Cherenkov Cone Research Articles

Cherenkov Gravitational Radiation during the Radiation Era

Cherenkov radiation may occur whenever the source is moving faster than the waves it generates. In a radiation dominated universe, with equation-of-state w=1/3, we have recently shown that the Bardeen scalar-metric perturbations contribute to the linearized Weyl tensor in such a manner that its wavefront propagates at acoustic speed w=1/3. In this work, we explicitly compute the shape of the Bardeen Cherenkov cone and wedge generated respectively by a supersonic point mass (approximating a primordial black hole) and a straight Nambu-Goto wire (approximating a cosmic string) moving perpendicular to its length. When the black hole or cosmic string is moving at ultra-relativistic speeds, we also calculate explicitly the sudden surge of scalar-metric induced tidal forces on a pair of test particles due to the passing Cherenkov shock wave. These forces can stretch or compress, depending on the orientation of the masses relative to the shock front’s normal.

The Application of Electromagnetic Sensors for Determination of Cherenkov Cone Inside and in the Vicinity of the Detector Volume in Any Environment Known.

The neutrinos of cosmic radiation, due to interaction with any known medium in which the Cherenkov detector is used, produce energy radiation phenomena in the form of a Cherenkov cone, in very large frequency spectrum. These neutrinos carry with them the information about the phenomena that produced them and by detecting the electromagnetic energies generated by the Cherenkov cone, we can find information about the phenomena that formed in the universe, at a much greater distance, than possibility of actually detection with current technologies. At present, a very high number of sensors for detection electromagnetic energy is required. Thus, some sensors may detect very low energy levels, which can lead to the erroneous determination of the Cherenkov cone, thus leading to information errors. As a novelty, we propose, to use these sensors for determination of the dielectrically permittivity of any known medium in which the Cherenkov detector is used, by preliminary measurements, the subsequent simulation of the data and the reconstruction of the Cherenkov cone, leading to a significant reduction of problems and minimizing the number of sensors, implicitly the cost reductions. At the same time, we offer the possibility of reconstructing the Cherenkov cone outside the detector volume.

Normal Doppler Frequency Shift in Negative Refractive‐Index Systems

AbstractBesides the well‐known negative refraction, a negative refractive‐index material can exhibit another two hallmark features, which are the inverse Doppler effect and backward Cherenkov radiation. The former is known as the motion‐induced frequency shift that is contrary to the normal Doppler effect, and the latter refers to the Cherenkov radiation whose cone direction is opposite to the source's motion. Here these two features are combined and the Doppler effect inside the backward Cherenkov cone is discussed. It is revealed that the Doppler effect is not always inversed but can be normal in negative refractive‐index systems. A previously un‐reported phenomenon of normal Doppler frequency shift is proposed in a regime inside the backward Cherenkov cone, when the source's velocity is two times faster than the phase velocity of light. A realistic metal–insulator–metal structure, which supports metal plasmons with an effective negative refractive index, is adopted to demonstrate the potential realization of this phenomenon.

Threshold-less and focused Cherenkov radiations using sheet electron-beams to drive sub-wavelength hole arrays.

Cherenkov radiation (CR) was one of the most famous discoveries in the last century and still has broad applications in modern physics. Recently, threshold-less and reversed CRs have attracted even more attention thanks to their unique characteristics and application prospects. Here we illustrated a threshold-less CR in vacuo by using a sheet free-electron beam (FEB) to excite an oblique-lined sub-wavelength hole array. It is achieved by setting the effective velocity of emitters-resonant modes successively excited by the sheet FEB-to be greater than the speed of light in vacuo. By letting the sub-wavelength holes line up along a designed curve, we further demonstrated a focused CR with radiation being convergent to specific focusing spots, which can be located at any designed positions in space, achieving backward (reversed) as well as forward (normal) CRs in effect. This focused CR does not have the conventional Cherenkov cone, and its intensity at the focusing spot is greatly enhanced. These newly revealed threshold-less and focused CRs may lead to broad interest and attractive applications, especially for developing integrated and focused light sources in the terahertz region.

