A Pyroelectric Crystal Particle Accelerator

1
A Pyroelectric Crystal Particle
Accelerator Amanda Gehring, Rose-Hulman Institute
of Technology Dr. Rand Watson, Texas AM
Cyclotron Institute
Results The purpose of this experiment was to
instigate d d fusion and optimize the neutron
output by varying the D2 gas pressure, optimize
parameters that determine the intensity and
energy of the particle beam, and to examine the
feasibility of using the system as a neutron
generator. Runs were conducted at 0.5 A, 1.0 A,
1.5 A, and 2.0 A heating currents under vacuum
condition with a Zr target. As heating currents
increased, beam intensity and energy also
increased. CdS and ZnS coating was added to the
target wheel so that the beam could be seen.
Why use a pyroelectric crystal? Pyroelectric
crystals can be used to produce a large
electrostatic field. Once heated, the random
crystal lattice dipole moments of the crystal
align, creating oppositely charged surfaces that
produce the electrostatic field. Upon cooling,
the polarity of the crystal reverses.
Heating Current (A)
2.0 A Temperature Cycle
Experimental Setup and Principles The lithium
tantalate pyroelectric crystal is attached to a
copper block, to which two heating resistors are
attached. The front face of the crystal becomes
positively charged causing the creation of
positive ions due to field ionization of gas
molecules in the vicinity. The positive ions are
accelerated toward the target by the
electrostatic field.
X-Ray Counts
D D ? 3He n (820 KeV)
(2.45 MeV) D D ? T p
(1.01 MeV) (3.02 MeV)
Time (10 s Interval)
Simultaneously, electrons from the target are
accelerated toward the crystal where they collide
with atoms at the surface producing x rays and
bremsstrahlung which are measured with a Si(Li) x
ray detector. When the crystal is cooled, the
polarity reverses and the electrons are
accelerated toward the target. If the
accelerating potential reaches 100 keV, the d
d fusion reaction can be initiated. Deuterium gas
must be introduced to the chamber, and a
deuterated polyethylene target must be added as
well. A liquid scintillation neutron detector is
used to measure the neutron output.
A 2.0 A current produced the highest beam
intensity and energy. The maximum energy reached
was 88 keV. This heating current was used in the
deuterium gas experiments.
Runs were carried out at deuterium pressures
ranging from 5x10-3 to 1x10-4 Torr, but in all
cases the observed neutron counting rates were
never above the background rate.
Future research may involve minimizing
discharges, running additional deuterium gas
pressures, and adding another pyroelectric
crystal to the system in order to double the
accelerating potential.
Inner Chamber
Entire System