Peiyun Shi - Academia.edu (original) (raw)

Papers by Peiyun Shi

Physical Review Letters, Jan 11, 2022

Non-Maxwellian electron velocity distribution functions composed of a warm bulk population and a ... more Non-Maxwellian electron velocity distribution functions composed of a warm bulk population and a cold beam are directly measured during electron-only reconnection with a strong out-of-plane (guide) magnetic field in a laboratory plasma. Electron heating is localized to the separatrix, and the electron temperature increases continuously along the separatrix. The measured gain in enthalpy flux is 70% of the incoming Poynting flux. The electron beams are oppositely directed on either side of the X point, and their velocities are comparable to, and scale with, the electron Alfvén speed. Particle-in-cell simulations are consistent with the measurements. The experimental results are consistent with, and go beyond, recent observations in the magnetosheath.

Simulation data as appearing in the Supplementary of the paper titled "Laboratory Observatio... more Simulation data as appearing in the Supplementary of the paper titled "Laboratory Observations of Electron Heating and non-Maxwellian Distributions at the Kinetic1Scale During Electron-Only Magnetic Reconnection".

Physics of Plasmas, 2022

Using incoherent Thomson scattering, electron heating and acceleration at the electron velocity d... more Using incoherent Thomson scattering, electron heating and acceleration at the electron velocity distribution function (EVDF) level are investigated during electron-only reconnection in the PHAse Space MApping (PHASMA) facility. Reconnection arises during the merger of two kink-free flux ropes. Both push and pull type reconnection occur in a single discharge. Electron heating is localized around the separatrix, and the electron temperature increases continuously along the separatrix with distance from the X-line. The local measured gain in enthalpy flux is up to 70% of the incoming Poynting flux. Notably, non-Maxwellian EVDFs comprised of a warm bulk population and a cold beam are directly measured during the electron-only reconnection. The electron beam velocity is comparable to, and scales with, electron Alfvén speed, revealing the signature of electron acceleration caused by electron-only reconnection. The observation of oppositely directed electron beams on either side of the X-p...

MagNetUS 2021 - Day 2<br> Speaker: Peiyun Shi<br> Title: Alfvénic modes excited by th... more MagNetUS 2021 - Day 2<br> Speaker: Peiyun Shi<br> Title: Alfvénic modes excited by the kink instability in PHASMA

Physical Review Letters, 2022

Non-Maxwellian electron velocity distribution functions composed of a warm bulk population and a ... more Non-Maxwellian electron velocity distribution functions composed of a warm bulk population and a cold beam are directly measured during electron-only reconnection with a strong out-of-plane (guide) magnetic field in a laboratory plasma. Electron heating is localized to the separatrix, and the electron temperature increases continuously along the separatrix. The measured gain in enthalpy flux is 70% of the incoming Poynting flux. The electron beams are oppositely directed on either side of the X point, and their velocities are comparable to, and scale with, the electron Alfvén speed. Particle-in-cell simulations are consistent with the measurements. The experimental results are consistent with, and go beyond, recent observations in the magnetosheath.

Review of Scientific Instruments, 2021

A new incoherent Thomson scattering system measures the evolution of electron velocity distributi... more A new incoherent Thomson scattering system measures the evolution of electron velocity distribution functions perpendicular and parallel to the ambient magnetic field during kinking of a single flux rope and merging of two flux ropes through magnetic reconnection. The Thomson scattering system provides sub-millimeter spatial resolution, sufficient to diagnose the several millimeters sized magnetic reconnection electron diffusion region in the PHAse Space MAppgin experiment. Due to the relatively modest plasma density ∼1019 m-3 and electron temperature ∼1 eV, stray light suppression is critical for these measurements. Two volume Bragg gratings are used in series as a notch filter with a spectral bandwidth <0.1 nm in the collection branch. A CCD with a Gen III intensifier with peak quantum efficiency >47% is used as the detector in a 1.3 m spectrometer. Preliminary results of gun plasma electron temperature will be reported and compared with measurements obtained from a triple Langmuir probe.

