Pulsed High Magnetic Field Facility Research Articles

Realisation of the reconfigurable pulsed high magnetic field facility and its scientific application at Wuhan National Pulsed High Magnetic Field Centre

AbstractTo generate arbitrary shape magnetic field waveforms for advanced scientific research, a reconfigurable pulsed high magnetic field facility (PHMFF) was developed at Wuhan National Pulsed High Magnetic Field Centre (WHMFC). First, the basic elements of PHMFF are introduced, and a ternary physical model composed of energy storage unit, magnet, transmission circuits and other auxiliary units is summarised to describe various magnetic field systems. Second, in order to realise the reconfiguration of magnetic field systems based on detailed elements, the control system with the ability of dynamic construction and control sequence reconfiguration is designed. On this basis, the PHMFF has been realised and various magnetic field systems are constructed to produce arbitrary shape magnetic field waveforms, such as half‐sine, ultra‐high, flat‐top and repetitive field pulses, which not only enhances the capability and efficiency of PHMFF, but also makes more scientific research possible in pulsed magnetic fields. So far, a peak magnetic field of 94.8 T, a flat‐top magnetic field of 64 T/10 ms and a repetitive magnetic field waveform of 20 T/60 Hz have been achieved, and some experiments and studies on the physical properties of materials have been carried out at WHMFC.

Reliability Analysis of a Pulsed High Magnetic Field Facility at WHMFC

To accurately evaluate the reliability of Pulsed High Magnetic Field Facility (PHMFF) at the Wuhan National Pulsed High Magnetic Field Centre (WHMFC), a reliability analysis method based on a Markov chain is introduced in this paper. Because PHMFF is developed to generate a pulsed high magnetic field for scientific experiments by dynamically constructing diversified magnetic field systems, the reliability of PHMFF is in fact determined by the actual operating magnetic field system. Considering that all magnetic field systems are composed of pulsed power modules, magnets, control modules and experimental test systems, in this paper, the reliability of these critical modules is first discussed. In the analysis of modules, the failure mode and effect analysis (FMEA) method is used to determine the main failure modes, and then a Markov chain is established to analyze and calculate the reliability of the modules. Finally, based on the reliability of critical modules, the reliability of two typical magnetic field systems was estimated according to the reliability block diagram. The calculation results show that the reliability of all modules is above 95%, and although in complex magnetic field systems, the reliability still meets the experimental requirements.

A pulsed high magnetic field facility for electric polarization measurements

<sec>Multiferroic materials, which exhibit the coexistence of ferromagnetic, ferroelectric, or ferroelastic orders, are of particular interest for not only fundamental physics but also potential applications. An important physical property of multiferroic materials, especially those with magnetically driven ferroelectricity, is known as a strong magnetoelectric coupling between the magnetic order and the ferroelectric order. The external magnetic fields can directly interact with spins or magnetic moments of the materials and lead the spontaneous ferroelectricity to be suppressed, and in some cases result in field-induced ferroelectricity in a higher field. Depending on the exchange interactions, these ferroelectric phase transitions may take place in a critical magnetic field as high as several tens of tesla. The standard electric-polarization measurement based on a commercial PPMS system is limited by the strength of the static field consequently. As an extremely experimental condition, pulsed magnetic fields can be used to reveal new physical phenomena in multiferroic materials. Due to the short pulse duration and the effect of eddy current, this measurement technique under pulsed high magnetic fields is still a challenge to date although a few laboratories have developed it in recent years.</sec><sec>Wuhan National High Magnetic Field Center (WHMFC) of China is a newly built pulsed-field laboratory. This experimental station is equipped with the many measuring instruments such as for measuring electric transport, magnetization, electron spin resonance, magneto-optics, and high pressure, which were established after the national assessment at the end of 2014. Recently, using a pyroelectric technique we successfully constructed an electric-polarization measurement system based on the large-scaled facility at the WHMFC. The nondestructive magnet driven by discharging a 1.25 MJ capacitor bank can generate a pulsed field up to 60 T. By tuning the charging energy and voltages, the pulse duration time can be modulated from 4.3 ms to 10.8 ms. A helium-3 cryogenic system equipped on this facility can achieve a lowest temperature down to 0.5 K. A high-precision rotation probe is designed and fabricated with angle varying from –5° to 185° for an angular-dependent study. The pyroelectric current is detected by a shunt resistor of 10 kΩ and the electric polarization is derived by integrating the pyroelectric current over the time. The resulting data have a good accuracy and quality which are helpful in detecting weak ferroelectric phase transitions induced by pulsed fields with a fast field sweep rate. In this paper, we introduce this measurement system in detail including the method, principle and its advantages in comparison with those in static fields. Recent study and progress of magnetoelectric multiferroic materials under high magnetic fields are also reported.</sec>

Implementation of an Advanced Control and Data Acquisition System for the 100 T Pulsed Magnet at WHMFC

The 100 T pulsed magnetic field project is under development at the Wuhan National High Magnetic Field Center, Wuhan, China. Using the NI CompactRIO hardware and LabVIEW software platforms, a control and data acquisition system (CADAS) for the 100 T pulsed high magnetic field facility is designed and implemented. This paper briefly introduces the design of the control system and presents the aspects of the implementation. The CADAS developed in this paper communicates with three types of power supply systems and controls their discharge coordinately, and records discharge waveforms. It has been put into test, and 67.6 T pulsed magnetic field has been generated by a test three-coil magnet.

