Ray Emissivity Research Articles

Constraining the cosmic ray propagation halo thickness using Fermi-LAT observations of high-latitude clouds * *Supported by the National Key R&D Program of China (2018YFA0404202) and the National Natural Science Foundation of China (11635011, 11875264, 11722328, 11851305, U1738205, U2031110)

The diffusive halo is a basic characteristic of cosmic ray (CR) propagation and can advance our understanding of many CR-related phenomena and indirect dark matter. The method used to derive the halo size often has degeneracy problems and is thus affected by large uncertainties. The diffuse rays from high-latitude clouds might shed light on the halo size independently. Because predictions using the spatially dependent propagation (SDP) model have better agreement with the observed CRs than those of the conventional propagation model, in this work, we investigated halo thickness based on the SDP model using Fermi-LAT -ray observations of high- and intermediate-velocity clouds. We found that to avoid exceeding the relative -ray emissivity in high-latitude clouds, the halo thickness should be in the range of 3.3-9 kpc. Moreover, the spatial morphology of -rays estimated based on the SDP model for different values of the halo thickness are distinctive, which provides us with a tool to determine the halo size. This newly developed model can be tested and tuned using multi-wavelength observations in future studies.

High rate neutron and gamma ray spectroscopy of magnetic confinement fusion plasmas

An important instrumental development work has been done in the last two decades in the field of neutron and gamma ray spectroscopic measurements of magnetic confinement plasmas. Starting from the present state of the art instrumentation installed at JET, this paper reviews the recent development that has been carried out within the EUROFUSION programme for the forthcoming high power JET D and DT campaign. This development was dedicated to the realization of new compact neutron and gamma-ray spectrometers which combine very high energy resolution (typically better than 5%) and MHz counting rate capabilities allowing for time resolution in the 10 ms time scale. One of the advantages offered by the compact dimensions of these spectrometers is to make possible their use in multiple sight-line camera configurations, such as for future burning plasma reactors (ITER and DEMO). New compact neutron spectrometers based on single crystal diamond detectors have been developed and installed at JET for measurements of the 14 MeV neutron spectrum. Measurements on a portable DT neutron generator have shown that neutron spectroscopy of the accelerated beam ions at unprecedented energy resolution (∼1% at 14 MeV) is possible, which opens up new opportunities for diagnosing DT plasmas. For what concerns gamma ray measurements, the JET gamma ray camera has been recently upgraded with new compact spectrometers based on a LaBr3 scintillator coupled to Silicon Photomultiplier with the dual aim to improve the spectroscopic and rate capabilities of the detectors. The upgrade camera system will reconstruct the spatial gamma ray emissivity from the plasma in the MeV energy range at MHz counting rates and energy resolution in the 2–4% range. This will allow physics studies of gamma rays produced by the interaction of fast ions with impurities in the plasma and bremsstrahlung emission from runaway electrons.

Gamma-ray emission of hot astrophysical plasma

Very hot plasmas with ion temperature exceeding $10^{10}$ K can be formed in certain astrophysical environments. The distinct radiation signature of such plasmas is the $\gamma$-ray emission dominated by the prompt de-excitation nuclear lines and $\pi^0$-decay $\gamma$-rays. Using a large nuclear reaction network, we compute the time evolution of the chemical composition of such hot plasmas and their $\gamma$-ray line emissivity. At higher energies, we provide simple but accurate analytical presentations for the $\pi^0$-meson production rate and the corresponding $\pi^0\to2\gamma$ emissivity derived for the Maxwellian distribution of protons. We discuss the impact of the possible deviation of the high energy tail of the particle distribution function from the "nominal" Maxwellian distribution on the plasma $\gamma$-ray emissivity.