Bulletin of the American Physical Society, 2020

Bulletin of the American Physical Society, 2016

Mirror with AXisymmeticity, is a tandem mirror machine with a length of˜10 meters and diameters o... more Mirror with AXisymmeticity, is a tandem mirror machine with a length of˜10 meters and diameters of 1.2 meters in the central cell and 0.3 meters in the mirror throat. In the past experiments, the plasma was generated by helicon wave launched from the west end. We obtained the blue core mode in argon discharge, however, it cannot provide sufficient plasma for hydrogen discharge, which is at least 10ˆ12cm-3 required for effective ICRF heating. Several attempts have thus been tried or under design to increase the central cell's plasma density: (1) a washer gun with aperture of 1cm has been successfully tested, and a plasma density of 10ˆ13 cm-3 was achieved in the west cell near the gun, however, the plasma is only˜10ˆ11 cm-3 in the central cell possible due to the mirror trapping and/or neutral quenching effect (2) a larger washer gun with aperture of 2.5 cm and a higher power capacitor bank are being assembled in order to generate more plasmas. In addition, how to mitigate the neutrals is under consideration (3) A hot cathode is been designed and will be tested in combination with plasma gun or alone. Preliminary results from those plasma sources will be presented and discussed.

Physics of Plasmas, 2021

Magnetic flux ropes have been successfully created with plasma guns in the newly commissioned PHA... more Magnetic flux ropes have been successfully created with plasma guns in the newly commissioned PHAse Space MApping (PHASMA) experiment. The flux ropes exhibit the expected m = 1 kink instability. The observed threshold current for the onset of this kink instability is half of the Kruskal–Shafranov current limit, consistent with predictions for the non-line tied boundary condition of PHASMA. The helicity, paramagnetism, and growth rate of the observed magnetic fluctuations are also consistent with kink instability predictions. The observed fluctuation frequency appears to be a superposition of a real frequency due to a Doppler shift of the kink mode arising from plasma flow ( ∼ 2 kHz) and a contribution from a wave mode ( ∼ 5 kHz). The dispersion of the wave mode is consistent with an Alfven wave. Distinct from most previous laboratory studies of flux ropes, the working gas in PHASMA is argon. Thus, the ion cyclotron frequency in PHASMA is quite low and the frequency of the Alfvenic mode plateaus at ∼ 0.5 of the ion gyro frequency with increasing background magnetic field strength.

2019 International Conference on Electromagnetics in Advanced Applications (ICEAA), 2019

Magnetic reconnection is a fundamental process in plasmas that can release magnetic energy via ch... more Magnetic reconnection is a fundamental process in plasmas that can release magnetic energy via changing field line topology, resulting in a variety of violent phenomena. The reconnection has been extensively studied in low temperature experiments. Field reversed configuration (FRC) is a compact toroid with closed field geometry and is being pursued as an alternative fusion concept. We propose to use collision-merging FRC to study the reconnection in high parameter regime. Preliminary results from KMAX-FRC shows the evolution of field reversed configure measured by internal probe, and burst of light emission during merging taken by fast camera.

2021 International Conference on Electromagnetics in Advanced Applications (ICEAA), 2021

A new experiment, called the PHAse Space MApping (PHASMA) experiment, features laser induced fluo... more A new experiment, called the PHAse Space MApping (PHASMA) experiment, features laser induced fluorescence diagnostics for ion measurements, Thomson scattering diagnostics for electron velocity distribution function measurements, and a microwave scattering system for turbulence measurements. PHASMA is designed to enable the direct measurement of ion and electron vdfs in space-relevant plasma phenomena including reconnection, shocks, and turbulence. To create the conditions necessary for different experimental regimes, PHASMA employs a 2 kW, steady-state helicon source capable of generating variable-density background hydrogen, helium, argon, krypton, and xenon plasmas with controllable plasma pressure (relative to the magnetic pressure), collisionality, and azimuthal flow shear. Reconnecting flux ropes arise through the merging of discharges from two pulsed plasma guns.

