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A A Ivanov - One of the best experts on this subject based on the ideXlab platform.

  • study of sublevel population mixing effects in hydrogen Neutral Beams
    Review of Scientific Instruments, 2014
    Co-Authors: S V Polosatkin, A A Ivanov, A Listopad, I. V. Shikhovtsev
    Abstract:

    Intensity of hydrogen Balmer-alpha line is sensitive to distribution of populations of sublevels of excited state due to difference of radiative decay branching ratio for sublevels with different orbital quantum number. Since these sublevels are degenerate transitions between sublevels and mixing of its population may be caused by very weak action of environment. A beam of fast hydrogen atoms is a system in which these fine effects of population mixing can be observed. Experimental data of Hα line radiation intensities in hydrogen Neutral Beams are compared with calculations assumed different models of sublevel population. The comparison most probably point out that population mixing effects cause transitions from long-lived 3s to 3p sublevel with corresponding changes in Hα radiation intensities. Discussed effects may influence to results of Doppler-shift spectroscopy measurements of the Neutral beam parameters such as species and impurities content and Neutralizing efficiency.

  • study of sublevel population mixing effects in hydrogen Neutral Beams
    arXiv: Plasma Physics, 2013
    Co-Authors: S V Polosatkin, A A Ivanov, A Listopad, I. V. Shikhovtsev
    Abstract:

    Intensities of hydrogen Balmer-series lines are sensitive to distribution of populations of sublevels of excited state due to difference of radiative decay branching ratio for sublevels with different orbital quantum number. Since these sublevels are degenerate transitions between sublevels and mixing of its population may be caused by very weak action of environment. A beam of fast hydrogen atoms is a system in which these fine effects of population mixing can be observed. Experimental data of H-alpha line radiation intensities in hydrogen Neutral Beams are compared with calculations assumed different models of sublevel population. The comparison most probably point out that population mixing effects cause transitions from long-lived 3s to 3p sublevel with corresponding changes in H-alpha radiation intensities. Discussed effects may influence to results of Doppler-shift spectroscopy measurements of the Neutral beam parameters such as species and impurities content and Neutralizing efficiency.

  • commissioning of heating Neutral Beams for compass d tokamaka
    Review of Scientific Instruments, 2012
    Co-Authors: P P Deichuli, A. V. Sorokin, A A Ivanov, V I Davydenko, V P Belov, A I Gorbovsky, V V Mishagin, A Dranichnikov, A F Abdrashitov, V V Kolmogorov
    Abstract:

    Two Neutral beam injectors have been developed for plasma heating on COMPASS-D tokamak (Institute of Plasma Physics, Prague). The 4-electrodes multihole ion-optical system with beam focusing was chosen to provide the low divergence 300 kW power in both deuterium and hydrogen atoms. The accelerating voltage is 40 kV at extracted ion current up to 15 A. The power supply system provides the continuous and modulated mode of the beam injection at a maximal pulse length 300 ms. The optimal arrangement of the cryopanels and the beam duct elements provides sufficiently short-length beamline which reduces the beam losses. The evolution of the impurities and molecular fraction content is studied in the process of the high voltage conditioning of the newly made ion sources. Two injectors of the same type have been successfully tested and are ready for operation at tokamak in IPP, Prague.

  • development of focused Neutral Beams with small angular divergence for plasma heating and diagnostics
    Fusion Science and Technology, 2011
    Co-Authors: A A Ivanov, V I Davydenko, P P Deichuli, V P Belov, A I Gorbovsky, V V Mishagin, I. V. Shikhovtsev
    Abstract:

    A series of Neutral beam injectors for plasma heating and diagnostics in modern magnetic fusion devices has been developed in the Budker Institute of Nuclear Physics. In ion sources of these injectors arc discharge or RF plasma boxes are used. Ion optical systems are optimized to produce ion Beams with a low enough angular divergence. In order to provide beam focusing, the grids are formed as spherical segments. Such ballistically focused Beams are further Neutralized in a gas target and subsequently are used to heat or diagnose plasma. Obtained diagnostic Neutral Beams with precise focusing are widely used to measure plasma parameters by beam emission spectroscopy methods in tokamaks, stellarators, reversed field pinches and open traps. High power focused Beams with small divergence are also necessary for heating of localized regions of plasma and in the devices with narrow access ports through which only small size, high power density Beams can be transported. Transition to steady state operation regime of the injectors is discussed.