Influence of mass sample thickness on quantitative analysis of neutron activation and its modification

With traditional neutron activation analysis, the increase of sample quality leads to some problems in both irradiation process and measurement process. These problems include the neutron flux gradient in the range of the sample, the decrease of the thermal neutron flux rate around the sample and the influence of self-shielding in the sample in the irradiation process, In the process of measurement, the self-attenuation of <i>γ</i>-ray in the sample and the geometric effect of the sample lead to the effect of the detector on the measurement of characteristic <i>γ</i>-ray emissivity due to the difference in the detection efficiency of each point of the sample. So the neutron activation analysis of mass sample needs to make some additional modifications. By using the neutron activation analysis technique, the content of <sup>24</sup>Mg and <sup>28</sup>Si in a large amount of flour can be detected, and the content of talc powder in the flour can be given, so that the quality of flour can be monitored. The flour mainly contains C, H, O, N, Ca, and F element, but the main chemical constituent of talc powder is Mg<sub>3</sub>[Si<sub>4</sub>0<sub>10</sub>](OH)<sub>2</sub>. Therefore, the measured content of Si and Mg element can be used to judge whether the flour contains talcum powder and to determine its exact content. When the content of <sup>24</sup>Mg and <sup>28</sup>Si in flour are measured by the neutron activation analysis, the variation of neutron flux and energy with thickness in the measured sample and the effect of <i>γ</i>-ray self-absorption will have great influence on the measurement results. The relationship between the neutron flux and energy and the thickness of the sample is simulated by MCNP5 (Monte Carlo N-particle transport code system 5), and the neutron fluxes at different thickness of the sample are measured by a <sup>3</sup>He proportional counter tube. The results show that the simulation results of MCNP5 are basically consistent with the experimental results. Using the simulation by MCNP5 and the measurements by a sodium iodide detector, the relationship between <i>γ</i>-ray self-absorption effect and sample thickness is studied, and the sample thickness is determined to be 6.6.cm that is adopted as an optimal experimental condition. Based on the simulated data, the function relationship between the counting of 1.779 MeV <i>γ</i>-ray and the thickness of the sample is obtained as follows: <i>A</i> = 1401 + 3815<i>x</i> – 720<i>x</i><sup>2</sup> + 64<i>x</i><sup>3</sup> – 2.8<i>x</i><sup>4</sup> + 0.05<i>x</i><sup>5</sup>. The curve trend of the experimental results is basically the same as that of the simulation results.

Radial distribution of the diffuseγ-ray emissivity in the Galactic disk

The Fermi-LAT data accumulated over 7 years of $\ensuremath{\gamma}$-ray observations, together with the high resolution gas (CO HI) and the dust opacity maps, are used to study the emissivity of $\ensuremath{\gamma}$-rays induced by interactions of cosmic rays (CRs) with the interstellar medium. Based on the dust opacity templates, the $\ensuremath{\gamma}$-ray emissivity was measured for 36 segments of the Galactic plane. Furthermore, the $\ensuremath{\gamma}$-ray emissivity was evaluated in six Galactocentric rings. Both the absolute emissivity and the energy spectra of $\ensuremath{\gamma}$-rays derived in the interval 0.2--100 GeV show significant variations along the galactic plane. The density of CRs, derived under the assumption that $\ensuremath{\gamma}$-rays are predominately produced in CR interactions with the interstellar gas, is characterized by a strong radial dependence. In the inner Galaxy the CR density substantially exceeds the density in the outer parts of the Galaxy: by a factor of a few at 10 GeV, and by more than an order of magnitude at 1 TeV. Remarkably, the energy distribution of CRs appears to be substantially harder than the energy spectrum obtained from direct measurements of local CRs. At the same time, the flux and the energy spectrum of multi-GeV protons derived from $\ensuremath{\gamma}$-ray data in the outskirts of the Galaxy is quite close to the measurements of local CRs.

