Controlled fusion and plasma heating (Report on the 17th European Conference, Amsterdam, The Netherlands, 25–29 June 1990)

Donné, A. J. H.; Westerhof, E.

doi:10.1088/0029-5515/31/1/018

Cited by 7 publications

(10 citation statements)

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“…Further evidence of the control of particle recirculation is given by the analysis of the particle flux to the target plate measured with a Langmuir probe, and the measure of the neutral inflow computed from a full image of the target plate in H α light. For both signals one finds the same dependence in a density scan, and, for reasonable estimates of the wetted surface, quantitative agreement is observed [12]. Direct analysis of the H α image also exhibits a localized neutral influx (Fig.…”

Section: Control Of Particle Recirculationsupporting

confidence: 73%

“…This is defined as the ratio of the divertor density to the core volume averaged density [11]. It has long been found and reported in the literature [12,3] that the ergodic divertor is effective in lowering the impurity inflow, both for metallic impurities [11,2] and light impurities such as carbon [3]. Control of the main ion species, deuterium or helium, provides another measure of the divertor performance.…”

Section: Control Of Particle Recirculationmentioning

confidence: 99%

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Ergodic divertor experiments on the route to steady state operation of Tore Supra

Ghendrih¹,

Bécoulet²,

Costanzo³

et al. 2001

Nucl. Fusion

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Ergodic divertor operation on Tore Supra is characterized by good performance in terms of divertor physics. Control of particle recirculation and impurity screening are related to the symmetry, both poloidally and toroidally, of the shell of open field lines and to its radial extent, ∆r ≈ 0.16 m. Feedback control of the divertor plasma temperature has led to controlled radiative divertor experiments. In particular, good performance is obtained when the plasma is controlled to be at a temperature comparable to the energy involved in the atomic processes (15-20 eV). For standard discharges with 5 MW total power and ICRH heating, the low parallel energy flux ≈10 MW m −2 is reduced to ≈3 MW m −2 with nitrogen injection. This is achieved at a modest cost in core dilution, ∆Z eff ≈ 0.3. Despite the large volume of open field lines (≈36%), the ergodic divertor does not reduce the possible current in the discharge since stable discharges are achieved with qsep ≈ 2. It is shown that the reorganization of the current profile in conjunction with a transport barrier in the electron temperature on the separatrix stabilizes the (2,1) tearing mode. Confinement follows the standard L mode confinement. In a few cases at high density and with no gas injection (wall fuelled discharges), 'RI-like' modes are reported with a modest increase in confinement (≈40%). Despite the lack of core fuelling on Tore Supra, high densities during ICRH pulses can be achieved with Greenwald fractions fG ≈ 1. Compatibility with both ICRH and LH is demonstrated. In particular, long pulse operation with a flat-top in excess of 20 s is achieved with LHCD.

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Section: Control Of Particle Recirculationsupporting

confidence: 73%

Section: Control Of Particle Recirculationmentioning

confidence: 99%

Ergodic divertor experiments on the route to steady state operation of Tore Supra

Ghendrih¹,

Bécoulet²,

Costanzo³

et al. 2001

Nucl. Fusion

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“…These values are rather low, as is expected for beryllium. Injection of some higher Z impurity in the divertor region will probably be required in order to reduce the power load on the target plates [18].…”

Section: Predicted Entrainment and Radiated Power Of Beryllium In The...mentioning

confidence: 99%

“…This model has been used to simulate experimental results from JET [16] and to predict the performance of the pumped divertor planned for JET [17,18,19] regarding impurity retention. Different divertor configurations have been considered and used to study the dependence of the results on parameters such as deuterium and impurity levels in the SOL, the power flow entering the SOL via the electron and ion channels, the connection length in the divertor region and the distribution of neutrals re-injected into the SOL.…”

Section: Introductionmentioning

confidence: 99%

Scrape-off layer model for the study of impurity retention in the pumped divertor planned for JET

et al. 1991

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The paper presents a model of the plasma boundary region that has been developed to study the flow of impurities generated at the target plates in the pumped divertor configuration planned for JET. For the flow equations the model is one-dimensional, parallel to the magnetic field, but the neutral species is treated in two dimensions. All ionization stages of an impurity can be treated separately or, alternatively, an average charge impurity species can be considered. The validity of this approximation is assessed. The presented results show that impurities can be retained near the target plates by a forced flow of plasma generated by recirculating, across the separatrix from the main plasma to the scrape-off layer, a fraction of the flow reaching the target plates.

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“…Line radiation from C2+, C3+ and C4+ ions emitted, respectively, at 229.6 nm (2s2p 'P0-2p2 'D), 253.0 nm (4f 'F0-5g 'G) and 227.1 nm (2s 3S-2p 3P0) has been used for Doppler broadening and intensity measurements. The level of contamination associated with the density of different carbon ions has been compared with the effective plasma charge (Zeff), derived from bremsstrahlung in the visible range [9].…”

Section: Introductionmentioning

confidence: 99%

Study of plasma contamination during ICRF heating under boronized wall conditions in TEXTOR

Telesca¹,

Claaßen²,

Pospieszczyk³

et al. 1994

Nucl. Fusion

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The impurity content of the plasma during the steady state phase of ICRF minority heating in TEXTOR is found to be, for boronized wall conditions, a function of the thermal load on the limiter only. This new experimental result, which is to be related to the RF power absorption characteristics of the TEXTOR plasmas, has been established by comparing, at different RF power levels, the plasma effective charge with the thermal deuteron flux to the limiter. During the transient phase of the RF pulse, however, relevant RF-specific effects in the boundary plasma have been observed. These effects, which are accompanied by a release of impurities, are suppressed almost completely if a high energy RF induced tail of minority ions is previously built up in the target plasma. This is due to a large increase of the damping of the fast wave. The RF pre-heating at the moderate power level of 0.8 MW has been found experimentally to be very effective, in agreement with the predictions of a full wave Fokker-Planck simulation code. Comparison of Z , , with spectra in the UV, VUV and SXR ranges leads to the conclusion that the carbon influx dominates the plasma contamination.

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Controlled fusion and plasma heating (Report on the 17th European Conference, Amsterdam, The Netherlands, 25–29 June 1990)

Cited by 7 publications

References 0 publications

Ergodic divertor experiments on the route to steady state operation of Tore Supra

Ergodic divertor experiments on the route to steady state operation of Tore Supra

Scrape-off layer model for the study of impurity retention in the pumped divertor planned for JET

Study of plasma contamination during ICRF heating under boronized wall conditions in TEXTOR

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