We investigate the spectral and angular distribution of the electromagnetic radiation from a chain of relativistic charged particles uniformly rotating along equatorial orbit around a dielectric ...ball. It is shown that, for weak absorption in the ball material and under relatively mild conditions on the distribution of the particles, the radiation intensity at specific rotation frequencies is essentially stronger than the corresponding radiation for a chain circulating in free space or in a homogeneous transparent medium with the same dielectric constant as that for the ball. We determine the values of parameters of the problem for which the charges in the chain emit coherently and the radiation intensity on a given harmonic increases in proportion to the square of the number of emitting charges. We also show that relative shifts in the particles locations up to 10% do not destroy the coherence properties of the radiation. It is demonstrated that the coherence effects may also dominate in the radiation intensity for chains with non-equidistant distributions of particles. The numerical results obtained for different dielectric balls have revealed the emitted radiation to be in the GHz/THz frequency ranges. The high-power radiation from the chain is confined near the rotation plane within the angular region determined by the Cherenkov angle for the velocity of the chain image on the ball surface. In the special case of an equidistant distribution of charged particles along the orbit the results of the present paper for angle integrated frequency distribution of the radiation are in agreement with those previously obtained by our group. We argue that similar coherence effects will be present in the radiation from a chain of bunches circulating around the ball.
•At certain rotation frequencies the radiation intensity becomes essentially higher.•Values of parameters are determined for which the charges radiate coherently.•Relative shifts in the particles locations up to 10% do not destroy the coherence.•Coherence effects may also dominate for non-equidistant distributions of charges.•Angular range of the radiation propagation is determined by the Cherenkov condition.
The SPHERE-2 balloon-borne detector designed for extensive air shower (EAS) observations using EAS optical Vavilov-Cherenkov radiation (“Cherenkov light”), reflected from the snow-covered surface of ...Lake Baikal is described. We briefly discuss the concept behind the reflected Cherenkov light method, characterize the conditions at the experimental site and overview the construction of the tethered balloon used to lift the SPHERE-2 telescope above the surface. This paper is mainly dedicated to a detailed technical description of the detector, including its optical system, sensitive elements, electronics, and data acquisition system (DAQ). The results of some laboratory and field tests of the optical system are presented.
Polaritons in two-dimensional (2D) materials have shown their unique capabilities to concentrate light into deep subwavelength scales. Precise control of the excitation and propagation of 2D ...polaritons has remained a central challenge for future on-chip nanophotonic devices and circuits. To solve this issue, we exploit Cherenkov radiation, a classic physical phenomenon that occurs when a charged particle moves at a velocity greater than the phase velocity of light in that medium, in low-dimensional material heterostructures. Here, we report an experimental observation of Cherenkov phonon polariton wakes emitted by superluminal one-dimensional plasmon polaritons in a silver nanowire and hexagonal boron nitride heterostructure using near-field infrared nanoscopy. The observed Cherenkov radiation direction and radiation rate exhibit large tunability through varying the excitation frequency. Such tunable Cherenkov phonon polaritons provide opportunities for novel deep subwavelength-scale manipulation of light and nanoscale control of energy flow in low-dimensional material heterostructures.
We report the results of the measurements of three pieces of the new Photonis miniPLANACON microchannel-plate photomultipliers (MCP-PMTs) intended for use in the demanding environment of the Large ...Hadron Collider (LHC) beamline as a part of the AFP Time-of-Flight detector. These photomultipliers were modified in cooperation with the manufacturer by using a custom backend and were subjected to numerous tests, with the focus on the rate capability and crosstalk behaviour. We determined that the two of them with a lower MCP resistance are able to operate without significant saturation at an anode current density of 1μA/cm2. These two are, therefore, suitable for the intended use and are currently installed as part of the AFP detector packages.
Photodynamic therapy (PDT) has emerged as an attractive option for cancer treatment. However, conventional PDT is activated by light that has poor tissue penetration depths, limiting its ...applicability in the clinic. Recently the idea of using X‐ray sources to activate PDT and overcome the shallow penetration issue has garnered significant interest. This can be achieved by external beam irradiation and using a nanoparticle scintillator as transducer. Alternatively, research on exploiting Cherenkov radiation from radioisotopes to activate PDT has also begun to flourish. In either approach, the most auspicious success is achieved using nanoparticles as either a scintillator or a photosensitizer to mediate energy transfer and radical production. Both X‐ray induced PDT (X‐PDT) and Cherenkov radiation PDT (CR‐PDT) contain a significant radiation therapy (RT) component and are essentially PDT and RT combination. Unlike the conventional combination, however, in X‐PDT and CR‐PDT, one energy source simultaneously activates both processes, making the combination always in synchronism and the synergy potential maximized. While still in early stage of development, X‐PDT and CR‐PDT address important issues in the clinic and hold great potential in translation.
