Alpha particle loss in the TFTR DT experiments

Zweben, S. J.; Darrow, D.S.; Herrmann, H. W.; Batha, S. H.; Budny, R.; Chang, Choong-Seock; Chang, Z.; Fredrickson, E. D.; Jassby, D. L.; Johnson, L. C.; Levinton, F. M.; Mynick, H.E.; Owens, D. K.; Schivell, J.; Scott, S. D.; Redi, M. H.; Strachan, J.; Tobita, K.; Young, K. M.

doi:10.1088/0029-5515/35/8/i01

Cited by 51 publications

(75 citation statements)

References 33 publications

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“…The behaviour of alpha loss in TFTR as a function of plasma current is shown in figure 1 for the detector at the vessel bottom. The alpha loss rate (normalized by the neutron source rate) decreases with increasing plasma current, as expected from the classical first-orbit loss model, and the lost alpha pitch angle, energy, and time dependences are also consistent with this model [1]. This result sets a very low upper limit of D 0.1 m 2 s −1 for the radial diffusion rate of confined counter-passing alphas near the plasma centre, which is similar to diffusion coefficients measured for other fast ions in MHD-quiescent tokamaks [2].…”

Section: Classical Alpha Confinement and Thermalizationsupporting

confidence: 76%

Alpha-particle physics in the tokamak fusion test reactor DT experiment

Zweben

Arunasalam

Batha

et al. 1997

Plasma Phys. Control. Fusion

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Abstract.A summary is presented of recent alpha-particle experiments on the tokamak fusion test reactor. Alpha particles are generally well confined in MHD-quiescent discharges, and alpha heating of electrons has been observed. The theoretically predicted toroidicity-induced Alfvén eigenmode has been seen in discharges of 1 MW of alpha power, but only in plasmas with weak magnetic shear. Classical alpha confinement and thermalizationAlpha-particle heating is the basis for ignition in DT tokamaks, so it is important to understand the confinement and stability of energetic alphas before building a power plant based on this reaction. Efficient alpha-particle heating requires that almost all the 3.5 MeV alpha-particle power (i.e. 20% of the total fusion power) should be transferred to the thermal plasma before it is lost to the vessel wall. Therefore, the alpha-particle confinement time needs to be longer than the collisional alpha thermalization time, which itself is very much longer than the alpha transit time. For example, the alpha transit time in the tokamak fusion test reactor (TFTR) is τ trans = 2πR/v α ≈ 10 −6 s, while the alpha thermalization time is τ therm ≈ 0.3 s, with R = 2.5 m, I p = 2.5 MA, T e (0) = 10 keV and n e (0) = 10 14 cm −3 . † General Atomics ORAU fellow at PPPL.

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Section: Classical Alpha Confinement and Thermalizationsupporting

confidence: 76%

Alpha-particle physics in the tokamak fusion test reactor DT experiment

Zweben

Arunasalam

Batha

et al. 1997

Plasma Phys. Control. Fusion

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“…This is consistent with the alpha particles being well confined. Experimental results from the a-CHERS [23] and the escaping alpha [24] diagnostics on TFTR, both of which are absolutely calibrated, corroborate this classical picture of alpha behavior and also show that massive prompt losses of alphas do not occur in MHD quiescent plasma discharges.…”

Section: Alpha Particle and Triton Measurementsmentioning

confidence: 69%

Measurements of confined alphas and tritons in the MHD quiescent core of TFTR plasmas using the pellet charge exchange diagnostic

Medley

Budny

Mansfield

et al. 1996

Plasma Phys. Control. Fusion

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The energy distributions and radial density profiles of the fast confined trapped alpha particles in DT experiments on TFTR are being measured in the energy range 0.5-3.5 MeV using the pellet charge exchange (PCX) diagnostic. A brief description of the measurement technique which involves active neutral particle analysis using the ablation cloud surrounding an injected impurity pellet as the neutralizer is presented. This paper focuses on alpha and triton measurements in the core of MHD quiescent TFTR discharges where the expected classical slowing-down and pitch angle scattering effects are not complicated by stochastic ripple diffusion and sawtooth activity. In particular, the first measurement of the alpha slowing-down distribution up to the birth energy, obtained using boron pellet injection, is presented. The measurements are compared with predictions using either the TRANSP Monte Carlo code and/or a Fokker-Planck Post-TRANSP processor code, which assumes that the alphas and tritons are well confined and slow down classically. Both the shape of the measured alpha and triton energy distributions and their density ratios are in good agreement with the code calculations. We can conclude that the PCX measurements are consistent with classical thermalization of the fusion-generated alphas and tritons.

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“…The theory for first-orbit alpha loss was well known before TFTR [6][7][8], and it was expected that the alpha loss due to this process would be large at low plasma currents (i.e. >50% globally at I<0.5 MA), and small at high plasma currents (i.e.…”

Section: First-orbit Alpha Lossmentioning

confidence: 99%

“…the Lorentz ORBIT code for alpha loss [8,57], the ORBIT code for TF ripple loss [13,15,17], the FPPT code for sawtooth redistribution [87,90], and the NOVA-K [126,134] and ORNL [136] models for TAE instability studies. The analysis functions of these codes are summarized briefly in Table 8.…”

Section: Alpha Particle Modelingmentioning

confidence: 99%

Alpha particle physics experiments in the Tokamak Fusion Test Reactor

Zweben¹,

Budny²,

Darrow³

et al. 2000

Nucl. Fusion

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104

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Alpha particle physics experiments were done on the Tokamak Fusion Test Reactor (TFTR) during its deuterium-tritium (DT) run from 1993-1997. These experiments utilized several new alpha particle diagnostics and hundreds of DT discharges to characterize the alpha particle confinement and wave-particle interactions. In general, the results from the alpha particle diagnostics agreed with the classical singleparticle confinement model in magnetohydrodynamic (MHD) quiescent discharges. Also, the observed alpha particle interactions with sawteeth, toroidal Alfvén eigenmodes (TAE), and ion cyclotron resonant frequency (ICRF) waves were roughly consistent with theoretical modeling. This paper reviews what was learned and identifies what remains to be understood.2

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Alpha particle loss in the TFTR DT experiments

Cited by 51 publications

References 33 publications

Alpha-particle physics in the tokamak fusion test reactor DT experiment

Alpha-particle physics in the tokamak fusion test reactor DT experiment

Measurements of confined alphas and tritons in the MHD quiescent core of TFTR plasmas using the pellet charge exchange diagnostic

Alpha particle physics experiments in the Tokamak Fusion Test Reactor

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