traditional Hall-probe measurement method is relatively low,which is difficult to meet the measurement needs of large quantities of undulators.I...Purpose More undulators are required of HEPS in future.The efficiency of traditional Hall-probe measurement method is relatively low,which is difficult to meet the measurement needs of large quantities of undulators.In order to improve debugging efficiency,the pulsed-wire method is required further improvement.Methods A pulsed-wire method is an effective method to achieve magnetic field distribution through narrow aperture of undulator.The pulsed-wire method works by sending a square current pulse through the wire,which will induce an interaction with the magnetic field due to the Lorentz force.This force causes the wire to be displaced,and this displacement travels along the wire in both directions as an acoustic wave.Measurement of the displacement in the wire over time using a motion detector yields the first or second integrals of the magnetic field.Results The accuracy and repeatability are the important requirements.The repeatability of the first field integral of the pulsed-wire system is better than 1‰which meets the design requirements.Conclusions This paper illustrates the effectiveness of pulsed-wire system by test results.Through comparison,the accuracy of the system is proved.It provides a new important measurement system for undulators in future.展开更多
The BEPCⅡis the upgrade project of the Beijing Electron Positron Collider(BEPC).According to the BEPCⅡdouble ring design scheme,a new ring will be added in the existing BEPC tunnel.The machine will provide electron ...The BEPCⅡis the upgrade project of the Beijing Electron Positron Collider(BEPC).According to the BEPCⅡdouble ring design scheme,a new ring will be added in the existing BEPC tunnel.The machine will provide electron and positron beams with an energy range from 1.0GeV to 2.1GeV for high energy physics research,and an electron beam of 2.SGeV,250mA for synchrotron radiation.So actually there are three storage rings for the BEPCⅡmachine.Due to the limited space of the existing BEPC tunnel and the requirement of high luminosity,the antechamber type vacuum chamber is used,that makes the BEPCⅡmagnets'design and fabrication very difficult.In the paper the general features of the design and fabrication of several kinds of main magnets for the BEPCⅡstorage ring and its interaction region are introduced.And the magnetic field measurement results are presented.展开更多
基金the National Natural Science Foundation of China (Grant No. 59734080), the National Key Basic Research and Development Programme of China (Grant No. G1998061510) and the Project of National High Te
文摘In order to know the distribution of magnetic field in a novel flow control of mold (NFC Mold) and to provide the experimental data for the electromagnetic structure design and the analysis of flow control in continuous casting mold, the magnetic field in a NFC Mold were measured by Tesla meter of Model CT-3. The method of vector synthesis was adopted in the measurement of magnetic fields. The results showed that the magnetic field in the NFC Mold was composed of two main magnetic areas that were symmetrical. Although there was leaking magnetic flux between the lower surface of the upper pole and the upper surface of the lower pole on the sides, it was restrained by the main magnetic fields effectively. Therefore the NFC Mold was more preferably satisfied to be used in controlling the molten steel flow in continuous casting mold.
基金Supported by the National Basic Research Program of China(No 2011CB921200)the Strategic Priority Research Program(B)of the Chinese Academy of Sciences under Grant (No XDB01030200)+1 种基金the National Natural Science Foundation of China(No11374290)the Fundamental Research Funds for the Central Universities and the Foundation for Authors of National Excellent Doctoral Dissertation of China
文摘The maximum entangled number state (NOON state) can improve the sensitivity of physical quantity measure- ment to the Heisenberg limit 1/N. In this work, the magnetic field measurement based on the individual solid spin NOON state is investigated. Based on the tunable effective coupling coefficient, we propose a generation scheme of the three-spin NOON state, i.e, the Creenberger-Horne-Zeilinger (CHZ) state, and discussed the mea- surement resolution reduction due to decoherence. It is unnecessary to entangle spins as many as possible when decoherence exists. In practice, defect spins in diamond and alp donors with long coherence time can be applied with current techniques in the nano-scaled high resolution magnetic measurement.
文摘The article designs a new type of bridge circuit with a controlled source—when the resistance on the bridge arm of the controlled source bridge circuit meets the bridge balance condition, and the bridge branch contains only one Current-Controlled Current Source (CCCS), a Voltage-Controlled Current Source (VCCS), a Current-Controlled Voltage Source (CCVS), or a Voltage-Controlled Voltage Source (VCVS), the circuit is called a controlled bridge circuit, which has the characteristics of bridge balance. Due to the relationship between the controlled source and the bridge arm, the sensitivity of the components on the bridge is higher mathematically and logically. When applied to measurement, engineering, automatic control, and other fields, the controlled bridge circuit has higher control ac-curacy. Mathematical derivation and simulation results prove the correctness of the bridge balance conclusion and the special properties of this bridge when applied to the measurement field.
