Transcript ppt

Inertial Electrostatic Confinement Deuterium Plasma Neutron Production Study Using Multiple
Cathode Geometries
Jorge R. Gaudier, Eric D. Lukosi, Ryan M. Meyer, Mark A. Prelas
Nuclear Science & Engineering Institute
University of Missouri-Columbia
Abstract. An Inertial Electrostatic Confinement with a spherical
anode of 20in diameter and maximum voltage of 50kV was used
with deuterium to study the relation between IEC parameters
and neutrons production rates. Our aim was to improve neutron
production with geometric variations to the cathode. A voltage
up to 30kV was applied to multiple cathodes. Counts of
neutrons were compared for two spherical cathodes, one of 2in
in diameter made with 3 rings and the other 3.25in in diameter
made with 7 rings. Asymmetrical cathodes are also explored as
recommended by Meyer [1] (2007). One is an oval shaped
cathode made with 9 rings, 4in from top to bottom and 3.5in
from side to side. The other two asymmetrical cathodes have an
opening which a jet escapes. Results show that asymmetrical
cathodes are not optimal for neutron production and that there is
and ideal cathode to anode ratio that can be attained. Data also
shows that higher currents will increase neutron production as
well as higher voltages which is constant with other studies.
The asymmetric jet cathodes showed fewer counts in general.
The shapes of these two cathodes do not provide any
advantages in neutron production. On the other hand the
spherical cathodes produced a very symmetrical star mode
with many arms.
The inlet gas, the current as well as the voltage applied, all impacted
neutron production rates. If the current is too low, the counts will be
low, even if the voltage is high.
As the voltage increases more neutrons are produced. In
Figure 8 there is one point with high (second highest)
neutron production rates using 16kV (a low voltage), but
this point had a current of 37mA (which is high for our
system). On the other hand we have a point at the end with
30kV and low neutron production; for this point the
current is low (5.8mA). All points from 20kV to 30kV that
have low number of neutron per second had a
corresponding low current.
When the voltage generator indicates a relatively
high current (meaning high for our system), more
neutrons are detected as Figure 9 illustrates. The
lower neutron per seconds count rates from 20mA
to 30mA corresponds to a lower voltage.
Conclusion
Asymmetrical cathodes that force a jet mode are not suitable for
neutron production as the jet weaken the rest of the channels;
perhaps for an application where a single jet of charged particles is
needed as space propulsion, this cathode design might be of interest.
The medium spherical cathode produced the most neutrons. The
oval cathode contains two more rings than the medium spherical
cathode having less transparency creating more ion-cathode
collisions, producing fewer counts. Probably its oval shape
contributed in producing weaker plasma because it did not produce
as bright plasma as a spherical cathode. On the other hand the
smaller spherical cathode could not generate a plasma strong enough
to produce detectable neutrons despite being constructed with 3
rings to minimize ion loss by cathode collisions.
The voltage applied to the cathode dictates neutron production but
inlet gas, current and cathode geometry can improve production
efficiency. As deuterium flow rates increases, the current rises and
more neutrons are produced which indicates that more reactions
occur. There is an ideal anode cathode ratio for maximum
production which this study points towards. A balance of applied
voltage, current and cathode size can be optimized. In order to
determine best cathode size, spherical cathodes with same number
of ring and different diameters must be tested. Once the size is
determined the ideal number of cathode rings can be studied as well.