Line Radiation Research Articles

Analogue Hawking Radiation in Nonlinear LC Transmission Lines

Analogue systems are used to test Hawking radiation, which is hard to observe in actual black holes. One such system is the electrical transmission line, but it suffers the inevitable issue of excess heat that collapses the successfully generated analogue black holes. Soliton provides a possible solution to this problem due to its stable propagation without unnecessary energy dissipation in nonlinear transmission lines. In this work, we propose analogue Hawking radiation in a nonlinear LC transmission line including nonlinear capacitors with a third-order nonlinearity in voltage. We show that this line supports voltage soliton that obeys the nonlinear Schrödinger equation by using the discrete reductive perturbation method. The voltage soliton spatially modifies the velocity of the electromagnetic wave through the Kerr effect, resulting in an event horizon where the velocity of the electromagnetic wave is equal to the soliton velocity. Therefore, Hawking radiation bears soliton characteristics, which significantly contribute to distinguishing it from other radiation.

WEST tokamak hard x-ray tomography inversion

Long-pulse steady-state discharges with lower hybrid current drive were successfully obtained in the limiter configuration machine, Tore Supra. The hard x-ray (HXR) diagnostic system in Tore Supra associated with tomographic inversion provided a good approximation of the lower hybrid power deposition profile. The accurate plasma current control through this tomographic reconstruction leads to an improvement of plasma confinement. Tore Supra was upgraded to WEST, Tungsten (W) Environment in Steady-state Tokamak. The plasma geometry was changed to the D-shaped geometry. Therefore, a novel inversion code for WEST has been developed. The method used in the code is based on the Bessel function of the first kind of order zero. The code validation was performed using phantom emissivity profiles and WEST experimental data. It has been found that the line radiation of the tungsten divertor in WEST and noise significantly affect the inversion. The local HXR emissivity profile with acceptable accuracy can be achieved by applying a singular value decomposition filter and suppressing the lines of sight that intersect the divertors.

A global view on star formation: the GLOSTAR Galactic plane survey

The Cygnus X complex is covered by the Global View of Star Formation in the Milky Way (GLOSTAR) survey, an unbiased radio-wavelength Galactic plane survey, in 4–8 GHz continuum radiation and several spectral lines. The GLOSTAR survey observed the 6.7 GHz transition of methanol (CH3OH), an exclusive tracer of high-mass young stellar objects. Using the Very Large Array in both the B and D configurations, we observed an area in Cygnus X of 7° × 3° in size and simultaneously covered the methanol line and the continuum, allowing cross-registration. We detected thirteen sources with Class II methanol maser emission and one source with methanol absorption. Two methanol maser sources are newly detected; in addition, we found four new velocity components associated with known masers. Five masers are concentrated in the DR21 ridge and W75N. We determined the characteristics of the detected masers and investigated the association with infrared, (sub)millimeter, and radio continuum emission. All maser sources are associated with (sub)millimeter dust continuum emission, which is consistent with the picture of masers tracing regions in an active stage of star formation. On the other hand, only five masers (38 ± 17%) have radio continuum counterparts seen with GLOSTAR within ~1″, testifying to their youth. Comparing the distributions of the bolometric luminosity and the luminosity-to-mass ratio of cores that host 6.7 GHz methanol masers with those of the full core population, we identified lower limits LBol ~ 200 L⊙ and LBol/Mcore ~ 1 L⊙M⊙−1 for a dust source to host maser emission.

Effects of Spatial Discretization in Lyα Line Radiation Transfer Simulations

Abstract We describe the addition of Lyα resonant line transfer to our dust continuum radiation transfer code SKIRT, verifying our implementation with published results for spherical problems and using some self-designed three-dimensional setups. We specifically test spatial discretization through various grid types, including hierarchical octree grids and unstructured Voronoi tessellations. We then use a radiation transfer postprocessing model for one of the spiral galaxies produced by the Auriga cosmological zoom simulations to investigate the effect of spatial discretization on the synthetic observations. We find that the calculated Lyα line profiles exhibit an extraordinarily strong dependence on the type and resolution of the spatial grid, rendering the results untrustworthy at best. We attribute this effect to the large gradients in the hydrogen density distribution over small distances, which remain significantly underresolved in the input model. We therefore argue that further research is needed to determine the required spatial resolution of a hydrodynamical simulation snapshot to enable meaningful Lyα line transfer postprocessing.

