Generation of Unprecedented high Electric Fields with Pyroelectric Crystals

Since a few years pyroelectric crystals in a deuterium gas environment have been used to produce neutrons via the $^{2}$H(d,n)$^{3}$He reaction. The figure-of-merit for neutron production in the energy region of interest is about IE$^{3/2}$, where I is the deuterium ion current and E is the associated ion energy. Therefore, it is important to maximize E. Using single and double crystal arrangements with electric field enhancing nano-tips, the highest positive potentials reported in the literature were 115 keV [1] and 250 keV [2], respectively. Using longer LiTaO$_{3}$ crystals than commonly employed (2.5 cm versus 1.0 cm) and without attaching a nano-tip, we have produced positive deuterium ion beams of energies up to 325 keV with a single crystal during the cooling phase from 130 $^{\circ}$C to 0 $^{\circ}$C. In a double crystal arrangement we have obtained positive ion energies of up to 390 keV. Details of our experimental approach will be presented.\\[4pt] [1] B. Naranjo et al., Nature 434, 1115 (2005).\\[0pt] [2] D. Gillich et al., Nucl. Instr. Meth. in Phys. Res. A 602, 306 (2009).