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1

Digitale Medien

Laser–plasma interactions in ignition-scale hohlraum plasmas (1996)

MacGowan, B. J. ; Afeyan, B. B. ; Back, C. A. ; [weitere]

[S.l.] : American Institute of Physics (AIP)

Physics of Plasmas 3 (1996), S. 2029-2040

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ISSN: 1089-7674

Quelle: AIP Digital Archive

Thema: Physik

Notizen: Scattering of laser light by stimulated Brillouin scattering (SBS) and stimulated Raman scattering (SRS) is a concern for indirect drive inertial confinement fusion (ICF). The hohlraum designs for the National Ignition Facility (NIF) raise particular concerns due to the large scale and homogeneity of the plasmas within them. Experiments at Nova have studied laser–plasma interactions within large scale length plasmas that mimic many of the characteristics of the NIF hohlraum plasmas. Filamentation and scattering of laser light by SBS and SRS have been investigated as a function of beam smoothing and plasma conditions. Narrowly collimated SRS backscatter has been observed from low density, low-Z, plasmas, which are representative of the plasma filling most of the NIF hohlraum. SBS backscatter is found to occur in the high-Z plasma of gold ablated from the wall. Both SBS and SRS are observed to be at acceptable levels in experiments using smoothing by spectral dispersion (SSD). © 1996 American Institute of Physics.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1063/1.872000

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2

Digitale Medien

Enhancement of Tokamak Fusion Test Reactor performance by lithium conditioning (1996)

Mansfield, D. K. ; Hill, K. W. ; Strachan, J. D. ; [weitere]

[S.l.] : American Institute of Physics (AIP)

Physics of Plasmas 3 (1996), S. 1892-1897

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ISSN: 1089-7674

Quelle: AIP Digital Archive

Thema: Physik

Notizen: Wall conditioning in the Tokamak Fusion Test Reactor (TFTR) [K. M. McGuire et al., Phys. Plasmas 2, 2176 (1995)] by injection of lithium pellets into the plasma has resulted in large improvements in deuterium–tritium fusion power production (up to 10.7 MW), the Lawson triple product (up to 1021 m−3 s keV), and energy confinement time (up to 330 ms). The maximum plasma current for access to high-performance supershots has been increased from 1.9 to 2.7 MA, leading to stable operation at plasma stored energy values greater than 5 MJ. The amount of lithium on the limiter and the effectiveness of its action are maximized through (1) distributing the Li over the limiter surface by injection of four Li pellets into Ohmic plasmas of increasing major and minor radius, and (2) injection of four Li pellets into the Ohmic phase of supershot discharges before neutral-beam heating is begun. © 1996 American Institute of Physics.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1063/1.871984

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3

Digitale Medien

Gas-filled targets for large scale-length plasma interaction experiments on Nova (1995)

Powers, L. V. ; Berger, R. L. ; Kauffman, R. L. ; [weitere]

[S.l.] : American Institute of Physics (AIP)

Physics of Plasmas 2 (1995), S. 2473-2479

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ISSN: 1089-7674

Quelle: AIP Digital Archive

Thema: Physik

Notizen: Stimulated Brillouin backscatter from large scale-length gas-filled targets has been measured on the Nova laser. These targets were designed to approximate conditions in indirect drive ignition target designs in underdense plasma electron density (ne∼1021/cm3), temperature (Te(approximately-greater-than)3 keV), and gradient scale lengths (Ln∼2 mm, Lv(approximately-greater-than)6 mm) as well as calculated gain for stimulated Brillouin scattering (SBS). The targets used in these experiments were gas-filled balloons with polyimide walls (gasbags) and gas-filled hohlraums. Detailed characterization using x-ray imaging and x-ray and optical spectroscopy verifies that the calculated plasma conditions are achieved. Time-resolved SBS backscatter from these targets is 〈3% for conditions similar to ignition target designs. © 1995 American Institute of Physics.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1063/1.871208

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4

Digitale Medien

Enhanced performance of deuterium–tritium-fueled supershots using extensive lithium conditioning in the Tokamak Fusion Test Reactor (1995)

Mansfield, D. K. ; Strachan, J. D. ; Bell, M. G. ; [weitere]

[S.l.] : American Institute of Physics (AIP)

Physics of Plasmas 2 (1995), S. 4252-4256

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ISSN: 1089-7674

Quelle: AIP Digital Archive

Thema: Physik

Notizen: In the Tokamak Fusion Test Reactor (TFTR) [K. M. McGuire et al., Phys. Plasmas 2, 2176 (1995)] a substantial improvement in fusion performance has been realized by combining the enhanced confinement due to tritium fueling with the enhanced confinement due to extensive conditioning of the limiter with lithium. This combination has resulted in not only significantly higher global energy confinement times than have previously been obtained in high current supershots, but also in the highest central ratio of thermonuclear fusion output power to input power observed to date. © 1995 American Institute of Physics.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1063/1.871050

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5

Digitale Medien

Experiments utilizing ion cyclotron range of frequencies heating on the TFTR tokamak (1991)

Wilson, J. R. ; Hosea, J. C. ; Bell, M. G. ; [weitere]

New York, NY : American Institute of Physics (AIP)

Physics of Fluids 3 (1991), S. 2270-2276

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ISSN: 1089-7666

Quelle: AIP Digital Archive

Thema: Physik

Notizen: 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.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1063/1.859646

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6

Digitale Medien

Anomalous losses of deuterium–deuterium fusion products in the Tokamak Fusion Test Reactorf| (1994)

Zweben, S. J. ; Bush, C. E. ; Chang, C. S. ; [weitere]