  • results of recent experiments on gdt device after upgrade of heating Neutral Beams
    Fusion Science and Technology, 2010
    Co-Authors: A A Ivanov, A D Beklemishev, E P Kruglyakov, P A Bagryansky, A A Lizunov, V V Maximov, S V Murakhtin, V V Prikhodko
    Abstract:

    AbstractThe status of the experiments on the axially symmetric magnetic mirror device gas dynamic trap (GDT) is discussed. The plasma has been heated by skewed injection of 20-keV, 3.5-MW, 5-ms deuterium/hydrogen Neutral Beams at the center of the device, which produces anisotropic fast ions. Neither enhanced transverse losses of the plasma nor anomalies in the fast ion scattering and slowing down were observed. Extension of Neutral beam injection pulse duration from 1 to 5 ms resulted in an increase in the on-axis transverse beta (ratio of the transverse plasma pressure to magnetic field pressure) from 0.4 at the fast ion turning points near the end mirrors to about 0.6. The measured beta value is rather close to or even higher than that expected in different versions of the GDT-based 14-MeV neutron source for fusion materials testing. The density of fast ions with the mean energy of 10 to 12 keV reached 5 × 1019 m−3 near the turning points. The electron temperature at the same time reached ≈200 eV. The ...

I. V. Shikhovtsev - One of the best experts on this subject based on the ideXlab platform.

  • Recent progress in development of Neutral Beams for fusion studies
    2016
    Co-Authors: V. Davydenko, P. Deichuli, A. Ivanov, N. Stupishin, V. A. Kapitonov, A. Kolmogorov, I. Ivanov, A. V. Sorokin, I. V. Shikhovtsev
    Abstract:

    A number of Neutral Beams with ballistic focusing were developed in several recent years for fusion studies in the Budker Insitute. Diagnostic Neutral beam injectors for large stellarator W-7X and tokamak T-15 were produced and tested. A high power, relatively low energy Neutral beam injector was developed to upgrade the Neutral beam system of the gas dynamic trap device and C2-U/W experiments. This injector produces a proton beam with the particle energy of 15 keV, ion current of up to 175 A, and pulse duration up to 30 ms. For tokamaks Globus-M and TCV heating injectors of focused Neutral Beams with power ∼1 MW and duration ∼1 s were elaborated and produced. Future development of diagnostic and heating Neutral beam injectors is discussed in the paper.

  • study of sublevel population mixing effects in hydrogen Neutral Beams
    Review of Scientific Instruments, 2014
    Co-Authors: S V Polosatkin, A A Ivanov, A Listopad, I. V. Shikhovtsev
    Abstract:

    Intensity of hydrogen Balmer-alpha line is sensitive to distribution of populations of sublevels of excited state due to difference of radiative decay branching ratio for sublevels with different orbital quantum number. Since these sublevels are degenerate transitions between sublevels and mixing of its population may be caused by very weak action of environment. A beam of fast hydrogen atoms is a system in which these fine effects of population mixing can be observed. Experimental data of Hα line radiation intensities in hydrogen Neutral Beams are compared with calculations assumed different models of sublevel population. The comparison most probably point out that population mixing effects cause transitions from long-lived 3s to 3p sublevel with corresponding changes in Hα radiation intensities. Discussed effects may influence to results of Doppler-shift spectroscopy measurements of the Neutral beam parameters such as species and impurities content and Neutralizing efficiency.

