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| January '02 Issue |
LBNL-PUB-844-02-01
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mbronte
08/01/2001 |
500 kV ion
source test stand commissioned
 STS-500, the 500 kV ion-source test stand pictured,
successfully operates at full voltage for a 17 µs pulse with a 1.2 µs
rise time as shown. This performance is well within the acceptance criteria
for operations to begin on the test stand. By fine-tuning the pulse forming
network, the flat top pulse width, flatness, and rise time should improve
slightly. We also
achieved our vacuum requirement (< 1x10-7 Torr) for the column and diagnostic
tank. STS-500 is an important new tool for development of ion sources
for heavy ion fusion. Heavy ion fusion not only requires high current
ion sources, typically ~1 amp of beam current, but also high brightness,
with ion temperatures < eV, in a compact structure. These requirements
motivate advances in both source technology, and our physics understanding
of ion extraction and low energy beam transport. In designing this system,
we require high enough voltage to extract a high-current beam and transport
it to diagnostics for measurement, and flexibility to test a wide variety
of sources and provide easy access for changes to the system. Thus, the
system was designed as a 500 kV system in air. The pulsed power system
provides a 500 kV pulse to a hot box, that is supported by fiberglass
legs above a ceramic insulator column which grades the voltage back down
to ground potential. The insulator column together with a diagnostic tank
provides the vacuum chamber in which sources will be placed, ions extracted,
and measurements performed. - Larry Ahle
Neutralized Transport Experiment (NTX)
A power plant driver beam can be transported through
the final focus section by several strong magnetic quadrupoles that
will focus it onto a target. Achieving a sufficiently small focal spot
at the target, with ballistic tr
 transport
of ions with GeV-range energy, depends on reducing space-charge forces
with neutralizing plasma in low-density (millitorr) gas. To investigate
nonlinear phenomena, both in the magnetic section as well as in the
neutralized transport section, construction of the Neutralized Transport
Experiment (NTX) has begun at LBNL. The experimental setup shown consists
of three major sections, a low-emittance potassium-ion source, a magnetic
transport section with 4 pulsed quadrupoles, and a 1-m long drift section
with plasma neutralization. The plasma source has been constructed by
PPPL (HIF News July/August, 2001), and after initial characterization
will be installed in the NTX beamline. The pulsed quadrupoles are under
construction, and the ion source is being tested, using a refurbished
version of the 400kV Marx pulser at the former MBE-4 machine. The WARP-3D
code has been used to design the ion source and the magnetic lattice,
and predict nonlinear forces. The MRC electromagnetic code LSP has been
used to specify the requirements for the plasma source, and the degree
of neutralization as a function of the various beam and plasma parameters.
These predictions will be compared against the NTX experiments. Higher
order corrections to quadrupoles can be implemented in the later stages
of NTX. - Simon Yu2 MV Injector upgrade
for HCX completed |