Properties and manufacture technique of the functional bamboo charcoal/metal complex fabrics

Functional textiles of far infrared emissivity and electromagnetic shielding are attracting increasing attention, thus in this research we fabricated the bamboo charcoal/metal complex yarns with stainless steel wires or copper wires as the core yarn and bamboo charcoal polyester textured yarn as the wrapped yarn, using a rotor twister machine. The two manufacture parameters were rotor speed (7000–11,000 r/min) and wrapped number (2–7 turns/cm), and the bamboo charcoal/metal complex yarns which had optimum breaking strength and elongation became the weft yarns of the bamboo charcoal/metal complex woven fabrics. After the complex woven fabrics were tested in tensile strength and tensile strain, they were changed with different lamination numbers for the tests of the far infrared emissivity, anion density and air permeability. When the core yarn was 80 ìm stainless steel wires, the complex woven fabrics had the optimum tensile strength and air permeability of 364.8 N and 174.8 cm3/s/cm2. When the lamination number was 2, the complex woven fabrics had the optimum far infrared ray emissivity of 0.94.

Pilot Study of PET/Bamboo Charcoal Warp-Knitted Fabric

In recent years, as improvement of human living life, people begin to focus on themselves health. It is certain that bamboo charcoal has many properties, including water purification, deodorization, anion release and far-infrared ray radiation. This study aims to prepare PET/BC warp-knitted fabric composed of polyester yarn (PET) as warp yarn and bamboo charcoal polyamine yarn (BC) as weft yarn using Velcro Crochet Machine. Afterwards, air permeability, elastic resilience and far-infrared ray emissivity of resulting knitted fabric were discussed by changing weft yarn type. Result shows that, for knitted fabrics, weft yarn type cannot affect the elastic resilience; yet PET weft yarn makes air permeability decreasing.

Synthesis of zirconium carbide (ZrC) nanoparticles covered with graphitic “windows” by pulsed plasma in liquid

Cubic phase zirconium carbide (ZrC) nanoparticles encapsulated in graphitic carbon with an average size of about 10 nm were produced using pulsed plasma in liquid (PPL), in which zirconium metal electrodes provided the zirconium source and liquid ethanol the carbon. The quenching effect and near vacuum environment inherent in this pulsed plasma in liquid method resulted in the synthesis of nanoparticles with a uniform small size distribution and high purity. Lattice parameters of the obtained samples refined by the Rietveld method were larger than other reported data. Also, the emission lines of atoms Zr I, ions Zr II, atoms C I, ions C II and atoms H I were observed by an optical emission spectrum to gather information on the synthesis mechanism. The results of thermogravimetric and infrared ray emissivity of the nanoparticles showed that the graphitic carbon shells composed of a mere several layers with high transmissivity serve to act as “windows”, helping both to protect the ZrC nanoparticle inside from oxidation and to preserve its high infrared ray emissivity.

Physical properties of the functional bamboo charcoal/stainless steel core-sheath yarns and knitted fabrics

In this study, bamboo charcoal/stainless steel (B/S) core-sheath yarns were made of stainless steel wires and bamboo charcoal polyester textured yarn using a rotor twister machine. The speed of rotor twister was from 7000 to 11000 rpm and the wrapped amount varied from 2 to 7 turns/cm. The tenacity of 3.08 g/d was obtained when the speed of rotor twister was 8000 rpm and wrapped amount was 4.0 turns/cm. The tensile strain of 24.9% was yielded when the speed of the rotor twister was 7000 rpm and the wrapped amount was 5.0 turns/cm. The laminated amount of the knitted fabrics varied from 1 to 6 layers. The far infrared ray emissivity of the knitted fabrics was 0.934 when the laminated amount was 2 layers and wrapped amount was 6 turns/cm. Finally, the optimum anion density of the knitted fabrics was 610 ions/cm3.

원적외선 방출 특성을 갖는 나노 웹의 제조 및 원적외선 방사 특성에 관한 연구

The interest in textile which has far-infrared ray emissive property has been increased in the field of biophysics and medicine. In this study, far-infrared ray emissive polyurethane nano-web was obtained using electrospinning of polyurethane(PU) solution mixed with ceramics powder and far-infrared ray emissive properties of nano-web were evaluated by measuring far-infrared ray emission power and emissivity(%). To investigate the influence of concentration of ceramics powder in PU solution and temperature for far-infrared ray emissive properties, far-infrared ray emissivity was measured at varied temperature using various nano-web including varied concentration of ceramics powder. Polyurethane nano-web was characterized by SEM to observe the deposition of ceramics powder on polyurethane nano-web surface. The far-infrared ray emissivity was increased with the concentration of ceramics powder in the nano-web. The far-infrared ray emission power was enhanced with increasing temperature of the samples; however, far-infrared ray emissivity was decreased with increasing temperature because the increase of emission power of ceramic containing nano-web was lower than the emission power of black body one.

