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
Filter
  • 1990-1994  (11)
Source
Material
Years
Year
  • 1
    Electronic Resource
    Electronic Resource
    Rotational soft x-ray tomography of noncircular tokamak plasmas : 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. 4757-4759 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A rotational tomography technique for noncircular tokamak plasmas has been developed. Using a linear transformation from an elliptic coordinate system to the circular one, and compensating for the Shafranov shift, the elliptic plasma shape is transformed to the concentric circular shape. Fitting the data of a quarter rotation to the Fourier–Bessel expansions, the tomography is performed. This technique is applied to the snake oscillation, to the slow sawtooth crash, and to the post-cursor oscillations of noncircular plasmas on JET.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1143631
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 2
    Electronic Resource
    Electronic Resource
    Measurement of the nonaxisymmetric heat load distribution on the first wall of TFTR due to locked modes : 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. 4720-4723 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: The first wall of TFTR is covered in large part (23%) by an inner-wall bumper limiter which is the primary power handling structure in TFTR. The limiter is comprised of more than 2000 tiles, and is instrumented with a large number ((approximately-greater-than)100) of thermocouples in a two-dimensional (2D) array, primarily for protection of the wall. While only about 5% of the tiles are monitored, this thermocouple system is nevertheless capable of mapping details in the nonaxisymmetric, as well as symmetric, heat load patterns encountered under different conditions. In particular, helical heating patterns are observed in discharges which have locked modes. The helical patterns clearly match the expected trajectories based on the m/n mode numbers obtained from Mirnov coils (m/n=2/1 and 4/1), so that the thermocouple system can and was used to identify the existence and mode number of a locked mode. While TFTR discharges rarely suffer from locked modes, locked modes always alter the heating pattern. The locked modes are found to very significantly redistribute the heat load for both ohmic and NBI heated discharges. Locked modes can make what were the coldest areas into the hottest areas, and vice versa. Locked modes also can alter the heat pattern resulting from the frequent disruptions which occur as a result of a locked mode.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1143618
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 3
    Electronic Resource
    Electronic Resource
    Investigation of magnetic reconnection during a sawtooth crash in a high-temperature tokamak plasma (1994)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 1 (1994), S. 3269-3276 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: In this paper a laboratory investigation is made on magnetic reconnection in high-temperature Tokamak Fusion Test Reactor (TFTR) plasmas [Plasma Physics and Controlled Nuclear Fusion Research 1986 (International Atomic Energy Agency, Vienna, 1987), Vol. 1, p. 51]. The motional Stark effect (MSE) diagnostic is employed to measure the pitch angle profile of magnetic field lines, and hence the q profile. An analytical expression that relates pitch angle to q profile is presented for a toroidal plasma with circular cross section. During the crash phase of sawtooth oscillations in plasma discharges, the ECE (electron cyclotron emission) diagnostic measures a fast flattening of the two-dimensional (2-D) electron temperature profile in a poloidal plane, an observation consistent with the Kadomtsev reconnection theory. On the other hand, the MSE measurements indicate that central q values do not relax to unity after the crash, but increase only by 5%–15%, typically from 0.7 to 0.8. The latter result is in contradiction with the 2-D models of Kadomtsev and/or Wesson. In the present study this puzzle is addressed by a simultaneous analysis of electron temperature and q profile evolutions. Based on a heuristic model for magnetic reconnection during the sawtooth crash, the small change of q, i.e., partial reconnection, is attributed to the precipitous drop of pressure gradients that drive the instability and the reconnection process, as well as flux conserving plasma dynamics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.870479
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 4
    Electronic Resource
    Electronic Resource
    Tomography on tokamak fusion test reactor (1994)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 65 (1994), S. 3415-3422 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Reconstruction techniques have been developed to obtain 2D images of plasmas from the electron cyclotron emission (ECE) and soft x-ray emission signals by taking advantage of the large toroidal rotation rate on the tokamak fusion test reactor (TFTR). From the numerical examination using the sawtooth crash model, we found that the rotational tomography is effective if the crash time is longer than the two rotation periods.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1144515
