Description
All submissions accepted as "Poster" should provide a poster conforming to the rules published in the conference announcement and by the Local Organizing Committee.
As a recommendation the presenter should at least be present at his poster during 80% of the poster session duration.
The behavior of 1 MeV triton in KSTAR deuterium plasma is studied using triton burnup neutron (TBN) diagnostics and classical burnup calculation code. In KSTAR, TBN is measured by neutron activation system (NAS) and scintillation detectors. Shot-integrated TBN yield is evaluated by NAS with silicon sample. Two kinds of scintillation detectors, stilbene and scintillating-fiber detectors,...
Fast ion loss detector (FILD) measurements indicate intermittent bursts of losses associated with Alfvén Eigenmode (AE) induced critical-gradient transport [1]. During the current ramp phase of a DIII-D inner wall limited, oval shaped, L-mode plasma with reversed-shear magnetic safety factor profile, the total AE activity increases with neutral beam injected (NBI) power. A mix of both...
Time-resolved triton burnup studies have been carried out to estimate the behavior of alpha particles in DD fusion experimental devices. In those studies, 14 MeV neutrons emitted through DT reactions in DD plasmas should be measured selectively in the backgrounds of DD neutrons and gamma rays. For that purpose, a scintillating fiber (Sci-Fi) based fast-neutron detector has been adapted...
The aim of the study is to analyze the stability of the Energetic Particle Modes (EPM) and Alfven Eigenmodes (AE) in Helitron J and LHD plasma if the electron cyclotron current drive (ECCD) is applied. The analysis is performed using the code FAR3d that solves the reduced MHD equations describing the linear evolution of the poloidal flux and the toroidal component of the vorticity in a full 3D...
We report observation and numerical analysis of fast ion loss and Alfvenic activities driven by 3D magnetic field in KSTAR. Experimental observation in KSTAR indicates a sudden increase of fast ion prompt loss by resonant magnetic perturbation (RMP) when the applied RMP field exceeds a threshold amplitude. Full orbit simulation with 3D perturbed equilibrium computed by the ideal plasma...
In tokamak plasmas, the interaction among the microturbulence, the zonal flow (ZF) and the energetic particles (EPs) can affect the turbulence saturation level and the consequent confinement quality and thus, is important for future burning plasmas. The zonal flow residual for isotropic particles has been studied [1, 2, 3]. For tokamak plasmas, anisotropic EPs can be produced by NBI or ICRF...
Recently, spontaneous toroidal flows have been observed in electron cyclotron heating (ECH) plasma in many tokamak and helical devices such as JT-60U, LHD, and HSX. To clarify the underlying mechanism, many experimental [1] and theoretical [2] studies have been undertaken. Particularly, in LHD, when ECH was applied into the neutral beam injection (NBI) heated plasma, the radial profile of the...
Energetic particle (EP) transport in the presence of Alfvenic mode determines the EP profiles and plays a crucial role in confinement. In order to model the EP transport efficiently, mixed linear-nonlinear recipes are used in various codes [1,2,3], in which the mode structure is from linear simulation and is used in the EP transport calculation. For “perturbative” approach, the linear mode...
Neutral beam injection (NBI) is one of the trusted methods of plasma heating and is widely used in the present-day tokamaks and stelalrator experimental devices, as well as ITER. The fast ions produced by NBI generally have strongly anisotropic velocity distribution depending on the injection direction. A perpendicular NBI produces fast ions in the trapped orbit that are trapped and localized...
NBI heating is a reliable method to heat the plasma to high-temperature. Energetic beam ions are generated, and nuclear fusion occurs if we choose the deuterium as a beam ion. Many D-D fusion reaction experiments have been performed in tokamaks[1] and helicals[2]. The neutrons by D-D fusion reactions are measured to study the confinement of energetic beam ions and neutron counts are compared...
FIDASIM is a synthetic diagnostic code that simulates fast ion D-alpha (FIDA) and neutral particle analyzer (NPA) signals produced by charge exchange (CX) with neutrals. The experimental configuration and a theoretical distribution function are inputs to the code. Previously, FIDASIM only simulated CX with injected neutrals in axisymmetric devices. However, the magnitude of passive signals...