基金Supported by the National Natural Science Foundation of China under Grant No 11104091the Guangxi Key Laboratory of Information Materials of Guilin University of Electronic Technology under Grant No 1210908-05-K
文摘The magnetization behavior of a CuFeO2 single crystal grown by the floating zone technique is investigated with a pulsed high magnetic field. We observe a series of field-induced multi-step-like transitions with hysteresis, of which the critical magnetic fields are temperature-dependent and show anisotropy. By using a pulsed high magnetic field up to 75 T, the magnetization behavior shows that the critical transition magnetic fields of spin- flip/flop shift to lower field regions with an increase in temperature. According to the magnetization curves, a complete magnetic phase diagram is depicted.
基金Project supported by the National Natural Science Foundation of China(Grant No.42074216).
文摘Most triaxial-vectorial magnetic field measurements with spin-exchange relaxation free(SERF)atomic magnetometer(AM)are based on the quasi-steady-state solution of the Bloch equation.However,the responding speed of these methods is greatly limited because the frequency of the modulation signal should be slow enough to ensure the validity of the quasi-steady-state solution.In this work,a new model to describe the response of the three-axis sensitive SERF AM with high modulation frequency is presented and verified.The response of alkali-atomic spin to high-frequency modulation field is further investigated by solving the Bloch equation in a modulation-frequency-dependence manner.This solution is well verified by our experiments and can offer a reference for selection of modulation frequencies.The result shows a potential to achieve a SERF AM operating in a geomagnetic field without heavy aluminum shielding when the modulation frequencies are selected properly.
基金supported by the National Natural Science Foundation of China(Nos.12005218 and 52130510).
文摘Nitrogen-vacancy color centers can perform highly sensitive and spatially resolved quantum measurements of physical quantities such as magnetic field,temperature,and pressure.Meanwhile,sensing so many variables at the same time often introduces additional noise,causing a reduced accuracy.Here,a dual-microwave time-division multiplexing protocol is used in conjunction with a lock-in amplifier in order to decouple temperature from the magnetic field and vice versa.In this protocol,dual-frequency driving and frequency modulation are used to measure the magnetic and temperature field simultaneously in real time.The sensitivity of our system is about 3.4 nT=√Hz p and 1.3 mK=√Hz p,respectively.Our detection protocol not only enables multifunctional quantum sensing,but also extends more practical applications.
基金This work was supported by Beijing Natural Science Foundation(Grant No.4191002)Key Research&Development Program of Zhejiang,China(Grant No.2020C01037)+1 种基金the National Key Research&Development Program of China(Grant No.2018YFB2002405)the National Natural Science Foundation of China(Grant No.62073014).
文摘We demonstrate a method for quickly and automatically detecting all three components of a remanent magnetic field around a shielded spin-exchange relaxation-free(SERF)atomic magnetometer(AM)using the trisection algorithm(TSA)for zero-field resonance(ZFR).To satisfy the measurement of AMs,a resonance light of the ^(87)Rb D1 line with a spectral width of less than 1 MHz is converted to circular polarization by a linear polarizer and a quarter-wave plate.After the light beam has passed through the alkali metal vapor cell,the residual magnetic field can be measured by searching for triaxial ZFR optical peaks.The TSA stably reduces the measurement time to 2.41 s on average and improves the measurement accuracy,significantly outpacing existing methods.The weighted averages of all measurements with corresponding uncertainties are(–15.437±0.022)nT,(6.062±0.021)nT,and(–14.158±0.052)nT on the x-,y-,and z-axes,respectively.These improvements could facilitate more extremely weak magnetic studies in real time,such as magnetoencephalography(MEG)and magnetocardiography(MCG)measurements.
