Trapped protons cool via collisions with trapped electrons at 4 K. This first demonstration of sympathetic cooling by trapped species of opposite sign of charge utilizes a nested Penning trap. The demonstrated interaction of electrons and protons at very low relative velocities, where recombination is predicted to be most rapid, indicates that this may be a route towards the study of low temperature recombination. The production of cold antihydrogen is of particular interest, and electron cooling of highly stripped ions may also be possible.Trapped protons cool via collisions with trapped electrons at 4 K. This first demonstration of sympathetic cooling by trapped species of opposite sign of charge utilizes a nested Penning trap. The demonstrated interaction of electrons and protons at very low relative velocities, where recombination is predicted to be most rapid, indicates that this may be a route towards the study of low temperature recombination. The production of cold antihydrogen is of particular interest, and electron cooling of highly stripped ions may also be possible.

Physical Review LettersSep 2, 199696 citations

The Amazing Electron

Victor Francis Hess

ThoughtJan 1, 19470 citations

Single-pass stochastic cooling for electron microscopy

River Robles, Peter Hommelhoff

Scientific applications of free electrons, such as in electron microscopes and particle accelerators, are limited by the brightness of available electron sources. Accelerators can use phase space cooling to surpass these source limitations, whereas electron microscopes can only rely on particle filtering to increase beam coherence at the cost of reduced brightness. We show that strong electron-light coupling in nanophotonic structures makes it possible to achieve single-pass stochastic cooling inside an electron microscope for a lossless improvement of longitudinal emittance. This approach is laser-free and compatible with normal CW operation of electron microscopes. We derive a fully quantum mechanical model of stochastic cooling valid in the strong coupling regime, finding an analytic asymptotic formula for the optimal cooled energy spread $σ_{E_f}\simeq0.88(\hbarω)^{2/3}σ_{E_0}^{1/3}$ , with $\hbar ω$ the cooling photon energy and $σ_{E_0}$ the initial energy spread. Numerical simulations confirm that the energy spread reduction is reflected in an increase in the purity of the electron's quantum state and a reduction of the longitudinal phase space area. Our work paves a path towards even brighter beams for electron microscopy, promising higher image quality, enhanced spectral resolution, and a route to reaching fundamental quantum limits on electron beam phase space area.Scientific applications of free electrons, such as in electron microscopes and particle accelerators, are limited by the brightness of available electron sources. Accelerators can use phase space cooling to surpass these source limitations, whereas electron microscopes can only rely on particle filtering to increase beam coherence at the cost of reduced brightness. We show that strong electron-light coupling in nanophotonic structures makes it possible to achieve single-pass stochastic cooling inside an electron microscope for a lossless improvement of longitudinal emittance. This approach is laser-free and compatible with normal CW operation of electron microscopes. We derive a fully quantum mechanical model of stochastic cooling valid in the strong coupling regime, finding an analytic asymptotic formula for the optimal cooled energy spread $σ_{E_f}\simeq0.88(\hbarω)^{2/3}σ_{E_0}^{1/3}$, with $\hbar ω$ the cooling photon energy and $σ_{E_0}$ the initial energy spread. Numerical simulations confirm that the energy spread reduction is reflected in an increase in the purity of the electron's quantum state and a reduction of the longitudinal phase space area. Our work paves a path towards even brighter beams for electron microscopy, promising higher image quality, enhanced spectral resolution, and a route to reaching fundamental quantum limits on electron beam phase space area.

physics.acc-phCross-listedarXiv:2611.03581Nov 3, 2026

These Amazing Electrons

Robert B. Morrissey

ThoughtJan 1, 19390 citations

A picture of the electron

Marta C. Bunge

Il Nuovo CimentoJun 1, 195536 citations

Response of a SINIS Detector with Electron Cooling to Submillimeter-Wave Radiation

Aleksandra A. Gunbina, S. A. Lemzyakov, Michael A. Tarasov +2 more

The response of a detector fabricated on a silicon substrate in the form of a metamaterial that is a 10 × 10 matrix of split rings containing superconductor-insulator-normal metal-insulator-superconductor tunnel structures to submillimeter wave radiation has been experimentally studied. At voltages below the superconducting gap, the electron temperature T e at the substrate temperature T ∼ 0.1 K is ∼0.23 K due to overheating by spurious radiation. At the substrate temperature T ∼ 0.3 K, the electron temperature is close to the substrate temperature T e ≈ T. In both cases, with increasing voltage, T e decreases due to electron cooling and reaches 0.19 K at a voltage corresponding to the maximum response. The response at T = 0.1 K is greater than that at T ∼ 0.3 K by a factor of 5–6. Thus, cooling of only electrons does not provide the same responsivity as cooling of the detector as a whole.The response of a detector fabricated on a silicon substrate in the form of a metamaterial that is a 10 × 10 matrix of split rings containing superconductor-insulator-normal metal-insulator-superconductor tunnel structures to submillimeter wave radiation has been experimentally studied. At voltages below the superconducting gap, the electron temperature T e at the substrate temperature T ∼ 0.1 K is ∼0.23 K due to overheating by spurious radiation. At the substrate temperature T ∼ 0.3 K, the electron temperature is close to the substrate temperature T e ≈ T. In both cases, with increasing voltage, T e decreases due to electron cooling and reaches 0.19 K at a voltage corresponding to the maximum response. The response at T = 0.1 K is greater than that at T ∼ 0.3 K by a factor of 5–6. Thus, cooling of only electrons does not provide the same responsivity as cooling of the detector as a whole.

Journal of Experimental and Theoretical Physics LettersMay 1, 20205 citations

σ_{E_f}\simeq0.88(\hbarω)^{2/3}σ_{E_0}^{1/3}

, with

\hbar ω

the cooling photon energy and

σ_{E_0}

the initial energy spread. Numerical simulations confirm that the energy spread reduction is reflected in an increase in the purity of the electron's quantum state and a reduction of the longitudinal phase space area. Our work paves a path towards even brighter beams for electron microscopy, promising higher image quality, enhanced spectral resolution, and a route to reaching fundamental quantum limits on electron beam phase space area.