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Title: A Description of the Full Particle Orbit Following SPIRAL Code for Simulating Fast-ion Experiments in Tokamaks

Abstract

The numerical methods used in the full particle-orbit following SPIRAL code are described and a number of physics studies performed with the code are presented to illustrate its capabilities. The SPIRAL code is a test-particle code and is a powerful numerical tool to interpret and plan fast-ion experiments in Tokamaks. Gyro-orbit effects are important for fast ions in low-field machines such as NSTX and to a lesser extent in DIII-D. A number of physics studies are interlaced between the description of the code to illustrate its capabilities. Results on heat loads generated by a localized error-field on the DIII-D wall are compared to measurements. The enhanced Triton losses caused by the same localized error-field are calculated and compared to measured neutron signals. MHD activity such as tearing modes and Toroidicity-induced Alfven Eigenmodes (TAEs) have a profound effect on the fast-ion content of Tokamak plasmas and SPIRAL can calculate the effects of MHD activity on the confined and lost fast-ion population as illustrated for a burst of TAE activity in NSTX. The interaction between Ion Cyclotron Range of Frequency (ICRF) heating and fast ions depends solely on the gyro-motion of the fast ions and is captured exactly in the SPIRAL code.more » A calculation of ICRF absorption on beam ions in ITER is presented. The effects of high harmonic fast wave heating on the beam-ion slowing-down distribution in NSTX is also studied.« less

Authors:
; ; ; ; ; ; ; ;
Publication Date:
Research Org.:
Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States); University of California-Irvine, Irvine, CA (United States); General Atomics, San Diego, CA (United States)
Sponsoring Org.:
USDOE Office of Science (SC)
OSTI Identifier:
1056825
Report Number(s):
PPPL-4788
DOE Contract Number:
DE-ACO2-09CH11466
Resource Type:
Technical Report
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY; Heating; ICRF; Computer Simulation; Neutral Beams; Transport Phenomena; Energetic Particles

Citation Formats

Kramer, G.J., Budny, R.V., Bortolon, A., Fredrickson, E.D., Fu, G.Y., Heidbrink, W.W., Nazikian, R., Valeo, E., and Van Zeeland, M.A. A Description of the Full Particle Orbit Following SPIRAL Code for Simulating Fast-ion Experiments in Tokamaks. United States: N. p., 2012. Web. doi:10.2172/1056825.
Kramer, G.J., Budny, R.V., Bortolon, A., Fredrickson, E.D., Fu, G.Y., Heidbrink, W.W., Nazikian, R., Valeo, E., & Van Zeeland, M.A. A Description of the Full Particle Orbit Following SPIRAL Code for Simulating Fast-ion Experiments in Tokamaks. United States. doi:10.2172/1056825.
Kramer, G.J., Budny, R.V., Bortolon, A., Fredrickson, E.D., Fu, G.Y., Heidbrink, W.W., Nazikian, R., Valeo, E., and Van Zeeland, M.A. Fri . "A Description of the Full Particle Orbit Following SPIRAL Code for Simulating Fast-ion Experiments in Tokamaks". United States. doi:10.2172/1056825. https://www.osti.gov/servlets/purl/1056825.
@article{osti_1056825,
title = {A Description of the Full Particle Orbit Following SPIRAL Code for Simulating Fast-ion Experiments in Tokamaks},
author = {Kramer, G.J. and Budny, R.V. and Bortolon, A. and Fredrickson, E.D. and Fu, G.Y. and Heidbrink, W.W. and Nazikian, R. and Valeo, E. and Van Zeeland, M.A.},
abstractNote = {The numerical methods used in the full particle-orbit following SPIRAL code are described and a number of physics studies performed with the code are presented to illustrate its capabilities. The SPIRAL code is a test-particle code and is a powerful numerical tool to interpret and plan fast-ion experiments in Tokamaks. Gyro-orbit effects are important for fast ions in low-field machines such as NSTX and to a lesser extent in DIII-D. A number of physics studies are interlaced between the description of the code to illustrate its capabilities. Results on heat loads generated by a localized error-field on the DIII-D wall are compared to measurements. The enhanced Triton losses caused by the same localized error-field are calculated and compared to measured neutron signals. MHD activity such as tearing modes and Toroidicity-induced Alfven Eigenmodes (TAEs) have a profound effect on the fast-ion content of Tokamak plasmas and SPIRAL can calculate the effects of MHD activity on the confined and lost fast-ion population as illustrated for a burst of TAE activity in NSTX. The interaction between Ion Cyclotron Range of Frequency (ICRF) heating and fast ions depends solely on the gyro-motion of the fast ions and is captured exactly in the SPIRAL code. A calculation of ICRF absorption on beam ions in ITER is presented. The effects of high harmonic fast wave heating on the beam-ion slowing-down distribution in NSTX is also studied.},
doi = {10.2172/1056825},
journal = {},
number = ,
volume = ,
place = {United States},
year = {Fri Jul 27 00:00:00 EDT 2012},
month = {Fri Jul 27 00:00:00 EDT 2012}
}

