Historical research guide · 0682 · 2012
Neutron production from the fracture of piezoelectric rocks
A Widom · J Swain · Y N Srivastava
In one minute
The authors cite reports of neutron emission during rock fracture and propose a theoretical route from mechanical force to nuclear reaction. In their model, a piezoelectric crystal such as quartz converts elastic energy into electric energy as micro-cracks open. The energy drives radio-frequency and microwave fields along fresh crack surfaces; those fields accelerate electrons already in the material. An electron that reaches the required energy could be captured by a proton to make a neutron and a neutrino through the weak interaction. Using stated quartz parameters, the authors calculate electron energy near 15 MeV, about thirty times the electron rest energy, and an estimated neutron yield near 10¹⁵ per second per square centimetre of crack surface. These values are predictions from the paper’s model, not a measurement made by the authors or a verified yield for every fractured rock.
Connection
This paper gives chapter 12 a concrete proposed chain from rock fracture through piezoelectric fields to a weak-interaction neutron reaction. It connects mechanical energy, electron acceleration and nuclear products in one model. The cited neutron observations and the authors’ calculated energies and yields have different evidentiary roles; journal publication of the model does not by itself confirm those predicted yields or establish broad experimental agreement.
From the source
The authors propose an explanation for reported neutron emission during piezoelectric rock fracture: the route is a chain of ordinary conversions: elastic energy becomes electric field energy through the piezoelectric effect, that field energy decays into radio-frequency and microwave oscillations, and those fields accelerate condensed matter electrons until an electron can be captured by a proton to yield a neutron and a neutrino.Abstract; Section I, Introduction, Eq. (1)
In the paper’s piezoelectric model, the coupling tensor relates a change in polarization to strain at fixed electric field, and a change in stress to electric field at fixed strain. That coupling allows mechanical and electrical energy to interact; the authors then derive a contribution from mechanical phonon modes to the dynamical dielectric response.Section II, Piezoelectric interactions, Eqs. (5)-(12) and figure 2
Using stated fused-quartz parameters, the authors estimate a surface tension near 10² erg per square centimetre, a bond stress near 10¹² erg per cubic centimetre, and a fracture stress near 10⁹ erg per cubic centimetre. Their model puts a critical micro-crack half width near one micron; the paper cites roughly twenty-micron observed crack lengths. These are example values and estimates, not universal fracture thresholds.Section III A and III B, Eqs. (4), (15)-(17)
In the authors’ model, fracture fields rather than heat raise the calculated electron energy: an electric field of order 10⁵ gauss driving electrons at a dominant frequency of about 10⁹ per second gives an energy ratio of about 30 times the electron rest energy, roughly 15 MeV, against a threshold ratio for the reaction of about 2.53 — above threshold by a wide margin.Section IV A and IV B, Eqs. (23)-(28)
The authors estimate a neutron yield near 10¹⁵ per second per square centimetre of fresh crack surface from an assumed proton density of roughly 2 × 10¹⁴ per square centimetre. Their printed intermediate rate of 0.6 hertz per proton at an energy ratio of 30 conflicts with their own formula: 7 × 10⁻³ × 30² = 6.3 hertz. The stated areal yield is consistent with about 6.3 hertz, not 0.6 hertz. The paper further estimates a tenfold increase with more water. These are order-of-magnitude model estimates; the paper does not measure those yields.Section IV B, Eqs. (29)-(31)
The same mechanism predicts a checkable electromagnetic signature: when the sound mode localised on a micro-crack is turned into an electromagnetic mode by the piezoelectric effect, microwave emission should be observed, and large-scale rock fracturing in earthquakes should radiate across many frequencies — the authors connect this to reported earthquake lights and lightning.Section IV B, Eq. (27); Section V, Conclusions
Read the sources
Read the journal article and the separate 2012 arXiv version at their source pages. The summary and claim locators above describe the proposed mechanism; this page does not host the paper text or figures.
The way in
https://doi.org/10.1088/0954-3899/40/1/015006How to cite it
A Widom, J Swain, Y N Srivastava (2012) Neutron production from the fracture of piezoelectric rocks doi:10.1088/0954-3899/40/1/015006