A Pyroelectric Crystal Particle Accelerator Amanda Gehring, Rose-Hulman Institute of Technology Rand Watson, Texas A&M Cyclotron Institute

Pyroelectric Crystals 1) When heated, a pyroelectric crystal produces an electric field. The atoms shift, and the dipoles of the individual crystal lattices realign, creating a uniform polarity. The faces of the crystal become oppositely charged. When the crystal cools, the polarity and electric field reverse.

Experimental Setup D +D  3He + n (820 KeV) (2.45 MeV) D + D  T + p Recent experiments have shown that the electric field produced by the pyroelectric crystal can be utilized to accelerate deuterons to sufficient energies to initiate the d + d fusion reaction. This suggests the possibility of developing a pyroelectric crystal neutron generator. Upon heating, the front face of the crystal becomes positively charged, creating positive deuterium ions from field ionization of nearby gas molecules. The deuterons are accelerated toward the deuterated polyethylene target, and electrons from the target are accelerated toward the crystal where they collide with the surface producing x rays and bremsstrahlung. Spectra of this radiation are measured with a Si(Li) detector and the endpoint of the bremsstrahlung is used to determine the accelerating potential. Upon cooling, the polarity reverses. D +D  3He + n (820 KeV) (2.45 MeV) D + D  T + p (1.01 MeV) (3.02 MeV)

Goals of Experiment 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 Examine feasibility of using the system as a neutron generator

Pyroelectric Crystals LiNbO3 and LiTaO3

Inner System

First Set of Experiments Energy calibrated Si(Li) x-ray detector using a 241-Am source Conducted runs under vacuum at the heating currents of 0.5 A, 1.0 A, 1.5 A, and 2.0 A Recorded the number of x-rays in 10 s intervals Acquired x-ray spectra

Temperature Change and X-ray Count Rate

X-ray Spectrum at Heating Cycle

X-ray Spectrum at Cooling Cycle In order to determine the maximum accelerating potential, x-ray spectra were taken in order to determine the endpoint of the bremstraahlung spectrum.

Heating Current Effect on Energy

Heating Current Effect on Beam Intensity

Second Set of Experiments Energy calibrated liquid scintillator neutron detector using a 252-Cf source Conducted runs with D2 gas at pressures of 5.0, 2.5, 1.2, 0.5, and 0.1 mtorr. Recorded the number of neutrons and x-rays in 10 s intervals Acquired x-ray spectra

Temperature Change and Neutron Count Rate

X-ray Spectrum at Heating Cycle

X-ray Spectrum at Cooling Cycle In order to determine the maximum accelerating potential, x-ray spectra were taken in order to determine the endpoint of the bremstraahlung spectrum.

D2 Pressure Effect on Energy

D2 Pressure Effect on Beam Intensity

Future Research Address discharges and unfocused beam Run experiments under different deuterium gas pressures Replicate previous results Use of two pyroelectric crystals

Acknowledgements National Science Foundation Department of Energy Texas A&M Cyclotron Institute Dr. Rand Watson Jon Kalodimos

Results Run Current (A) Max x-ray Heating Energy (keV) Max x-ray Cooling Energy (keV) Max Heating Count Rate (counts/s) Avg. Max Heating Count Rate (counts/s) Max Cooling Count Rate (counts/s) Avg. Max Cooling Count Rate (counts/s) 2 0.5 36 - 154 3 1.0 53 43 4118 3664 117 72 4 61 30 1505 1097 5 1.5 66 65 11175 6806 441 182 8 2.0 74 76 13591 10573 1470 735 11 55 71 13220 8148 1509 493 12 88 15063 11687 1641 1066 13 80 15816 12980