Author: G. Rewoldt
Publisher:
ISBN:
Category :
Languages : en
Pages : 37
Book Description
Alpha-particle Effects on High-toroidal Mode Number Instabilities in Tokamaks
Alpha-particle Effects on High-n Instabilities in Tokamaks
Author:
Publisher:
ISBN:
Category :
Languages : en
Pages :
Book Description
Hot .cap alpha.-particles and thermalized helium ash particles in tokamaks can have significant effects on high toroidal mode number instabilities such as the trapped-electron drift mode and the kinetically calculated magnetohydrodynamic ballooning mode. In particular, the effects can be stabilizing, destabilizing, or negligible, depending on the parameters involved. In high-temperature tokamaks capable of producing significant numbers of hot .cap alpha.-particles, the predominant interaction of the mode with the .cap alpha.-particles is through resonances of various sorts. In turn, the modes can cause significant anomalous transport of the .cap alpha.-particles and the helium ash. Here, results of comprehensive linear eigenfrequency-eigenfunction calculations are presented for relevant realistic cases to show these effects. 24 refs., 12 figs., 6 tabs.
Publisher:
ISBN:
Category :
Languages : en
Pages :
Book Description
Hot .cap alpha.-particles and thermalized helium ash particles in tokamaks can have significant effects on high toroidal mode number instabilities such as the trapped-electron drift mode and the kinetically calculated magnetohydrodynamic ballooning mode. In particular, the effects can be stabilizing, destabilizing, or negligible, depending on the parameters involved. In high-temperature tokamaks capable of producing significant numbers of hot .cap alpha.-particles, the predominant interaction of the mode with the .cap alpha.-particles is through resonances of various sorts. In turn, the modes can cause significant anomalous transport of the .cap alpha.-particles and the helium ash. Here, results of comprehensive linear eigenfrequency-eigenfunction calculations are presented for relevant realistic cases to show these effects. 24 refs., 12 figs., 6 tabs.
Beam-ion and Alpha-particle Effects on Microinstabilities in Tokamaks
Comparison of High-n Instabilities Including Alpha-particle Effects in BPX and TFTR.
Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 28
Book Description
Three distinct types of high toroidal mode number instabilities are obtained from a comprehensive kinetic calculation, using as input transport code results from the analysis of a recent design for the Burning Plasma Experiment (BPX). These instabilities are: the collisionless trapped-electron ion-temperature-gradient mode, the magnetohydrodynamic ballooning mode, and a high toroidal mode number version of the toroidicity-induced Alfven eigenmode or gap'' mode. The dependence of the instability linear eigenfrequencies on minor radius, beta, and toroidal mode number are investigated, along with the effects of hot alpha particles. Relative quasilinear fluxes of particles and energy for each species are also obtained. In addition, the beta dependence of the magnetohydrodynamic ballooning mode is investigated for a case using as input the results of a transport code calculation for the Tokamak Fusion Test Reactor (TFTR) in an extrapolation to a deuterium-tritium mixture. The effects of alpha particles and the relative quasilinear fluxes are also investigated for this case. 13 refs., 13 figs., 4 tabs.
Publisher:
ISBN:
Category :
Languages : en
Pages : 28
Book Description
Three distinct types of high toroidal mode number instabilities are obtained from a comprehensive kinetic calculation, using as input transport code results from the analysis of a recent design for the Burning Plasma Experiment (BPX). These instabilities are: the collisionless trapped-electron ion-temperature-gradient mode, the magnetohydrodynamic ballooning mode, and a high toroidal mode number version of the toroidicity-induced Alfven eigenmode or gap'' mode. The dependence of the instability linear eigenfrequencies on minor radius, beta, and toroidal mode number are investigated, along with the effects of hot alpha particles. Relative quasilinear fluxes of particles and energy for each species are also obtained. In addition, the beta dependence of the magnetohydrodynamic ballooning mode is investigated for a case using as input the results of a transport code calculation for the Tokamak Fusion Test Reactor (TFTR) in an extrapolation to a deuterium-tritium mixture. The effects of alpha particles and the relative quasilinear fluxes are also investigated for this case. 13 refs., 13 figs., 4 tabs.
