NASA Scientific and Technical Aerospace Reports

simplifying or eliminating the need for charge-state separation downstream. Very large currents (hundreds of amperes) can be
extracted from this type of source. Several arrangements are possible. For example, the laser plasma could be tailored for
storage in a magnetic bucket, with beam extracted from the bucket. A different approach, described in this report, is direct
beam extraction from the expanding laser plasma. They discuss extraction and focusing for the particular case of a 4.1-MV
beam of Xe(sup 16+) ions. The maximum duration of the beam pulse is limited by the total charge in the plasma, while the
practical pulse length is determined by the range of plasma radii over which good beam optics can be achieved. The extraction
electrode contains a solenoid for beam focusing. The design studies were carried out first with an envelope code and then with
a self-consistent particle code. Results from the initial model showed that hundreds of amperes could be extracted, but that
most of this current missed the solenoid entrance or was intercepted by the wall and that only a few amperes were able to pass
through. They conclude with an improved design which increases the surviving beam to more than 70 amperes.
NTIS
Ion Beams; Extraction
20040111141 Princeton Univ., NJ, USA
Development of Compact Quasi-Axisymmetric Stellarator Reactor Configurations
Sep. 2003; In English
Report No.(s): DE2003-815147; PPPL-3874; No Copyright; Avail: National Technical Information Service (NTIS)
We have started to examine the reactor potential of quasi-axisymmetric (QA) stellarators with an integrated approach that
includes systems evaluation, engineering considerations, and plasma and coil optimizations. In this paper, we summarize the
progress made so far in developing QA configurations with reduced alpha losses while retaining good MHD stability
properties. The minimization of alpha losses is achieved by directly targeting the collisionless orbits to prolong the average
resident times. Configurations with an overall energy loss rate of(approx)10% or less, including collisional contributions, have
been found. To allow remotely maintaining coils and machine components in a reactor environment, there is a desire to
simplify to the extent possible the coil design. To this end, finding a configuration that is optimized not only for the alpha
confinement and MHD stability but also for the good coil and reactor performance, remains to be a challenging task.
NTIS
Magnetohydrodynamic Stability; Plasmas (Physics); Systems Engineering
20040111146 Princeton Univ., NJ
Anomalous Skin Effect for Anisotropic Electron Velocity Distribution Function
Kaganovich, I.; Startsev, E.; Shvets, G.; Feb. 2004; 16 pp.; In English
Report No.(s): DE2004-821688; PPPL-3925; No Copyright; Avail: Department of Energy Information Bridge
The anomalous skin effect in a plasma with a highly anisotropic electron velocity distribution function (EVDF) is very
different from skin effect in a plasma with the isotropic EVDF. An analytical solution was derived for the electric field
penetrated into plasma with the EVDF described as a Maxwellian with two temperatures Tx>> Tz, where x is the direction
along the plasma boundary and z is the direction perpendicular to the plasma boundary. The skin layer was found to consist
of two distinctive regions of width of order nTx/w and nTz/w, where nTx,z/w= (Tx, z/m)1/2 is the thermal electron velocity
and w is the incident wave frequency.
NTIS
Plasmas (Physics); Velocity Distribution; Electron Distribution
20040111698 Rutgers - The State Univ., New Brunswick, NJ
Basic Studies in Plasma Physics
Lebowitz, Joel L.; Jan. 2004; 23 pp.; In English
Contract(s)/Grant(s): F49620-01-1-0154; Proj-2301
Report No.(s): AD-A425853; AFRL-SR-AR-TR-04-0469; No Copyright; Avail: CASI; A03, Hardcopy
An approximate analytic theory was developed and implemented numerically for calculating the space charge limited
current and electric field of a thin cylindrical beam or current sheet between two wide parallel electrodes. It was found that
the average current density scaled as the reciprocal of the beam width when the latter becomes very small. The total cylindrical
beam current thus decreases proportionally to its diameter while the total current of a sheet becomes almost independent of
the width in this regime.
DTIC
Plasma Physics; Plasmas (Physics)
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