Review of Scientific Instruments, 2021

In the past decades, laboratory experiments have contributed significantly to the exploration of ... more In the past decades, laboratory experiments have contributed significantly to the exploration of the fundamental physics of space plasmas. Since 1908, when Birkeland invented the first terrella device, numerous experimental apparatuses have been designed and constructed for space physics investigations, and beneficial achievements have been gained using these laboratory plasma devices. In the present work, we review the initiation, development, and current status of laboratory plasma devices for space physics investigations. The notable experimental apparatuses are categorized and discussed according to the central scientific research topics they are related to, such as space plasma waves and instabilities, magnetic field generation and reconnection, and modeling of the Earth's and planetary space environments. The characteristics of each device, including the plasma configuration, plasma generation, and control method, are highlighted and described in detail. In addition, their contributions to reveal the underlying physics of space observations are also briefly discussed. For the scope of future research, various challenges are discussed, and suggestions are provided for the construction of new and enhanced devices. The objective of this work is to allow space physicists and planetary scientists to enhance their knowledge of the experimental apparatuses and the corresponding experimental techniques, thereby facilitating the combination of spacecraft observation, numerical simulation, and laboratory experiments and consequently promoting the development of space physics.

Plasma Physics and Controlled Fusion, 2019

The transient nature of magnetic reconnection dictates that it must be accompanied by rich electr... more The transient nature of magnetic reconnection dictates that it must be accompanied by rich electromagnetic wave activity, which can in turn affect the reconnection process. Interaction between Alfvén waves and reconnection has been simulated and recently observed in space. In this paper we report the first laboratory observation of a kinetic Alfvén wave (KAW) mode during reconnection in a linear device. The reconnection was measured by magnetic probes and the enhancement of light emission during reconnection was captured by a fast camera. The perpendicular wave pattern suggests it is an m =−2 mode rotating in ion diamagnetism direction. The wave data agrees with the theoretical prediction of KAW. The temporal correlation between KAW amplitude and reconnection rate indicates waves are generated by reconnection.

Physics of Plasmas, 2019

A spectrometer for high-precision ion temperature and velocity measurements in lowtemperature pla... more A spectrometer for high-precision ion temperature and velocity measurements in lowtemperature plasmas Review of Scientific Instruments 90, 063502 (2019);

Physics of Plasmas, 2019

Rayleigh–Taylor instability (RTI) is a primary hurdle for many different fusion approaches, most ... more Rayleigh–Taylor instability (RTI) is a primary hurdle for many different fusion approaches, most of which rely on external pressure to stabilize the plasma by impeding plasma displacement. In this paper, we report a novel method that utilizes a rotating magnetic field (RMF) to drive an azimuthal electron current to reduce the charge separation caused by RTI. The fluctuation measured in the central cell of the mirror device, approximately half a device length away from the RMF, is identified as the m = 1 mode and is suppressed by the RMF in the plug cell. The azimuthal electric fields of the fluctuation are found to decrease to almost zero, and the radial confinement is improved by more than a factor of ten. The separation of the RMF region from the central cell makes this stabilization method unique because the RMF, which can complicate the local magnetic field lines, has little influence on the magnetic field configuration in the central cell. This study may shed light on the use of resonant magnetic perturbations in tokamaks as well as on stabilization methods for many other fusion experiments.Rayleigh–Taylor instability (RTI) is a primary hurdle for many different fusion approaches, most of which rely on external pressure to stabilize the plasma by impeding plasma displacement. In this paper, we report a novel method that utilizes a rotating magnetic field (RMF) to drive an azimuthal electron current to reduce the charge separation caused by RTI. The fluctuation measured in the central cell of the mirror device, approximately half a device length away from the RMF, is identified as the m = 1 mode and is suppressed by the RMF in the plug cell. The azimuthal electric fields of the fluctuation are found to decrease to almost zero, and the radial confinement is improved by more than a factor of ten. The separation of the RMF region from the central cell makes this stabilization method unique because the RMF, which can complicate the local magnetic field lines, has little influence on the magnetic field configuration in the central cell. This study may shed light on the use of resonant magnetic p...

