Research at the
Virtual National Laboratory for Heavy-Ion Fusion
The Virtual National Laboratory for Heavy-Ion Fusion (HIF-VNL) was
established in 1999 to develop heavy-ion accelerators capable of igniting
inertial-fusion targets for electric-power production. The collaboration,
which presently involves Lawrence Berkeley National Laboratory (LBNL),
Lawrence Livermore National Laboratory (LLNL), and Princeton Plasma Physics
Laboratory, is funded through the Office of Fusion Energy at the US Department
of Energy. According the memorandum creating the partnership, the
HIF-VNL is chartered with "promoting more rapid progress in the development
of heavy ion drivers through technical management integration of the laboratories
scientific staff, equipment, and experimental facilities." The current
focus of HIF-VNL research is the design of an Integrated Research Experiment
(IRE), a multiple-beam induction accelerator that would address, at a smaller
scale, many of the critical technological and physics issues of a inertial-fusion
driver. Induction accelerators are used for several reasons.
They can handle much higher currents than the radio-frequency (rf) accelerators
used for high-energy physics, and they allow a beam to be beam to be compressed
during acceleration, eliminating the need for storage rings. Also,
induction accelerators have a lower-cost development path than rf accelerators
because the critical physics questions occur a low energies, allowing them
to be studied on small-scale experiments. Initial studies have shown
that this approach should have significant cost advantages over designs
based on rf accelerators.
The IRE is intended as an integrated experiment to test simultaneously
all aspects of a driver-scale accelerator, the injecting, transport through
electrostatic and magnetic quadrupole lattices, final focusing, and transport
through a reactor chamber. Together with the target-physics database
from laser-based National
Ignition Facility, the IRE should provide the scientific and technological
basis for an Engineering Test Facility, the final step toward an inertial-fusion
demonstration power plant. To a large extent, this goal determines
the scale of the experiment. A hundred or more lattice periods are
needed to demonstrate an understanding of beam dynamics in a transport
lattice. In order for beam loading to resemble that in a driver,
the total current at the end of the IRE must be about 100 A, and tens of
parallel beamlets are needed to carry this amount of current. To
allow useful focusing experiments, the ion energy must be 100 MeV or greater,
the final perveance must be in the range 10-5 to 10-4,
and the normalize emittance must be less than about 15 mm-mrad. Finally,
to validate beam-target interaction physics, the target temperature must
reach about 50 eV, requiring a flux of 3 x 1012 W/cm and a total
beam energy exceeding 1 kJ. The precise accelerator requirements
will, of course, emerge as design work proceeds.
A wide range of HIF-VNL research is currently underway to develop the
physics and technological understanding needed to design the IRE.
This research falls into three general categories.
Small-scale experiments to study aspects accelerator physics of an IRE.
These experiments include the High-Current Transport Experiment (HCX) and
Multiple-Beamlet Injector Experiment, both currently being planned, as
well as recent projects like the Scaled
Final-Focus Experiment, the Beam-Combiner
Experiment, and the Plasma-Lens
Theory and simulation using analysis and a variety of numerical models,
ranging from zero-dimensional systems codes to 3-D particle-in-cell simulations.
The numerical tools are able to model all parts of an accelerator from
source to target at an appropriate level of detail, and they are used now
both to design the IRE and supporting experiments and to help understand
experimental results. In the accelerator, the areas presently being
studied include beam matching, emittance growth, lattice-error tolerances,
beam-halo formation, and bunch compression. Beam transport in the
reactor chamber is also being examined to determine the best ways to neutralize
the beam and to minimize the focal spot.
- Engineering research and development work to develop the innovative approaches
to fabricating affordable and reliable accelerator components. The
evaluation of low-cost magnetic-core materials and the design of superconducting
magnetic-quadrupole arrays are active areas of IRE reasearch.
- Work in these areas is co-ordinated through frequent teleconferences
involving the HIV-VNL partners and through frequent internal reviews.
It is expected that conceptual-design work on the IRE will begin early
to the US Heavy-Ion Fusion Program Homepage
This document was written by W. M. Sharp and D. P. Grote, and has been
reviewed and approved by HIF-VNL Director Roger Bangerter and by the AFRD
Director William Barletta. For comments or questions contact WMSharp@lbl.gov
or DPGrote@lbl.gov. Work described
here was supported by the Office of Fusion Energy at the U.S. Department
of Energy under contracts DE-AC03-76SF00098 and W-7405-ENG-48.
This document was last revised February, 2000.