Design Features of Antenna Arrays of Automotive Radars Based on Transmitting and Receiving Multi-Element Modules

Introduction. Modern vehicles are equipped with radars, which serve as the main sensors of driver assistance systems detecting objects in all weather conditions. Antenna arrays (AA) are the most common type of radar antennas. The coefficient of mutual coupling between adjacent antenna channels has a significant effect on the formed radiation pattern (RP) of an AA. This aspect is important for achieving the required values of gain and side-lobe level (SLL). This article analyses the effect of the proposed design solutions on the main parameters of an automotive radar AA, in particular, on the mutual coupling coefficient between the channels and the SLL of the DP.Aim. To develop an optimal approach to constructing an AA topology in terms of reducing the level of mutual influence of adjacent array channels and obtaining a DP with specified characteristics.Materials and methods. To achieve the required parameters of the designed AA topology, the coplanar and microstrip lines were calculated using the finite element method and shield models.Results. An electrodynamic modeling of a millimetre-wave AA was carried out. The effect of coplanar transmission lines on the RP was shown. The features of applying shielding elements in the AA structure were investigated. Antenna patterns were obtained for both an AA designed based on coplanar transmission lines and that based on the use of shields. The conducted comparative analysis determined the parameters of the substrate optimal for achieving a better level of decoupling between adjacent antenna channels. The values of AA RP obtained during modeling were presented.Conclusion. The use of coplanar transmission lines can significantly reduce the SLL of the DP in the elevation plane. When implementing the module structure of an array (using of sub-arrays), the power dividers are realized. In this case, instead of coplanar lines, it is advisable to use specific microstrip constructions covered with shielding surfaces. In this case, the formation of a given amplitude-phase distribution over aperture is possible. A comparative analysis of the AA topologies with different substrates was carried out with the purpose of achieving improved decoupling. The obtained values of the coefficient of mutual influence of adjacent array channels correspond to those of modern AA of automotive radars. The methods of reducing the parasitic radiation of transmission lines were considered. The AA RP obtained via electrodynamic modeling were presented. The use of a thin substrate with a higher dielectric constant makes it possible to improve the AA characteristics.

General theory and observation of Cherenkov radiation induced by multimode solitons

Advancements in computational capabilities along with the possibility of accessing high power levels have stimulated a reconsideration of multimode fibers. Multimode fibers are nowadays intensely pursued in terms of addressing longstanding issues related to information bandwidth and implementing new classes of high-power laser sources. In addition, the multifaceted nature of this platform, arising from the complexity associated with hundreds and thousands of interacting modes, has provided a fertile ground for observing novel physical effects. However, this same complexity has introduced a formidable challenge in understanding these newly emerging physical phenomena. Here, we provide a comprehensive theory capable of explaining the distinct Cherenkov radiation lines produced during multimode soliton fission events taking place in nonlinear multimode optical fibers. Our analysis reveals that this broadband dispersive wave emission is a direct byproduct of the nonlinear merging of the constituent modes comprising the resulting multimode soliton entities, and is possible in both the normal and anomalous dispersive regions. These theoretical predictions are experimentally and numerically corroborated in both parabolic and step-index multimode silica waveguides. Effects arising from different soliton modal compositions can also be accounted for, using this model. At a more fundamental level, our results are expected to further facilitate our understanding of the underlying physics associated with these complex “many-body” nonlinear processes.

STOCHASTIC MECHANISM OF BROADENING SPECTRAL DENSITY OF SYNCHROTRON RADIATION OF RELATIVISTIC ELECTRON

The consideration is based on the study of the spectral profile of the synchrotron radiation (SR) line of a relativistic electron orbiting in a circular orbit in the uniform magnetic field. Fast stochastic fluctuations accompanying the motion of the electron during emission of SR quanta lead to the formation of spectral contour of each SR harmonic and it’s broadening. It is shown that the joint broadening of the set of harmonics causes broadening of the SR spectrum as the whole. The results of numerical calculations on the formation of the final SR spectral density of a relativistic electron are presented. In order to obtain precision characteristics, the formation of SR density in the frequency range exceeding the critical frequency has been studied.

The Combination of Trametinib, a MEK Inhibitor, and Temsirolimus, an mTOR Inhibitor, Radiosensitizes Lung Cancer Cells.