Alpha Storage Regime in High Temperature Sub-ignited D-T Tokamaks
Author:
Publisher:
ISBN:
Category :
Languages : en
Pages :
Book Description
Alpha particle parameters in sub-ignited D-T tokamaks like TFTR can be optimized in a high temperature ''alpha storage regime '' in which the alpha particle thermalization time [tau]/sub .cap alpha./ is long (approx. 1.0 sec) and in which the alpha particle source rate S/sub .cap alpha./ is enhanced due to a beam-target and beam-beam reactions (by a factor of approx. 2-3). Near reactor-level alpha instability parameters .beta./sub .cap alpha./(0) approx. n/sub .cap alpha./(0)/n/sub e/(O) approx. 1% are predicted by simulation codes when Q approx. 0.5-1, while present TFTR ''supershots'' already have .beta./sub .cap alpha./(O) approx. n/sub [alpha](O)/n/sub e/(O) /approx/ 0.1-0.2%. Plasmas in this regime can be used to test theories of collective alpha instabilities for the first time, and can be used to provide a strong (but transient) alpha heating pulse. An experimental scenario to exploit this regime is described. 28 refs., 5 figs., 5 tabs.,
Publisher:
ISBN:
Category :
Languages : en
Pages :
Book Description
Alpha particle parameters in sub-ignited D-T tokamaks like TFTR can be optimized in a high temperature ''alpha storage regime '' in which the alpha particle thermalization time [tau]/sub .cap alpha./ is long (approx. 1.0 sec) and in which the alpha particle source rate S/sub .cap alpha./ is enhanced due to a beam-target and beam-beam reactions (by a factor of approx. 2-3). Near reactor-level alpha instability parameters .beta./sub .cap alpha./(0) approx. n/sub .cap alpha./(0)/n/sub e/(O) approx. 1% are predicted by simulation codes when Q approx. 0.5-1, while present TFTR ''supershots'' already have .beta./sub .cap alpha./(O) approx. n/sub [alpha](O)/n/sub e/(O) /approx/ 0.1-0.2%. Plasmas in this regime can be used to test theories of collective alpha instabilities for the first time, and can be used to provide a strong (but transient) alpha heating pulse. An experimental scenario to exploit this regime is described. 28 refs., 5 figs., 5 tabs.,
Excitation of High-n Toroidicity-induced Shear Alfven Eigenmodes by Energetic Particles and Fusion Alpha Particles in Tokamaks
Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 36
Book Description
The stability of high-n toroidicity-induced shear Alfven eigenmodes (TAE) in the presence of fusion alpha particles or energetic ions in tokamaks is investigated. The TAE modes are discrete in nature and thus can easily tap the free energy associated with energetic particle pressure gradient through wave particle resonant interaction. A quadratic form is derived for the high-n TAE modes using gyro-kinetic equation. The kinetic effects of energetic particles are calculated perturbatively using the ideal MHD solution as the lowest order eigenfunction. The finite Larmor radius (FLR) effects and the finite drift orbit width (FDW) effects are included for both circulating and trapped energetic particles. It is shown that, for circulating particles, FLR and FDW effects have two opposite influences on the stability of the high-n TAE modes. First, they have the usual stabilizing effects by reducing the wave particle interaction strength. Second, they also have destabilizing effects by allowing more particles to resonate with the TAE modes. It is found that the growth rate induced by the circulating alpha particles increase linearly with toroidal mode number n for small?{sub?}?{sub?}, and decreases as 1/n for?{sub?}?{sub?} {much gt} 1. The maximum growth rate is obtained at?{sub?}?{sub?} on the order of unity and is nearly constant for the range of 0.7
Publisher:
ISBN:
Category :
Languages : en
Pages : 36
Book Description
The stability of high-n toroidicity-induced shear Alfven eigenmodes (TAE) in the presence of fusion alpha particles or energetic ions in tokamaks is investigated. The TAE modes are discrete in nature and thus can easily tap the free energy associated with energetic particle pressure gradient through wave particle resonant interaction. A quadratic form is derived for the high-n TAE modes using gyro-kinetic equation. The kinetic effects of energetic particles are calculated perturbatively using the ideal MHD solution as the lowest order eigenfunction. The finite Larmor radius (FLR) effects and the finite drift orbit width (FDW) effects are included for both circulating and trapped energetic particles. It is shown that, for circulating particles, FLR and FDW effects have two opposite influences on the stability of the high-n TAE modes. First, they have the usual stabilizing effects by reducing the wave particle interaction strength. Second, they also have destabilizing effects by allowing more particles to resonate with the TAE modes. It is found that the growth rate induced by the circulating alpha particles increase linearly with toroidal mode number n for small?{sub?}?{sub?}, and decreases as 1/n for?{sub?}?{sub?} {much gt} 1. The maximum growth rate is obtained at?{sub?}?{sub?} on the order of unity and is nearly constant for the range of 0.7