Library

X
feed icon rss

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
  • 1
    Electronic Resource
    Electronic Resource
    q-profile measurement in tokamaks using fueling pellets (1988)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 59 (1988), S. 1623-1625 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Fuel pellets ablating in a hot, magnetically confined plasma generate cold, self-luminous filaments which seem to orient themselves along the local magnetic field direction. This distinctive ablation pattern has been used for local measurements of the q profile. In the Texas Experimental Tokamak (TEXT), this technique was investigated experimentally, and the results were compared to other q-profile measurements to examine limits of applicability. It is found that the technique may be applied only to limited regions of the plasma. Although the mechanism which causes the filaments to align along the magnetic field lines is not completely understood, comparisons between this technique and other techniques tend to support its use. Inclination angle profiles for the local magnetic field and q profiles obtained on TEXT by this technique are presented. The q profiles are compared with predictions based on various resistivity models, specifically classical, neoclassical, and q-clamped.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1140166
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 2
    Electronic Resource
    Electronic Resource
    Convergence, electrostatic potential, and density measurements in a spherically convergent ion focus (1997)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 4 (1997), S. 4-15 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Unique measurements of the basic plasma-flow characteristics in a low pressure (≤53 mPa H2) spherically convergent ion focus are obtained using high-voltage (≤5 kV) emissive and double probes. The radial plasma potential distribution agrees with a collisionless, recirculating, space-charge-limited current model. Flow convergence increases with voltage and neutral pressure and decreases with cathode grid wire spacing and current. Core radii within 4–5 times the ideal geometric limit are measured, and the observed core sizes are consistent with predictions from a multipass orbit model which includes asymmetries in the accelerating potential well. A virtual anode is observed in the converged core region, and no evidence for multiple potential well structures in the core is found. Measurements of the core ion density (nic∼1015 m−3) are consistent with simple flow convergence models. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.872110
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 3
    Electronic Resource
    Electronic Resource
    Rotational and magnetic shear stabilization of magnetohydrodynamic modes and turbulence in DIII-D high performance discharges (1996)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 3 (1996), S. 1951-1958 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The confinement and the stability properties of the DIII-D tokamak [Plasma Physics and Controlled Nuclear Fusion Research 1986 (International Atomic Energy Agency, Vienna, 1987), Vol. 1, p. 159] high-performance discharges are evaluated in terms of rotational and magnetic shear, with an emphasis on the recent experimental results obtained from the negative central magnetic shear (NCS) experiments. In NCS discharges, a core transport barrier is often observed to form inside the NCS region accompanied by a reduction in core fluctuation amplitudes. Increasing negative magnetic shear contributes to the formation of this core transport barrier, but by itself is not sufficient to fully stabilize the toroidal drift mode (trapped-electron-ηi mode) to explain this formation. Comparison of the Doppler shift shear rate to the growth rate of the ηi mode suggests that the large core E×B flow shear can stabilize this mode and broaden the region of reduced core transport. Ideal and resistive stability analysis indicates the performance of NCS discharges with strongly peaked pressure profiles is limited by the resistive interchange mode to low βN≤2.3. This mode is insensitive to the details of the rotational and the magnetic shear profiles. A new class of discharges, which has a broad region of weak or slightly negative magnetic shear (WNS), is described. The WNS discharges have broader pressure profiles and higher β values than the NCS discharges, together with high confinement and high fusion reactivity. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.871991
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 4
    Electronic Resource
    Electronic Resource