文摘A 16-pole superconducting multipole wiggler with a large gap of 68 mm was designed and fabricated to serve as a multipole wiggler for HEPS-TF.The wiggler consists of 16 pairs of NbTi superconducting coils with a period length of 170 mm,and its maximum peak field is 2.6 Tesla.In magnet design,magnet poles were optimized.Furthermore,the Lorentz force on the coils and electromagnetic force between the upper and lower halves were computed and analyzed along with the stored energy and inductance at different currents.To enhance the critical current of the magnet coil,all the pole coils selected for the magnet exhibited excellent performance,and appropriate prestress derived from the coil force analysis was applied to the pole coils during magnet assembly.The entire magnet structure was immersed in 4.2-K liquid helium in the cryostat cooled solely by four two-stage cryocoolers,and the performance test of the superconducting wiggler was appropriately completed.Based on the measured results,the first and second field integrals on the axis of the superconducting wiggler were significantly improved at different field levels after the compensation of the corrector coils.Subsequently,the wiggler was successfully installed in the storage ring of BEPCII operation with beams.
基金supported by E.S.E METROSALUD and Instituto Tecnologico Metropolitano—ITM.
文摘This paper presents a study on the effects of radiation from electronic equipment in hospitals. This study was performed in Argentinean, Colombian and Spanish hospitals. The work consists of two parts: a survey to determine the hospital personnel’s knowledge of the problem and a technical part consisting of a measurements campaign to determine the levels of radiated electrical and magnetic fields in several hospitals due to the presence of electromagnetic interferences, such as the use of mobile phones. The study of this problem has been of special interest in countries such as the USA and Canada, and this paper attempts to convey the necessity of creating regulations that can be applied to the hospitals of the countries analyzed. More than fifty hospitals were studied in these three countries, considering the following aspects: the hospital personnel’s awareness of the problem, whether the hospitals have performed previous studies of this type, the appearance of problems in medical equipment due to this interference, the origin of the interference, and the failures that have appeared in computers due to electromagnetic interference. The results show that, most hospitals have a lack of knowledge regarding this issue and that field levels above those allowed by international regulations are present. Therefore, a regulation must be established to avoid the problem.
基金supported by the National Basic Research Program of China(No.2005CB724506)the National Natural Science Foundation of China(Nos. 10604058 and 10974215)the Open Research Fund of State Key Laboratory of Precision Spectroscope.
文摘An experiment on measuring the magnetic field in Ramsey interaction region of the atomic fountain clock by detecting the Zeeman frequency shift of 87Rb hyperfine transition is presented.By mu-metal shielding and coils compensating,the magnetic fluctuations resulting from asymmetry and instability are less than 10 and 0.025 nT,respectively.The relative frequency uncertainty of atomic fountain clock caused by the magnetic field is less than 5.4×10-16.
基金Supported by National Key Basic Research Program of China(2015CB856701)National Natural Science Foundation of China(NSFC)(11475187,11575198,11521505)100 Talents Program of CAS(U-25)
文摘Based on cosmic ray events without a magnetic field taken with the BESIII detector during the summer shutdown of BEPCII in 2012 and di-muon events from a data sample taken at center-of-mass energy of 3.686 GeV in 2009, we compare the coordinates of hits registered in the BESIII muon counter with the expected interaction point extrapolated from reconstructed tracks from the inner tracking system in the absence of a magnetic field. By minimizing the difference, we align the muon counter with the inner tracking system. Moreover, the strength of the magnetic field in the muon counter is measured for the first time with di-muon events from data taken at a center- of-mass energy of 3.686 GeV. After the Mignment and the magnetic field strength measurement, the offsets in the reconstructed hit positions for muon tracks are reduced, which improves the muon identification. The alignment and magnetic field strength measurement have been adopted in the latest version of the BESIII offiine software system. This addition to the software reduces the systematic uncertainty for the physics analysis in cases where the muon counter information is used.
文摘Background High Energy Photon Source(HEPS)is the fourth-generation synchrotron radiation source to be established in China.HEPS is a high-performance and high-energy synchrotron radiation light source with a beam energy of 6 GeV and an ultra-low emittance of better than 0.06 nm×rad(http://english.ihep.cas.cn/heps/index.html).Superconducting 3W1 wiggler magnet is one of the insertion devices in High Energy Photon Source Test Facility project(HEPS-TF).And it is also the key component to obtain higher brightness in high photon energy range.Purpose In the development process of superconducting wiggler,in order to ensure the magnetic field quality of each processing,it is necessary to monitor the magnetic field performance of before and after the full length bare magnet installed with cryostat.Therefore,different magnetic field measuring devices are being developed for different develop stages.Methods The magnetic field performance of the full length bare magnet should be tested in vertical at low temperature.After the magnetic structure is installed in the horizontal cryostat,the horizontal test is carried out.In view of these two processes,the vertical magnetic field measurement system and the horizontal magnetic field measurement system have been developed,respectively.Results The magnetic performances of the full length bare magnet and assembled with the horizontal cryostat were measured by the vertical and horizontal magnetic field measurement system.The first and second field integrals are corrected to better than the Physical requirements according to the magnetic field measurement results.Detailed magnetic field performances are described in this paper.Conclusion After more than a year operation of 3W1-SCW on the BII line station,the characteristic energy and photon flux of synchrotron radiation have been greatly improved,and the performance is excellent.It indicates that the measurement results of the magnetic field measurement system are reliable and credible.