FERMILAT OBSERVATION OF DIFFUSE GAMMA RAYS PRODUCED THROUGH INTERACTIONS BETWEEN LOCAL INTERSTELLAR MATTER AND HIGH-ENERGY COSMIC RAYS

Observations by the Large Area Telescope (LAT) on the \textit{Fermi} mission of diffuse $\gamma$-rays in a mid-latitude region in the third quadrant (Galactic longitude $l$ from $200\arcdeg$ to $260\arcdeg$ and latitude $| b |$ from $22\arcdeg$ to $60\arcdeg$) are reported. The region contains no known large molecular cloud and most of the atomic hydrogen is within 1 kpc of the solar system. The contributions of $\gamma$-ray point sources and inverse Compton scattering are estimated and subtracted. The residual $\gamma$-ray intensity exhibits a linear correlation with the atomic gas column density in energy from 100 MeV to 10 GeV. The measured integrated $\gamma$-ray emissivity is $(1.63 \pm 0.05) \times 10^{-26} {\rm photons s^{-1} sr^{-1} H\mathchar`-atom^{-1}}$ and $(0.66 \pm 0.02) \times 10^{-26} {\rm photons s^{-1} sr^{-1} H\mathchar`-atom^{-1}}$ above 100 MeV and above 300 MeV, respectively, with additional systematic error of $\sim 10%$. The differential emissivity in 100 MeV--10 GeV agrees with calculations based on cosmic ray spectra consistent with those directly measured, at the 10% level. The results obtained indicate that cosmic ray nuclei spectra within 1 kpc from the solar system in regions studied are close to the local interstellar spectra inferred from direct measurements at the Earth within $\sim 10%$.

Non-linear cosmic ray interaction with solar wind: Monitoring of flare energetic particle and solar wind matter space-time distributions by gamma rays

For great solar flare events we calculate expected gamma-ray fluxes in periods of flare energetic particle (FEP) generation and propagation. We calculate the expected space-time-energy distribution of these particles in the Heliosphere in the periods of FEP events. On the basis of investigations of cosmic ray non-linear interaction with solar wind we determine also the expected space-time distribution of solar wind matter. Then we calculate the expected generation of gamma rays by decay of neutral pions generated in nuclear interactions of FEP with solar wind matter and determine the expected space-time distribution of gamma ray emissivity. We based on the simplest model of FEP generation (source function is supposed proportional to delta function in time and in space) and the simplest model of propagation (isotropic diffusion). The aim of these rough calculations – to estimate approximately expected space-time distribution of gamma ray emissivity and then expected angle-time distribution of gamma ray fluxes during great FEP events in dependence of angle between direction of view and direction on the Sun, to answer on question: “Is it possible to monitor these fluxes by present-day gamma ray telescopes or not?”. Our calculations gave positive answer on this question. We note that the used simplest model of FEP propagation can be applied to observation data only 15–30 min after the onset of FEP event on the Earth when the FEP distribution became near isotropic. For the beginning stage when the FEP distribution is usually sufficiently anisotropic (and when the expected gamma ray fluxes are expected much bigger) necessary to use more complicated model of anisotropic diffusion. These results we suppose to present in near future. We hope that by observations of gamma rays generated by solar FEP interactions with solar wind matter can be obtained some additional information on FEP time generation and spectrum in the source, on mode of FEP propagation in the interplanetary space, on the character of the non-linear interaction of cosmic rays with solar wind, and on matter distribution in the Heliosphere.