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 5
    Electronic Resource
    Electronic Resource
    High poloidal beta equilibria in the Tokamak Fusion Test Reactor limited by a natural inboard poloidal field null (1991)
    New York, NY : American Institute of Physics (AIP)
    Physics of Fluids 3 (1991), S. 2277-2284 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Recent operation of the Tokamak Fusion Test Reactor (TFTR) [Plasma Phys. Controlled Nucl. Fusion Research 1, 51 (1986)] has produced plasma equilibria with values of Λ≡βp eq+li/2 as large as 7, εβp dia≡2μ0ε〈p⊥〉/〈〈Bp〉〉2 as large as 1.6, and Troyon normalized diamagnetic beta [Plasma Phys. Controlled Fusion 26, 209 (1984); Phys. Lett. 110A, 29 (1985)], βNdia≡108〈βt⊥〉aB0/Ip as large as 4.7. When εβp dia(approximately-greater-than)1.25, a separatrix entered the vacuum chamber, producing a naturally diverted discharge that was sustained for many energy confinement times, τE. The largest values of εβp and plasma stored energy were obtained when the plasma current was ramped down prior to neutral beam injection. The measured peak ion and electron temperatures were as large as 24 and 8.5 keV, respectively. Plasma stored energy in excess of 2.5 MJ and τE greater than 130 msec were obtained. Confinement times of greater than 3 times that expected from L-mode predictions have been achieved. The fusion power gain QDD reached a value of 1.3×10−3 in a discharge with Ip=1 MA and εβp dia=0.85. A large, sustained negative loop voltage during the steady-state portion of the discharge indicates that a substantial noninductive component of Ip exists in these plasmas. Transport code analysis indicates that the bootstrap current constitutes up to 65% of Ip. Magnetohydrodynamic (MHD) ballooning stability analysis shows that, while these plasmas are near, or at the βp limit, the pressure gradient in the plasma core is in the first region of stability to high-n modes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.859647
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 6
    Electronic Resource
    Electronic Resource
    Investigation of global Alfvén instabilities in the Tokamak Fusion Test Reactor (1992)
    New York, NY : American Institute of Physics (AIP)
    Physics of Fluids 4 (1992), S. 2122-2126 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Toroidal Alfvén eigenmodes (TAE) were excited by the energetic neutral beam ions tangentially injected into plasmas at low magnetic field in the Tokamak Fusion Test Reactor (TFTR) [Proceedings of the 11th International Conference on Plasma Physics and Controlled Fusion Research (IAEA, Vienna, 1987), Vol. 1, p. 51]. The injection velocities were comparable to the Alfvén speed. The modes were identified by measurements from Mirnov coils and beam emission spectroscopy (BES). TAE modes appear in bursts whose repetition rate increases with beam power. The neutron emission rate exhibits sawtoothlike behavior and the crashes always coincide with TAE bursts. This indicates ejection of fast ions from the plasma until these modes are stabilized. The dynamics of growth and stabilization were investigated at various plasma currents and magnetic fields. The results indicate that the instability can effectively clamp the number of energetic ions in the plasmas. The observed instability threshold is discussed in light of recent theories. In addition to these TAE modes, intermittent oscillations at three times the fundamental TAE frequency were observed by Mirnov coils, but no corresponding signal was found in BES. It appears that these high-frequency oscillations do not have a direct effect on the plasma neutron source strength.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.860462
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 7
    Electronic Resource
    Electronic Resource
    Experiments utilizing ion cyclotron range of frequencies heating on the TFTR tokamak (1991)
    New York, NY : American Institute of Physics (AIP)