Superlight inverse Doppler effect

It has long been thought1 that the inverse Doppler frequency shift of light2–13 is impossible in homogeneous systems with a positive refractive index. Here we break this long-held tenet by predicting a previously unconsidered Doppler effect of light inside a radiation cone, the so-called Vavilov–Cherenkov cone, under specific circumstances. It has been known from the classic work of Ginzburg and Frank that a superlight (that is, superluminal) normal Doppler effect14–18 appears inside the Vavilov–Cherenkov cone if the velocity of the source v is larger than the phase velocity of light vp. By further developing their theory, we discover that an inverse Doppler frequency shift will arise if v > 2vp. We denote this as the superlight inverse Doppler effect. Moreover, we show that the superlight inverse Doppler effect can be spatially separated from the other Doppler effects by using highly squeezed polaritons (such as graphene plasmons), which may facilitate the experimental observation. The authors theoretically investigate a novel form of a Doppler effect in homogeneous systems with positive refractive index that occurs under certain conditions. It is suggested that this Doppler effect can be experimentally separated from other Doppler effects by using polaritons such as those found in graphene.

Mixed optical Cherenkov–Bremsstrahlung radiation in vicinity of the Cherenkov cone from relativistic heavy ions: Unusual dependence of the angular distribution width on the radiator thickness

The Cherenkov radiation (ChR) angular distribution is usually described by the Tamm–Frank (TF) theory, which assumes that relativistic charged particle moves uniformly and rectilinearly in the optically transparent radiator. According to the TF theory, the full width at half maximum (FWHM) of the ChR angular distribution inversely depends on the radiator thickness. In the case of relativistic heavy ions (RHI) a slowing-down in the radiator may sufficiently change the angular distribution of optical radiation in vicinity of the Cherenkov cone, since there appears a mixed ChR–Bremsstrahlung radiation. As a result, there occurs a drastic transformation of the FWHM of optical radiation angular distribution in dependence on the radiator thickness: from inversely proportional (TF theory) to the linearly proportional one. In our paper we present the first analysis of this transformation taking account of the gradual velocity decrease of RHI penetrating through a radiator.

Characteristics of Cherenkov radiation in naturally occurring ice

We revisit the theory of Cherenkov radiation in uniaxial crystals. Historically, a number of flawed attempts have been made at explaining this radiation phenomenon, and a consistent error-free description is nowhere available. We apply our calculation to a large modern day telescope---IceCube. Located in Antarctica, this detector makes use of the naturally occurring ice as a medium to generate Cherenkov radiation. However, due to the high pressure at the depth of the detector site, large volumes of hexagonal ice crystals are formed. We calculate how this affects the Cherenkov radiation yield and angular dependence. We conclude that the effect is small, at most about a percent, and would only be relevant in future high-precision instruments like e.g. Precision IceCube Next Generation Upgrade (PINGU). For radio-Cherenkov experiments which use the presence of a clear Cherenkov cone to determine the arrival direction, any variation in emission angle will directly and linearly translate into a change in apparent neutrino direction. In closing, we also describe a simple experiment to test this formalism and calculate the impact of anisotropy on light yields from lead tungstate crystals as used, for example, in the CMS calorimeter at the CERN LHC.

Orthogonal Cherenkov sound in spin-orbit coupled systems.

Conventionally the Cherenkov sound is governed by orbital degrees of freedom and is excited by supersonic particles. Additionally, it usually has a forward nature with a conic geometry known as the Cherenkov cone whose axis is oriented along the supersonic particle motion. Here we predict Cherenkov sound of a unique nature entirely resulting from the electronic spin degree of freedom and demonstrate a fundamentally distinct Cherenkov effect originating from essentially subsonic electrons in two-dimensional gases with both Bychkov-Rashba and Dresselhaus spin-orbit interactions. Specifically, we show that the axis of the conventional forward Cherenkov cone gets a nontrivial quarter-turn and at the same time the sound distribution strongly localizes around this rotated axis being now orthogonal to the subsonic particle motion. Apart from its fundamentally appealing nature, the orthogonal Cherenkov sound could have applications in planar semiconductor technology combining spin and acoustic phenomena to develop, e.g., acoustic amplifiers or sound sources with a flexible spin dependent orientation of the sound propagation.

Optical radiation from channeled relativistic heavy ions in vicinity of the Cherenkov angle

We investigated by means of computer simulations the influence of 2000MeV/u relativistic heavy ions (RHI) planar channeling on the angular and spectral distributions of optical radiation in a diamond crystal, in vicinity of the classical Cherenkov cone. The case of RHI is attractive since the dechanneling length is much greater compared to electrons and other light particles having similar relativistic factor. Although the effect turned out to be rather small, further studies of peculiarities in spectral-angular properties of optical radiation from channeled RHI at other emission angles and in other spectral regions will be continued.

Controlling Cherenkov radiation with transformation-optical metamaterials.