Understanding sawtooth activity during intense electroncyclotron heating experiments on TCV

Different types of central relaxation oscillations areobserved in the presence of ECH dependingon the location of the deposited power. In the TCV tokamak, normal sawteeth, i.e. triangular sawteeth similar toohmic sawteeth, and saturated sawteeth are observed with central ECHpower deposition, while giant sawteeth and `humpback'oscillations occur when heating close to the sawtooth inversionsurface of the local soft X ray emissivity. New measurements with hightemporal resolution show that the crash phase of these sawtooth typesis accompanied by a reconnection process associated with an m/n = 1 resistiveinternal kink mode. After the sawtooth crash, full magneticreconnection is observed in normal and in saturated sawteeth, whilefor giant and humpback sawteeth the reconnection process is incompleteand poloidally asymmetric temperature profiles persist after the crash. The detailed dynamics of the magnetic island associatedwith the resistive internal kink mode are described by a displacementfunction which is inferred from the experimental data. In normalsawteeth, the kink mode is destabilized just before the crash, whilein all other sawtooth types a magnetic island exists for a significantfraction of the sawtooth period. The different types of sawteeth havebeen simulated using a numerical code based on a theoretical modelwhich describes the evolution of the electron temperature in thepresence of localized heat sources and of a magnetic m/n = 1/1 island.

Radial impurity transport in the H mode transport barrier region in Alcator C-Mod

Measurements of profiles of soft X ray emissivity with 1.5 mm radial resolution are combinedwith high resolution electron densityand temperature measurements in the edge region of the Alcator C-Mod tokamakto facilitate transport analysis of medium-Z impurities during H modes. Results from detailed modelling of the radiation and transport of fluorineare compared with experimental measurements, yielding information about thetransport coefficients in the H mode transport barrier region. Evidence is foundfor a strong inward impurity pinch just insidethe separatrix. The region of strong inward pinch agrees very well with theregion of strong electron density gradient, suggesting that the inward pinchcould be driven by the ion density gradient, as predicted by neoclassicaltheory. Simulations using the neoclassical impurity convection profile agreevery well with experiments. Transport modelling shows that the X ray pedestal width islargely determined by the diffusion coefficient in the transport barrier.This allows diagnosis of changes in the edge diffusion coefficient on thebasis of observations of X ray pedestal width changes. Significantdifferences in the edge diffusion coefficient are seen between different types of H mode. Several scalings for the edge diffusion coefficient in the enhancedDα H mode are also identified. This may help elucidate the physical processes responsible for this attractive confinement mode.

Laser blow-off injected impurity transport in L mode Tore Supra plasmas

Metal impurity ions have been injected in Tore Supra discharges by laser blow-off. The ion transport is studied by means of an impurity ion transport code; the radial profiles of the diffusion coefficient D and of the inward convection velocity V are obtained by simulating soft X ray brightness and emissivity time evolutions. Three different experimental situations are considered: a discharge with sawteeth stabilized by LH heating, a high-ne discharge with ICR heating and a strongly sawtoothing discharge with combined ICR and LH heating. In all cases, the simulations show the presence of two transport regions, the central core having reduced transport coefficients, and the outer region where there is the necessity to increase transiently the diffusion coefficient D during the first few milliseconds after the injection. It has been previously suggested that the shear s = 0.5 is the critical physical parameter governing the transition from low to high transport coefficients. The s = 0.5 criterion seems satisfied in the first two cases, whereas the closeness of the s = 0.5 and q = 1 surfaces does not allow a conclusion to be made in the combined heating case.

Enhanced transport of impurity ions and electron heat in Tore Supra ohmic discharges following nickel laser blow-off injection