    Physics of Fluids 3 (1991), S. 2270-2276 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A variety of experiments have been performed on the TFTR tokamak [Wilson et al., Plasma Physics and Controlled Nuclear Fusion Research 1988 (IAEA, Vienna, 1989), Vol. 1, p. 691] utilizing ion cyclotron range of frequencies (ICRF) heating. Of special interest has been the insight into plasma performance gained by utilizing a different heating scheme other than the usual neutral beam injection (NBI). Utilizing ICRF heating allows control over the power deposition profile independent of the plasma fueling profile. In addition, by varying the minority concentration the power split between ion and electron heating can be varied. Confinement has been examined in high recycling gas fueled discharges, low recycling supershot plasmas, and peaked density pellet fueled discharges. Global confinement is found not to be affected by the method or localization of plasma heating, but the calculated local diffusivities vary with the power deposition profile to yield similar global values. In addition, sawtooth stabilization observed with ICRF heating has been investigated and found to occur in qualitative agreement with theory. ICRF sawtooth stabilized discharges exhibit peaked temperature and density profiles and have a safety factor q that appears to fall well below unity on axis.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.859646
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 8
    Electronic Resource
    Electronic Resource
    Image reconstructions of ECE and x-ray signals for high β plasmas on TFTR : Eight topical conference on high−temperature plasma diagnostics (1990)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 61 (1990), S. 3265-3267 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Reconstruction techniques have been developed to obtain 2-D images of high β plasmas by taking advantage of the large toroidal rotation rate on TFTR. The Shafranov shift, which is large in high β plasmas, is taken into account in the reconstructions. A 2-D image of the electron temperature is reconstructed from the electron cyclotron emission with the assumption of rigid poloidal rotation. The soft x-ray tomography is performed using the Fourier–Bessel expansion technique from two x-ray cameras. The reconstruction techniques are tested numerically through the use of model islands. The image is reproduced from the source function with these techniques; however, the x-ray tomography without rotation using the two cameras gives unacceptable results.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1141609
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 9
    Electronic Resource
    Electronic Resource
    Diagnostics for investigation of magnetic reconnection in sawtooth crash on TFTR : 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. 4623-4626 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Magnetic reconnection phenomena are documented by a set of noninvasive fast diagnostics during the crash phase of sawtooth oscillations. The electron cyclotron emission diagnostic system provides the highest resolution for measuring time evolution of electron temperature profile during a typical Tokamak Fusion Test Reactor fast sawtooth crash. The x-ray tomography also contains fast time scale information of the electron temperature profile and additionally the impurity concentration. Just before the crash, a shrinking circular hot peak and growing crescent-shaped flat island appear in the inside of the inversion radius on a bird's-eye view of the electron temperature profile. The electron temperature gradient inside the inversion radius diminishes to nearly zero after the crash. Concomitantly, q(r) profile [q(r)=local safety factor] is measured by the motional stark effect (MSE) diagnostics to verify a magnetic field line reconnection during the sawtooth oscillation. Initial MSE data indicate that central q values increases by 5%–10% during the sawtooth crash phase even when the pressure gradient diminishes inside the q=1 region.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1143637
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 10
    Electronic Resource
    Electronic Resource
    Investigation of ballooning modes in high poloidal beta plasmas in the Tokamak Fusion Test Reactorf| (1993)
    New York, NY : American Institute of Physics (AIP)
    Physics of Fluids 5 (1993), S. 2571-2577 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Medium-n (toroidal mode number) instabilities with ballooning characteristics were investigated using x-ray and electron-cyclotron emission (ECE) imaging techniques in the Tokamak Fusion Test Reactor (TFTR) [R. J. Hawryluk et al., Plasma Phys. Controlled Fusion 33, 1509 (1991)]. The poloidal mode numbers were determined by fitting the data to soft x-ray signals simulated with a wave-packet model, and the toroidal mode numbers were determined from the phase difference between the soft x-ray and ECE signals. The modes are identified as ideal ballooning modes from the observation that the identified mode numbers are much higher than that of the usual kink or tearing modes, the mode has a strong ballooning characteristic, the growth rate is consistent with the theoretical prediction, and the equilibrium is theoretically predicted to be marginal to the infinite n ballooning mode. The ballooning mode accompanies a β collapse which happens near the Troyon limit in TFTR. The ballooning mode has also been observed just before a major disruption in TFTR.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.860692
    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...