It is shown that trapped fast ions can destabilize the electron drift wave because fast ions reverse their precession direction in RS plasmas to electron diamagnetic direction and can resonate with electron drift wave.[1] A local stability analysis of this new instability is performed and consequent quasi-linear transport is calculated using gyrokinetic equations in toroidal geometry [2,3]...
A magnetic confinement fusion reactor requires the sustainment of plasma by energetic alpha particles from fusion reaction. Therefore, it is important to understand the behavior of energetic particles in the magnetic confinement device. To investigate the behavior of energetic particles, a Fast-Ion D Alpha (FIDA) diagnostic system was installed on the Large Helical Device (LHD) [1,2]. In LHD,...
Fast-ion Dα (FIDA) diagnostics has been widely employed to investigate fast-ion characteristics in many fusion devices. In KSTAR FIDA diagnostic system has been developed and the commissioning has been performed since 2018 KSTAR experimental campaign. The system consists of the grism, two tele-lens sets, blocking strip and EMCCD. A narrow neutral density filter (transmittance < 0.1%) strip was...
Recent experiments in KSTAR have exhibited the evidence of the non-diffusive avalanche-like electron heat transport events from the L-mode and the weak internal transport barrier (ITB) plasmas without magnetohydrodynamic instabilities[1]. During the events, corrugated profiles of electron temperature are observed, which suggest the existence of $E\times B$ staircase. Based on Self-Organized...
Experiments in the ASDEX Upgrade (AUG) tokamak have shown that externally applied 3D fields may be used to control Toroidally Induced Alfven Eigenmodes (TAE) in neutral beam heated discharges with elevated q-profile and low collisionality [1]. TAEs have been fully suppressed or excited in identical discharges with $n$=2 3D fields by varying their poloidal spectrum.
The non-linear hybrid...
Externally applied magnetic perturbations (MPs) are amongst the most effective tools to mitigate and suppress edge localized modes [1]. Recent experiments have highlighted that the plasma response to the externally applied 3D fields plays a key role in the ELM suppression mechanism [2,3]. In this work, we study how changes in the plasma density and rotation correlate with the orbit topology of...
The neutron and tritium production at pre-DT phase of ITER operation need to be quantified in view of the plans for commissioning and operation of the heating systems, as discussed in the ITER Research Plan (IRP) [1]. An assessment of neutron production has been carried out for the whole set of scenarios foreseen by the IRP for the pre-DT phase, Pre-Fusion Plasma Operation, (PFPO-1 and...
Spontaneous toroidal flows have been observed during ECH without direct momentum input in tokamak and helical plasmas[1-3]. In LHD, when we applied ECH to the NBI heated plasma, the toroidal velocity profile changed drastically. We assume that the radial flux of supra-thermal electron enhances the bulk ion canceling current. This current generates the JxB torque, which would play an essential...
The COMPASS Upgrade tokamak [1] will be a tokamak of major radius R0~0.894 m with high-field (Bt~5 T) and high-current (Ip~2 MA). The machine should be completed by 2022. It will be located in Prague, Czech Republic and is currently in design phase. The main auxiliary heating system used to access H-mode will be 4 MW of Neutral Beam Injection (NBI) power with an injection energy of 80 keV....
Information of confined energetic ions can be obtained by the neutron measurement because neutrons are mainly emitted from the reactions between energetic and thermal ions in current deuterium plasmas.
The large helical device (LHD) has several neutron measurement systems, and energetic-particle physics studies have been performed based on the neutron measurement.
When the deuteron velocity...
A newly developed beam emission spectroscopy (BES) diagnostic system has been installed on HL-2A tokamak. Initial 48 channels has been deployed and high spatial (Δr ≤ 1 cm, Δz ≤ 1.5 cm) and temporal (Δt = 0.5 μs) have been achieved. In last campaign, the second neutral beam line has been installed on HL-2A tokamak, providing an opportunity to utilize BES system to study the energetic particle...