    Technique for the experimental estimation of nonlinear energy transfer in fully developed turbulence (1996)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 3 (1996), S. 3998-4009 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A new procedure for calculating the nonlinear energy transfer and linear growth/damping rate of fully developed turbulence is derived. It avoids the unphysically large damping rates typically obtained using the predecessor method of Ritz [Ch. P. Ritz, E. J. Powers, and R. D. Bengtson, Phys. Fluids B 1, 153 (1989)]. It enforces stationarity of the turbulence to reduce the effects of noise and fluctuations not described by the basic governing equation, and includes the fourth-order moment to avoid the closure approximation. The new procedure has been implemented and tested on simulated, fully developed two-dimensional (2-D) turbulence data from a 2-D trapped-particle fluid code, and has been shown to give excellent reconstructions of the input growth rate and nonlinear coupling coefficients with good noise rejection. However, in the experimentally important case where only a one-dimensional (1-D) averaged representation of the underlying 2-D turbulence is available, this technique does not, in general, give acceptable results. A new 1-D algorithm has thus been developed for analysis of 1-D measurements of intrinsically 2-D turbulence. This new 1-D algorithm includes the nonresonant wave numbers in calculating the bispectra, and generally gives useful results when the width of the radial wave number spectrum is comparable to or less than that of the poloidal spectrum. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.871572
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 5
    Electronic Resource
    Electronic Resource
    Measurements of the radial structure and poloidal spectra of toroidal Alfvén eigenmodes in the Tokamak Fusion Test Reactor (1992)
    New York, NY : American Institute of Physics (AIP)
    Physics of Fluids 4 (1992), S. 3707-3712 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Toroidal Alfvén eigenmodes (TAE) have been excited by tangential neutral beam injection in the Tokamak Fusion Test Reactor (TFTR) [Proceedings of the Thirteenth International Conference on Plasma Physics and Controlled Nuclear Fusion Research, 1990, Washington, D.C. (International Atomic Energy Agency, Vienna, 1990), Vol. I, p. 9]. Beam emission spectroscopy (BES) has been used to study the radial structure and the poloidal power spectra of these modes. Radial profiles show a global, standing wave structure with a node near r/a=0.6 and a maximum displacement of about 5–10 mm. The cross-phase profiles and the power spectra both imply that the mode is composed of a mixture of components with various poloidal and toroidal mode numbers, as expected for the TAE. Measurements of the poloidal mode spectrum via BES show good agreement with theoretical simulations performed by a nonvariational, kinetic magnetohydrodynamics stability code (nova−k [Cheng, Phys. Rep. 211, 1 (1992)]). In particular, the dominant harmonics in the poloidal spectrum obey the expected relation m+1/2≈q(r)n.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.860326
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 6
    Electronic Resource
    Electronic Resource
    Measurements of long-wavelength density fluctuations in TFTR (1992)
    New York, NY : American Institute of Physics (AIP)
    Physics of Fluids 4 (1992), S. 2922-2928 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Several experiments have been devised to measure plasma fluctuations in an effort to help elucidate a possible connection between plasma microturbulence and anomalous transport. Results from microwave scattering on the Tokamak Fusion Test Reactor (TFTR) [Nucl. Fusion 18, 1089 (1978)] show that the level of plasma fluctuations increases toward the long-wavelength region (k⊥ρs≤0.2), at which point the fluctuations cannot be spatially resolved. The desire to measure long-wavelength fluctuations has motivated the development of two fluctuation diagnostics, beam emission spectroscopy (BES), and microwave reflectometry on TFTR. BES measures long-wavelength density fluctuations (k⊥≤2 cm−1) by observing the fluorescence emitted from collisionally excited atoms in a TFTR heating beam. In L-mode discharges with relatively flat density profiles, the fluctuations measured with BES are concentrated in the low-frequency region (≤30 kHz). In the laboratory frame, the fluctuations have a poloidal propagation velocity that is approximately equal to that of the plasma rotation, and the frequency spectra are broadened by Doppler effects. Measured fluctuation levels are 5%–10% at the edge of the plasma. In the core, the level falls to less than 1%, which is comparable to observations made with microwave reflectometry and scattering. The fluctuation level in the core (r/a=0.7) is seen to increase with injected beam power, as is observed with microwave scattering at shorter wavelengths (k⊥≈2–10 cm−1). In contrast, the fluctuation level in the edge region does not change significantly with neutral beam power.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.860165
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 7
    Electronic Resource
    Electronic Resource
