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Initial Commissioning Test Results of the Wendelstein 7-X Continuous Pellet Fueling System. FUSION SCIENCE AND TECHNOLOGY 2023. [DOI: 10.1080/15361055.2023.2174335] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 03/18/2023]
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2
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Issues in Formation of Cryogenic Pellets for Fusion Applications. FUSION SCIENCE AND TECHNOLOGY 2021. [DOI: 10.1080/15361055.2021.1887715] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
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3
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Shear Strength and Release of Large Cryogenic Pellets from the Barrel of a Shattered Pellet Injector for Disruption Mitigation. FUSION SCIENCE AND TECHNOLOGY 2021. [DOI: 10.1080/15361055.2021.1874766] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
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4
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Pressure Response Optimization of an Eddy Current-Driven Flyer Plate Valve for the ITER Shattered Pellet Injection System. FUSION SCIENCE AND TECHNOLOGY 2021. [DOI: 10.1080/15361055.2021.1906149] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
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5
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Analysis of the Shattered Pellet Injection Fragment Plumes Generated by Machine Specific Shatter Tube Designs. FUSION SCIENCE AND TECHNOLOGY 2021. [DOI: 10.1080/15361055.2020.1842682] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
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6
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Shatter Thresholds and Fragment Size Distributions of Deuterium–Neon Mixture Cryogenic Pellets for Tokamak Thermal Mitigation. FUSION SCIENCE AND TECHNOLOGY 2020. [DOI: 10.1080/15361055.2020.1812991] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
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7
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Development of Solenoid-Driven and Pneumatic Punches for Launching High-Z Cryogenic Pellets for Tokamak Disruption Mitigation Experiments. FUSION SCIENCE AND TECHNOLOGY 2019. [DOI: 10.1080/15361055.2019.1592997] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
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8
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Design and Modeling of Vacuum Pumping for Steady-State Pellet Fueling Systems. FUSION SCIENCE AND TECHNOLOGY 2018. [DOI: 10.1080/15361055.2018.1541399] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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9
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Pellet-Injector Technology—Brief History and Key Developments in the Last 25 Years. FUSION SCIENCE AND TECHNOLOGY 2018. [DOI: 10.1080/15361055.2017.1421367] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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10
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Comparison of an Electrothermal Plasma Source to a Light Gas Gun for Launching Large Cryogenic Pellets for Tokamak Disruption Mitigation. FUSION SCIENCE AND TECHNOLOGY 2018. [DOI: 10.1080/15361055.2017.1372683] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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11
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Gas Gun Model and Comparison to Experimental Performance of Pipe Guns Operating with Light Propellant Gases and Large Cryogenic Pellets. FUSION SCIENCE AND TECHNOLOGY 2017. [DOI: 10.1080/15361055.2017.1333824] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
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12
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New ORNL Pellet Injection System and Installation/Initial Operations on MST. FUSION SCIENCE AND TECHNOLOGY 2017. [DOI: 10.13182/fst03-a388] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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13
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Development of a Twin-Screw D2Extruder for the ITER Pellet Injection System. FUSION SCIENCE AND TECHNOLOGY 2017. [DOI: 10.13182/fst09-20] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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A Technique for Producing Large Dual-Layer Pellets in Support of Disruption Mitigation Experiments. FUSION SCIENCE AND TECHNOLOGY 2017. [DOI: 10.13182/fst60-473] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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16
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Tritium Challenges and Plans for ITER Pellet Fueling and Disruption Mitigation Systems. FUSION SCIENCE AND TECHNOLOGY 2017. [DOI: 10.1080/15361055.2017.1290969] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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17
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Tritium Aspects of Fueling and Exhaust Pumping in Magnetic Fusion Energy. FUSION SCIENCE AND TECHNOLOGY 2017. [DOI: 10.1080/15361055.2017.1288421] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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18
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Results from Laboratory Testing of a New Four-Barrel Pellet Injector for the TJ-II Stellarator. FUSION SCIENCE AND TECHNOLOGY 2017. [DOI: 10.13182/fst13-a19144] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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19
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Experimental Study of the Propellant Gas Load Required for Pellet Injection with ITER-Relevant Operating Parameters. FUSION SCIENCE AND TECHNOLOGY 2017. [DOI: 10.13182/fst14-925] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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Design of a digital holography system for PFC erosion measurements on Proto-MPEX. THE REVIEW OF SCIENTIFIC INSTRUMENTS 2016; 87:11D624. [PMID: 27910428 DOI: 10.1063/1.4960488] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
A project has been started at ORNL to develop a dual-wavelength digital holography system for plasma facing component erosion measurements on prototype material plasma exposure experiment. Such a system will allow in situ real-time measurements of component erosion. Initially the system will be developed with one laser, and first experimental laboratory measurements will be made with the single laser system. In the second year of development, a second CO2 laser will be added and measurements with the dual wavelength system will begin. Adding the second wavelength allows measurements at a much longer synthetic wavelength.
