Radiation Spectrum Research Articles

Efficient simulations of ionized ISM emission lines: a detailed comparison between the FIRE high-redshift suite and observations

ABSTRACT The Atacama Large Millimeter/Submillimeter Array (ALMA) in the submillimetre and the JWST in the infrared have achieved robust spectroscopic detections of emission lines from the interstellar medium (ISM) in some of the first galaxies. These unprecedented measurements provide valuable information regarding the ISM properties, stellar populations, galaxy morphologies, and kinematics in these high-redshift galaxies and, in principle, offer powerful tests of state of the art galaxy formation models, as implemented in hydrodynamical simulations. To facilitate direct comparisons between simulations and observations, we develop a fast post-processing pipeline to predict line emission from the H ii regions around simulated star particles, accounting for spatial variations in the surrounding gas density, metallicity, and incident radiation spectrum. Our ISM line emission model currently captures H α, H β, and all of the [O iii] and [O ii] lines targeted by ALMA and JWST at z > 6. We illustrate the power of this approach by applying our line emission model to the publicly available Feedback In Realistic Environments (FIRE) high-z simulation suite and perform a detailed comparison with current observations. We show that the FIRE mass–metallicity relation is in 1σ agreement with ALMA/JWST measurements after accounting for the inhomogeneities in the ISM properties. We also quantitatively validate the description of the one-zone model, which is widely used for interpreting [O iii] and H β line luminosity measurements. This model is publicly available and can be implemented on top of a broad range of galaxy formation simulations for comparison with JWST and ALMA measurements.

Tunability of a broad-band selective metamaterial emitter in thermophotovoltaic systems

In a thermophotovoltaic (TPV) system, it is crucial to realize the excellent matching between the radiation spectrum of emitter and the photovoltaic cells, which will be helpful to improve the conversion efficiency and output power. We have focused on the study of tunability of a multi-layer metamaterial (MTM) selective emitter with the dielectric-metal pyramid structure to screen and optimize the material combinations and geometric parameters for matching GaSb and InGaAsSb cells. It is found that the selective metamaterial emitter composed of various material combinations can achieve the broadband emission, which is formed by overlapping of multiple resonance peaks at the region below the cutoff wavelength. The MTM emitters composed of W/Ta/Mo−BeO, W/Ta/Mo−SiO2, W/Mo−Si3N4, and W−HfO2, respectively, are characterized by the extraordinary emission spectrum for matching GaSb cells. We have selected the material combination of Ta−SiO2 with the excellent emission spectrum to obtain an excellent emission spectrum matching the bandgap of GaSb cells by optimizing the geometric parameters. The optimal geometric parameters of emitter composed of the material combination of Ta−SiO2 have been obtained. Moreover, the efficiency and output power of TPV system reaches 17.52% and 0.025 W/cm2 at 1000 K and even approaches 36.27% and 0.79 W/cm2 at 1500 K. It is indicated that the optimized emitter can achieve the near-perfect utilization of in-band photons and well suppress the sub-band loss. It can be also found that the MTM emitter composed of W−HfO2 exhibits an excellent matching degree with InGaAsSb cells. It is also demonstrated that the MTM emitter with pyramid structure has a good scalability for matching other available PV cells. The high conversion efficiency realized by materials screening and geometric optimization provides a potential pathway for the design of TPV emitter.

A review on radionuclide pollution in global soils with environmental and health hazards evaluation.

