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Title: Simulation of Alpha Particles in Rotating Plasma Interacting with a Stationary Ripple

Abstract

Superthermal ExB rotation can provide magnetohydrodynamic (MHD) stability and enhanced confinement to axisymmetric mirrors. However, the rotation speed has been limited by phenomena at end electrodes. A new prediction is that rotation might instead be produced using a magnetic ripple and alpha particle kinetic energy, in an extension of the alpha channeling concept. The interaction of alpha particles with the ripple results in visually interesting and practically useful orbits.

Authors:
Publication Date:
Research Org.:
Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States)
Sponsoring Org.:
USDOE Office of Science (SC)
OSTI Identifier:
1001685
Report Number(s):
PPPL-4594
TRN: US1101050
DOE Contract Number:
DE-ACO2-09CH11466
Resource Type:
Technical Report
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY; ALPHA PARTICLES; CHANNELING; CONFINEMENT; ELECTRODES; FORECASTING; KINETIC ENERGY; MAGNETOHYDRODYNAMICS; MIRRORS; ROTATING PLASMA; ROTATION; SIMULATION; STABILITY; VELOCITY; Alpha Particles, Rotating Plasmas, Wave Interaction, Particles

Citation Formats

Abraham J. Fetterman and Nathaniel J. Fisch. Simulation of Alpha Particles in Rotating Plasma Interacting with a Stationary Ripple. United States: N. p., 2011. Web. doi:10.2172/1001685.
Abraham J. Fetterman and Nathaniel J. Fisch. Simulation of Alpha Particles in Rotating Plasma Interacting with a Stationary Ripple. United States. doi:10.2172/1001685.
Abraham J. Fetterman and Nathaniel J. Fisch. Tue . "Simulation of Alpha Particles in Rotating Plasma Interacting with a Stationary Ripple". United States. doi:10.2172/1001685. https://www.osti.gov/servlets/purl/1001685.
@article{osti_1001685,
title = {Simulation of Alpha Particles in Rotating Plasma Interacting with a Stationary Ripple},
author = {Abraham J. Fetterman and Nathaniel J. Fisch},
abstractNote = {Superthermal ExB rotation can provide magnetohydrodynamic (MHD) stability and enhanced confinement to axisymmetric mirrors. However, the rotation speed has been limited by phenomena at end electrodes. A new prediction is that rotation might instead be produced using a magnetic ripple and alpha particle kinetic energy, in an extension of the alpha channeling concept. The interaction of alpha particles with the ripple results in visually interesting and practically useful orbits.},
doi = {10.2172/1001685},
journal = {},
number = ,
volume = ,
place = {United States},
year = {Tue Jan 11 00:00:00 EST 2011},
month = {Tue Jan 11 00:00:00 EST 2011}
}

Technical Report:

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  • An extension of the alpha channeling effect to supersonically rotating mirrors shows that the rotation itself can be driven using alpha particle energy. Alpha channeling uses radiofrequency waves to remove alpha particles collisionlessly at low energy. We show that stationary magnetic fields with high nθ can be used for this purpose, and simulations show that a large fraction of the alpha energy can be converted to rotation energy.
  • Predictions for ripple loss of fast ions from TFTR are investigated with a guiding center code including both collisional and ripple effects. A synergistic enhancement of fast ion diffusion is found for toroidal field ripple with collisions. The total loss is calculated to be roughly twice the sum of ripple and collisional losses calculated separately. Discrepancies between measurements and calculations of plasma beta at low current and large major radius are resolved when both effects are included for neutral beam ions. A 20--30% reduction in alpha particle heating is predicted for q{sub a} = 6--14, R = 2.6 m DTmore » plasmas on TFTR due to first orbit and collisional stochastic ripple diffusion.« less
  • Modelling of TF ripple loss of alphas in DT experiments on TFTR now includes neoclassical calculations of first orbit loss, stochastic ripple diffusion, ripple trapping and collisional effects. A rapid way to simulate experiment has been developed which uses a simple stochastic domain model for TF ripple loss within the TRANSP analysis code, with the ripple diffusion threshold evaluated by comparison with more accurate but computationally expensive Hamiltonian coordinate guiding center code simulations. Typical TF collisional ripple loss predictions are 6-10% loss of alphas for TFTR D-T experiments at I{sub p} = 1.0-2.0 MA and R = 2.52 m.
  • Quantitative evaluation of TF ripple loss of DT alpha particles is a central issue for reactor design because of potentially severe first wall heat load problems. DT experiments on TFTR allow experimental measurements to be compared to modeling of the underlying alpha physics, with code validation an important goal. Modeling of TF ripple loss of alphas in TFTR now includes neoclassical calculations of alpha losses arising from first orbit loss, stochastic ripple diffusion, ripple trapping and collisional effects. Recent Hamiltonian coordinate guiding center code (ORBIT) simulations for TFTR have shown that collisions enhance the stochastic TF ripple losses at TFTR.more » A faster way to simulate experiment has been developed and is discussed here which uses a simple stochastic domain model for TF ripple loss within the TRANSP analysis code.« less
  • Predictions for ripple loss of fast ions from TFTR are investigated with a guiding center including both collisional and ripple effects. Discrepancies between measurements and calculations of plasma beta at low current and large major radius are resolved when both effects are included for neutral beam ions. A synergistic enhancement of fast ion diffusion is found for toroidal field ripple with collisions. S = 5.4 for neutral beam ions and S = 1.4--2.4 for alpha particles. A 20--30% reduction in alpha particle heating is predicted for R = 2.6 m DT plasmas on TFTR due to first orbit and collisionalmore » stochastic ripple diffusion, although these losses will be reduced if q{sub a} and R are smaller, as for most planned DT experiments.« less