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Photography and video footage, captured by researchers and tourists on board two vessels, provided insights into the predation techniques employed by an adult male killer whale Orcinus orca in Mossel Bay, South Africa. The incapacitation of its prey, a juvenile white shark Carcharodon carcharias (∼2.5 m TL), followed by consumption of the liver, occurred within less than 2 minutes, highlighting the predator proficiency of the killer whale. Notably, another adult male killer whale, and constant traveling companion with the first, was observed approximately 100 m away and was not involved during the predation. The following day a second carcass of a different eviscerated white shark (3.55 m TL) washed ashore in the vicinity, indicating that at least two white sharks may have been killed during the interaction. [ABSTRACT FROM AUTHOR]

Here, we present a frequency tuning mechanism for microwave cavities designed for axion dark matter searches and show that it provides a range of at least 200 MHz for the fundamental mode T M 010 resonant at ∼10 GHz. The apparatus is based on a clamshell cavity, with the two semi-cells held together at a fixed joint while the other side opens to tune the frequency of the resonant modes. Measurements of the cavity frequencies and quality factor were taken at liquid helium temperature as the aperture was increased incrementally to ∼2°. We show that the frequency shift is approximately linear with respect to the angle of aperture with no mode crossings present for an aperture less than 2°. Furthermore, the form factor and quality factor of the T M 010 mode remain relatively constant throughout the tuning as predicted by simulation. [ABSTRACT FROM AUTHOR]

We present a preliminary study to develop a large area photodetector, based on a semiconductor crystal placed inside a superconducting resonant cavity. Laser pulses are detected through a variation of the cavity impedance, as a consequence of the conductivity change in the semiconductor. A novel method, whereby the designed photodetector is simulated by finite element analysis, makes it possible to perform pulse-height spectroscopy on the reflected microwave signals. We measure an energy sensitivity of 100 fJ in the average mode without the employment of low noise electronics and suggest possible ways to further reduce the single-shot detection threshold, based on the results of the described method. [ABSTRACT FROM AUTHOR]

In this work, we experimentally explore the possibility to realize a sensor whose basic building block is a laser cavity that hosts a target crystal for the incident ionizing radiation. Two possible detection mechanisms are considered: a process of coherent scintillation related to the rapid decay via stimulated emission of the excited atomic or molecular levels of the target material and the activation of states that absorb intracavity photons. We use a solid-state laser to study the dynamic response of our prototype sensor and the related intrinsic limitations and demonstrate capability to detect x-ray energy down to 10 GeV. [ABSTRACT FROM AUTHOR]

A photon-magnon hybrid system can be realized by coupling the electron spin resonance of a magnetic material to a microwave cavity mode. The quasiparticles associated with the system dynamics are the cavity magnon polaritons, which arise from the mixing of strongly coupled magnons and photons. We illustrate how these particles can be used to probe the magnetization of a sample with a remarkable sensitivity, devising suitable spin-magnetometers, which ultimately can be used to directly assess oscillating magnetic fields. Specifically, the capability of cavity magnon polaritons of converting magnetic excitations to electromagnetic ones allows for translating to magnetism the quantum-limited sensitivity achieved by state-of-the-art microwave detectors. Here, we employ hybrid systems composed of microwave cavities and ferrimagnetic spheres to experimentally implement two types of novel spin-magnetometers. [ABSTRACT FROM AUTHOR]

Searches for dark matter axions involve the use of microwave resonant cavities operating in a strong magnetic field. Detector sensitivity is directly related to the cavity quality factor, which is limited, until recently, to the use of non-superconducting metals by the presence of the external magnetic field. In this paper, we present a cavity of novel design whose quality factor is not affected by a magnetic field. It is based on a photonic structure by the use of sapphire rods. The quality factor at cryogenic temperature is in excess of 5 × 105 for a selected mode. [ABSTRACT FROM AUTHOR]

A module of a wireless high voltage generator was tested immersed in both gaseous and liquid environments providing electrical insulation. The overall performance of the module as well as a detailed performance of the key components are reported, and a comparison between the results in gas and liquid is given. The tests performed on the liquid dielectric show that it is a valid alternative to high pressure gas electrical insulation. [ABSTRACT FROM AUTHOR]

This article presents the measurements of the luminescence and scintillation under X-ray of undoped, Si-doped, and Si, B codoped gallium-arsenide (GaAs) samples at cryogenic temperature over a wide infrared (IR) region using Si and InGaAs photodetectors. The undoped GaAs has a narrow emission band at 838 nm (1.48 eV) and a low light output of about 2 ph/keV. The GaAs:Si has three broad luminescence bands at 830 nm (1.49 eV), 1070 nm (1.16 eV), and 1335 nm (0.93 eV) and a light output of about 67 ph/keV. GaAs:(Si, B) has four luminescence bands at 860 nm (1.44 eV), 930 nm (1.33 eV), 1070 nm (1.16 eV), and 1335 nm (0.93 eV) with a light yield of approximately 119 ph/keV. With advances in photodetection, GaAs promises to be a useful cryogenic scintillator for the detection of electron recoils from MeV/c2 dark matter. [ABSTRACT FROM AUTHOR]

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Lowenergy threshold detectors are necessary in many frontier fields of the experimental physics. In this work, we present a novel detection approach based on pure or doped matrices of inert gases solidified at cryogenic temperatures. The small energy release of the incident particle can be transferred directly (in pure crystals) or through a laser-driven ionization (in doped materials) to the electrons of the medium that are then converted into free electrons. The charge collection process of the electrons that consists in their drift within the crystal and their extraction through the solid–vacuum interface gives rise to an electric signal that we exploit for preliminary tests of charge collection and crystal quality. Such tests are carried out in different matrices of neon and methane using an UV-assisted apparatus for electron injection in crystals. [ABSTRACT FROM AUTHOR]

We report on a scheme for particle detection based on the infrared quantum counter concept. Its operation consists of a two-step excitation process of a four level system, which can be realized in rare earth-doped crystals when a cw pump laser is tuned to the transition from the second to the fourth level. The incident particle raises the atoms of the active material into a low lying, metastable energy state, triggering the absorption of the pump laser to a higher level. Following a rapid non-radiative decay to a fluorescent level, an optical signal is observed with a conventional detector. In order to demonstrate the feasibility of such a scheme, we have investigated the emission from the fluorescent level 4S3/2 (540 nm band) in an Er3+ -doped YAG crystal pumped by a tunable titanium sapphire laser when it is irradiated with 60 keV electrons delivered by an electron gun. We have obtained a clear signature that this excitation increases the 4I13/2 metastable level population that can efficiently be exploited to generate a detectable optical signal. [ABSTRACT FROM AUTHOR]