Tootfinder

Acoustic Signatures of Pinch-Off Cavities During Water-Entry
Zirui Liu, Tongtong Ding, Mingyue Kuang, Zimeng Li, Junyi Zhao, A-Man Zhang, Shuai Li
https://arxiv.org/abs/2602.22761 https://arxiv.org/pdf/2602.22761 https://arxiv.org/html/2602.22761
arXiv:2602.22761v1 Announce Type: new
Abstract: This study experimentally, numerically, and theoretically investigates the cavity/bubble dynamics and radiated acoustics during the water entry of a centimeter-scale cylindrical projectile with a conical nose. Experiments were conducted in a laboratory tank, employing synchronized high-speed imaging and hydrophone measurements to characterize the cavity closure modes and their resultant acoustic signatures across a range of Froude numbers. The acoustic signal features a weak radiated signal upon impact, followed by significant pressure oscillations spanning more than 20 cycles in the flow field after cavity elongation and pinch-off. A numerical model based on the Finite Volume Method (FVM) successfully captures these physical processes. Subsequently, a semi-theoretical model that incorporates the projectile's boundary effect is developed from potential flow theory. The model not only yields a dominant cavity oscillation frequency that agrees well with experimental data, but also reveals that the boundary effect leads to a cavity oscillation frequency markedly higher than the Minnaert frequency of an equivalent-volume ellipsoidal bubble containing an internal rigid core. The dominant cavity frequency falls nearly linearly with Fr, governed by nose geometry and projectile inertia. This study clarifies the underlying physics connecting cavity dynamics during water entry to underwater acoustic radiation.
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"A porous liquid is a liquid solvent combined with a porous solid material — a combination that essentially creates a liquid full of tiny cavities. Those cavities create empty space inside the liquid, allowing it to absorb and store gas molecules."
https://www.eurekalert.org/news-releases/1

Pore choices: A new twist on gas capture
Food scraps, manure and sewage are natural byproducts of the U.S. agricultural industry. They are also rich in biogas, a mixture that contains methane and other valuable chemicals. A team of researchers at Sandia National Laboratories are developing chemistry that could help capture methane from biogas and separate it from other gases so it can be put to good use.

Acoustic Signatures of Pinch-Off Cavities During Water-Entry
Zirui Liu, Tongtong Ding, Mingyue Kuang, Zimeng Li, Junyi Zhao, A-Man Zhang, Shuai Li
https://arxiv.org/abs/2602.22761

Basics of RF Electronics
Amos Christopher Dexter
https://arxiv.org/abs/2602.15205 https://arxiv.org/pdf/2602.15205 https://arxiv.org/html/2602.15205
arXiv:2602.15205v1 Announce Type: new
Abstract: The focus of this educational text is selected examples of high-frequency electronic circuits and their components employed for the accurate phasing and synchronisation of accelerator cavities. Examples have been chosen to describe the basics of RF electronics. The starting point is transmission lines, connectors, discontinuities, and the handling of reflection. The application of simple surface mount components is discussed. The use of the Kuroda identities for converting lumped circuit designs to printed circuit designs is demonstrated. The accelerator example used to demonstrate the use of components is a circuit designed for the synchronisation of the CLIC crab cavities. This example employs co-planar waveguide, SMA connectors, Wilkinson splitters, and surface-mount double-balanced mixers. For the control of cavity phase and amplitude, the benefit of I&Q controllers will be explained. The text will then discuss the operation and use of I&Q modulators and VCOs.
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Cryogenics and the use of superfluid helium in high-energy particle accelerators (1980-2000)
Philippe Lebrun
https://arxiv.org/abs/2602.14298 https://arxiv.org/pdf/2602.14298 https://arxiv.org/html/2602.14298
arXiv:2602.14298v1 Announce Type: new
Abstract: The period 1980-2000 saw the impressive development of applied superconductivity in high-energy particle accelerators, from single components to long strings of superconducting magnets and high-frequency acceleration cavities. Large and powerful cryogenic systems were designed ancillary to superconducting devices operating generally close to the normal boiling point of helium, but also above 4.2 K in supercritical and below 2 K in superfluid. Low-temperature operation in accelerators also involves considerations of ultra-high vacuum, limited stored energy and beam stability. We recall the rationale for cryogenics in high-energy particle accelerators and review its development over the period of interest, with reference to the main engineering domains of cryostat design and heat loads, cooling schemes, efficient power refrigeration and cryogenic fluid management. In view of its importance and novelty, a specific section is devoted to the developments that led to the LHC at CERN.
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