基金supported by the Key R&D Program of China(No.2017YFB0405503)the Youth Innovation Promotion Association of CAS(No.2016106)
文摘A novel distributed feedback(DFB) fiber laser sensor, which can measure acoustic and magnetic fields simultaneously, is proposed. The magnetic field can be measured by detecting the change of resonant frequency of the fiber laser, and the acoustic pressure can be measured by detecting the phase shift of the fiber laser. Both of the signals can be simultaneously demodulated in the frequency domain without affecting each other. Experimental studies show that the acoustic pressure sensitivity of this sensor is about-130 d B(0 dB re 1 pm∕μPa) and the sensor has a good linearity with a magnetic field sensitivity of 0.57 Hz∕mT.
基金This work was supported by the National Natural Science Foundation of China(Grant No.62075022)the Chongqing Technology Innovation and Development Project(Grant No.cstc2020jscxmsxmX0216)+1 种基金the Special Project of Science and Technology Innovation and Entrepreneurship Fund of Tiandi Technology Co.,Ltd.(Grant No.2020-TDZD007)the Science and Technology Plan Project Support of Jiulongpo District(Grant No.2020-02-004-Z).
文摘A novel fiber-optic magnetic field sensor with high interrogation speed and resolution by using an etched fiber Bragg grating(FBG)in conjunction with a dual-loop optoelectronic oscillator(OEO)is proposed and experimentally demonstrated.A commercial FBG is firstly dipped into mixed hydrofluoric acid solution to remove the cladding layer and then is embedded with the magnetic fluid(MF)as a sensing element.The central wavelength reflected from the FBG is related to the overall time delay of the dual-loop OEO,which determines the oscillating frequency of the OEO.Therefore,the magnetic field can be estimated by measuring the oscillating frequency shift of OEO.The experimental results show that the oscillating frequency linearly increases with the increment of the magnetic field,achieving the sensitivity of 16.3 Hz/Oe with a R-square of 0.991 in the range of 5 mT-10 mT.In addition,the maximum error is within±0.05 mT in the range of 7 mT-8 mT,which offers potentials in many fields where the high-precision magnetic field measurement is required.
基金the National Natural Science Foundation of China(No.10574092)the National Basic Research Program"973"of China(No.2007CB307000)the Shanghai Leading Academic Discipline Project(No.B201)
文摘The response time and transmittivity of the magnetic fluid (MF) for different concentrations at room temperature were investigated in this letter. The volume fraction of the investigated sample ranged from 0.44% to 6.47%. It was found that the transmittivity decreased with increasing concentration under a given magnetic field, and the evolution time was changed with different concentrations. Moreover the light intensity decreased rapidly at the beginning and then became stable when the magnetic field was applied.