Journal of Instrumentation, 2018

This study aims to assess the Social Studies material contained in the book of integrated themati... more This study aims to assess the Social Studies material contained in the book of integrated thematic curriculum in 2013 the fourth grade of primary school. Selection of the fourth grade of primary school due to the initial implementation of integrated thematic learning in curriculum 2013 in a high-class curriculum. This study used a qualitative approach with a particular method of discourse analysis and content analysis of the data obtained through text analysis and documentation. Which is the object of this research is the book of integrated thematic curriculum fourth grade of primary school in curriculum 2013. Social Studies material is organized from the teaching materials and simple close around the child to a more extensive and complex. Depth presentation of the material in the textbook Social Studies the fourth grade of primary school thematic curriculum is associated with students' knowledge. The level of difficulty of the material adapted to the development of learners who are at the stage of "concrete-operational", giving the students in understanding the material.

Plasma Science and Technology, 2019

A series of experimental results of field-reversed configurations (FRCs) on a KMAX (Keda Mirror w... more A series of experimental results of field-reversed configurations (FRCs) on a KMAX (Keda Mirror with AXisymmetricity) tandem mirror machine are reported. Single-side FRC translation processes with three different gas species were measured by avalanche photodiodes. Consistent with the theoretical prediction, the measured FRC speeds were inversely proportional to the square root of the ion mass. However, the speeds of the hydrogen FRC increased even in a uniform magnetic field region while the speeds of the helium and argon FRCs decreased. Possible mechanisms are discussed. The speed of the second pass due to the reflection of the mirror fields was found to be ~1/3 of the first pass speed. The internal magnetic fields were measured for a colliding-merging argon FRC, and the results show that, even for very slow-moving FRCs, merging can occur.

Physics of Plasmas, 2019

Why the particle-in-cell method captures instability enhanced collisions

Physics of Plasmas, 2019

The azimuthal electric field E θ ω, which is induced by the axial oscillating magnetic field B z ... more The azimuthal electric field E θ ω, which is induced by the axial oscillating magnetic field B z ω of the odd-parity Rotating Magnetic Field (RMF) scheme, is experimentally found to play an important role in driving the toroidal plasma current. In the odd-parity RMF scheme, E θ ω at the middle plane of the field reversed configuration can generate the so-called punctuated betatron-orbital electrons to drive the toroidal current in addition to the current driven by the transverse component of RMF B r ω, whereas B r ω is the only driving mechanism in the even-parity scheme. In this work, E θ ω (or B z ω) and B r ω are each studied to account for different current driving mechanisms. We report that E θ ω accounts for the more efficient current driving in our experiments.The azimuthal electric field E θ ω, which is induced by the axial oscillating magnetic field B z ω of the odd-parity Rotating Magnetic Field (RMF) scheme, is experimentally found to play an important role in driving the toroidal plasma current. In the odd-parity RMF scheme, E θ ω at the middle plane of the field reversed configuration can generate the so-called punctuated betatron-orbital electrons to drive the toroidal current in addition to the current driven by the transverse component of RMF B r ω, whereas B r ω is the only driving mechanism in the even-parity scheme. In this work, E θ ω (or B z ω) and B r ω are each studied to account for different current driving mechanisms. We report that E θ ω accounts for the more efficient current driving in our experiments.

Review of Scientific Instruments, 2018

A Field-Reversed Configuration (FRC) is formed by an in-vessel odd-parity rotating magnetic field... more A Field-Reversed Configuration (FRC) is formed by an in-vessel odd-parity rotating magnetic field (RMF) antenna in a tandem mirror device, Keda mirror with axisymmetricity. The 40-cm diameter antenna is fed independently by four IGBT-based power units with an output current of 1500 A each at 84 kHz, and their phases are adjustable to launch odd or even parity RMFs. A medium-sized washer gun is utilized to generate a highly ionized seed hydrogen plasma. Driven by RMF, the resultant FRC is formed with a separatrix radius of ∼17 cm, external field of ∼50 G, and trapped poloidal flux of ∼0.15 mWb. The formation process of FRCs is evidenced by the measurement of an array of internal two-dimensional probes; a comparison with the rigid rotor model is presented in this paper. In addition, substantial toroidal electron current is found to be driven, despite the partial RMF penetration. Moreover, the dependence of the driven current on the antenna current is reported and is found to be consistent with the RMF current driving model.