Recently, a high q min scenario has been developed in KSTAR by controlling the plasma current ramp-up rate and the heating/shaping timing. An interesting finding is that a steady-state high and broad q profile has been sustained even without strong off-axis current drive scheme. Time-traces of magnetics/ECE spectrogram clearly show that Alfvenic kind activities appeared as the high/broad q...
In future tokamak reactors such as ITER and DEMO, the intermittent heat flux released by edge localized modes (ELMs) should be avoided or mitigated to low level enough to remain within heat load constraints on plasma facing components. One of the critical issues is therefore to understand nonlinear dynamics underling ELMs and resultant energy loss process. For simulation studies on impact of...
Energetic deuterons leave pronounced signatures in the neutron emission spectrum from fusion plasmas. In this work, this is exploited in order to obtain information about the properties of ICRF-accelerated deuterons using the neutron camera system at JET. By combining data from the ten horizontal, and nine vertical lines of sight, a spectroscopic analysis of each detector's pulse height...
In stellarators, low levels of plasma current induced by neutral beam injection or EC heating may cause non-negligible modifications of the plasma equilibrium and, therefore, of the shear Alfvén waves spectrum. Experiments carried out in the TJ-II stellarator [1] and other helical devices [2, 3] have addressed this issue clearly illustrating this effect.
Numerical analysis of TJ-II (B0=1 T,...
The particle transport is an important research topic for burning control in DEMO reactors. For example, the hollow density profile is often seen after pellet injection or gas-puff. In such a case, the inverted density gradient appears in the edge region which produces the particle pinch. To understand particle pinch mechanism, we have performed local gyrokinetic simulation using DEFEFI...
Advanced operation scenarios such as high poloidal beta (β$_P$) or high ${q_{min}}$ and so on are the promising concepts to achieve the steady-state high beta fusion plasmas. Those scenarios, however, are prone to excitation of the strong Alfvénic mode activities causing fast-ion transport and losses due to its fast-ion pressure gradient and broad current profile as the heating power and the...
Neutron diagnostics have played an essential role in magnetic confinement fusion, in particular, in terms of enhancement of energetic-particle (EP) physics studies. To explore a new confinement regime utilizing isotope effects and obtain deeper understanding of EP-related physics in the Large Helical Device (LHD), the deuterium operation has been conducted in LHD since March, 2017. An...
The pitch angle scattering rates of deuterium beam ions in low density, nearly MHD-quiescent plasmas are measured using an imaging neutral particle analyzer (INPA) in DIII-D. The INPA is a scintillator-based diagnostic that provides energy and radially resolved measurements of confined fast ions [1]. The main purpose of this study is to validate this novel diagnostic system during classical...
Alfvén Eigenmodes (AEs) were studied in low magnetic shear flexible heliac TJ-II (B0=1 T, <R>=1.5 m, =0.22 m). The modes were excited by hydrogen co-NBI in L-mode hydrogen plasmas (P_NBI=0.56 MW, E_NBI=32 keV), and diagnosed with Heavy Ion Beam Probe (HIBP) [1], Mirnov probes and bolometer arrays. An earlier published paper [2] shows that for any observed AE, its frequency fAE could be well...
The fast ion transport plays a key role in the simulation for developing operational scenarios. But the transport of fast ions in the perturbed field, such as a resonant magnetic perturbation or MHD, is complex compared with that of thermal ions. The transport depends on energy and pitch angle as well as a spatial coordinate. The Monte-Carlo approach can handle the transport in the straight...
Energetic ions knock the thermal ions in the higher energy range via nuclear elastic scattering (NES) [1], and create knock-on tails in ion velocity distribution functions. A large fraction of the energetic-ion energy is transferred to the bulk ion in a single NES event, and the energetic-ion slowing-down properties are affected by the collisional energy-transfer process as well as Coulomb...
The effects of trapped energetic ions(TEI) on double tearing modes (DTMs) are studied by hybrid simulation. It is shown that TEI have a stabilizing effect on DTMs for small energetic ion beta. A new energetic particle driven mode is found when energetic ion beta larger than a threshold. This mode is an ideal mode, which is a fishbone-like mode. The threshold increases with resisitivity, and...