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High-speed digital holography for neutral gas and electron density imaging. THE REVIEW OF SCIENTIFIC INSTRUMENTS 2016; 87:053507. [PMID: 27250423 DOI: 10.1063/1.4949505] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/06/2015] [Accepted: 05/01/2016] [Indexed: 06/05/2023]
Abstract
An instrument was developed using digital holographic reconstruction of the wavefront from a CO2 laser imaged on a high-speed commercial IR camera. An acousto-optic modulator is used to generate 1-25 μs pulses from a continuous-wave CO2 laser, both to limit the average power at the detector and also to freeze motion from sub-interframe time scales. Extensive effort was made to characterize and eliminate noise from vibrations and second-surface reflections. Mismatch of the reference and object beam curvature initially contributed substantially to vibrational noise, but was mitigated through careful positioning of identical imaging lenses. Vibrational mode amplitudes were successfully reduced to ≲1 nm for frequencies ≳50 Hz, and the inter-frame noise across the 128 × 128 pixel window which is typically used is ≲2.5 nm. To demonstrate the capabilities of the system, a piezo-electric valve and a reducing-expanding nozzle were used to generate a super-sonic gas jet which was imaged with high spatial resolution (better than 0.8 lp/mm) at high speed. Abel inversions were performed on the phase images to produce 2-D images of localized gas density. This system could also be used for high spatial and temporal resolution measurements of plasma electron density or surface deformations.
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Fast imaging of intact and shattered cryogenic neon pellets. THE REVIEW OF SCIENTIFIC INSTRUMENTS 2014; 85:11E805. [PMID: 25430370 DOI: 10.1063/1.4886426] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
Compact condensed-matter injection technologies are increasingly used in magnetic fusion. One recent application is in disruption mitigation. An imaging system with less-than-100-µm- and sub-µs-resolution is described and used to characterize intact and shattered cryogenic neon pellets. Shattered pellets contain fine particles ranging from tens of µm to about 7 mm. Time-of-flight analyses indicate that pellets could slow down if hitting the wall of the guide tube. Fast high-resolution imaging systems are thus useful to neon and other condensed-matter injector development.
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Digital holography for in situ real-time measurement of plasma-facing-component erosion. THE REVIEW OF SCIENTIFIC INSTRUMENTS 2014; 85:11D810. [PMID: 25430223 DOI: 10.1063/1.4886435] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
In situ, real time measurement of net plasma-facing-component (PFC) erosion/deposition in a real plasma device is challenging due to the need for good spatial and temporal resolution, sufficient sensitivity, and immunity to fringe-jump errors. Design of a high-sensitivity, potentially high-speed, dual-wavelength CO2 laser digital holography system (nominally immune to fringe jumps) for PFC erosion measurement is discussed.
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Reduction of edge-localized mode intensity using high-repetition-rate pellet injection in tokamak H-mode plasmas. PHYSICAL REVIEW LETTERS 2013; 110:245001. [PMID: 25165932 DOI: 10.1103/physrevlett.110.245001] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/06/2012] [Indexed: 06/03/2023]
Abstract
High repetition rate injection of deuterium pellets from the low-field side (LFS) of the DIII-D tokamak is shown to trigger high-frequency edge-localized modes (ELMs) at up to 12× the low natural ELM frequency in H-mode deuterium plasmas designed to match the ITER baseline configuration in shape, normalized beta, and input power just above the H-mode threshold. The pellet size, velocity, and injection location were chosen to limit penetration to the outer 10% of the plasma. The resulting perturbations to the plasma density and energy confinement time are thus minimal (<10%). The triggered ELMs occur at much lower normalized pedestal pressure than the natural ELMs, suggesting that the pellet injection excites a localized high-n instability. Triggered ELMs produce up to 12× lower energy and particle fluxes to the divertor, and result in a strong decrease in plasma core impurity density. These results show for the first time that shallow, LFS pellet injection can dramatically accelerate the ELM cycle and reduce ELM energy fluxes on plasma facing components, and is a viable technique for real-time control of ELMs in ITER.
