scholarly journals Analytic stability boundaries for compressional and global Alfvén eigenmodes driven by fast ions. II. Interaction via Landau resonance

2020 ◽  
Vol 27 (2) ◽  
pp. 022512 ◽  
Author(s):  
J. B. Lestz ◽  
N. N. Gorelenkov ◽  
E. V. Belova ◽  
S. X. Tang ◽  
N. A. Crocker
Keyword(s):  
Stability Boundaries ◽  
Fast Ions ◽  
Alfven Eigenmodes ◽  
Analytic Stability

scholarly journals Analytic stability boundaries for compressional and global Alfvén eigenmodes driven by fast ions. I. Interaction via ordinary and anomalous cyclotron resonances

2020 ◽  
Vol 27 (2) ◽  
pp. 022513 ◽  
Author(s):  
J. B. Lestz ◽  
N. N. Gorelenkov ◽  
E. V. Belova ◽  
S. X. Tang ◽  
N. A. Crocker
Keyword(s):  
Stability Boundaries ◽  
Fast Ions ◽  
Alfven Eigenmodes ◽  
Analytic Stability

scholarly journals Global gyrokinetic particle simulation of toroidal Alfvén eigenmodes excited by antenna and fast ions

2012 ◽  
Vol 19 (2) ◽  
pp. 022507 ◽  
Author(s):  
Wenlu Zhang ◽  
Ihor Holod ◽  
Zhihong Lin ◽  
Yong Xiao
Keyword(s):  
Particle Simulation ◽  
Fast Ions ◽  
Alfven Eigenmodes

Alfvén cascade eigenmodes above the TAE-frequency and localization of Alfvén modes in D- 3 He plasmas on JET

2021 ◽  
Author(s):  
Mykola Dreval ◽  
Sergei E Sharapov ◽  
Yevgen Kazakov ◽  
Jozef Ongena ◽  
Massimo Nocente ◽  
...  
Keyword(s):  
High Frequency ◽  
Low Frequency ◽  
High Energy ◽  
Negative Ion ◽  
Energetic Ions ◽  
Fast Ions ◽  
Alfven Eigenmodes ◽  
Different Types ◽  
Central Regions ◽  
High Frequency Ac

Abstract Various types of Alfvén Eigenmodes (AEs) have been destabilized by fast ions over a broad frequency range from ~80 kHz to ~700 kHz in a series of JET experiments in mixed D-3He plasmas heated with the three-ion ICRF scenario [M. Nocente et al., Nucl. Fusion 60, 124006 (2020)]. In this paper, we identify the radial localization of AEs using an X-mode reflectometer, a multiline interferometer and soft X-ray diagnostics. The analysis is focused on the most representative example of these measurements in JET pulse #95691, where two different types of Alfvén cascade (AC) eigenmodes were observed. These modes originate from the presence of a local minimum of the safety factor qmin. In addition to ACs with frequencies below the frequency of toroidal Alfvén eigenmodes (TAEs), ACs with frequencies above the TAE frequency were destabilized by energetic ions. Both low- (f ≈80-180 kHz) and high-frequency (f ≈ 330-450 kHz) ACs were localized in the central regions of the plasma. The characteristics of the high-frequency ACs are investigated in detail numerically using HELENA, CSCAS and MISHKA codes. The resonant conditions for the mode excitation are found to be determined by passing ions of rather high energy of several hundred keV and similar to those established in JT-60U with negative-ion-based NBI [M. Takechi et al., Phys. Plasmas 12, 082509 (2005)]. The computed radial mode structure is found to be consistent with the experimental measurements. In contrast to low-frequency ACs observed most often, the frequency of the high-frequency ACs decreases with time as the value of qmin decreases. This feature is in a qualitative agreement with the analytical model of the high-frequency ACs in [B.N. Breizman et al., Phys. Plasmas 10 3649 (2003)]. The high-frequency AC could be highly relevant for future ITER and fusion reactor plasmas dominated by ~ MeV energetic ions, including a significant population of passing fast ions.

Effect of toroidal Alfvén eigenmodes on fast particle confinement in the spherical tokamak Globus-M

2015 ◽  
Vol 81 (6) ◽  
Author(s):  
Yu. V. Petrov ◽  
N. N. Bakharev ◽  
V. K. Gusev ◽  
V. B. Minaev ◽  
V. A. Kornev ◽  
...  
Keyword(s):  
Neutral Particle ◽  
Magnetic Measurements ◽  
Early Stage ◽  
High Energy ◽  
Plasma Phys ◽  
Fast Particle ◽  
Fast Ions ◽  
Target Plasma ◽  
Alfven Eigenmodes ◽  
Particle Confinement

In experiments with neutral beam injection at the early stage of a Globus-M discharge, instabilities were observed that were excited by fast ions in the frequency range of 50–200 kHz, which were identified as toroidal Alfvén eigenmodes (TAE) (Petrov et al., Plasma Phys. Rep., vol. 37, 2011, pp. 1001–1005). In contradiction with the NSTX and MAST tokamaks, a regime of TAE generation was realized with strongly developed single modes. Magnetic measurements with fast Mirnov probes have shown that most of the modes have toroidal number $n=1$. The influence of the modes on the fast particle confinement was recorded by means of a tangentially directed neutral particle analyser (NPA) and neutron detector. Hydrogen and deuterium were used as target plasma and injected beam for study of the isotopic effect. At deuterium injection into the deuterium plasma, TAE led to the neutron rate dropping by 25 %, whereas NPA fluxes of high energy dropped by 75 %. At hydrogen injection, the drop in the measured NPA fluxes did not exceed 25 %.

Symmetrizable Difference Dchemes

2005 ◽  
Vol 5 (1) ◽  
pp. 3-50 ◽  
Author(s):  
Alexei A. Gulin
Keyword(s):  
Initial Data ◽  
Difference Scheme ◽  
Difference Schemes ◽  
Time Dependent ◽  
Stability Boundaries ◽  
Typical Representative ◽  
Variable Weight ◽  
The Stability ◽  
Conditions Of Stability ◽  
The Right

AbstractA review of the stability theory of symmetrizable time-dependent difference schemes is represented. The notion of the operator-difference scheme is introduced and general ideas about stability in the sense of the initial data and in the sense of the right hand side are formulated. Further, the so-called symmetrizable difference schemes are considered in detail for which we manage to formulate the unimprovable necessary and su±cient conditions of stability in the sense of the initial data. The schemes with variable weight multipliers are a typical representative of symmetrizable difference schemes. For such schemes a numerical algorithm is proposed and realized for constructing stability boundaries.

Stability boundaries of gas hydrates helped by methane—structure-H hydrates of methylcyclohexane and cis-1,2-dimethylcyclohexane

2003 ◽  
Vol 58 (2) ◽  
pp. 269-273 ◽  
Author(s):  
Toshiyuki Nakamura ◽  
Takashi Makino ◽  
Takeshi Sugahara ◽  
Kazunari Ohgaki
Keyword(s):  
Gas Hydrates ◽  
Stability Boundaries

scholarly journals Simulation of the loss of passing fast ions induced by magnetic islands in EAST tokamak plasmas

AIP Advances ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 025020
Author(s):  
Limin Yu ◽  
Erbing Xue ◽  
Debing Zhang ◽  
Shuyu Zheng ◽  
Xianmei Zhang ◽  
...  
Keyword(s):  
Tokamak Plasmas ◽  
Magnetic Islands ◽  
Fast Ions
Sign in / Sign up

Export Citation Format

Share Document