During a disruption event a strong electric field is generated, causing supra thermal electrons to reach relativistic speeds. Due to the severe damage the runaway electrons can inflict upon ITER’s plasma facing components and cooling systems, developing strategies to both prevent the formation of and to safely dissipate the runaways is critically important to ITER’s success. However,...
In the present work, the extended hybrid MHD-gyrokinetic code (XHMGC) [1,2] with both energetic particles and thermal ions treated kinetically is used to study the frequency chirping of a single toroidal number mode. Anisotropic slowing-down distribution with single pitch angles are used to describe the energetic ion velocity space distributions, and isotropic Maxwellian distribution is used...
The mitigation of runaway electrons (RE) that may be generated in disruptions is among the key priorities for the safe operation of the ITER tokamak. The most pursued mitigation techniques are currently based on the injection of a high Z impurity in the plasma (predominantly Argon) as a way to achieve RE dissipation. Examples are experiments based on Massive Gas Injection (MGI) at the ASDEX...
For a long time, direct initial value gyrokinetic simulations of Alfvén eigenmodes with global structures in realistic tokamak conditions have proven very challenging. While MHD-kinetic hybrid models have been able to simulate these modes with varying reductions in the model, global gyrokinetic codes have struggled with electromagnetic simulations using realistic plasma beta and in realistic...
In the present work, Alfvén modes are investigated by means of simulations performed with the global, gyro-kinetic, particle-in-cell code ORB5. The obtained results are compared with the outcomes from the gyro-kinetic, non-perturbative, eigenvalue solver LIGKA.
Results of global, collisionless simulations with both analytical and experimental Tokamak magnetic equilibria are discussed....
The full abstract with figures can be found here:
https://docs.google.com/document/d/17Fvahzdj03hl4ligouFJladkZVHlq1ij7Kafp3g9kJo/edit?usp=sharing
The text of the abstract is reproduced below:
HALO : A GPU code for calculating the non-linear evolution of fast particle driven eigenmodes in Tokamaks
M. Fitzgerald (1), J. Buchanan (1), R. Akers (1), S. Sharapov (1), B. Breizman...
Magnetohydrodynamic (MHD) and energetic particle hybrid simulation code, MEGA, is applied to Heliotron J, an advanced stellarator/heliotron device with low magnetic shear, helical axis, and finite vacuum magnetic well. Due to the low magnetic shear, the global Alfvén eigenmode (n/m=2/4) has been dominantly observed, along with the energetic particle mode (n/m=1/2) in the experiment. In a...
Recently, a lot of attentions have been paid to the role of poloidal asymmetries of electrostatic potential in magnetic confined plasmas. It is known that poloidal asymmetries of the $E\times B$ plasma flow are instrumental in neoclassical transport. Nevertheless, this kind of structures are often neglected in standard neoclassical theory, since the amplitude of poloidal asymmetries is...
Enhancement of the plasma heating efficiency is one of the most important issue for magnetically confined fusion devices. In general, the plasma heating in fusion devices is achieved by the kinetic energy transfer from fast ions, which are generated by the neutral beam (NB) injection, the radio frequency waves, and the fusion reactions, to bulk plasmas through Coulomb collision. To obtain the...
A Frontier Science experiment in the DIII-D tokamak explored the compressional Alfvén eigenmodes (CAEs) and coherent ion cyclotron emission (ICE) dependence on the plasma ion species mix, magnetic field strength, and energetic ion species and their phase space distribution. The results from this experiment advance understanding of energetic ion-driven instabilities in the radiation...
Unstable Alfvén eigenmodes (AEs) can lead to frequency chirping
events and enhanced particle transport in magnetic fusion devices. Refs. [1, 2] explain the frequency sweeping events in terms of evolution of coherent structures (holes and clumps), in the energetic particles (EPs) phase-space using a perturbative method. This method implies small deviations of frequency from the initial...
