Plasma fuelling with cryogenic pellets in the stellarator TJ-II

McCarthy, K. J.; Panadero, N.; Velasco, J. L.; Combs, S. K.; Caughman, J. B. O.; Fontdecaba, J. M.; Foust, C.; García, R.; Hernández Sánchez, J.; Navarro, M.; Pastor, I.; Soleto, A.

doi:10.1088/1741-4326/aa64fd

Title: Plasma fuelling with cryogenic pellets in the stellarator TJ-II

Journal Article · Tue Apr 04 00:00:00 EDT 2017 · Nuclear Fusion

DOI:https://doi.org/10.1088/1741-4326/aa64fd· OSTI ID:1376533

McCarthy, K. J. ^[1]; Panadero, N. ^[1]; Velasco, J. L. ^[1]; Combs, S. K. ^[2]; Caughman, J. B. O. ^[2]; Fontdecaba, J. M. ^[1]; Foust, C. ^[2]; García, R. ^[1]; Hernández Sánchez, J. ^[1]; Navarro, M. ^[1]; Pastor, I. ^[1]; Soleto, A. ^[1]

Research Centre for Energy, Environment and Technology (CIEMAT), Madrid (Spain)
Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)

Cryogenic pellet injection is a widely used technique for delivering fuel to the core of magnetically confined plasmas. Indeed, such systems are currently functioning on many tokamak, reversed field pinch and stellarator devices. A pipe-gun-type pellet injector is now operated on the TJ-II, a low-magnetic shear stellarator of the heliac type. Cryogenic hydrogen pellets, containing between 3×10¹⁸ and 4×10¹⁹ atoms, are injected at velocities between 800 and 1200 m s^-1 from its low-field side into plasmas created and/or maintained in this device by electron cyclotron resonance and/or neutral beam injection heating. In this paper, the first systematic study of pellet ablation, particle deposition and fuelling efficiency is presented for TJ-II. From this, light-emission profiles from ablating pellets are found to be in reasonable agreement with simulated pellet ablation profiles (created using a neutral gas shielding-based code) for both heating scenarios. In addition, radial offsets between recorded light-emission profiles and particle deposition profiles provide evidence for rapid outward drifting of ablated material that leads to pellet particle loss from the plasma. Finally, fuelling efficiencies are documented for a range of target plasma densities (~4×10¹⁸– ~2×10¹⁹ m^-3). These range from ~20%– ~85% and are determined to be sensitive to pellet penetration depth. Additional observations, such as enhanced core ablation, are discussed and planned future work is outlined.

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Research Organization:: Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)

Sponsoring Organization:: USDOE Office of Science (SC)

Contributing Organization:: the TJ-II Team

Grant/Contract Number:: AC05-00OR22725

OSTI ID:: 1376533

Journal Information:: Nuclear Fusion, Vol. 57, Issue 5; ISSN 0029-5515

Publisher:: IOP ScienceCopyright Statement

Country of Publication:: United States

Language:: English

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Cited by: 15 works

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References (31)

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