Physical Review Letters, Jan 11, 2022

Non-Maxwellian electron velocity distribution functions composed of a warm bulk population and a ... more Non-Maxwellian electron velocity distribution functions composed of a warm bulk population and a cold beam are directly measured during electron-only reconnection with a strong out-of-plane (guide) magnetic field in a laboratory plasma. Electron heating is localized to the separatrix, and the electron temperature increases continuously along the separatrix. The measured gain in enthalpy flux is 70% of the incoming Poynting flux. The electron beams are oppositely directed on either side of the X point, and their velocities are comparable to, and scale with, the electron Alfvén speed. Particle-in-cell simulations are consistent with the measurements. The experimental results are consistent with, and go beyond, recent observations in the magnetosheath.

Simulation data as appearing in the Supplementary of the paper titled "Laboratory Observatio... more Simulation data as appearing in the Supplementary of the paper titled "Laboratory Observations of Electron Heating and non-Maxwellian Distributions at the Kinetic1Scale During Electron-Only Magnetic Reconnection".

Physics of Plasmas, 2022

Using incoherent Thomson scattering, electron heating and acceleration at the electron velocity d... more Using incoherent Thomson scattering, electron heating and acceleration at the electron velocity distribution function (EVDF) level are investigated during electron-only reconnection in the PHAse Space MApping (PHASMA) facility. Reconnection arises during the merger of two kink-free flux ropes. Both push and pull type reconnection occur in a single discharge. Electron heating is localized around the separatrix, and the electron temperature increases continuously along the separatrix with distance from the X-line. The local measured gain in enthalpy flux is up to 70% of the incoming Poynting flux. Notably, non-Maxwellian EVDFs comprised of a warm bulk population and a cold beam are directly measured during the electron-only reconnection. The electron beam velocity is comparable to, and scales with, electron Alfvén speed, revealing the signature of electron acceleration caused by electron-only reconnection. The observation of oppositely directed electron beams on either side of the X-p...

MagNetUS 2021 - Day 2<br> Speaker: Peiyun Shi<br> Title: Alfvénic modes excited by th... more MagNetUS 2021 - Day 2<br> Speaker: Peiyun Shi<br> Title: Alfvénic modes excited by the kink instability in PHASMA

Physical Review Letters, 2022

Non-Maxwellian electron velocity distribution functions composed of a warm bulk population and a ... more Non-Maxwellian electron velocity distribution functions composed of a warm bulk population and a cold beam are directly measured during electron-only reconnection with a strong out-of-plane (guide) magnetic field in a laboratory plasma. Electron heating is localized to the separatrix, and the electron temperature increases continuously along the separatrix. The measured gain in enthalpy flux is 70% of the incoming Poynting flux. The electron beams are oppositely directed on either side of the X point, and their velocities are comparable to, and scale with, the electron Alfvén speed. Particle-in-cell simulations are consistent with the measurements. The experimental results are consistent with, and go beyond, recent observations in the magnetosheath.

Review of Scientific Instruments, 2021

A new incoherent Thomson scattering system measures the evolution of electron velocity distributi... more A new incoherent Thomson scattering system measures the evolution of electron velocity distribution functions perpendicular and parallel to the ambient magnetic field during kinking of a single flux rope and merging of two flux ropes through magnetic reconnection. The Thomson scattering system provides sub-millimeter spatial resolution, sufficient to diagnose the several millimeters sized magnetic reconnection electron diffusion region in the PHAse Space MAppgin experiment. Due to the relatively modest plasma density ∼1019 m-3 and electron temperature ∼1 eV, stray light suppression is critical for these measurements. Two volume Bragg gratings are used in series as a notch filter with a spectral bandwidth <0.1 nm in the collection branch. A CCD with a Gen III intensifier with peak quantum efficiency >47% is used as the detector in a 1.3 m spectrometer. Preliminary results of gun plasma electron temperature will be reported and compared with measurements obtained from a triple Langmuir probe.