Fast ion driven Alfvén instabilities are often observed to persist at sustained/steady amplitudes in experiments for 105 to 106 Alfvén times ($\tau_{Alfvén}$ = $R_0/\vee_A$). Nonlinear saturation effects and mechanisms that lead to self-organized states are important since they influence the mode intermittency and associated fast ion transport levels. Gyro-Landau fluid models (TAEFL/FAR3D)...
The two leading helical confinement devices, Wendelstein 7-X (W7-X) and the Large Helical Device (LHD) use neutral beam injection (NBI) heating to produce fast ions. The ASCOT code is now equipped to model NBI ions in both devices.
The proposed contribution compares fusion rates and NBI wall loads in the two machines. Neutron rates are only measured in LHD, which started deuterium operation...
Effects of two-fluid and ion finite Larmor radius (FLR) effects on equilibrium with flow in reduced MHD equations for high-beta toroidal plasmas are investigated numerically. Equilibrium flow plays an important role in the suppression of instability and turbulence in fusion plasmas. In the region of steep gradient in the improved confinement mode achieved by the flow shear, small scale effects...
The Energetic particle driven Interchange mode (EIC) is a mode that was observed reccently [1] in the Large Helical Device (LHD) in the presence of strong perpendicular Neutral Beam Injection (NBI). The EIC is a magnetohydrodynamic (MHD) instability with $m$/$n$=1/1 (where $m$ and $n$ are the poloidal and toroidal mode numbers respectively) that occurs in bursts and causes losses of energetic...
Toroidal Alfvén Eigenmodes (TAEs) driven by energetic ions play a critical role in the transport of the resonant energetic ions by relaxing their pressure gradient. It is important to predict the linear stability of TAE in various conditions for optimizing burning plasma scenarios. However, it requires considerable computational resources for MHD/gyrokinetic simulations to explore the diverse...
To investigate energetic runaway electron dynamics we developed a code that is solving relativistic guiding-center equations of motion. Relativistic high parallel velocities may cause the zero parallel component of the effective magnetic field, so we adopt the toroidally regularized guiding-center theory [1] to avoid that singularity. Because there is a discrepancy between the standard...
The code HYMAGYC [1] is a hybrid code suited to study the interaction between energetic particles (EPs) and Alfvénic modes. The thermal plasma is described as a single fluid by fully, resistive, linear MHD equations written in general curvilinear coordinates, while the EPs are described by nonlinear gyrokinetic Vlasov equations [2]. The code capabilities will be fully exploited: realistic...
A method is developed to analytically determine the resonance broadening function in quasilinear theory, due to either Krook or Fokker-Planck scattering collisions of marginally unstable plasma systems where discrete resonance instabilities are excited without any mode overlap. It is demonstrated that a quasilinear system that employs the calculated broadening functions reported here...
The axi-symmetric Alfvenic perturbations were observed on TFTR almost two decades ago and on JET more recently. They are global Alfven eigen-modes (GAEs) with characteristic frequency like that in cyclindrical plasmas, and the dominant poloidal mode number m=+/-1. The ellipticity of cross section is invoked to explain the splitting of the cylindrical ideal MHD Alfven continuum in a recent...
We report on the impact of anisotropy and flow to tokamak plasma configuration and stability in several different regimes.
First, we conduct a preliminary analysis of the impact of anisotropy on ITER pre-fusion power operation 5MA, B=1.8T ICRH scenarios, where a RF calculation gives the fast ion distribution function. To model ITER scenarios remapping tools are developed that iterate the...
The energy channels established during the energetic particle driven geodesic acoustic modes (EGAMs) in the Large Helical Device (LHD) plasmas are investigated using MEGA code. MEGA is a hybrid simulation code for energetic particles interacting with a magnetohydrodynamic (MHD) fluid. In the present work, both the energetic particles and bulk ions are described by the kinetic equations. A...
The controlled and reliable generation of a high-power burning plasma in ITER requires an
understanding of energetic particle (EP) dynamics and subsequent wall heat loads [1]. Detailed
studies must however include realistic 3D magnetic equilibria, which are widely thought to
worsen EP confinement; this is particularly true for the interaction between edge-localised NBI
ions and RMP fields...