  • study of sublevel population mixing effects in hydrogen Neutral Beams
    arXiv: Plasma Physics, 2013
    Co-Authors: S V Polosatkin, A A Ivanov, A Listopad, I. V. Shikhovtsev
    Abstract:

    Intensities of hydrogen Balmer-series lines are sensitive to distribution of populations of sublevels of excited state due to difference of radiative decay branching ratio for sublevels with different orbital quantum number. Since these sublevels are degenerate transitions between sublevels and mixing of its population may be caused by very weak action of environment. A beam of fast hydrogen atoms is a system in which these fine effects of population mixing can be observed. Experimental data of H-alpha line radiation intensities in hydrogen Neutral Beams are compared with calculations assumed different models of sublevel population. The comparison most probably point out that population mixing effects cause transitions from long-lived 3s to 3p sublevel with corresponding changes in H-alpha radiation intensities. Discussed effects may influence to results of Doppler-shift spectroscopy measurements of the Neutral beam parameters such as species and impurities content and Neutralizing efficiency.

  • development of focused Neutral Beams with small angular divergence for plasma heating and diagnostics
    Fusion Science and Technology, 2011
    Co-Authors: A A Ivanov, V I Davydenko, P P Deichuli, V P Belov, A I Gorbovsky, V V Mishagin, I. V. Shikhovtsev
    Abstract:

    A series of Neutral beam injectors for plasma heating and diagnostics in modern magnetic fusion devices has been developed in the Budker Institute of Nuclear Physics. In ion sources of these injectors arc discharge or RF plasma boxes are used. Ion optical systems are optimized to produce ion Beams with a low enough angular divergence. In order to provide beam focusing, the grids are formed as spherical segments. Such ballistically focused Beams are further Neutralized in a gas target and subsequently are used to heat or diagnose plasma. Obtained diagnostic Neutral Beams with precise focusing are widely used to measure plasma parameters by beam emission spectroscopy methods in tokamaks, stellarators, reversed field pinches and open traps. High power focused Beams with small divergence are also necessary for heating of localized regions of plasma and in the devices with narrow access ports through which only small size, high power density Beams can be transported. Transition to steady state operation regime of the injectors is discussed.

W W Heidbrink - One of the best experts on this subject based on the ideXlab platform.

  • using Neutral Beams as a light ion beam probe invited
    Review of Scientific Instruments, 2014
    Co-Authors: Xi Chen, W W Heidbrink, M A Van Zeeland, G J Kramer, D C Pace, C C Petty, M E Austin, R K Fisher, J M Hanson, R Nazikian
    Abstract:

    By arranging the particle first banana orbits to pass near a distant detector, the light ion beam probe (LIBP) utilizes orbital deflection to probe internal fields and field fluctuations. The LIBP technique takes advantage of (1) the in situ, known source of fast ions created by beam-injected Neutral particles that naturally ionize near the plasma edge and (2) various commonly available diagnostics as its detector. These born trapped particles can traverse the plasma core on their inner banana leg before returning to the plasma edge. Orbital displacements (the forces on fast ions) caused by internal instabilities or edge perturbing fields appear as modulated signal at an edge detector. Adjustments in the q-profile and plasma shape that determine the first orbit, as well as the relative position of the source and detector, enable studies under a wide variety of plasma conditions. This diagnostic technique can be used to probe the impact on fast ions of various instabilities, e.g., Alfven eigenmodes (AEs) and neoclassical tearing modes, and of externally imposed 3D fields, e.g., magnetic perturbations. To date, displacements by AEs and by externally applied resonant magnetic perturbation fields have been measured using a fast ion loss detector. Comparisons with simulations are shown. In addition, nonlinear interactions between fast ions and independent AE waves are revealed by this technique.

  • design of solid state Neutral particle analyzer array for national spherical torus experiment upgrade
    Review of Scientific Instruments, 2014
    Co-Authors: W W Heidbrink, K Tritz, A.l. Roquemore, S.s. Medley
    Abstract:

    A new compact, multi-channel Solid State Neutral Particle Analyzer (SSNPA) diagnostic based on silicon photodiode array has been designed and is being fabricated for the National Spherical Torus Experiment-Upgrade (NSTX-U). The SSNPA system utilizes a set of vertically stacked photodiode arrays in current mode viewing the same plasma region with different filter thickness to obtain fast temporal resolution (∼120 kHz bandwidth) and coarse energy information in three bands of >25 keV, >45 keV, and >65 keV. The SSNPA system consists of 15 radial sightlines that intersect existing on-axis Neutral Beams at major radii between 90 and 130 cm, 15 tangential sightlines that intersect new off-axis Neutral Beams at major radii between 120 and 145 cm. These two subsystems aim at separating the response of passing and trapped fast ions. In addition, one photodiode array whose viewing area does not intersect any Neutral Beams is used to monitor passive signals produced by fast ions that charge exchange with background ...