[S.l.] : American Institute of Physics (AIP)

Physics of Plasmas 1 (1994), S. 1469-1478

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ISSN: 1089-7674

Quelle: AIP Digital Archive

Thema: Physik

Notizen: In the Tokamak Fusion Test Reactor (TFTR) [International Conference on Plasma Physics and Controlled Nuclear Fusion Research, Wurzburg, Paper No. A-2-2 (International Atomic Energy Agency, Vienna, 1993)] there have been at least three types of anomalous loss of alpha-like deuterium–deuterium (D–D) fusion products: (1) a magnetohydrodynamic (MHD)-induced loss of D–D fusion products correlated with Mirnov and fishbone-type oscillations and sawtooth crashes, (2) a slow "delayed'' loss of partially thermalized D–D fusion products occurring without large MHD activity, and (3) ion cyclotron resonance heating (ICRH)-induced loss of D–D fusion products ions observed during direct electron heating experiments, and possibly also during 3He minority heating. In this paper each of these will be reviewed, concentrating on those due to MHD activity, which are the largest of these anomalous losses. The experimental results are compared with numerical models of various fusion product transport mechanisms.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1063/1.870697

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7

Digitale Medien

Hot electron production and heating by hot electrons in fast ignitor research : The 39th annual meeting of division of plasma physics of APS (1998)

Key, M. H. ; Cable, M. D. ; Cowan, T. E. ; [weitere]

[S.l.] : American Institute of Physics (AIP)

Physics of Plasmas 5 (1998), S. 1966-1972

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ISSN: 1089-7674

Quelle: AIP Digital Archive

Thema: Physik

Notizen: In an experimental study of the physics of fast ignition, the characteristics of the hot electron source at laser intensities up to 1020 W cm−2 have been measured and a diagnosis of the heating at depth by hot electrons has been initiated. Generation of hot electrons with more than 30% efficiency has been observed. Preliminary heating data suggest temperatures kT in the range 300–800 eV.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1063/1.872867

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8

Digitale Medien

Production and characterization of large plasmas from gas bag targets on Nova (1995)

Kalantar, D. H. ; Klem, D. E. ; MacGowan, B. J. ; [weitere]

[S.l.] : American Institute of Physics (AIP)

Physics of Plasmas 2 (1995), S. 3161-3168

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ISSN: 1089-7674

Quelle: AIP Digital Archive

Thema: Physik

Notizen: Large plasmas are created by illuminating gas-filled thin-walled balloon-like targets using the Nova laser [E. Campbell et al., Rev. Sci. Instrum. 57, 2101 (1986)]. The targets consist of a 5000–6000 A(ring) skin surrounding 1 atm of neopentane, which, when ionized, becomes a plasma with an electron density of 1021 electrons/cm3. X-ray images of the gas bag target are used to evaluate the size and uniformity of the plasma by comparison with LASNEX [R. M. More, J. Quant. Spectrosc. Radiat. Transfer 27, 345 (1982)] simulations. The gas bags are heated with converging and diverging beam spots. The most uniform plasmas are created by illuminating the target with large converging beam spots that overlap to cover most of the surface of the gas bag. The gas bag plasma is heated to a peak temperature of approximately 3.5 keV, with 25 kJ of 3ω laser light in a 1 ns square pulse. © 1995 American Institute of Physics.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1063/1.871148

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9

Digitale Medien

The Oxford electron-beam ion trap: A device for spectroscopy of highly charged ions : Proceedings of the 5th international conference on ion sources (1994)

Silver, J. D. ; Varney, A. J. ; Margolis, H. S. ; [weitere]

[S.l.] : American Institute of Physics (AIP)

Review of Scientific Instruments 65 (1994), S. 1072-1074

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ISSN: 1089-7623

Quelle: AIP Digital Archive

Thema: Physik , Elektrotechnik, Elektronik, Nachrichtentechnik

Notizen: An electron-beam ion trap (EBIT) has just been completed in the Clarendon Laboratory, Oxford. The design is similar to the devices installed at the Lawrence Livermore National Laboratory. It is intended that the Oxford EBIT will be used for x-ray and UV spectroscopy of hydrogenic and helium-like ions, laser resonance spectroscopy of hydrogenic ions and measurements of dielectronic recombination cross sections, in order to test current understanding of simple highly charged ions.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1063/1.1145066

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10

Digitale Medien

Phase stability for the in situ growth of Nd1+xBa2−xCu3Oy films using pulsed-laser deposition (1999)

Cantoni, C. ; Norton, D. P. ; Kroeger, D. M. ; [weitere]

Woodbury, NY : American Institute of Physics (AIP)

Applied Physics Letters 74 (1999), S. 96-98

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ISSN: 1077-3118

Quelle: AIP Digital Archive

Thema: Physik

Notizen: We have determined the stability line in the 1/T−log[P(O2)] phase space for the synthesis of Nd1+xBa2−xCu3Oy (NdBCO) films. A systematic study of Tc, Jc, and ρ(T) dependence on oxygen partial pressure and temperature for the deposition of thin NdBCO films grown by pulsed-laser deposition was performed. The conditions for optimal NdBCO film growth were determined by varying oxygen partial pressure from 0.02 to 400 mTorr, and substrate temperature between 730 and 800 °C. The results show that the best NdBCO films are obtained at oxygen pressures in the range of 0.2–1.2 mTorr, depending on the substrate temperature. This is more than two orders-of-magnitude lower than the correspondent oxygen pressure appropriate for YBa2Cu3O7−δ film growth. © 1999 American Institute of Physics.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1063/1.123162

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