In high energy physics, unknown particles are identified by determining their mass from the Cherenkov radiation cone that is emitted as they pass through the detector apparatus. However, at higher particle momentum, the angle of the Cherenkov cone saturates to a value independent of the mass of the generating particle, making it difficult to effectively distinguish between different particles. Here, we show how the geometric formalism of transformation optics can be applied to describe the Cherenkov cone in an arbitrary anisotropic medium. On the basis of these results, we propose a specific anisotropic metamaterial to control Cherenkov radiation, leading to enhanced sensitivity for particle identification at higher momentum.

Propagation of electromagnetic waves generated by modulated moving source in dispersive lossy media

AbstractWe apply the complex two‐dimensional stationary‐phase method for problems of electromagnetic waves radiation from the moving modulated sources in dispersive and lossy medium. The explicit formulas for fields generated by a moving source, the Doppler effect, and the retarded time are obtained. We apply the developed approach to numerical study of the Cherenkov radiation in a dispersive medium (Drude model). Our simulations have shown that in double negative dispersive metamaterials, the Cherenkov cone splits in two branches. Copyright © 2014 John Wiley & Sons, Ltd.

Coherent radiation from extensive air showers in the ultrahigh frequency band

Using detailed Monte Carlo simulations we have characterized the features of the radio emission of inclined air showers in the ultrahigh frequency band (300 MHz--3 GHz). The Fourier spectrum of the radiation is shown to have a sizable intensity well into the GHz frequency range. The emission is mainly due to transverse currents induced by the geomagnetic field and the excess charge produced by the Askaryan effect. At these frequencies only a significantly reduced volume of the shower around the axis contributes coherently to the signal observed on the ground. The size of the coherently emitting volume depends on frequency, shower geometry and observer position, and is interpreted in terms of the relative time delays at observation dominated by the curvature of the shower front. At ground level, the maximum emission at high frequencies is concentrated in an elliptical ringlike region around the intersection of a Cherenkov cone with its vertex at shower maximum and the ground. The frequency spectrum of inclined showers when observed at positions that view shower maximum in the Cherenkov direction, is shown to be in broad agreement with the pulses detected by the Antarctic Impulsive Transient Antenna experiment, making the interpretation that they are due to ultrahigh energy cosmic ray atmospheric showers consistent with our simulations. These results are also of great importance for experiments aiming to detect molecular bremsstrahlung radiation in the GHz range as they present an important background for its detection.

Probing ultrafast optomagnetism by terahertz Cherenkov radiation

We put forward Cherenkov-type terahertz emission from a moving pulse of magnetization as a method to explore ultrafast optomagnetic phenomena. We propose to use a structure comprising a slab of transparent magnetooptic material coupled to an output prism. An ultrashort laser pulse propagates in the slab and produces transient magnetization via the inverse Faraday effect. The moving magnetization emits a Cherenkov cone of terahertz waves in the output prism. We developed a theory that predicts the detectability of the radiation for a terbium gallium garnet slab covered with a Si prism.

Angular distribution of Cherenkov radiation from relativistic heavy ions taking into account deceleration in the radiator

Numerical methods are used to study the dependence of the structure and the width of the angular distribution of Vavilov-Cherenkov radiation with a fixed wavelength in the vicinity of the Cherenkov cone on the radiator parameters (thickness and refractive index), as well as on the parameters of the relativistic heavy ion beam (charge and initial energy). The deceleration of relativistic heavy ions in the radiator, which decreases the velocity of ions, modifies the condition of structural interference of the waves emitted from various segments of the trajectory; as a result, a complex distribution of Vavilov-Cherenkov radiation appears. The main quantity is the stopping power of a thin layer of the radiator (average loss of the ion energy), which is calculated by the Bethe-Bloch formula and using the SRIM code package. A simple formula is obtained to estimate the angular distribution width of Cherenkov radiation (with a fixed wavelength) from relativistic heavy ions taking into account the deceleration in the radiator. The measurement of this width can provide direct information on the charge of the ion that passes through the radiator, which extends the potentialities of Cherenkov detectors. The isotopic effect (dependence of the angular distribution of Vavilov-Cherenkov radiation on the ion mass) is also considered.

Coherent Cherenkov Radiation from Cosmic-Ray-Induced Air Showers

Very energetic cosmic rays entering the atmosphere of Earth will create a plasma cloud moving with almost the speed of light. The magnetic field of Earth induces an electric current in this cloud which is responsible for the emission of coherent electromagnetic radiation. We propose to search for a new effect: Because of the index of refraction of air, this radiation is collimated in a Cherenkov cone. To express the difference from usual Cherenkov radiation, i.e., the emission from a fast-moving electric charge, we call this magnetically induced Cherenkov radiation. We indicate its signature and possible experimental verification.