Analysis and design of a control system for the 100T pulsed high magnetic field facility at WHMFC

A pulsed high magnetic field of 90.6 T has been achieved by discharging the energy in a capacitor bank to a nondestructive magnet at Wuhan National High Magnetic Field Center (WHMFC), and recently, the project for a 100-T magnetic field has been under development. The pulsed magnet with a 100-T magnetic field will be composed of three coils, which are driven by three types of power sources. Based on the existing control subsystems of these power sources, the design of the control system that can control different types of power supplies to discharge would be taken into consideration for the implementation of the 100-T magnetic field. This paper first analyzes the control process for the 100-T system, which can divided into three stages, and the time requirement for each stage. Based on the analysis, the structure and main functions of the control system are discussed, and then the main control program and the global control block are designed. To protect the safety of the system, some protection measures are finally discussed. This paper provides design bases for the realization of the control system.

Short and Long Pulse High Magnetic Field Facility at the Wuhan National High Magnetic Field Center

The pulsed high magnetic field facility funded by the Chinese National Development and Reformation Committee has been developed at the Wuhan National High Magnetic Field Center (WHMFC). Magnets of short pulse, long pulse and the combination of both with bore sizes from 12 to 34 mm have been developed and are operational for electric transport, magnetization, magneto-optics and electron spin resonance at temperatures in the range from 100 mK to 350 K. The power supplies for these magnets consist of a capacitor bank with 12 modules of 1 MJ/25 kV each and 2 modules of 0.8 MJ/25 kV each, a 100 MVA/100 MJ flywheel pulse generator and a 771 V/180 kAh battery bank. A dual-coil magnet driven by the capacitor banks has successfully generated 86.3 T field with a total pulse duration over 350 ms in a 12-mm bore. A dual-coil long pulse magnet wound from soft copper wire energized by the flywheel generator produces 50 T peak field with a 100 ms flat-top and a total 1.1 s pulse duration in a 22 mm bore. A battery bank driven long pulse magnet composed by the series connection of two nested coils generates 32 T peak field with the pulse duration of 1.5 s in a 21-mm bore.

Safety Analysis and Protection Measures of the Control System of the Pulsed High Magnetic Field Facility in WHMFC

A Pulsed High Magnetic Field Facility (PHMFF) has been established in Wuhan National High Magnetic Field Center (WHMFC) and various protection measures are applied in its control system. In order to improve the reliability and robustness of the control system, the safety analysis of the PHMFF is carried out based on Fault Tree Analysis (FTA) technique. The function and realization of 5 protection systems, which include sequence experiment operation system, safety assistant system, emergency stop system, fault detecting and processing system and accident isolating protection system, are given. The tests and operation indicate that these measures improve the safety of the facility and ensure the safety of people.

Design and Realization of the Control and Measurement System of the Long Pulsed High Magnetic Field Facility Supplied by Battery

A Control and Measurement System (CMS) is designed to ensure the reliable operation in the long pulsed high magnetic field facility supplied by lead-acid batteries. The CMS is mainly composed of a Programmable Logic Controller (PLC), a fault monitor and protection circuit, a signal processing and data acquisition unit, a local triggering sequence generator and the main control program. The system architecture and kernel parts of the CMS are analyzed and described in detail. The results prove that the designed CMS could perform efficiently and reliably.

Function Design and Implementation of a Central Control System of a Pulsed High Magnetic Field Facility

A user-friendly Central Control System (CCS) for the pulsed high magnetic field facility has been designed and implemented at the Wuhan National High Magnetic Field Center (WHMFC). The CCS is composed of the server, the Human Machine Interface (HMI) and the configuration tool. The controlled objects and functions of the CCS are introduced first, and then the design and implementation of key functions are given. The CCS is developed on basis of a client/server mode, so multiple users can use the system simultaneously. To achieve higher pulsed magnetic fields, a synchronous trigger sequence is used, which can trigger up to 13 power modules to be discharged into a magnet with multiple coils. Benefiting from component technology and the TCP/IP communication protocol, the CCS can monitor signals in real time and receive experimental data from recording devices running on different platforms. The test results show that the CCS meets the requirements of experiments and simplifies the control operation.