Bulletin of the American Physical Society, 2020

Bulletin of the American Physical Society, 2016

Mirror with AXisymmeticity, is a tandem mirror machine with a length of˜10 meters and diameters o... more Mirror with AXisymmeticity, is a tandem mirror machine with a length of˜10 meters and diameters of 1.2 meters in the central cell and 0.3 meters in the mirror throat. In the past experiments, the plasma was generated by helicon wave launched from the west end. We obtained the blue core mode in argon discharge, however, it cannot provide sufficient plasma for hydrogen discharge, which is at least 10ˆ12cm-3 required for effective ICRF heating. Several attempts have thus been tried or under design to increase the central cell's plasma density: (1) a washer gun with aperture of 1cm has been successfully tested, and a plasma density of 10ˆ13 cm-3 was achieved in the west cell near the gun, however, the plasma is only˜10ˆ11 cm-3 in the central cell possible due to the mirror trapping and/or neutral quenching effect (2) a larger washer gun with aperture of 2.5 cm and a higher power capacitor bank are being assembled in order to generate more plasmas. In addition, how to mitigate the neutrals is under consideration (3) A hot cathode is been designed and will be tested in combination with plasma gun or alone. Preliminary results from those plasma sources will be presented and discussed.

Physics of Plasmas, 2021

Magnetic flux ropes have been successfully created with plasma guns in the newly commissioned PHA... more Magnetic flux ropes have been successfully created with plasma guns in the newly commissioned PHAse Space MApping (PHASMA) experiment. The flux ropes exhibit the expected m = 1 kink instability. The observed threshold current for the onset of this kink instability is half of the Kruskal–Shafranov current limit, consistent with predictions for the non-line tied boundary condition of PHASMA. The helicity, paramagnetism, and growth rate of the observed magnetic fluctuations are also consistent with kink instability predictions. The observed fluctuation frequency appears to be a superposition of a real frequency due to a Doppler shift of the kink mode arising from plasma flow ( ∼ 2 kHz) and a contribution from a wave mode ( ∼ 5 kHz). The dispersion of the wave mode is consistent with an Alfven wave. Distinct from most previous laboratory studies of flux ropes, the working gas in PHASMA is argon. Thus, the ion cyclotron frequency in PHASMA is quite low and the frequency of the Alfvenic mode plateaus at ∼ 0.5 of the ion gyro frequency with increasing background magnetic field strength.

2019 International Conference on Electromagnetics in Advanced Applications (ICEAA), 2019

Magnetic reconnection is a fundamental process in plasmas that can release magnetic energy via ch... more Magnetic reconnection is a fundamental process in plasmas that can release magnetic energy via changing field line topology, resulting in a variety of violent phenomena. The reconnection has been extensively studied in low temperature experiments. Field reversed configuration (FRC) is a compact toroid with closed field geometry and is being pursued as an alternative fusion concept. We propose to use collision-merging FRC to study the reconnection in high parameter regime. Preliminary results from KMAX-FRC shows the evolution of field reversed configure measured by internal probe, and burst of light emission during merging taken by fast camera.

2021 International Conference on Electromagnetics in Advanced Applications (ICEAA), 2021

A new experiment, called the PHAse Space MApping (PHASMA) experiment, features laser induced fluo... more A new experiment, called the PHAse Space MApping (PHASMA) experiment, features laser induced fluorescence diagnostics for ion measurements, Thomson scattering diagnostics for electron velocity distribution function measurements, and a microwave scattering system for turbulence measurements. PHASMA is designed to enable the direct measurement of ion and electron vdfs in space-relevant plasma phenomena including reconnection, shocks, and turbulence. To create the conditions necessary for different experimental regimes, PHASMA employs a 2 kW, steady-state helicon source capable of generating variable-density background hydrogen, helium, argon, krypton, and xenon plasmas with controllable plasma pressure (relative to the magnetic pressure), collisionality, and azimuthal flow shear. Reconnecting flux ropes arise through the merging of discharges from two pulsed plasma guns.

