  The Penning trap has been investigated as the basis of a small nuclear fusion
reactor using a superconducting solenoid magnet. To extend this investigation,
we designed, constructed, and evaluated a permanent magnet Penning trap. The
device consists of a solenoid formed from an annular array of neodymium bar
magnets between two iron pole pieces designed to give a uniform magnetic field
in the central volume of the device. Critical to achieving the uniform
solenoidal field is an iron equatorial ring supported within the annular array
of magnets. A nonmagnetic titanium Penning trap with hyperbolic surfaces
designed to produce a spherical potential well was mounted inside the permanent
magnet assembly. The trap was fitted with a nonmagnetic hairpin filament
electron source and demonstrated to produce electron trapping at the
theoretically predicted magnetic fields and trap potentials. Trap potentials
achievable were limited by electrical breakdown within the trap operating in
constant potential mode. Efforts were made to extend the trap potentials using
pulsed anode voltages, but nuclear fusion in a Penning trap has not yet been
demonstrated. The design and construction of the permanent magnet solenoid and
nonmagnetic trap are presented here as potentially useful also in other
studies.
