First of all, classically speaking about coulomb barriers, 115 keV isn't nearly enough energy to hurl one nuclei into another. However, as pointed out by Gamow and others, thanks to quantum tunneling phenomena, particles can tunnel through the barrier with much lower energies. This is why the deuterons are able to fuse when accelerated to only 115 keV. Both Cockcroft and Walton's linear accelerator and then Lawrence's cyclotron made use of tunneling to perform the first nuclear disintegrations. It's interesting to think that they might have been able to accomplish a similar feat with a much more compact setup than either experimental team actually used. For an excellent reference on the history of particle accelerators, see .
The crystal used in the experiment was made of lithium tantalate. This is a type of crystal that spontaneously polarizes and develops its own electric field as its temperature is raised. Crystals with this property are known as pyroelectric. The inherent electric field created by these crystals is what was used by the UCLA researchers to provide the accelerating potential for the deuterons.
The fist reference I could find to research on the pyroelectric properties of lithium tantalate was in an article from Bell Labs' researchers B.T. Matthias and J.P. Remeika. Their article was published in 1949 which puts this particular crystal outside the reach of both accelerator teams mentioned above who were doing their work in the 1930s.
Rochelle salt crystals can be grown in supersaturated solution.When I was growing them, Rochelle salt was still available as a laxative in some older pharmacies in town. Trying to get enough raw material to grow a crystal, I had more than one pharmacist in Hobbs, NM wondering what a 12 year old kid was doing buying them out of their stock of old-school laxative.
Because pyroelectric crystals can have an inherent electric field independent of any applied electric field, they exhibit hysteresis in an applied electric field in the same manner that a ferromagnetic material does when a magnetic field is applied. The term ferroelectirc was coined to denote the similar hysteretic behavior and doesn't necessarily denote the presence of iron in pyroelectric/ferroelectric crystals The hysteresis curve for Rochelle salt is shown below. (picture 3)
1. Nature article on bentchtop fusion
Naranjo B., Gimzewski J.K. & Putterman S. (2005). Observation of nuclear fusion driven by a pyroelectric crystal, Nature, 434 (7037) 1115-1117. DOI: 10.1038/nature03575
2. Gamow on tunneling
GAMOW G. (1928). The Quantum Theory of Nuclear Disintegration, Nature, 122 (3082) 805-806. DOI: 10.1038/122805b0
3. An excellent masters' thesis on the history of the particle accelerator by Andrew Steere
4. Lithium tantalate as a pyroelectric, (ferroelectric)
Matthias B. & Remeika J. (1949). Ferroelectricity in the Ilmenite Structure, Physical Review, 76 (12) 1886-1887. DOI: 10.1103/PhysRev.76.1886.2
5. Rochelle Salt properties
Valasek J. (1921). Piezo-Electric and Allied Phenomena in Rochelle Salt, Physical Review, 17 (4) 475-481. DOI: 10.1103/PhysRev.17.475
6. More Rochelle Salt properties
Mueller H. (1935). Properties of Rochelle Salt, Physical Review, 47 (2) 175-191. DOI: 10.1103/PhysRev.47.175
7. Rochelle salt crystals