Human populations are being exposed to a wide spectrum of radiation from soils as a result of the availability of radiation sources. Assessing the ecological and health effects of radionuclides in soils is crucial to support the optimal soil management practices but large-scale studies are limited. This study compiled data on radionuclides (226Ra, 232Th, 40K, 238U, and 137Cs) in soils located across the world (44 countries and 159 places) between 2008 and 2022 and applied radiological hazards indices and several multivariate statistical approaches. The average activity concentration (Bq/kg) of 226Ra, 232Th, 40K, 238U, and 137Cs were 408.56, 144.80, 508.78, 532.78, and 83.12, respectively, whereas 226Ra, 232Th, 40K, and 238U exceeded the standard limits. The principal component analysis explained more than 91% of variation in soils. Based on the geoaccumulation index, 40K posed moderately to heavy contamination whereas 238U and 226Ra posed moderate contamination in soils. Moreover, the mean values of radiological hazards evaluation such as radium equivalent activity (487.17Bq/kg), external radiation hazard indices (1.32), internal hazard indices (2.15), absorbed dose rate (247.86 nGyh-1), annual effective dose rate (1.82 mSvy-1), activity utilization index (4.54) and excess lifetime cancer risk (63.84 × 10-4) were higher than recommended limit suggesting significant radiological risks in study region soils. The findings indicated that the study area soils were contaminated by radionuclides and unsafe for hazards in terms of the health risks linked with studied radioactive contents. The study is valuable for mapping radioactivity across the globe to determine the level of radioactivity hazards.

Potential of prospective plans in MENA countries for green hydrogen generation driven by solar and wind power sources

This study is focused on exploring the potential of green hydrogen production in distinctive geographical locations in the Middle East and North Africa (MENA) by leveraging solar and wind energies. Those locations include Egypt, Morocco, and the Gulf region, as prospective hydrogen hubs. The current mathematical model has been developed using Matlab/Simulink and validated with the respective literature. Using realistic meteorological data of those cities, the hourly hydrogen yield, energetic and exergetic efficiencies have been predicted. A levelized cost of hydrogen and carbon dioxide mitigation has been examined. Besides, a holistic map of hydrogen cost depending on a widespread spectrum of solar radiation and wind speed has been developed. The results demonstrate that hydrogen production rates using solar energy are staggering compared to those using wind energy, specifically for the economic zone of Ain Sokhna in Egypt. The results reveal that Hurghada has a significant hydrogen cost of 4.4 $/kg, notably by exploiting wind energy. Using solar energy, Aswan and Salalah have a distinguished hydrogen cost of 5 $/kg, while NEOM, Hurghada, Al Maktoum, and Duqm have a hydrogen cost of 5.1 $/kg. Based on environmental perspectives, exploiting solar energy can alleviate 47.6 tons/year in Aswan, while harnessing wind resources in Hurghada mitigates 77.9 tons of annual carbon dioxide emissions.

Analysis of Maximum Possible Utilization of Solar Radiation on a Solar Photovoltaic Cell with A Proposed Model

The paper proposes a possible solution to absorb and utilize all the solar radiation spectrum including ultraviolet and infrared along with the visible radiation. A typical solar PV cell usually absorb only the visible solar radiation to covert to electricity which is 46% of the total solar radiation but it can’t use the other non-visible spectrum like infrared (longer wavelength) and ultraviolet (shorter wavelength) which consists of the other 54% of solar energy. This non-visible solar radiation is either absorbed by the earth surface and atmosphere or reflected back to the space and it is wasted as far as the solar cell absorption is concerned. There are lots of researches going on in the semiconductor level to design a solar cell which can absorb the solar radiation in non-visible region using band-gap engineering but if we could somehow convert the non-visible solar radiation into visible range before it comes to the solar cell (semiconductor level) then the overall efficiency of a solar PV system would surely be increased to a satisfactory amount. After converting the non-visible spectrum into visible spectrum, we will then incident this radiation on a typical solar PV cell. In this paper the possible arrangement for such conversion is proposed which is still at a preliminary stage concept and yet to be implemented

Smart Approaches for Evaluating Photosynthetically Active Radiation at Various Stations Based on MSG Prime Satellite Imagery