We evaluated the radiosensitizing effect of the combination treatment of trametinib, a MEK inhibitor, and temsirolimus, an mTOR inhibitor, on non-small-cell lung carcinoma (NSCLC) cells. The effects of combining trametinib and temsirolimus with radiation in NSCLC cell lines were evaluated using clonogenic survival and apoptosis assays. DNA double-strand breaks and cell cycle distribution were analyzed using flow cytometry. Tumor volume was measured to determine the radiosensitivity in lung cancer xenograft models. Exposure of lung cancer cells to a combination of trametinib and temsirolimus reduced clonogenic survival and promoted radiation-induced apoptosis. Combined inhibition of MEK and mTOR induced prolonged expression of γH2AX after irradiation and resulted in prolonged G2/M cell cycle arrest after irradiation in A549 cells. In vivo studies revealed that co-administration of the drugs sensitizes lung cancer xenografts to radiotherapy. The combination of trametinib and temsirolimus can enhance lung cancer radiosensitivity in vitro and in vivo.

3D radiation, density, and MHD structures following neon shattered pellet injection into stable DIII-D Super H-mode discharges

Six nominally repeat neon shattered pellet injection (SPI) shutdowns of stable DIII-D Super H-modes are studied to understand the 3D properties of the radiation and impurity transport. The radiation efficiency and radiation peaking determine whether first wall melting is expected following disruption mitigation in ITER. Previous studies make use of axisymmetric approximations to infer radiation efficiencies, but validating the high efficiency required by ITER necessitates improved accuracy, and this work contributes by exploring the 3D radiation and density structures that will inform forward modeling. When the neon shatter plume produced by the SPI reaches the plasma edge, m/n = 3/1 and 2/1 island O-points are observed to align with the injection trajectory in five out of six cases, suggesting that the injected material seeds the island O-points. Field aligned neon structures emitting Ne-I line radiation drift at 1 km s−1 in the ion diamagnetic drift direction during the pre-thermal quench, tracking the motion of the m/n = 2/1 island O-point. Neon fragments penetrate to the q = 2 surface by the time of the thermal quench. Techniques to constrain the 3D emissivity are explored, and one method constrains a 3D flux tube that is consistent with the radiation data, and when mapped to the interferometers, intersects the lasers that measure the highest density. The resulting structure derived from the radiation measurements exists near the 2/1 island X-point. In five repeatable discharges, the peak of the radiation in the toroidal direction exists in a 120° toroidal sector where the injection occurs, in contrast with the outlier discharge where the toroidal peak exists in the complementary 240° toroidal sector far from the injector, and where a 50% lower density rise is observed. The n = 1 phase behavior is markedly different in the outlier discharge, suggesting a possible dependence of the radiation structure and the assimilation efficiency on MHD.

Collisional redistribution of hydrogen line radiation in low- and moderate-density magnetized plasmas.

A computer simulation technique has been applied to the modeling of radiation redistribution functions in low- and moderate-density magnetized hydrogen plasmas. The radiating dipole is described within the Heisenberg picture, and perturbations by the plasma microfield are accounted for through a time-dependent Stark effect term in the Hamiltonian. Numerical applications are presented for the first Lyman and Balmer lines at plasma conditions relevant to tokamak divertors and magnetized white dwarf atmospheres. In both cases, the collisional redistribution of the radiation frequency is shown to be incomplete. Comparisons with a previously developed impact model are performed, and results are discussed.

Spherical plasma focus operated with nitrogen and neon gases for soft x-rays (bremsstrahlung radiation, line radiation, and radiative recombination)

X-ray emissions (bremsstrahlung radiation, line radiation, and radiative recombination) from spherical plasma focus (SPF) device are investigated with the developed spherical MHD model for nitrogen (N) and neon (Ne) gases with respect to gas pressure, which is varied from 0.1 Torr to 7 Torr. Ion density, plasma velocity, pinch temperature, and peak current are also calculated for N and Ne gases. The total capacitance, external inductance, charging voltage, and stored energy as the operational conditions of the SPF device in this study are 432 µF, 36 nH, 25 kV, and 135 kJ. The maximum current is achieved at 7 Torr for both N (1561 kA) and Ne (1525 kA). It is found that there is an optimum pressure point for both x-rays (bremsstrahlung radiation, line radiation, and radiative recombination) and the used gases (N and Ne), separately. While the optimum pressure of bremsstrahlung radiation for N and Ne gases are 0.9 Torr and 1 Torr, respectively, these optimum pressures of radiative recombination and line radiation are 1 Torr for N gas and 1.1 Torr for Ne gas, respectively. It is also found that line radiation constitutes the big portion of the soft x-ray (SXR) emissions from SPF device. Line radiations of N at 1 Torr and Ne at 1.1 Torr are 911 J (91% of total N SXRs) and 3036.5 J (93.1% of total Ne SXRs), respectively, which shows that SPF device can be considered as a good SXR source. Ion densities and peak currents at 7 Torr are calculated as 21.88 × 1023 m−3 with 1561 kA peak current for N gas and 15.98 × 1023 m−3 with 1525 kA peak current for Ne gas.