Anomalous Cherenkov spin-orbit sound

The Cherenkov effect is a well known phenomenon in the electrodynamics of fast charged particles passing through transparent media. If the particle is faster than the light in a given medium, the medium emits a forward light cone. This beautiful phenomenon has an acoustic counterpart where the role of photons is played by phonons and the role of the speed of light is played by the sound velocity. In this case the medium emits a forward sound cone. Here, we show that in a system with spin-orbit interactions in addition to this {\it normal} Cherenkov sound there appears an {\it anomalous} Cherenkov sound with forward and {\it backward} sound propagation. Furthermore, we demonstrate that the transition from the normal to anomalous Cherenkov sound happens in a {\it singular} way at the Cherenkov cone angle. The detection of this acoustic singularities therefore represents an alternative experimental tool for the measurement of the spin-orbit coupling strength.

Čerenkov radio pulses from electromagnetic showers in the time domain

The electric field of the Cherenkov radio pulse produced by a single charged particle track in a dielectric medium is derived from first principles. An algorithm is developed to obtain the pulse in the time domain for numerical calculations. The algorithm is implemented in a Monte Carlo simulation of electromagnetic showers in dense media (specifically designed for coherent radio emission applications) as might be induced by interactions of ultra-high energy neutrinos. The coherent Cherenkov radio emission produced by such showers is obtained simultaneously both in the time and frequency domains. A consistency check performed by Fourier-transforming the pulse in time and comparing it to the frequency spectrum obtained directly in the simulations yields, as expected, fully consistent results. The reversal of the time structure inside the Cherenkov cone and the signs of the corresponding pulses are addressed in detail. The results, besides testing algorithms used for reference calculations in the frequency domain, shed new light into the properties of the radio pulse in the time domain. The shape of the pulse in the time domain is directly related to the depth development of the excess charge in the shower and its width to the observation angle with respect to the Cherenkov direction. This information can be of great practical importance for interpreting actual data.

Cherenkov radiation from relativistic heavy ions taking account of their slowing down in radiator

Combining the SRIM’06 computer code and the formula for spectral-angular distribution of radiation from a particle moving in a medium in arbitrary trajectory, we studied numerically the structure of angular distributions of Cherenkov radiation from moderately relativistic heavy ions (RHI) taking into account the decrease of the ion velocity due to stopping in the radiator. The results obtained clearly show that the width and the fine structure of the Cherenkov radiation in the vicinity of the Cherenkov cone depend strongly on several factors, e.g. the mean and total energy losses, the radiator thickness, the square of the ion charge, the emission wavelength and the refractive index of the radiator material. This might be useful for experiments using RICH detectors for relativistic heavy ions.

Current status of the ANTARES neutrino telescope

The ANTARES collaboration is currently installing a neutrino telescope in the Mediterranean Sea close to the French coast at Toulon. The complete detector will consist of 900 photomultipliers arranged on 12 detector lines in 2500 m depth, thus instrumenting a volume of 0.01 km3 sea water as target material. The incident neutrinos are detected by collecting the Cherenkov light from charged secondary particles, which are emitted by neutrino interactions with the sea water or the rock of the sea bed beneath. By reconstructing the Cherenkov cone and therewith the direction of the incident neutrinos with high accuracy, the principal objective of ANTARES is the search for point sources of high-energy cosmic neutrinos and dark matter. In this presentation, emphasis will be placed on the operation of the detector in the hostile deep sea environment and on the status of the project. Results of the first complete detector line will be shown.

Fine structure of the Vavilov–Cherenkov radiation

We found relativistic quantum corrections to the one-photon Cherenkov emission. It is proved that, in the absence of dispersion, the Vavilov–Cherenkov radiation fills the whole Cherenkov cone (in the Tamm–Frank theory the Vavilov–Cherenkov radiation for the fixed refractive index is confined to the surface of the Cherenkov cone). The radiation intensity reaches the maximum inside the Cherenkov cone. It turns out that photons with different energies fly at different angles in the interval from zero up to the Cherenkov angle corresponding to the initial charge velocity. The visible light region, where the Vavilov–Cherenkov radiation is usually observed, is surrounded by the low intensity infrared region and by the high intensity one corresponding to high energy photons. The ratio of the radiation intensity at the maximum lying in the Roentgen part of the radiation spectrum to the radiation intensity in its visible part is about 10 4 . Taking into account the medium dispersion leads to the appearance of the striped-like radiation structure inside the Cherenkov cone. Experimental data indicating the existence of a non-zero radiation field inside this cone are discussed. In the past, non-relativistic quantum corrections to the radiation intensity were found by Ginzburg. Yet, he did not analyse their influence for large energy–momentum transfer.