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SABRE and PHIP pumped RASER and the route to chaos.

ABSTRACT: In a RASER (Radio-frequency Amplification by Stimulated Emission of Radiation), the fast relaxing electromagnetic modes of an LC resonator are enslaved by the slow nuclear spin motion, whose coherence decays with the transverse relaxation rate γ_m=1/T₂^∗. Such a system obeys the slaving principle, mathematically identical with the adiabatic elimination procedure, leading to multi-mode RASER equations. If the pumping rate of nuclear spin polarization Γ>>γ_m, a second adiabatic elimination process applies and the spectral properties of the RASER can be predicted. The resulting model is similar to the model of two non-linear coupled oscillators and predicts the observed RASER phenomena, including frequency combs and mode collapse. If the second adiabatic elimination is not applicable, mode collapse is completely absent and successive period doubling processes and chaos occur at very high population inversions. We compare these theoretical predictions with experimental results from a PHIP (Para-Hydrogen Induced Polarization) pumped ¹H RASER. Moreover, in SABRE (Signal Amplification By Reversible Exchange) pumped ¹H experiments, RASER revivals are observed long after the parahydrogen pumping source has been switched off. All these findings shed light onto the links between NMR spectroscopy, RASER physics, synergetics and chaos theory. Several new applications are envisioned in the fields of quantum sensor technology, structure investigation or magnetic resonance imaging (MRI).

SUBMITTER: Appelt S

PROVIDER: S-EPMC8026265 | biostudies-literature | 2021 Jan

REPOSITORIES: biostudies-literature

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SABRE and PHIP pumped RASER and the route to chaos.

Appelt Stephan S Lehmkuhl Sören S Fleischer Simon S Joalland Baptiste B Ariyasingha Nuwandi M NM Chekmenev Eduard Y EY Theis Thomas T

Journal of magnetic resonance (San Diego, Calif. : 1997) 20200828

In a RASER (Radio-frequency Amplification by Stimulated Emission of Radiation), the fast relaxing electromagnetic modes of an LC resonator are enslaved by the slow nuclear spin motion, whose coherence decays with the transverse relaxation rate γm=1/T2∗. Such a system obeys the slaving principle, mathematically identical with the adiabatic elimination procedure, leading to multi-mode RASER equations. If the pumping rate of nuclear spin polarization Γ>>γm</sub ...[more]

PMID: 33423756

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Project description:The route to chaos and the phase dynamics of the large scales in a rotating shallow-water model have been rigorously examined through the construction of an autonomous five-mode Galerkin truncated system employing complex variables, useful in investigating how large/meso-scales are destabilized and how their dynamics evolves and transits to chaos. This investigation revealed two distinct transitions into chaotic behaviour as the level of energy introduced into the system was incrementally increased. The initial transition manifests through a succession of bifurcations that adhere to the established Feigenbaum sequence. Conversely, the subsequent transition, which emerges at elevated levels of injected energy, is marked by a pronounced shift from quasi-periodic states to chaotic regimes. The genesis of the first chaotic state is predominantly attributed to the preeminence of inertial forces in governing nonlinear interactions. The second chaotic state, however, arises from the augmented significance of free surface elevation in the dynamical process. A novel reformulation of the system, employing phase and amplitude representations for each truncated variable, elucidated that the phase components present a temporal piece-wise locking behaviour by maintaining a constant value for a protracted interval, preceding an abrupt transition characterised by a simple rotation of ±π, even as the amplitudes display chaotic behaviour. It was observed that the duration of phase stability diminishes with an increase in injected energy, culminating in the onset of chaos within the phase components at high energy levels. This phenomenon is attributed to the nonlinear term of the equations, wherein the phase components are introduced through linear combinations of triads encompassing disparate modes. When the locking durations vary across modes, the resultant dynamics is a stochastic interplay of multiple π phase shifts, generating a stochastic dynamic within the coupled phase triads, observable even at minimal energy injections.

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SABRE and PHIP pumped RASER and the route to chaos.

Publications

SABRE and PHIP pumped RASER and the route to chaos.

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