Nickel has been injected into ohmic Tore Supra (TS) discharges with and without activation of the ergodic divertor (ED). The nickel ion transport is studied by means of an impurity transport code, and the radial profiles of the diffusion coefficient D and of the inward convection velocity V are obtained by simulating the soft X ray brightness and emissivity time evolutions. The simulations confirm two previously reported conclusions: the presence of a central core with reduced transport coefficients and, with the ED activated, the necessity of introducing a peripheral transport barrier (with increased inward convection and/or reduced diffusion). To make satisfactory simulations in both experimental conditions of the initial phase of the nickel ion inflow before the first inverted sawtooth, it is necessary to increase transiently the diffusion coefficient (by 1 order of magnitude or more) during the first few milliseconds after the injection. By comparison of the experimental and simulated bolometric signals, it is possible to verify quantitatively the available calculations of the global radiative losses for nickel. The observed discrepancy by a factor of 2 is discussed. The inward propagating cold wave, following the nickel injection, has been observed with a heterodyne radiometer (monitoring the electron temperature). Both with and without the ED, good simulations of the cold wave propagation are obtained using a predictive non-local transport model, previously successfully tested in JET during transient regimes. The model predicts large increases of the electron thermal diffusivity χe, by a factor of 5, immediately after the injection and describes well the electron temperature profile in the so-called heat transport dominated region outside the q = 1 surface. The experimental signals are smoothed with the `generalized singular value decomposition' technique, reducing the effect of the sawtooth modulation; the simulation can, therefore, be more clearly compared with the measurements. It is not possible, using present experimental data, to demonstrate the existence of an electron diffusivity transport barrier inside the q = 1 region, as done for the impurity transport, because the temperature profile is strongly affected by sawteeth in this region. Similarities have been found in the time evolutions of the electron temperature and of the Abel inverted soft X ray emissivities at fixed radii, implying similar time behaviour of D and χe outside the q = 1 surface.

The galactic gamma-ray distribution - Implications for galactic structure and the radial cosmic-ray gradient

The radial distribution of gamma ray emissivity in the Galaxy was derived from flux longitude profiles, using both the final SAS-2 results and the recently corrected COS-B results and analyzing the northern and southern galactic regions separately. The recent CO surveys of the Southern Hemisphere were used in conjunction with the Northern Hemisphere data, to derive the radial distribution of cosmic rays on both sides of the galactic plane. In addition to the 5 kpc ring, there is evidence from the radial asymmetry for spiral features which are consistent with those derived from the distribution of bright H II regions. Positive evidence was also found for a strong increase in the cosmic ray flux in the inner Galaxy, particularly in the 5 kpc region in both halves of the plane. 39 references.

The distribution of cosmic-ray electrons and nuclei in the Galaxy

A detailed analysis is made of gamma-ray data from the SAS II and COS B satellite experiments and the data are taken, together with a variety of information on the density of gas in the ISM, to give the distribution of cosmic-ray flux in the Galaxy. Particular attention is given to problems caused by uncertainties in the column densities of molecular hydrogen. It is claimed that both the electron and the nuclear particle fluxes vary with position both over a region of a few kpc round the sun and over a larger region. For most of the Galaxy the variations are not large but if the most recent estimates of very considerable masses of molecular gas within 2 kpc of the Galactic centre are correct then the particle flux in this region is only some 10% of the local value. An analysis of the correlation of the gamma -ray flux with local gas in atomic and molecular forms (at latitudes in the range mod b mod =10 degrees -20 degrees ) has enabled the local gamma -ray emissivity spectrum to be determined. It is found that at the highest energies the emissivity with respect to molecular gas is lower than that with respect to atomic gas; possible reasons are discussed.

The distribution of -ray emissivity in the Galaxy

The longitude distribution of gamma -ray intensity measured with the SAS-2 satellite has been unfolded to give the Calactic gamma -ray emissivity. It is found that the observations are consistent with either a cylindrically symmetric emissivity distribution, or a distribution uniform along spirals with tilt angles similar to those for spiral arms. The gamma -ray distribution in the Galaxy seems to be more in accord with models based on the molecular hydrogen distribution than those based on spiral structure.

Derivation of γ-ray emissivity in the Galaxy from satellite data

A method of deriving the gamma -ray emissivity in the Galaxy by unfolding the longitudinal distribution of gamma -ray intensity is proposed, and applied to the available data from the SAS-II and OSO-III instruments. The uncertainties in the analysis resulting from statistical errors in the data are estimated. A broad enhancement of emission 3-8 kpc from the Galactic centre is found. There is evidence for a drop in emissivity within 3 kpc of the centre, although the uncertainties in this region are very large.