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High speed digital holography for density and fluctuation measurements (invited). THE REVIEW OF SCIENTIFIC INSTRUMENTS 2010; 81:10E527. [PMID: 21034055 DOI: 10.1063/1.3492423] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
The state of the art in electro-optics has advanced to the point where digital holographic acquisition of wavefronts is now possible. Holographic wavefront acquisition provides the phase of the wavefront at every measurement point. This can be done with accuracy on the order of a thousandth of a wavelength, given that there is sufficient care in the design of the system. At wave frequencies which are much greater than the plasma frequency, the plasma index of refraction is linearly proportional to the electron density and wavelength, and the measurement of the phase of a wavefront passing through the plasma gives the chord-integrated density directly for all points measured on the wavefront. High-speed infrared cameras (up to ∼40,000 fps at ∼64×4 pixels) with resolutions up to 640×512 pixels suitable for use with a CO(2) laser are readily available, if expensive.
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A compact flexible pellet injector for the TJ-II stellarator. THE REVIEW OF SCIENTIFIC INSTRUMENTS 2008; 79:10F321. [PMID: 19044634 DOI: 10.1063/1.2955706] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
A compact pellet injector is being built for the TJ-II stellarator. It is an upgraded version of the "pellet injector in a suitcase" developed at Oak Ridge National Laboratory and installed on the Madison Symmetric Torus where it continues to be used in many plasma experiments. The design aim is to provide maximum flexibility at minimal cost, while allowing for future upgrades. It is a four-barrel system equipped with a cryogenic refrigerator for in situ hydrogen pellet formation, a combined mechanical punch/propellant valve system, pellet diagnostics, and an injection line, destined for use as an active diagnostic and for fueling. In order to fulfill both objectives it will be sufficiently flexible to permit pellets, with diameters from 0.4 to 1 mm, to be fabricated and accelerated to velocities from 150 to approximately 1000 m s(-1).
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Effect of parallel flows and toroidicity on cross-field transport of pellet ablation matter in tokamak plasmas. PHYSICAL REVIEW LETTERS 2005; 94:125002. [PMID: 15903925 DOI: 10.1103/physrevlett.94.125002] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/14/2004] [Indexed: 05/02/2023]
Abstract
The first complete set of time-dependent equations describing the cross-field drift of ionized pellet ablation matter in tokamak plasma caused by polarization in the nonuniform magnetic field has been developed and solved numerically. Important new features impacting the drift dynamics have been identified, including the effect of pressure profile variations in the tokamak plasma, curvature drive by near-sonic field-aligned (parallel) flows, and the rotational transform of the magnetic field lines, and are considered from the viewpoint of the parallel vorticity equation. These new features are necessary to obtain favorable quantitative agreement between theory and experimental fuel deposition profiles for both inner and outer wall launched pellet injection cases on the DIII-D tokamak.
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Investigations of H-mode plasmas triggered directly by pellet injection in the DIII-D tokamak. PHYSICAL REVIEW LETTERS 2001; 86:644-647. [PMID: 11177902 DOI: 10.1103/physrevlett.86.644] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/22/2000] [Revised: 11/20/2000] [Indexed: 05/23/2023]
Abstract
The transition from low-confinement (L-mode) to high-confinement (H-mode) plasmas has been directly produced by injecting frozen deuterium pellets in the DIII-D tokamak. H-mode transitions were produced at edge electron and ion temperatures below the L-mode values. This implies that a critical edge temperature is not necessary for H-mode transitions. The experimentally determined edge plasma parameters were well below those predicted by several theories of the H-mode transition to trigger the H-mode, indicating a need for revision of these theories.
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Experimental confirmation of impurity convection driven by the ion-temperature gradient in toroidal plasmas. PHYSICAL REVIEW LETTERS 2000; 84:282-285. [PMID: 11015891 DOI: 10.1103/physrevlett.84.282] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/09/1999] [Indexed: 05/23/2023]
Abstract
Strong, outward convection of low- Z impurity ions has been observed in DIII-D plasmas which have reduced anomalous transport, a weak density gradient, and a strong ion-temperature gradient. Comparing the measurements with theoretical predictions of collisional (neoclassical) transport indicates that the observed outward convection results from an effect known as "temperature screening." Taking into account the non-negligible effect of anomalous transport, quantitative agreement is found between the measured transport properties and the predicted values, including the strong Z dependence.
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Fluctuation and modulation transport studies in the Advanced Toroidal Facility (ATF) torsatron*. ACTA ACUST UNITED AC 1993. [DOI: 10.1063/1.860737] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022]
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Bootstrap-current experiments in a toroidal plasma-confinement device. PHYSICAL REVIEW LETTERS 1991; 66:707-710. [PMID: 10043880 DOI: 10.1103/physrevlett.66.707] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
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