Technical Report:

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  • The single particle orbit code, TIBRO, has been modified extensively to improve the interpolation methods used and to allow use of vector potential fields in the simulation of charged particle orbits on a 3D domain. A 3D cubic B-spline algorithm is used to generate spline coefficients used in the interpolation. Smooth and accurate field representations are obtained. When vector potential fields are used, the 3D cubic spline interpolation formula analytically generates the magnetic field used to push the particles. This field has del.BETA = 0 to computer roundoff. When magnetic induction is used the interpolation allows del.BETA does not equalmore » 0, which can lead to significant nonphysical results. Presently the code assumes quadrupole symmetry, but this is not an essential feature of the code and could be easily removed for other applications. Many details pertaining to this code are given on microfiche accompanying this report.« less
  • The angular dependence of the flux of fast neutrals was measured in conjunction with Ion Cyclotron Range of Frequency (ICRF) experiments on the Princeton Large Torus (PLT). We found a regime where the energetic tail of the charge-exchange neutral flux was strongly anisotropic. Unexpectedly, however, the flux from co-moving ions was peaked at an angle intermediate between perpendicular and parallel. This could be the consequence of a preferential filling of that class of banana orbits whose tips are localized within the ion cyclotron resonance layer.
  • The radial diffusivity of fast ions was evaluated from vertical neutral particle measurements in experiments where a short pulse of neutral deuterium beams was injected into a TFTR ohmic deuterium plasma. A comparison between the temporal evolution of the measured neutral particle flux and theoretical calculations showed that the spatially-averaged diffusion coefficient of fast ions is {le} 0.1 m{sup 2}/sec. This value is approximately an order of magnitude less than the diffusion coefficient for thermal ions and is consistent with results obtained previously on TFTR from other diagnostics.
  • The radial diffusivity of fast ions was evaluated from vertical neutral particle measurements in experiments where a short pulse of neutral deuterium beams was injected into a TFTR ohmic deuterium plasma. A comparison between the temporal evolution of the measured neutral particle flux and theoretical calculations showed that the spatially-averaged diffusion coefficient of fast ions is {le} 0.1 m{sup 2}/sec. This value is approximately an order of magnitude less than the diffusion coefficient for thermal ions and is consistent with results obtained previously on TFTR from other diagnostics.
  • The computer code described is used to study ripple beam injection into a tokamak plasma. The collisionless guiding center equations of motion are integrated to find the orbits of single particles in realistic magnetic fields for ripple injection. In order to determine if the ripple is detrimental to the plasma, the magnetic flux surfaces are constructed by integration of the field line equations. The numerical techniques are described, and use of the code is outlined. A program listing is provided, and the results of sample cases are presented.