Review of Scientific Instruments, 2021

In the past decades, laboratory experiments have contributed significantly to the exploration of ... more In the past decades, laboratory experiments have contributed significantly to the exploration of the fundamental physics of space plasmas. Since 1908, when Birkeland invented the first terrella device, numerous experimental apparatuses have been designed and constructed for space physics investigations, and beneficial achievements have been gained using these laboratory plasma devices. In the present work, we review the initiation, development, and current status of laboratory plasma devices for space physics investigations. The notable experimental apparatuses are categorized and discussed according to the central scientific research topics they are related to, such as space plasma waves and instabilities, magnetic field generation and reconnection, and modeling of the Earth's and planetary space environments. The characteristics of each device, including the plasma configuration, plasma generation, and control method, are highlighted and described in detail. In addition, their contributions to reveal the underlying physics of space observations are also briefly discussed. For the scope of future research, various challenges are discussed, and suggestions are provided for the construction of new and enhanced devices. The objective of this work is to allow space physicists and planetary scientists to enhance their knowledge of the experimental apparatuses and the corresponding experimental techniques, thereby facilitating the combination of spacecraft observation, numerical simulation, and laboratory experiments and consequently promoting the development of space physics.

Plasma Physics and Controlled Fusion, 2019

The transient nature of magnetic reconnection dictates that it must be accompanied by rich electr... more The transient nature of magnetic reconnection dictates that it must be accompanied by rich electromagnetic wave activity, which can in turn affect the reconnection process. Interaction between Alfvén waves and reconnection has been simulated and recently observed in space. In this paper we report the first laboratory observation of a kinetic Alfvén wave (KAW) mode during reconnection in a linear device. The reconnection was measured by magnetic probes and the enhancement of light emission during reconnection was captured by a fast camera. The perpendicular wave pattern suggests it is an m =−2 mode rotating in ion diamagnetism direction. The wave data agrees with the theoretical prediction of KAW. The temporal correlation between KAW amplitude and reconnection rate indicates waves are generated by reconnection.

Physics of Plasmas, 2019

A spectrometer for high-precision ion temperature and velocity measurements in lowtemperature pla... more A spectrometer for high-precision ion temperature and velocity measurements in lowtemperature plasmas Review of Scientific Instruments 90, 063502 (2019);

Physics of Plasmas, 2019

Rayleigh–Taylor instability (RTI) is a primary hurdle for many different fusion approaches, most ... more Rayleigh–Taylor instability (RTI) is a primary hurdle for many different fusion approaches, most of which rely on external pressure to stabilize the plasma by impeding plasma displacement. In this paper, we report a novel method that utilizes a rotating magnetic field (RMF) to drive an azimuthal electron current to reduce the charge separation caused by RTI. The fluctuation measured in the central cell of the mirror device, approximately half a device length away from the RMF, is identified as the m = 1 mode and is suppressed by the RMF in the plug cell. The azimuthal electric fields of the fluctuation are found to decrease to almost zero, and the radial confinement is improved by more than a factor of ten. The separation of the RMF region from the central cell makes this stabilization method unique because the RMF, which can complicate the local magnetic field lines, has little influence on the magnetic field configuration in the central cell. This study may shed light on the use of resonant magnetic perturbations in tokamaks as well as on stabilization methods for many other fusion experiments.Rayleigh–Taylor instability (RTI) is a primary hurdle for many different fusion approaches, most of which rely on external pressure to stabilize the plasma by impeding plasma displacement. In this paper, we report a novel method that utilizes a rotating magnetic field (RMF) to drive an azimuthal electron current to reduce the charge separation caused by RTI. The fluctuation measured in the central cell of the mirror device, approximately half a device length away from the RMF, is identified as the m = 1 mode and is suppressed by the RMF in the plug cell. The azimuthal electric fields of the fluctuation are found to decrease to almost zero, and the radial confinement is improved by more than a factor of ten. The separation of the RMF region from the central cell makes this stabilization method unique because the RMF, which can complicate the local magnetic field lines, has little influence on the magnetic field configuration in the central cell. This study may shed light on the use of resonant magnetic p...