A Theoretical Verification to Enhancing Effect of Ferrites on Magnetic Field and Line Radiation of a Dense Plasma Focus Device

In this work, the effects of ferrites on the generated magnetic field as well as the emitted line radiation in a dense plasma focus device have been theoretically investigated. The computations have been performed using a magnetic field calculation method represented in the modified Lee model. The results have shown that the ferrite magnetization contributes to the uniformity of the total magnetic field. The derived equations showed linear dependence of the average magnetic field on the ferrite susceptibility. Also, with including the maximum inductance of the device in the line radiation formula, it has been seen that the line power relates to the susceptibility in a linear manner.

Long Characteristics versus Short Characteristics in 3D Radiative Transfer Simulations of Polarized Radiation

Abstract We compare maps of scattering polarization signals obtained from three-dimensional (3D) radiation transfer calculations in a magnetoconvection model of the solar atmosphere using formal solvers based on the “short characteristics” (SC) and the “long characteristics” (LC) methods. The SC method requires less computational work, but it is known to introduce spatial blurring in the emergent radiation for inclined lines of sight. For polarized radiation this effect is generally more severe due to it being a signed quantity and to the sensitivity of the scattering polarization to the model’s inhomogeneities. We study the differences in the polarization signals of the emergent spectral line radiation calculated with such formal solvers. We take as a case study already published results of the scattering polarization in the Sr i 4607 Å line obtained with the SC method, demonstrating that in high-resolution grids it is accurate enough for that type of study. In general, the LC method is the preferred one for accurate calculations of the emergent radiation, which is the reason why it is now one of the options in the public version of the 3D radiative transfer code PORTA.

Wavelet Spectra of a Chirped Gaussian Pulsed-Driven Harmonic Oscillator

We investigate the nature of spectral lines of emitted radiation due to of a non-dissipative single-mode quantized harmonic oscillator (HO) with train of n-chirped Gaussian pulses. Specifically, we analyze the transient emitted spectrum through two window wavelet functions of the radiation detector, namely the Haar wavelet and Morlet wavelet. Computational display of the exact analytical results shows how the driving pulse parameters (strength and number of pulses, chirping, repetition time) act as control knobs to shape the detected emitted spectrum as desired.

Relativistic magnetic flux quantum - a unique radiation carrier

The work found the shape of spectral lines of electromagnetic radiation produced by a relativistic quantum of magnetic flux moving in a Josephson transmission line under the action of a purely fluctuating external current and dissipation. It is shown that even in the case of a Gaussian noise current, the shape of the spectral lines of electromagnetic radiation has an essentially non-Gaussian form. The limited dispersion of the frequency of electromagnetic radiation (which is determined by the pinching of the spectral lines of radiation) is proved, due to the relativistic properties of the quantum magnetic flux. This is another unique aspect of the relativistic quantum magnetic flux - as a carrier of electromagnetic radiation in the Josephson transmission line.

Development of the gas puffing imaging diagnostic on J-TEXT tokamak.

Edge turbulence is important for plasma confinement, so the gas puffing imaging (GPI) diagnostic was proposed on the J-TEXT tokamak for the two-dimensional measurement of turbulence in the edge region. GPI is a diagnostic of plasma turbulence that uses a puff of neutral gas at the plasma edge to increase the local visible light emission for improved space-time resolution of plasma fluctuations. Considering the conditions of J-TEXT, the observation area is 21° away from the position of the optical system in the toroidal direction, and the observation area is 10 cm × 10cm inside and outside the last closed flux surface. To have a lower divergence of the gas flow, the gas puff nozzle is specially designed. An interface has been developed for operation. To photograph the line radiation generated by the neutral gas cloud along the magnetic field lines, the optical system is designed. It is composed of a quartz glass, mirrors, commercial lenses, filters, and high-speed cameras. The high-speed camera can capture the line radiation with a speed up to 180 000 frames/s with 256 pixels × 256 pixels and an exposure time of 5 µs. In a recent experiment, the new GPI diagnostic has obtained some preliminary pictures.

