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Title: Effects of q(r) on the Alpha Particle Ripple Loss in TFTR

Abstract

An experiment was done with TFTR DT plasmas to determine the effect of the q(r) profile on the alpha particle ripple loss to the outer midplane. The alpha particle loss measurements were made using a radially movable scintillator detector 20 degrees below the outer midplane. The experimental results were compared with TF ripple loss calculations done using a Monte Carlo guiding center orbit following code, ORBIT. Although some of the experimental results are consistent with the ORBIT code modeling, the variation of the alpha loss with the q(r) profiles is not well explained by this code. Quantitative interpretation of these measurements requires a careful analysis of the limiter shadowing effect, which strongly determines the diffusion of alphas into the detector aperture.

Authors:
; ; ; ; ;
Publication Date:
Research Org.:
Princeton Plasma Physics Laboratory (PPPL), Princeton, NJ
Sponsoring Org.:
USDOE Office of Science (SC)
OSTI Identifier:
4507
Report Number(s):
PPPL-3264
ON: DE00004507
DOE Contract Number:
AC02-76CH03073
Resource Type:
Technical Report
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION; Plasma Waves; Wavelengths; Wave Forms; Alpha Particles; Helium Ions; Particle Losses; TFTR Tokamak; Limiters; Shadow Effect; Mathematical Models; Monte Carlo Method; O Codes; Experimental Data

Citation Formats

D.S. Darrow, M. Diesso, R.V. Budny, S. Batha, S.J. Zweben, and et al.. Effects of q(r) on the Alpha Particle Ripple Loss in TFTR. United States: N. p., 1997. Web. doi:10.2172/4507.
D.S. Darrow, M. Diesso, R.V. Budny, S. Batha, S.J. Zweben, & et al.. Effects of q(r) on the Alpha Particle Ripple Loss in TFTR. United States. doi:10.2172/4507.
D.S. Darrow, M. Diesso, R.V. Budny, S. Batha, S.J. Zweben, and et al.. Mon . "Effects of q(r) on the Alpha Particle Ripple Loss in TFTR". United States. doi:10.2172/4507. https://www.osti.gov/servlets/purl/4507.
@article{osti_4507,
title = {Effects of q(r) on the Alpha Particle Ripple Loss in TFTR},
author = {D.S. Darrow and M. Diesso and R.V. Budny and S. Batha and S.J. Zweben and et al.},
abstractNote = {An experiment was done with TFTR DT plasmas to determine the effect of the q(r) profile on the alpha particle ripple loss to the outer midplane. The alpha particle loss measurements were made using a radially movable scintillator detector 20 degrees below the outer midplane. The experimental results were compared with TF ripple loss calculations done using a Monte Carlo guiding center orbit following code, ORBIT. Although some of the experimental results are consistent with the ORBIT code modeling, the variation of the alpha loss with the q(r) profiles is not well explained by this code. Quantitative interpretation of these measurements requires a careful analysis of the limiter shadowing effect, which strongly determines the diffusion of alphas into the detector aperture.},
doi = {10.2172/4507},
journal = {},
number = ,
volume = ,
place = {United States},
year = {Mon Sep 01 00:00:00 EDT 1997},
month = {Mon Sep 01 00:00:00 EDT 1997}
}

Technical Report:

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  • 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
  • A method to extract energetic alphas from the edge of a tokamak plasma has been conceived and analyzed, and experiments to test the methods are being fabricated. The analysis addressed the region of alpha phase space sampled, the survivability of the foils required to implement the method, and the overall efficiency of the method. The experimental apparatus being fabricated include a detector head for a proof-of-concept test on PLT and a calibration-test stand as a support experiment for the PLT test and to support possible subsequent experiments on TFTR. A fast pulse height analysis data acquisition system was fabricated andmore » tested and is ready for use in the experiments discussed above.« less
  • Calculations of collisional stochastic ripple loss of alpha particles from the new 20 toroidal field (TF) coil International Thermonuclear Experimental Reactor (ITER) predict small alpha ripple losses, less than 0.4%, close to the loss calculated for the full current operation of the earlier 24 TF coil design. An analytic fit is obtained to the ITER ripple data field demonstrating the nonlinear height dependence of the ripple minimum for D shaped ripple contours. In contrast to alpha loss simulations for the Tokamak Fusion Test Reactor (TFTR), a simple Goldston, White, Boozer stochastic loss criterion ripple loss model is found to requiremore » an increased renormalization of the stochastic threshold {delta}{sub s}/{delta}{sub GWB} {ge} 1. Effects of collisions, sawtooth broadening and reversal of the grad B drift direction are included in the particle following simulations.« less
  • MHD-induced increases in alpha particle loss to the wall were observed for both coherent modes and transient reconnection events using an array of scintillator detectors near the wall of Tokamak Fusion Test Reactor (TFTR). The magnitude of the coherent MHD-induced alpha loss as seen by these detectors was normally comparable to the MHD-quiescent first-orbit or toroidal-field ripple loss, but the magnitude of the alpha loss during reconnection events was up to 1000 times higher than this for a short time. Modeling suggest that the coherent MHD loss mechanism will be even less significant for future reactor-scale deuterium-tritium tokamaks due tomore » the smaller ratio of the alpha gyroradius to minor radius.« less