Journal of Instrumentation, 2018

This study aims to assess the Social Studies material contained in the book of integrated themati... more This study aims to assess the Social Studies material contained in the book of integrated thematic curriculum in 2013 the fourth grade of primary school. Selection of the fourth grade of primary school due to the initial implementation of integrated thematic learning in curriculum 2013 in a high-class curriculum. This study used a qualitative approach with a particular method of discourse analysis and content analysis of the data obtained through text analysis and documentation. Which is the object of this research is the book of integrated thematic curriculum fourth grade of primary school in curriculum 2013. Social Studies material is organized from the teaching materials and simple close around the child to a more extensive and complex. Depth presentation of the material in the textbook Social Studies the fourth grade of primary school thematic curriculum is associated with students' knowledge. The level of difficulty of the material adapted to the development of learners who are at the stage of "concrete-operational", giving the students in understanding the material.

Plasma Science and Technology, 2019

A series of experimental results of field-reversed configurations (FRCs) on a KMAX (Keda Mirror w... more A series of experimental results of field-reversed configurations (FRCs) on a KMAX (Keda Mirror with AXisymmetricity) tandem mirror machine are reported. Single-side FRC translation processes with three different gas species were measured by avalanche photodiodes. Consistent with the theoretical prediction, the measured FRC speeds were inversely proportional to the square root of the ion mass. However, the speeds of the hydrogen FRC increased even in a uniform magnetic field region while the speeds of the helium and argon FRCs decreased. Possible mechanisms are discussed. The speed of the second pass due to the reflection of the mirror fields was found to be ~1/3 of the first pass speed. The internal magnetic fields were measured for a colliding-merging argon FRC, and the results show that, even for very slow-moving FRCs, merging can occur.

Physics of Plasmas, 2019

Why the particle-in-cell method captures instability enhanced collisions

Physics of Plasmas, 2019

The azimuthal electric field E θ ω, which is induced by the axial oscillating magnetic field B z ... more The azimuthal electric field E θ ω, which is induced by the axial oscillating magnetic field B z ω of the odd-parity Rotating Magnetic Field (RMF) scheme, is experimentally found to play an important role in driving the toroidal plasma current. In the odd-parity RMF scheme, E θ ω at the middle plane of the field reversed configuration can generate the so-called punctuated betatron-orbital electrons to drive the toroidal current in addition to the current driven by the transverse component of RMF B r ω, whereas B r ω is the only driving mechanism in the even-parity scheme. In this work, E θ ω (or B z ω) and B r ω are each studied to account for different current driving mechanisms. We report that E θ ω accounts for the more efficient current driving in our experiments.The azimuthal electric field E θ ω, which is induced by the axial oscillating magnetic field B z ω of the odd-parity Rotating Magnetic Field (RMF) scheme, is experimentally found to play an important role in driving the toroidal plasma current. In the odd-parity RMF scheme, E θ ω at the middle plane of the field reversed configuration can generate the so-called punctuated betatron-orbital electrons to drive the toroidal current in addition to the current driven by the transverse component of RMF B r ω, whereas B r ω is the only driving mechanism in the even-parity scheme. In this work, E θ ω (or B z ω) and B r ω are each studied to account for different current driving mechanisms. We report that E θ ω accounts for the more efficient current driving in our experiments.

Review of Scientific Instruments, 2018

A Field-Reversed Configuration (FRC) is formed by an in-vessel odd-parity rotating magnetic field... more A Field-Reversed Configuration (FRC) is formed by an in-vessel odd-parity rotating magnetic field (RMF) antenna in a tandem mirror device, Keda mirror with axisymmetricity. The 40-cm diameter antenna is fed independently by four IGBT-based power units with an output current of 1500 A each at 84 kHz, and their phases are adjustable to launch odd or even parity RMFs. A medium-sized washer gun is utilized to generate a highly ionized seed hydrogen plasma. Driven by RMF, the resultant FRC is formed with a separatrix radius of ∼17 cm, external field of ∼50 G, and trapped poloidal flux of ∼0.15 mWb. The formation process of FRCs is evidenced by the measurement of an array of internal two-dimensional probes; a comparison with the rigid rotor model is presented in this paper. In addition, substantial toroidal electron current is found to be driven, despite the partial RMF penetration. Moreover, the dependence of the driven current on the antenna current is reported and is found to be consistent with the RMF current driving model.