1 research outputs found
Investigation of a Magnetically Enhanced Inductively Coupled Negative Ion Plasma Source
Experiments and numerical models were used to investigate an
inductively coupled plasma source (ICPS) operating with a
magnetic filter field. The work shows that applying magnetic
filters transversely to the plasma offers several new control
parameters to help enhance the properties of a plasma source. The
application of these new results using magnetic enhancement is
discussed with respect to both industrial plasma fabrication
processes and neutral beam injection for fusion power.
Experimental measurements of the power transfer efficiency of the
ICPS were undertaken comparing the effect of the magnetic field
for both hydrogen and argon plasmas. The location and strength of
the magnetic field was varied while measurements of the plasma
resistance and power transfer efficiency were performed. The
changes in forward power transfer were correlated with plasma
density measurements and a numerical model of the electrical
plasma circuit was used to guide the optimal choice for the power
system components. The results demonstrate that the magnetic
field increases the total efficiency of the plasma source and
that the gains are strongly dependant on the choice of location
for the magnetic field.
Plasma properties were then investigated across the plasma source
1 cm intervals. Experimental measurements comparing the effect of
the magnetic filter on the plasma properties include: electron
densities using a hairpin probe, electron energy probability
functions using a compensated Langmuir probe, negative ion
densities by laser photo detachment and rotational gas
temperatures by optical emission spectroscopy. These measurements
revealed interesting new properties of the plasma when a magnetic
filter is applied including: the formation of a high density cold
particle trap, changes in particle transport and drift motions,
increased gas temperatures, and a peak in negative ion density
under the magnetic filter center.
Pulsing the plasma can greatly affect the plasma dynamics,
leading to electron cooling in the afterglow and increased
negative ion production. A combination of a pulsed plasma with a
magnetic filter was then investigated. Measurements of the
negative ion and electron populations were performed in the
plasma afterglow with the magnetic filter applied. The results
reveal a complex and dynamic afterglow process including strong
spatial dependencies measured for diffusive transport, ambipolar
breakdown and ion-ion plasma formation.
The applications for this work include offering new avenues for
control over processing plasma chemistry as well as initial
results toward the future viability of a caesium-free pulsed
negative ion neutral beam source