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  (6)
Source
Material
Years
Year
  • 1
    Electronic Resource
    Electronic Resource
    Alpha particle diagnostics using impurity pellet injection (invited) : 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. 4499-4504 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: We have proposed using impurity pellet injection to measure the energy distribution of the fast confined alpha particles in a reacting plasma [R. K. Fisher et al., Fusion Technol. 13, 536 (1988)]. The ablation cloud surrounding the injected pellet is thick enough that an equilibrium fraction F∞0(E) of the incident alphas should be neutralized as they pass through the cloud. By observing neutrals created in the large spatial region of the cloud which is expected to be dominated by the heliumlike ionization state, e.g., Li+ ions, we can determine the incident alpha distribution dnHe2+/dE from the measured energy distribution of neutral helium atoms dnHe0/dE using dnHe0/dE = dnHe2+/dE⋅F∞0 (E,Li+). Initial experiments were performed on the Texas Experimental Tokamak (TEXT) in which we compared pellet penetration with our impurity pellet ablation model [P. B. Parks et al., Nucl. Fusion 28, 477 (1988)], and measured the spatial distribution of various ionization states in carbon pellet clouds [R. K. Fisher et al., Rev. Sci. Instrum. 61, 3196 (1990)]. Experiments have recently begun on the Tokamak Fusion Test Reactor (TFTR) with the goal of measuring the alpha particle energy distribution during D–T operation in 1993–94. A series of preliminary experiments are planned to test the diagnostic concept. The first experiments will observe neutrals from beam-injected deuterium ions and the high energy 3He tail produced during ion cyclotron (ICH) minority heating on TFTR interacting with the cloud. We will also monitor by line radiation the charge state distributions in lithium, boron, and carbon clouds. Later experiments are planned to measure the energy distribution of the 3.7 MeV alphas created by 3He–D reactions during ICH minority heating. Observations of 3.7 MeV alphas should allow single-particle alpha physics to be studied now and result in a fully tested diagnostic prior to D–T operation of TFTR.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1143705
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 2
    Electronic Resource
    Electronic Resource
    Imaging of lithium pellet ablation trails and measurement of q profiles in 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. 5191-5194 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Video images with 2 μs exposures of the Li+ emission in Li pellet ablation clouds have been obtained in a variety of Tokamak Fusion Test Reactor tokamak discharges. The pellet clouds are viewed from behind the pellet, which is injected from the outside midplane. In this view, the emission forms an elongated cigar shape with the long dimension of the cigar aligned with the local magnetic field. In some cases, two distinct parallel cigars can be seen simultaneously, displaced vertically from one another by ∼5 cm. Measurements using a ten channel array of position sensitive photodiodes show that the mean position of the ablation cloud emission can oscillate vertically by ∼4 cm with periods in the 60–100 μs range, and that these oscillations are highly correlated with "bursts'' in the cloud emission. The tilt of the cloud is also measured as a function of time as the pellet traverses the plasma, and in this way the poloidal field profile is obtained. (The total transit time of the pellet is ∼1 ms.) Magnetohydrodynamic equilibrium reconstructions of q profiles have been determined using these measurements.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1143849
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 3
    Electronic Resource
    Electronic Resource
    Measurement of internal magnetic field pitch using Li pellet injection on TFTR (invited) : Eighth topical conference on high−temperature plasma diagnostics (1990)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 61 (1990), S. 2908-2913 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A diagnostic technique which measures the direction of the internal magnetic field pitch angle has been used successfully on TFTR. The technique requires the injection of high-speed Li pellets. The magnetic field direction is measured by observing the polarization direction of the intense visible line emission from Li+ (λ≈5485 A(ring), 1s2p 3P0,1,2→1s2s 3S0) in the pellet ablation cloud. The presence of the large (primarily toroidal) magnetic field causes the line to be split due to the Zeeman effect, and the unshifted π component is polarized with its polarization direction parallel to the local magnetic field. In devices with sufficiently strong fields (B(approximately-greater-than)4.5 T), the Zeeman splitting of the line is large enough, relative to the linewidth of each Zeeman component, that enough residual polarization remains. Because the pellet moves about 1 cm before the Li+ is ionized (τionization(approximately-less-than)10 μs), the time history of the polarization direction (as the pellet penetrates from the outside toward the plasma center) yields the local magnetic field direction. In the TFTR experiment, spatial resolution of the measurement is typically ∼7 cm, limited by the requirement that a large number of photons must be collected in order to make the measurement of the polarization angle. Typically, the pitch of the field is measured with an accuracy of ±0.01 rad, limited by the photon statistics. The measurements of the internal field pitch angle, combined with external magnetic measurements, have been used in a code which finds the solution of the Grad–Shafranov equation, yielding the equilibrium which is the best fit to the measured inputs. The q profile constructed from this equilibrium is believed to be accurate to ∼±10% over the region where there are internal magnetic measurements. Internal field measurements and equilibrium reconstructions have been performed for a variety of TFTR discharges, including 1.6 MA ohmic plasmas where the internal field is measured at the beginning of the current flat top (before the onset of sawteeth) and 2 s into the flat top (with sawteeth), and in extremely high βp(Ip=0.3 MA, βp≈4.5) discharges.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1141775