Evidence of bystander effect induced by radiofrequency radiation in a human neuroblastoma cell line

In previous studies we demonstrated that radiofrequency (RF) electromagnetic fields (EMF) is able to reduce DNA damage induced by a subsequent treatment with genotoxic agents, resembling the adaptive response, a phenomenon well known in radiobiology. In this study we report on the capability of the culture medium from SH-SY5Y neuroblastoma cells exposed to 1950 MHz to elicit, in recipient non-exposed cells, a reduction of menadione-induced DNA damage (P < 0.05; comet assay), indicating the capability of non-ionizing radiation to elicit a bystander effect. A comparable reduction was also detected in cultures directly exposed to the same EMF conditions (P < 0.05), confirming the adaptive response. In the same exposure conditions, we also evidenced an increase of heat shock protein 70 (hsp70) in culture medium of cells exposed to RF with respect to sham exposed ones (P < 0.05; western blot analysis), while no differences were detected in the intracellular content of hsp70. On the whole, our results evidence a protective effect of RF against menadione-induced DNA damage in directly and non-directly exposed cells, and suggest hsp70 pathway to be investigated as one of the potential candidate underpinning the interaction between RF exposure and biological systems.

A Nodal Model for Tokamak Burning Plasma Space-Time Dynamics

Fusion alpha heating introduces new phenomena into plasma dynamics and control. On the worrisome side is the well-known fact that the dependence of the predominantly central fusion heating mechanism, coupled with the less appreciated fact of the predominantly plasma edge location of bremsstrahlung and impurity line and recombination radiation cooling and of ion orbit loss cooling, suggests the possibility of a thermal runaway fusion power excursion in the plasma core. On the encouraging side is the fact that the fusion alpha energy is transferred first to heat the core electrons and produce electron cyclotron radiation that is transferred instantaneously, predominantly to outer plasma regions and the surrounding material wall, reducing its availability for further heating of core plasma ions. This paper discusses the temporal and spatial dependence of the various heating and cooling mechanisms involved in the burn dynamics of a fusion plasma, introduces a spatially coarse nodal space-time calculation model (suitable for dynamics and controller calculations) for the analysis of burning plasmas, and identifies the research needed to fully evaluate the parameters of such a model.

Pembrolizumab in vaginal and vulvar squamous cell carcinoma: a case series from a phase II basket trial

Vaginal and vulvar squamous cell carcinoma (SCC) are rare tumors that can be challenging to treat in the recurrent or metastatic setting. We present a case series of patients with vaginal or vulvar SCC who were treated with single-agent pembrolizumab as part of a phase II basket clinical trial to evaluate efficacy and safety. Two cases of recurrent and metastatic vaginal SCC, with multiple prior lines of systemic chemotherapy and radiation, received pembrolizumab. One patient had significant reduction (81%) in target tumor lesions prior to treatment discontinuation at cycle 10 following confirmed progression of disease with new metastatic lesions (stable disease by irRECIST criteria). In contrast, the other patient with vaginal SCC discontinued treatment after cycle 3 due to disease progression. Both patients had PD-L1 positive vaginal tumors and tolerated treatment well. One case of recurrent vulvar SCC with multiple surgical resections and prior progression on systemic carboplatin had a 30% reduction in her target tumor lesions following pembrolizumab treatment with a PD-L1 positive tumor. Treatment was discontinued for grade 3 mucositis after cycle 5. Pembrolizumab may provide some clinical benefit to some patients with vaginal or vulvar SCC and is overall safe to utilize in this population. Future studies are needed to evaluate the efficacy of pembrolizumab in these rare tumor types and to identify predictive biomarkers of response.

Application of Bayesian tomography method to the visible spectroscopic diagnostic on HL-2A tokamak

As the commission of a visible spectroscopic diagnostic to the HL-2A tokamak for the measurements of both bremsstrahlung continuum radiation and impurity line emission, a Bayesian tomography method has been developed to this diagnostic for the reconstruction of a 2D emission distribution from line-integrated data. In this method, Gaussian process prior is adopted as an effective way to regularize the smoothness of the emission field, which can be truncated to enforce non-negative constraint of the emission values. For the reliability and quality assessment, uncertainty of the reconstruction can be examined through its confidence interval derived from a posterior probability. Performance of this Gaussian processtomography method is exemplified by the reconstructions of the bremsstrahlung continuum emission, which coincide with the equilibrium magnetic flux surfaces with respect to position and shape. In another case the reconstruction of CVI line emission in the visible range (n = 8→7, 529.05 nm) disclose the existence of a bright radiation belt due to the plasma–wall interaction.