文摘In the present paper,a method for reliable estimation of defect profile in CK45 steel structures is presented using an eddy current testing based measurement system and post-processing system based on deep learning technique.So a deep learning method is used to determine the defect characteristics in metallic structures by magnetic field C-scan images obtained by an anisotropic magneto-resistive sensor.Having designed and adjusting the deep convolution neural network and applied it to C-scan images obtained from the measurement system,the performance of deep learning method proposed is compared with conventional artificial neural network methods such as multilayer perceptron and radial basis function on a number of metallic specimens with different defects.The results confirm the superiority of the proposed method for characterizing defects compared to other classical training-oriented methods。
文摘Examples of changes in the magnitude of the <b><span style="font-family:Verdana;">B</span></b><span style="font-family:Verdana;"><span style="font-family:Verdana;"><b><span style="font-family:Verdana;">-</span></b></span></span><span><span><span style="font-family:;" "=""><span style="font-family:Verdana;">field after the heliosphere termination shock (TS) with both Voyager spacecraft (SC) are presented. The work focuses on similarities and differences in the observations at their </span><i><span style="font-family:Verdana;">in-situ</span></i><span style="font-family:Verdana;"> measurements along divergent paths. The presented results were collected where the accuracy of the magnetometer is the highest. These locations are those wherein, four to seven times during the year, the SC performs about 330 minutes of slow rotations identified in the SC language as MAGROLs. They are next reviewed, with the understanding that after the TS, at MAGROLs, the solar wind (SW) flows appear to be mostly sub-magnetosonic and compressional in this region, region named helio-sheath (HS). This is a preliminary survey that uses </span><span style="font-family:Verdana;">48 sec</span> <b><span style="font-family:Verdana;">B</span></b><span style="font-family:Verdana;">-field averages. The time-intervals in this work fill gaps in the currently available studies for longer time intervals. The present study reinforces the view that in the HS after the TS the SW is most likely strongly compressional. </span><span style="font-family:Verdana;">Further</span><span style="font-family:Verdana;"> we discuss the fact that observed fluctuation intensity-modes of the </span><b><span style="font-family:Verdana;">B</span></b><span style="font-family:Verdana;">-field in our time-ranges appear to be much more pronounced at the Voyager 2 path than at the Voyager 1 path.</span></span></span></span>
文摘Purpose A new rotating coil measurement system based on the coordinate measurement machine(CMM)is developed for measuring high-gradient small-aperture quadrupole magnet in the Test Facility of High Energy Photon Source(HEPS-TF).Methods The CMMand two groups of Newport translate stages are combined to align the rotating coil relative to the magnet mechanical center.A high precision ceramic skeleton with bucked coil is made as a measurement sensor.The integrated field gradient,harmonics,magnetic center offset and excitation curve of a high-gradient small-aperture quadrupole prototype magnet are measured.Results The rotating coil is aligned to the magnet mechanical center within 10μm.The reproducibility of higher harmonics is within 0.2×10–4.The repeatability of the magnet center in horizontal direction is under 1.5μm,while that in vertical direction is less than 2.5μm in different days.The architecture of the measurement system,the measuring procedure and some primary results of the quadrupole prototype magnet are illustrated in this paper.Conclusion A rotating coil measurement system based on CMM has been well developed,and the collimation efficiency and precision are improved.The harmonic changes caused by iron fingers are measured by the measurement system.The difference between the measurement result and the OPERA-3D simulation result is less than 0.5×10–4.The performance of this measurement system can meet the magnet measurement requirements of HEPS-TF.
文摘Purpose More undulators are required of HEPS in future.The efficiency of traditional Hall-probe measurement method is relatively low,which is difficult to meet the measurement needs of large quantities of undulators.In order to improve debugging efficiency,the pulsed-wire method is required further improvement.Methods A pulsed-wire method is an effective method to achieve magnetic field distribution through narrow aperture of undulator.The pulsed-wire method works by sending a square current pulse through the wire,which will induce an interaction with the magnetic field due to the Lorentz force.This force causes the wire to be displaced,and this displacement travels along the wire in both directions as an acoustic wave.Measurement of the displacement in the wire over time using a motion detector yields the first or second integrals of the magnetic field.Results The accuracy and repeatability are the important requirements.The repeatability of the first field integral of the pulsed-wire system is better than 1‰which meets the design requirements.Conclusions This paper illustrates the effectiveness of pulsed-wire system by test results.Through comparison,the accuracy of the system is proved.It provides a new important measurement system for undulators in future.
文摘The BEPCⅡis the upgrade project of the Beijing Electron Positron Collider(BEPC).According to the BEPCⅡdouble ring design scheme,a new ring will be added in the existing BEPC tunnel.The machine will provide electron and positron beams with an energy range from 1.0GeV to 2.1GeV for high energy physics research,and an electron beam of 2.SGeV,250mA for synchrotron radiation.So actually there are three storage rings for the BEPCⅡmachine.Due to the limited space of the existing BEPC tunnel and the requirement of high luminosity,the antechamber type vacuum chamber is used,that makes the BEPCⅡmagnets'design and fabrication very difficult.In the paper the general features of the design and fabrication of several kinds of main magnets for the BEPCⅡstorage ring and its interaction region are introduced.And the magnetic field measurement results are presented.