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 4
    Electronic Resource
    Electronic Resource
    Measurement of the internal magnetic field in tokamaks utilizing impurity pellets: A new detection technique : Eighth topical conference on high—temperature plasma diagnostics (1990)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 61 (1990), S. 3081-3083 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Measurements on impurity pellet ablation trails indicate that the emission from these clouds extends much farther along the magnetic field than across it. For carbon pellets on TFTR, the aspect ratio of this cigar-shaped plume is of the order of 10. Strong visible line emission from one of the ionization states can be imaged with high time resolution, and since ions should be well confined along the field lines, it should be possible in this way to measure the radial profile of the pitch of the total internal magnetic field. For a pellet injected along a major radius in the plasma midplane, the appropriate viewing geometry consists of imaging the pellet along its flight from behind. A detector scheme capable of accomplishing the measurement, consisting of an array of 1-D spot-imaging photodiodes, is described. In order to make meaningful measurements with regard to the tokamak physics of interest, it is highly desirable to measure the field angle profile with a precision of ±10 mrad or better. In order to achieve this for a cigar with aspect ratio of 10, measurement of the mean vertical position for each slice of the cigar must be made with a precision of about 10% of the vertical thickness of the cigar on that slice.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1141687
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 5
    Electronic Resource
    Electronic Resource
    MLM-based monochromator for molybdenum impurity monitoring on the Alcator C-MOD tokamak in the 30–130 A(ring) range : 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. 5176-5178 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Molybdenum, from the vessel wall armor tiles and divertor plates, is expected to be the dominant high-Z impurity in the Alcator C-MOD tokamak plasma. To monitor the molybdenum emission in the extreme ultraviolet (XUV), a monochromator utilizing multilayer mirrors (MLMs) as dispersive elements will be installed on the C-MOD tokamak with a 10° above the mid-plane view across the plasma's center. Much of the strong Mo emission under the C-MOD experimental conditions will be emitted between 30–50 A(ring) and 65–90 A(ring) by M-shell ions (n=3–3 and n=3–4 transitions), at 116 A(ring) from MoXXXI and at 127 A(ring) from MoXXXII. The monochromator will have three MLMs and either three-channel electron multipliers or three XUV silicon photodiodes mounted on a single θ-2θ goniometer. Each MLM and detector unit will simultaneously monitor a separate molybdenum emission range with a 1–10-ms temporal resolution. The resolution of the MLMs range from 1 to 5 A(ring) depending on the wavelength, and each MLM will be optimized for one of the above spectral regions. This low-resolution monitoring of many charge states will enable radiative power loss estimates and can be used in impurity transport analysis. The design of the monochromator and the expected Mo emission will be presented and discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1143473
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 6
    Electronic Resource
    Electronic Resource
    Lithium pellet deposition and penetration in 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. 4984-4986 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: The electron deposition resulting from the injection of Li pellets into Tokamak Fusion Test Reactor, measured by a multichannel (10) infrared interferometer, is compared with that deduced from the pellet ablation cloud emission, measured by a filtered diode array which views the pellet from behind. By assuming that the ablation rate N(overdot)(r) is proportional to the pellet cloud emissivity, which is dominated by Li+ line emission in the 548.5±5 nm bandpass of the interference filter, the post-pellet, line averaged density perturbations along the interferometer chords were calculated and compared with those measured. Good agreement is observed. The experimental ablation rate profiles obtained using the emissivity have also been compared with predictions of the theoretical models. There is an agreement between the time history of the emissivity and the predicted ablation rate at the plasma edge where the electron temperature values are less than 1–1.5 keV. When the pellet penetrates more deeply, the experimental N(overdot)(r) values are systematically smaller than those predicted. This points out the necessity of taking into account plasma shielding and/or precooling of the target plasma during pellet injection in the ablation model.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1143521
    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...