Divertor experiment on particle and energy control in neutral beam heated JT-60 discharges

Nakamura, Hiroo; Ando, T.; Yoshida, H.; Niikura, S.; Nishitani, T.; Nagashima, Keisuke

doi:10.1088/0029-5515/28/1/004

Cited by 36 publications

(20 citation statements)

References 20 publications

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“…Beryllium and tungsten are currently considered as the materials of choice for the next step device ITER [4,41], while tungsten seems to be main plasma-facing material option for PFCs in DEMO. This came about despite the early experience that high-Z materials show unfavourable impact on plasma performance, as described for PLT [167,168] and JT-60 [169], as well as in earlier experiments. Tungsten and high-Z materials do pose problems in relation to plasma performance due to their strong radiative losses.…”

Section: Materials Tests In Tokamaksmentioning

confidence: 94%

Material testing facilities and programs for plasma-facing component testing

et al. 2017

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Component development for operation in a large-scale fusion device requires thorough testing and qualification for the intended operational conditions. In particular environments are necessary which are comparable to the real operation conditions, allowing at the same time for in situ/in vacuo diagnostics and flexible operation, even beyond design limits during the testing. Various electron and neutral particle devices provide the capabilities for high heat load tests, suited for material samples and components from lab-scale dimensions up to full-size parts, containing toxic materials like beryllium, and being activated by neutron irradiation. To simulate the conditions specific to a fusion plasma both at the first wall and in the divertor of fusion devices, linear plasma devices allow for a test of erosion and hydrogen isotope recycling behavior under well-defined and controlled conditions. Finally, the complex conditions in a fusion device (including the effects caused by magnetic fields) are exploited for component and material tests by exposing test mock-ups or material samples to a fusion plasma by manipulator systems. They allow for easy exchange of test pieces in a tokamak or stellarator device, without opening the vessel. Such a chain of test devices and qualification procedures is required for the development of plasma-facing components which then can be successfully operated in future fusion power devices. The various available as well as newly planned devices and test stands, together with their specific capabilities, are presented in this manuscript. Results from experimental programs on test facilities illustrate their significance for the qualification of plasma-facing materials and components. An extended set of references provides access to the current status of material and component testing capabilities in the international fusion programs.

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Section: Materials Tests In Tokamaksmentioning

confidence: 94%

Material testing facilities and programs for plasma-facing component testing

et al. 2017

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“…JT-60 was operated with a toroidal magnetic field of up to 4.5 T and a plasma current of up to 2.0 MA. Neutral beams (up to 75 keV) with a power level of up to 22 MW were injected into the plasma [3]. For a further reduction of impurities, the vacuum vessel was baked up to 350°C, and Taylor discharge cleaning was carried out before the experiments.…”

Section: Jt-60 Operating Conditions and Diagnosticsmentioning

confidence: 99%

“…in Fig. 4(b) was obtained in a diverted discharge with neutral beam heating of 11.6 MW, I p = 1.5 MA, B T = 4.5 T and He = 2.9X10 19 m" 3 . In this discharge, the metallic impurity lines were too weak to be observed.…”

Section: Analysis With a Transport Modelmentioning

confidence: 99%

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Spectroscopic study of impurities in neutral beam heated and ohmically heated JT-60 discharges

et al. 1989

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used. Quantitative spectroscopic measurements of Z eff , impurity concentrations and radiated power losses were made for ohmically heated and neutral beam heated discharges with limiter and divertor configurations. In the first phase with metallic first wall material, oxygen, carbon and titanium were identified as the main plasma impurities. In neutral beam heated, diverted discharges, Z efr was 1.6 at n,. = 4xlO 1 9 m" 3 . The concentrations of oxygen, carbon and titanium were 1%, 0.1% and 0.006% of n e , respectively. In the second phase with graphite material, the metallic impurities were reduced, and the contribution of metallic impurities to the radiated power loss was less than 1%. However, Z eff increased up to 3 in neutral beam heated discharges. In limited plasmas, the concentrations of oxygen and carbon were 1% and 5%, respectively, at Sj = 4xlO 1 9 m" 3 ; in diverted plasmas, these concentrations were 2% and 0.4% at the same r^. The radiated power loss from the main plasma was 20-40% of the input power in neutral beam heated, limited discharges, and 7-25% in diverted discharges. The contributions of oxygen and carbon to the radiated power in limited discharges were comparable, and in diverted discharges the contribution of oxygen was dominant.

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“…As tin is a high-Z material, contamination is a critical issue due to cooling by high radiation losses. Strong radiation losses with hollow or flat temperature profiles and impurity accumulation in the plasma core often lead to plasma disruptions [13,14]. For instance, tungsten (Z=74) concentration limit is ~10 -4 , while for Sn (Z=50), its concentration limit should be closer to molybdenum (Z=42) which is ~10 -3 [15].…”

Section: Introductionmentioning

confidence: 99%

Tin re-deposition and erosion measured by cavity-ring-down-spectroscopy under a high flux plasma beam

Kvon¹,

Al²,

Bystrov³

et al. 2017

Nucl. Fusion

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Cavity-Ring-Down Spectroscopy (CRDS) was implemented to measure the re-deposition of liquid tin under a high flux plasma beam in the linear plasma device Pilot-PSI. A capillary porous system (CPS) consisting of a molybdenum cup and tungsten meshes (pores diameters of 0.2 mm and 0.44 mm) was filled with tin and exposed to argon plasma. The absorption of a UV laser-beam at 286.331 nm was used to determine a number of sputtered neutral tin atoms. The incoming flux of argon ions of ~50 eV was 1.6−2.7x10 23 m-2 s-1 , and the sample temperature measured by pyrometry varied from 850 °C to 1200 °C during exposures. The use of CRDS for measuring absolute number of particles under such plasma exposure was demonstrated for the first time. The number of sputtered tin particles in the cavity region assuming no losses would be expected to be 5.5x10 11 −1.2x10 12 while CRDS measurements showed only 5.7−9.9x10 8. About 98−99.8% of sputtered particles were therefore found to not reach the CRDS observation volume. Spectroscopic ratios of Sn I to Sn II ions, as well as equilibrium considerations, indicate that fast ionization as well as plasma entrainment of neutrals is responsible for the discrepancy. This would lead to high re-deposition rates, implying a lowered contamination rate of core plasma and lower required replenishment rates at high-flux conditions than would otherwise be expected.

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Divertor experiment on particle and energy control in neutral beam heated JT-60 discharges

Cited by 36 publications

References 20 publications

Material testing facilities and programs for plasma-facing component testing

Material testing facilities and programs for plasma-facing component testing

Spectroscopic study of impurities in neutral beam heated and ohmically heated JT-60 discharges

Tin re-deposition and erosion measured by cavity-ring-down-spectroscopy under a high flux plasma beam

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