This article is categorized under:
Therapeutic Approaches and Drug Discovery > Nanomedicine for Oncologic Disease
X‐ray luminescence and Cherenkov radiation can be exploited to activate photosensitizers in situ, solving the tissue penetration issue that has limited the applications of PDT in the clinic.
A moving charged particle, such as an electron, can radiate light due to the interaction between its Coulomb field and surrounding matter. This phenomenon has spawned great interest in the fields of ...physics, electron microscopy, optics, biology, and materials science. Since the radiation generated by the charged particles strongly depends on the surrounding matter, artificially engineered materials with exotic electromagnetic and optic properties, including metamaterials and metasurfaces, provide an unprecedented opportunity to tailor the interaction between the charged particle and matter, and ultimately enable to manipulate the radiated light. In this review, the fundamentals of Cherenkov radiation and Smith–Purcell radiation are presented. Subsequently, the recent advances in the control of Cherenkov radiation and Smith–Purcell radiation based on metamaterials and metasurfaces are summarized. Finally, the applications using these two physical phenomena, including electron‐driven photon sources and electron accelerators, are discussed in this review.
Artificially engineered materials, such as metamaterials and metasurfaces, offer new degrees of freedom to tailor the emission of charged particles in an unprecedented manner. This review summarizes the recent progress of manipulating Cherenkov radiation and Smith–Purcell radiation by artificial structures, discusses the relevant applications, and provides an outlook for this emerging research area.
Radially polarized X-shaped terahertz (THz) pulses (RPXTPs) have unique properties such as spatio-temporal localization, self-reconstruction, nondispersion, and superluminality, making them ...attractive for various applications. However, the direct generation of RPXTPs is a challenging task that has not yet been achieved. We propose a set of easily implementable schemes to directly generate RPXTPs using either a pencil beam or a ring beam of electrons to drive a modified axicon. Cherenkov radiation is excited in the modified axicon in the THz region and then focused in the forward region, allowing direct generation of RPXTPs. We demonstrate the generation of single-cycle broadband RPXTPs with tunable spectral range, focusing depth, and pulse intensity. The field strength reaches tens of MV/m, much higher than that obtained by most available indirect methods. This high-intensity RPXTP has potential applications in THz spectroscopy, THz imaging, light-matter interactions, and THz-driven particle accelerators.
Testbeam studies of a TORCH prototype detector Brook, N.H.; García, L. Castillo; Conneely, T.M. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
11/2018, Volume:
908
Journal Article
Peer reviewed
Open access
TORCH is a novel time-of-flight detector that has been developed to provide charged-particle identification between 2 and 10 GeV/c momentum. TORCH combines arrival times from multiple Cherenkov ...photons produced within a 10 mm-thick quartz radiator plate, to achieve a 15 ps time-of-flight resolution per incident particle. A customised Micro-Channel Plate photomultiplier tube (MCP-PMT) and associated readout system utilises an innovative charge-sharing technique between adjacent pixels to obtain the necessary 70 ps time resolution of each Cherenkov photon. A five-year R&D programme has been undertaken, culminating in the construction of a small-scale prototype TORCH module. In testbeams at CERN, this prototype operated successfully with customised electronics and readout system. A full analysis chain has been developed to reconstruct the data and to calibrate the detector. Results are compared to those using a commercial Planacon MCP-PMT, and single photon resolutions approaching 80 ps have been achieved. The photon counting efficiency was found to be in reasonable agreement with a GEANT4 Monte Carlo simulation of the detector. The small-scale demonstrator is a precursor to a full-scale TORCH module (with a radiator plate of 660×1250×10mm3), which is currently under construction.
The Time-Of-Propagation detector is a Cherenkov particle identification detector based on quartz radiator bars for the Belle II experiment at the SuperKEKB e+e−− collider. The purpose of the detector ...is to identify the type of charged hadrons produced in e+e−− collisions, and requires a single photon timing resolution below 100 picoseconds. A novel front-end electronic system was designed, built, and integrated to acquire data from the 8192 microchannel plate photomultiplier tube channels in the detector. Waveform sampling of these analog signals is done by switched-capacitor array application-specific integrated circuits. The processes of triggering, digitization of windows of interest, readout, and data transfer to the Belle II data acquisition system are managed by Xilinx Zynq-7000 programmable system on a chip devices.
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