While progress in fusion research continues with magnetic1 and inertial2 confinement, alternative approaches—such as Coulomb explosions of deuterium clusters3 and ultrafast laser–plasma interactions4—also provide insight into basic processes and technological applications. However, attempts to produce fusion in a room temperature solid-state setting, including ‘cold’ fusion5 and ‘bubble’ fusion6, have met with deep scepticism7. Here we report that gently heating a pyroelectric crystal in a deuterated atmosphere can generate fusion under desktop conditions. The electrostatic field of the crystal is used to generate and accelerate a deuteron beam (> 100 keV and >4 nA), which, upon striking a deuterated target, produces a neutron flux over 400 times the background level. The presence of neutrons from the reaction D + D → 3He (820 keV) + n (2.45 MeV) within the target is confirmed by pulse shape analysis and proton recoil spectroscopy. As further evidence for this fusion reaction, we use a novel time-of-flight technique to demonstrate the delayed coincidence between the outgoing α-particle and the neutron. Although the reported fusion is not useful in the power-producing sense, we anticipate that the system will find application as a simple palm-sized neutron generator.
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The neutron detector was built with funds from DARPA. Funding for various stages of this project was provided by the NSF, ONR and DARPA. We thank W. Wright and K. O'Doherty for demonstrations of electron and ion emission from pyroelectrics, respectively; H. Lockart for machine workshop expertise; K. O'Doherty for evaporating the 50-nm film onto the plastic scintillator; R. Cousins for recommending the use of liquid scintillator for detection and pulse-shape identification of neutrons, and for overseeing the design and construction of a prototype detector using waveform digitization; and T. Venhaus, W. Harbin and J. Hoffer of LANL (ESA-TSE group) for supplying the deuterated target. S. P. thanks A. Erbil for bringing the phenomenon of ferroelectric emission to his attention, along with ref. 10.
The authors declare that they have no competing financial interests.
Neutron detection methods including energy scale calibration, pulse shape discrimination, and Monte Carlo efficiency calculation. (PDF 545 kb)
Supplementary Video S1
This movie is a real-time presentation of the crystal fusion raw data shown in Figure 2 including raw PMT traces of valid neutron hits. (MPG 10184 kb)
Supplementary Video S2
This movie shows the phosphor screen image (25.4 mm diameter) of an ion beam produced upon heating a pyroelectric crystal. Deuterium gas pressure was set to 0.2 Pa. The phosphor intensity, as measured by a CCD camera, is proportional to beam current density. In the central frame, the phosphor intensity is displayed topographically. (MPG 10292 kb)
Supplementary Figure S1
This figure shows the phosphor screen image (25.4 mm diameter) of an ion beam produced upon heating a pyroelectric crystal. The four frames were taken from Supplementary Movie 2. They were separately normalized and gamma corrected to enhance detail. Note the copper mesh's shadow and the FIM image of the tungsten tip. (JPG 64 kb)
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Naranjo, B., Gimzewski, J. & Putterman, S. Observation of nuclear fusion driven by a pyroelectric crystal. Nature 434, 1115–1117 (2005). https://doi.org/10.1038/nature03575
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