Initial Boronization of PBX-M Using Ablation from Solid Boronized Probes

Kugel, H.; Hirooka, Y.; Timberlake, J.; Bell, R. E.; England, A.C.; Isler, R. C.; Jones, Samuel E.; Kaita, R.; Kaye, S. M.; Khandagle, M.; Okabayashi, M.; Paul, S.; Takahashi, H.; Tighe, W.; Goeler, S. von; Post-Zwicker, Andrew

doi:10.13182/fst94-a30244

Cited by 8 publications

(2 citation statements)

References 12 publications

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“…Both reduce the neutron rate, and this has also been observed during the temporal evolution of a discharge: the high-Z impurity accumulation during the CH mode increases in time, with a corresponding decay in the neutron rate. With boronization, however, the impurity influx, especially of heavy impurities, is very much reduced in PBX-M [22].…”

Section: Formation Of Core Transport Barriermentioning

confidence: 99%

Magnetohydrodynamic behaviour during core transport barrier experiments with ion Bernstein wave heating in PBX-M: I ELMs, fluctuations and crash events

et al. 1998

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If the ion Bernstein wave (IBW) heating power in an H mode discharge of the PBX-M experiment exceeds a threshold power of about 200 kW, a core transport barrier is created in the central region of the plasma. At lower neutral beam injection (NBI) powers, the core barrier is accompanied by an edge L mode. The high edge localized mode (ELM) repetition frequency (1 kHz) prevents the creation of a strong barrier, so the edge first has to make an H-to-L transition before a strong core transport barrier can be created. At higher NBI powers, the ELM repetition frequency is lowered to less than 200 Hz, which allows the immediate creation of a strong core barrier. Edge localized mode loss, which propagates radially first on a fast (non-diffusive) and then on a slow (diffusive) time-scale all the way to the plasma core, is strongly reduced in the core barrier region. Correlated with the reduced ELM loss, the fluctuations in the core barrier region are also strongly reduced, both during the ELM and during the quiet periods between the ELMs. There is strong evidence that the IBW induced poloidal flow shear is responsible for the stabilization of core turbulence and the creation of the core transport barrier. The large perpendicular E × B flow shear component of the measured toroidal velocity in co-injection neutral beam heated discharges seems to be largely cancelled by the ion diamagnetic drift shear produced by large ion pressure gradients in the core barrier region. The value of IBW induced poloidal flow has not been experimentally determined, but its numerical value is found to be a factor of 4 larger than either the toroidal velocity or the ion diamagnetic drift shear components, leaving only IBW induced flow shear as the most probable cause for the turbulence stabilization. The core turbulence suppression and the creation of the core transport barrier is also consistent with expectations from a comparison between the E × B flow shear rate and a rough estimate of the linear ion temperature gradient (ITG) growth rate. The presence of the core barrier region also strongly modifies the other MHD events: crashes on the q = 1.5, 2 surfaces and the disruption.

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Section: Formation Of Core Transport Barriermentioning

confidence: 99%

Magnetohydrodynamic behaviour during core transport barrier experiments with ion Bernstein wave heating in PBX-M: I ELMs, fluctuations and crash events

et al. 1998

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“…Impurity influx during IBWH can be minimized by boronization of the vacuum vessel. Real time boronization using a boron probe is routinely performed [12] and the effect upon impurity intensity during IBWH is shown in Fig. 4.…”

Section: Ibwh Into Ohmic Plasmasmentioning

confidence: 99%

Impurity behaviour during ion Bernstein wave heating in the PBX-M tokamak

et al. 1995

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Ion Bernstein wave heating (IBWH) is used in the PBX-M tokamak to investigate active control of the pressure profile. A series of experiments was carried out to study impurity behaviour during IBWH under various discharge conditions. In all cases, impurity concentration increased and impurity transport was affected by application of IBWH. Core particle confinement was found to rise during IBWH, which resulted in an increase in the inward convective flow of impurities. Real time boronization of the vacuum vessel was successful in decreasing the overall impurity concentration

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Real-time boronization in PBX-M using erosion of solid boronized targets

Kugel

Timberlake

Bell

et al. 1995

Journal of Nuclear Materials

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Thirty one real-time boronizations were applied to PBX-M using the plasma ablation of solid target probes. More than 17 g of boron was deposited in PBX-M using this technique. The probes were positioned at the edge plasma to optimize ablation and minimize spallation. Auger depth profile analysis of poloidal and toroidal deposition sample coupon arrays indicate that boron was transported by the plasma around the torus and deep into the divertors. During discharges with continuous real-time boronization, Iow-Z and high-Z impurities decreased rapidly as plasma surfaces were covered during the first 20-30 discharges. After boronization, a shortterm improvement in plasma conditions persisted prior to significant boron erosion from plasma surfaces, and a longer term, but less significant, improvement persisted as boron farther from the edge continued gettering. Real-time solid target boronization has been found to be very effective for accelerating conditioning to new regimes and maintaining high performance plasma conditions. DISCLAIMERThis report was prepared as an account of work sponsored by an agency of the United States Government. Neither the United States Government nor any agency thereof, nor any of their employees, makes any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus,product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise does not necessarily constitute or imply its endorsement, recommendation, or favoring by the United States Government or any agency thereof. The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States Government or any agency thereof.

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Initial Boronization of PBX-M Using Ablation from Solid Boronized Probes

Cited by 8 publications

References 12 publications

Magnetohydrodynamic behaviour during core transport barrier experiments with ion Bernstein wave heating in PBX-M: I ELMs, fluctuations and crash events

Magnetohydrodynamic behaviour during core transport barrier experiments with ion Bernstein wave heating in PBX-M: I ELMs, fluctuations and crash events

Impurity behaviour during ion Bernstein wave heating in the PBX-M tokamak

Real-time boronization in PBX-M using erosion of solid boronized targets

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