Design of a Program-Controlled Precise Synchronous Triggering System Applied to Pulsed High Magnetic Field Facility

Recently, a Program-controlled Synchronous Triggering System (PSTS) is developed at Wuhan National High Magnetic Field Center. The designed system could generate triggering signal for thirteen power modules and eight magnets distributed in different experiment stations. By generating precise and synchronous triggering signals required for the facility, the multiple power modules could be discharged synchronously or in a preset time sequence. The PSTS is composed of triggering signal generator, fiber converter, expanded cell, and local sequence generator. The triggering signal generator, isolated from local device, is applied for sequential control of multi-module in the facility. The signal transmission is realized by optical fiber. A Digital Signal Processor (DSP) with specific type of TMS320F2812 is employed to design the triggering signal generator. The parameters of triggering channels and time-delay with the accuracy of 1 us could be configured through human machine interface. Local sequence generator unit is integrated in the local control unit on the basis of a Complex Programmable Logic Device (CPLD) with specific type of EPM7128. Local sequence generator is responsible for producing the time sequence signals to control and record the waveform of each power module, as well as the triggering signal waveform modulation for thyristor through expanded cell. Based on the designed system, the pulsed high magnetic field facility could be operated effectively. The test result illustrates that the system is of high performance.

A Software Approach for Real-Time Control of Operation and Experiments at the WHMFC Pulsed High Magnetic Field Facility

A newly developed Control Software System (CSS) designed to control and monitor the operation of the magnets and the experiments at the Wuhan High Magnetic Field Center (WHMFC) pulsed high magnetic field facility is described. The CSS implements the functions of status evaluation and experiment process control in real time as well as the functions of system structure configuration and data management off-line. Using software architecture based on component-oriented technology, scenarios about control flow rebuilding, interfacing with local control hardware, synchronous triggering and transfer of the results of measurements are discussed in detail. Hardware simulator design and human machine interface of the CSS are described as well. The test results show that the entire operation process is perfectly handled by the CSS which provides an integrated platform for scientific experiments and research.

Development of an Optical Digitized Local Control and Measurement System Applied to Pulsed High Magnetic Field Facility

A reliable controlling and measuring system in a pulsed high magnetic field facility is important for efficient operation. To control and monitor the status of switches, relays and thyristors, an optical digitized local controlling and measuring system (LCMS) was applied in Wuhan High Magnetic Field. On the basis of a digital signal processor (DSP) with specific type of TMS320F2812, LCMS receives and executes the commands including setting parameters, charging, dumping and discharging issued from the Human-Machine Interface (HMI) at the control room. Meanwhile, a fiber optic transmission system is needed to provide galvanic isolation. The discharge current and voltage of capacitor bank are measured by Rogowski coil and resistance divider respectively. The whole system test shows that the designed system is effective and reliable.

Prototype Test and Manufacture of a Modular 12.5 MJ Capacitive Pulsed Power Supply

A new Pulsed High Magnetic Field Facility (PHMFF) is under construction at the Huazhong University of Science and Technology (HUST) in Wuhan, China. In order to provide a wide spectrum range, a modular capacitive pulsed power supply is designed to energize 12.5 MJ at 25 kV and a large variety of coils are designed for magnetic fields in the 50-80 T with pulse duration 15-200 ms, respectively. In order to energize multi-coil systems, the 12.5 MJ power supply is divided into 11 independent 1 MJ modules with a short circuit current of 44.7 kA each and 2 independent 0.75 MJ modules for 61.2 kA each. Each module is provided with its own protection inductor, thyristor switch, crowbar circuit, dump circuit, polarity-changing circuit, charging unit and switchgear. The current pulses can be modified in shape, amplitude and duration by varying the charging voltage, the number of modules and the crowbar resistors. For verifying the design scheme and gaining experience in the construction and operation of pulsed power supply, a 1 MJ prototype that is used to energize pulsed magnets for 50-72 T fields with reversible polarity has been developed. In this paper, after the introduction of the system configuration with different module types and system settings, the design of both the 1 MJ and 0.75 MJ modules is described in detail. Finally, test results of the 1 MJ prototype are presented.

Design of Power Supplies for the Pulsed High Magnetic Field Facility at HUST

Two types of pulsed power supply, a modular 12 MJ/25 kV capacitor bank and a 100 MVA flywheel pulsed generator, are under construction for the pulsed high magnetic field facility at the Huazhong University of Science and Technology (HUST) in Wuhan, China. The capacitor bank consists of 11 independent 1 MJ modules with a short circuit current of 40 kA each and 2 independent 0.5 MJ modules for 50 kA each. The bank is used to energize coils for magnetic fields in the 50–80 T range with pulse duration from 15 to 200 ms. The pulsed flywheel-alternator is used to energize a 50 T/100 ms long-pulse magnet via two 12-pulse power converter modules. Each converter module is designed to operate in the 95 to 66 Hz frequency operation range of the generator and can provide a no-load voltage of 4.6 kV and a full-load voltage of 3.4 kV at the rated current of 20 kA. In this paper the design of these two types of power supply is presented.

Pulsed high magnetic field facility at Osaka University

The High Magnetic Field Laboratory of the Research Center for Extreme Materials, Osaka University, is described. In the laboratory, various types of non-destructive high field pulse magnets made of maraging steel have been developed to produce fields up to 80T with a pulse duration of 0.5 ms. Magnets having longer pulse durations of order 0.1 s are also installed, these are mainly used for the measurement of conductive metallic samples and for the microwave ESR experiment. Another long-pulse magnet with a pulse duration of 1 s is used for a high sensitivity magnetometer. Various experiments using these magnets are surveyed.