    Effect of high-energy neutron flux on fiber optics in an active diagnostic on TFTR (abstract)a) : Proceedings of the tenth topical conference on high temperature plasma diagnostics (1995)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 66 (1995), S. 919-919 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A bundle of 1-mm-diam fused silica optical fibers on an existing TFTR diagnostic has been exposed to 11 high-power DT discharges. Each shot subjected the fibers to a peak fast (14.7 MeV) neutron flux of ≈2×1012 n/cm2/s and a γ-dose rate of 500 rad(Si)/s for 0.75–1.0 s. The total fast-neutron fluence for these shots was ≈5×1012 n/cm2. A 15-m-long section of the bundle ran along the tokamak's toroidal field coils and the remaining 15 m ran radially away from the reactor. Fiber luminescence at 660 nm was ≈1010 photons/s/sr/cm2/A(ring) for the above flux (≈5%–10% of the bremsstrahlung emission), and varied linearly with DT neutron rate. Luminescence at 530 nm was 50% stronger, consistent with a Cerenkov radiation spectrum. Sensitivity to 3.5 MeV DD neutrons was ≈1/3 to 1/2 of that for DT neutrons. Fiber transmission decreased with the time integral of the neutron source rate and was reduced by 4% for the above flux. The fiber recovered rapidly: within 10 s, the transmission loss was only 2.5%. Shortly thereafter, the rate of recovery slowed to ≈0.05% per minute, but was sufficient to restore 75% of the transmission loss within two to four discharges. Recovery continued at ≈0.1% per hour and slowed overnight to ≈0.1% per day. Within the relative error of 〈0.2%, full transmission was recovered after five days. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1146205
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 8
    Electronic Resource
    Electronic Resource
    Effects of edge plasma turbulence on radial correlation length measurements with BES : Proceedings of the 9th topical conference on high temperature plasma diagnostics (1992)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 63 (1992), S. 4931-4933 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: The recently developed technique of beam emission spectroscopy (BES) provides a tool to study long-wavelength density turbulence (coherence length (very-much-greater-than) ion gyroradius) in hot tokamak plasmas. To provide an accurate conversion of the measured light intensity fluctuations to a local ñ/n density fluctuation and to assess the influence of density fluctuations in the neutral beam induced by large edge turbulence, a multistate neutral beam excitation/transport code for realistic experimental geometries has been written. Results from this code show that the attenuation of the beam density induced by edge turbulence can give rise to significant levels of common-mode fluctuation power in signals from the plasma core and that the derivation of quantitative values of ñ/n from experimental measurements depends weakly on the radial extent of the density fluctuations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1143553
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 9
    Electronic Resource
    Electronic Resource
    Beam emission imaging system for 2D plasma turbulence measurements : Proceedings of the tenth topical conference on high temperature plasma diagnostics (1995)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 66 (1995), S. 639-641 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A two-dimensional analog to the beam emission spectroscopy (BES) diagnostic has been designed to acquire vorticity and plasma flow-field information by resolving the spatial and temporal intermittency of plasma turbulent structures. The beam emission imaging diagnostic measures collisionally induced neutral beam fluorescence to infer local plasma density variations. It consists of a high-throughput, interline-transfer CCD camera viewing, with narrow spectral bandwidth, a 10 cm high diagnostic neutral beam as it traverses the plasma. The camera is coupled to a gated image intensifier that provides for two images with exposure times up to a few ms to be separated by as little as 10 μs. Sensitivity to density fluctuations of ñ/n(approximately-greater-than)1.0% is expected using the Phaedrus-T beam operating at 20–25 keV in He0 or D0. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1146533
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 10
    Electronic Resource
    Electronic Resource
    Mechanized selection of fiber optic arrays for spectroscopy measurements : Proceedings of the 9th topical conference on high temperature plasma diagnostics (1992)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 63 (1992), S. 4921-4923 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A 400-fiber optic bundle has been installed as part of the beam emission spectroscopy diagnostic for measuring density fluctuations in Tokamak Fusion Test Reactor. One hundred bundles, each composed of four 1-mm-diam fibers, transmit Hα light 50 m away to 20 detectors located outside the radiation area. To shorten the time spent manually switching the bundles among the 20 detectors, a mechanized fiber selector was installed. The fiber bundles were separated into radial and poloidal groups of 220 and 180 fibers and coupled by a computer-controlled, motorized precision translation stage. The fibers were fastened to a plate and placed less than 0.003 in. from an identical plate that holds a similar array of fibers which transmits the light to the detectors. Holding the fiber spacing tolerance to 0.001 in., and using refractive index matching fluid, the highest measured loss was less than 0.5 dB, and generally was very small compared to the fiber's insertion loss. The stages are actuated with precision encoded micrometers and controlled by the beam emission spectroscopy VAX-resident software via a RS-232/CAMAC interface allowing arbitrary selections of fibers between plasma discharges with a 5 min repetition rate.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1143549
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...