NASA Scientific and Technical Aerospace Reports

20040047250 Lawrence Livermore National Lab., Livermore, CA
Turbulence Simulations of X-point Physics on the L-H Transitions
Xu, X. Q.; Cohen, R. H.; Nevins, W. M.; Porter, G. D.; Rensink, M. E.; Sep. 28, 2000; 18 pp.; In English
Report No.(s): DE2004-15005849; UCRL-JC-137618; No Copyright; Avail: Department of Energy Information Bridge
We show that the resistive X-point mode is dominant mode in boundary plasmas in X-point divertor geometry. The
poloidal fluctuation phase velocity from the resistive X-point turbulence shows experimentally measured structure across
separatrix. The fluctuation phase velocity is larger than E x B velocity both in L and H mode phases, by at least a factor of
two. We also demonstrate that there is a strong poloidal asymmetry of particle flux in the proximity of the separatrix.
Turbulence suppression in the L-H transition results when sources of energy and particles drive sufficient gradients as
experiments.
NTIS
Turbulence; Diverters; Plasmas (Physics)
20040047252 Lawrence Livermore National Lab., Livermore, CA
Spheromak Formation Studies in SSPX
Hill, D. N.; Bulmer, R. H.; Cohen, B. I.; Hooper, E. B.; LoDestro, L. L.; Sep. 29, 2000; 12 pp.; In English
Report No.(s): DE2004-15005850; UCRL-JC-137828; No Copyright; Avail: Department of Energy Information Bridge
We present results from the Sustained Spheromak Physics Experiment (SSPX) at LLNL, which has been built to study
energy confinement in spheromak plasmas sustained for up to 2 ms by coaxial DC helicity injection. Peak toroidal currents
as high as 600kA have been obtained in the 1m dia. (0.23m minor radius) device using injection currents between 200-400kA;
these currents generate edge poloidal fields in the range of 0.2-0.4T. The internal field and current profiles are inferred from
edge field measurements using the CORSICA code. Density and impurity control is obtained using baking, glow discharge
cleansing, and titanium gettering, after which long plasma decay times ((tau)(ge) 1.5ms) are observed and impurity radiation
losses are reduced from (approx.)50% to lesser than 20% of the input energy. Thomson scattering measurements show peaked
electron temperature and pressure profiles with T(sub e) (0)(approx.)120eV and (beta)(sub e)(approx.)7%.
NTIS
Spheromaks; Electron Energy; Plasma Decay
20040050167 Lawrence Livermore National Lab., Livermore, CA
ECE Diagnostic of High Temperature ECRH Heated Plasmas on FTU
Zerbini, M.; Buratti, P.; Tudisco, O.; Giruzzi, G.; Jan. 31, 2000; 20 pp.; In English
Report No.(s): DE2004-15005771; UCRL-JC-142342; No Copyright; Avail: Department of Energy Information Bridge
The Electron Cyclotron Emission (ECE) diagnostic on FTU tokamak is routinely performed with a Michelson
interferometer with spectral range extending up to 1300 GHz. The diagnostic allowed accurate electron temperature
measurements during the recent 140 Ghz Electron Cyclotron Resonance Heating (ECRH) experiments on FTU. Very accurate
measurements have been performed on a wide range of electron temperatures and profile peaking. The ECE measurements
have been compared with Thomson Scattering and with observations of X-ray spectra from highly stripped molybdenum ions.
The suprathermal emission in these conditions has been studied.
NTIS
Tokamak Devices; Spectra
20040050171 Lawrence Livermore National Lab., Livermore, CA
WO21.3 Direct Drive Reentrant Cone Targets for Fast Ignition
Stephens, R. B.; Nikroo, A.; Hill, D.; Smith, J. N.; Hatchett, S. P.; Aug. 23, 2003; 12 pp.; In English
Report No.(s): DE2004-15005825; UCRL-JC-152045; No Copyright; Avail: Department of Energy Information Bridge
Targets designed for fast ignition must have clear access for the ignitor laser to the compressed core. This is provided in
current concepts by embedding a reentrant cone in the shell, the tip of the cone close to the center of the shell. We have
designed a gas-tight direct-drive FI target as the first step in developing a FI ignition target, and have studied its implosion
dynamics at Omega with back-lit and self-emission framing cameras. A step in the cone surface, and Al on the shell was
required to make the assembly gas-tight; these assemblies withstood greater than 10 atm and had a typical pressure half-life
of 2-6 hrs. The implosion of these targets was substantially different from that of previous indirect drive targets; there was
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