Updates to nucleonics notes

Author: mklilley

Nucleonics.md

@@ -35,7 +35,7 @@ It may be that manipulating nuclear states for the purposes of energy technology
 From the energy perspective that our mission statement focusses on, practicality means that we need to be able to:
 
 - Accelerate nuclear transitions by many orders of magnitude
-- Transfer nuclear energy non-radiatively from one nucleus to another
+- Transfer nuclear energy non-radiatively between nuclei
 - Control nuclear transitions with low frequency stimulation
 - Extract nuclear energy in benign forms
 
@@ -60,14 +60,39 @@ The specifics of $\rm ^{229m}Th$ require us to arrange the system to:
 - Maximise radiative decay over internal conversion. This can be achieved by excite half of the $\rm ^{229m}Th$ nuclei instead of all of them will give us $N^2$ enhancement of radiation and only $N/2$ enhancement of internal conversion.
 - Minimise the reflection of the UV laser light from the surface. This can be achived by embedding the $\rm ^{229m}Th$ into an UV transparent material.
 
-## Transferring nuclear energy non-radiatively from one nucleus to another
+## Transferring nuclear energy non-radiatively between nuclei
 
-Excitation transfer (also known as resonance energy transfer) is the key bit of physics responsible for moving energy from a donor system to a receiver system without the emission/absorption of radiation.  [Supertransfer](https://doi.org/10.1088/1367-2630/12/7/075020) is the Dicke acceleration of this process due to the coupling of many donors/receivers to a shared oscillator.
+Excitation transfer (also known as resonance energy transfer) is the key bit of physics responsible for moving energy from a donor system to a receiver system without the emission/absorption of radiation. [Supertransfer](https://doi.org/10.1088/1367-2630/12/7/075020) is the Dicke acceleration of this process due to the coupling of many donors/receivers to a shared oscillator.
 
 There are numerous examples of excitation transfer dynamics at the atomic scale such as exciton diffusion at room temperature e.g., [photosynthetic systems](https://www.annualreviews.org/content/journals/10.1146/annurev-physchem-040214-121713) and [organic semiconductors](https://www.nature.com/articles/s41467-022-30308-5). Supertransfer in engineered systems has also been demonstrated by Park and colleagues in a [2015 Nature Materials paper](https://www.nature.com/articles/nmat4448) at the atomic scale at room temperature.
 
 Nuclear supertransfer has not yet been demonstrated. 
 
 We seek to adapt the [Chumakov et.al 2017](https://www.nature.com/articles/s41567-017-0001-z) experiment to make it work for supertransfer instead of a superradiance. More specifically, we propose exciting $\rm ^{57}Fe$ nuclei and transferring the $14 \ \rm keV$ of nuclear energy to $\rm Pb$ atoms. The transfer needs to be achieved in a very short timescale in order to beat the natural radiative decay of the excited $\rm ^{57}Fe$. In other words, we need supertransfer.
 
-In order to couple the $\rm ^{57}Fe$ and $\rm Pb$ together non-radiatively, we need to mismatch the oscillator and nuclei. Supertransfer does not suffer the same challenges as superradiance when using mismatched oscillator and nuclei. This is because superradiance involves the radiation of many small quanta, whereas supertransfer involves none - it is radiationless. We can therefore use a low frequency (long wavelength) oscillating magnetic field provided by a solenoid to involve a macroscopically large number of nuclei that will produce the Dicke enhancements that we need.
+In order to couple the $\rm ^{57}Fe$ and $\rm Pb$ together non-radiatively, we need a mismatched oscillator and nuclei. Supertransfer does not suffer the same challenges as superradiance when using mismatched oscillator and nuclei. This is because superradiance involves the radiation of many small quanta, whereas supertransfer involves none - it is radiationless. We propose using a low frequency (long wavelength) oscillating magnetic field provided by a solenoid to involve a macroscopically large number of nuclei that will produce the Dicke enhancements that we need. 
+
+The advantage of using a magnetic field is that it's a well established coupling mechanism that's suitable for demonstration purposes. The disadvantages are:
+
+-  Magnetic dipole coupling is weak and so limits how practical this form of coupling can be
+- Excitation transfer rates with this coupling can be insensitive to frequency (depending on the details) so it does not give us a reliable way to control the transition rates.
+
+## Controlling nuclear transitions with low frequency stimulation
+
+For energy applications, it is necessary to have a type of nuclear coupling that's both strong and tuneable. For practical purposes such tunability more easily achieved via low frequency stimulation because it typically requires smaller and less expensive equipment.
+
+Peter Hagelstein [first proposed](https://arxiv.org/abs/1201.4377) a novel form of relativistic phonon nuclear coupling in 2012. It relies on a previously neglected aspect of relativity that couples vibrational energy (aka phonons) to nuclear energy. Relativistic phonon nuclear coupling is many orders of magnitude stronger than the electromagnetic coupling that's typically considered for nuclear interactions. It's also frequency dependent and so represents a controllable form nuclear coupling.
+
+Although the most developed form of relativistic phonon nuclear coupling was [peer reviewed in 2023](https://iopscience.iop.org/article/10.1088/1361-6455/acf3be), it has yet to be experimentally verified.
+
+We propose a nuclear excitation transfer experiment in which we seek to observe the spreading out of emission of excited $\rm ^{57}Fe$ as the nuclear energy is transferred from the excited $\rm ^{57}Fe$ to neighbouring ground state $\rm ^{57}Fe$. The excited nuclei are to generated from the decay of $\rm ^{57}Co$ that's deposited on the $\rm ^{57}Fe$ surface and the phonon coupling is generated via stimulation of the surface with a $\rm THz$ laser.
+
+## Extracting nuclear energy in benign forms
+
+Relativistic phonon nuclear coupling is so strong that experiments will be in a form of deep strong coupling regime that was first proposed as an academic curiosity in 2010 by [Casanova at.al](https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.105.263603) and only recently experimentally observed in "artificial atoms" in [2017 by Bayer at.al](https://pubs.acs.org/doi/10.1021/acs.nanolett.7b03103). The behaviour in this regime is very different from the usual weak coupling regime that informs peoples' intuitions via "perturbation theory".
+
+Deep strong coupling allows a free exchange of energy between the particles and the field. For the phonon-nuclear system this represents a free exchange of nuclear and vibrational energy. This presents an opportunity to "bleed off" nuclear energy into vibrational energy and ultimately into heat. It also presents the reverse opportunity to turn vibrational energy into nuclear energy, e.g. creating a controllable x-ray laser.
+
+Unlike artificial atoms, deep strong coupling for real atoms and nuclei requires a minimum field energy. Electromagnetic coupling is too small to make deep strong coupling possible for real atoms and nuclear. However, relativistic phonon nuclear coupling is so strong that only a very modest field energy of $\sim \rm 10 \ mJ$ is needed.
+
+We propose to test the free exchange of nuclear and vibrational energy by creating $>10 \ \rm mJ$ of phonon energy inside an otherwise stable material using a $\rm GHz$ piezoelectric driver and then detecting the gamma ray emission. Heavier elements give the largest coupling and header materials produce longer lasting phonons and so tungsten is an ideal choice.