  • initial measurements of the diii d off axis Neutral Beams
    Nuclear Fusion, 2012
    Co-Authors: W W Heidbrink, M A Van Zeeland, C C Petty, B A Grierson, C M Muscatello, J M Park, R Prater, Y B Zhu
    Abstract:

    Two of the eight Neutral-beam sources on the DIII-D tokamak were modified to allow injection below the midplane. To validate off-axis beam performance, the various Beams are injected sequentially into low-power plasmas that are optimized for accurate neutron, Neutral–particle, fast-ion D-alpha and fast-ion pressure measurements. As expected, the fast-ion profile is broader with off-axis injection than with on-axis injection. The driven toroidal rotation also broadens with off-axis injection and the central fast-ion density is several times smaller. The number of trapped ions in the core depends sensitively on the pitch of the magnetic field lines. Comparisons with classical predictions agree with the measurements for some diagnostics but are discrepant for others.

S H Batha - One of the best experts on this subject based on the ideXlab platform.

  • fusion power production from tftr plasmas fueled with deuterium and tritium
    Physical Review Letters, 1994
    Co-Authors: J D Strachan, H Adler, P Alling, C Ancher, H Anderson, J L Anderson, D Ashcroft, C Barnes, G Barnes, S H Batha
    Abstract:

    Peak fusion power production of 6.2 ± 0.4 MW has been achieved in TFTR plasmas heated by deuterium and tritium Neutral Beams at a total power of 29.5 MW. These plasmas have an inferred central fusion alpha particle density of 1.2 x 1017 m ₋3 without the appearance of either disruptive magnetohydrodynamics events or detectable changes in Alfven wave activity. The measured loss rate of energetic alpha particles agreed with the approximately 5% losses expected from alpha particles which are born on unconfined orbits.

C D Challis - One of the best experts on this subject based on the ideXlab platform.

  • exploring a small sawtooth regime in joint european torus plasmas with counterinjected Neutral Beams
    Physics of Plasmas, 2006
    Co-Authors: M F F Nave, C D Challis, H R Koslowski, S Coda, J P Graves, M Brix, R J Buttery, C Giroud, M Stamp, P De Vries
    Abstract:

    During a recent reversed toroidal field (BT) campaign at the Joint European Torus (JET), experiments were performed to investigate the effect on sawteeth of Neutral beam injection (NBI)-driven toroidal plasma rotation counter to the direction of the toroidal plasma current and BT. A power scan at constant density has permitted analytical continuation, into the reversed BT domain, of previous experiments with forward field and hence corotation. Earlier JET results were confirmed, indicating that counter-NBI results in sawtooth periods shorter than in the Ohmic regime. This study has demonstrated that, whereas with co-NBI the sawtooth period increases with power, with counter-NBI the sawtooth period initially decreases with power passing through a minimum at 4 MW. Clearly this trend also manifests itself in terms of the toroidal plasma rotation, for which a minimum is observed for counter-rotation frequency ∼3 kHz. Sawteeth smaller than Ohmic sawteeth are found to be easier to obtain with perpendicular coun...

  • jet quasistationary internal transport barrier operation with active control of the pressure profile
    Physical Review Letters, 2002
    Co-Authors: F Crisanti, X Litaudon, J Mailloux, D Mazon, E Barbato, Yu F Baranov, A Becoulet, M Becoulet, C D Challis, G D Conway
    Abstract:

    Quasistationary operation has been achieved on the Joint European Torus tokamak in internal-transport-barrier (ITB) scenarios, with the discharge time limited only by plant constraints. Full current drive was obtained over all the high performance phase by using lower hybrid current drive. For the first time feedback control on the total pressure and on the electron temperature profile was implemented by using, respectively, the Neutral Beams and the ion-cyclotron waves. Although impurity accumulation could be a problem in steady state ITBs, these experiments bring some elements to answer to it.