Photosynthetically active radiation (PAR) is the 400–700 nm portion of the solar radiation spectrum that photoautotrophic organisms including plants, algae, and cyanobacteria use for photosynthesis. PAR is a key variable in global ecosystem and Earth system modeling, playing a prominent role in carbon and water cycling. Alongside air temperature, water availability, and atmospheric CO2 concentration, PAR controls photosynthesis and consequently biomass productivity in general. The management of agricultural and horticultural crops, forests, grasslands, and even grasses at sports venues is a non-exhaustive list of applications for which an accurate knowledge of the PAR resource is desirable. Modern agrivoltaic systems also require a good knowledge of PAR in conjunction with the variables needed to monitor the co-located photovoltaic system. In situ quality-controlled PAR sensors provide high-quality information for specific locations. However, due to associated installation and maintenance costs, such high-quality data are relatively scarce and generally extend over a restricted and sometimes non-continuous period. Numerous studies have already demonstrated the potential offered by surface radiation estimates based on satellite information as reliable alternatives to in situ measurements. The accuracy of these estimations is site-dependent and is related, for example, to the local climate, landscape, and viewing angle of the satellite. To assess the accuracy of PAR satellite models, we inter-compared 11 methods for estimating 30 min surface PAR based on satellite-derived estimations at 33 ground-based station locations over several climate regions in Europe, Africa, and South America. Averaged across stations, the results showed average relative biases (relative to the measurement mean) across methods of 1 to 20%, an average relative standard deviation of 25 to 30%, an average relative root mean square error of 25% to 35% and a correlation coefficient always above 0.95 for all methods. Improved performance was seen for all methods at relatively cloud-free sites, and quality degraded towards the edge of the Meteosat Second Generation viewing area. A good compromise between computational time, memory allocation, and performance was achieved for most locations using the Jacovides coefficient applied to the global horizontal irradiance from HelioClim-3 or the CAMS Radiation Service. In conclusion, satellite estimations can provide a reliable alternative estimation of ground-based PAR for most applications.

Sub-nanosecond time-resolved radiation measurement using x-ray focusing crystal spectrometers

In this paper, we describe a technique using a crystal spectrometer, a silicon-diode detector, and a filtered photoconductive detector to monitor photon energies in the L-shell (0.9–1 keV) and K-shell regimes for nickel and copper hybrid X-pinch x-ray sources. The detectors, system cabling, and an 8 GHz digital oscilloscope in combination enable time resolution better than 200 ps for photoconductive detectors and 700 ps for silicon-diode detectors of the K- and L-shell radiation signals, respectively. We substantially improve the relative timing of signals obtained using the oscilloscope by using an x-ray streak camera with a crystal spectrometer to monitor the L-shell line spectra and, separately, the K-shell line spectra relative to the continuum burst to better than 17 ps time resolution. This combination of instruments enabled and validated a new method by which plasma conditions in nickel and copper X-pinches can be assessed immediately before and after the ∼30 ps continuum x-ray burst produced by 370 kA hybrid X-pinches. In general, the method described here can be applied to observe otherwise highly filter-absorbed radiation in the presence of a broad spectrum of higher energy radiation by combining x-ray crystals and detectors.

Effect of 10.6 μm laser moxibustion on inflammation in diabetic peripheral neuropathy rats.

Diabetic peripheral neuropathy (DPN) is the main cause of disability in diabetes patients but the efficacy of available drugs is poor. Moxibustion is an adjunctive treatment for DPN that can reduce symptoms. The peak value of the far infrared wavelength of 10.6 μm laser moxibustion is close to the infrared radiation spectrum of traditional moxibustion. Its effect is similar to that of moxibustion and does not cause pain, infection or produce irritating smoke. Twenty-four male SD rats were divided into control (Con), DPN, laser moxibustion (LM), and pyrrolidine dithiocarbamate (PDTC) groups (n=6/group). The DPN, LM and PDTC group rats were intraperitoneally injected with 1% streptozotocin (STZ) to induce a model of DPN. LM group rats were irradiated with a laser at bilateral ST36 acupoints for 15min, once every other day, for 14 days. PDTC group rats were intraperitoneally injected with PDTC once a day. Body weight, blood glucose, and paw withdrawal mechanical threshold (PWMT) were measured and laser speckle imaging (LSI) performed before and after modeling and at 1 and 2 weeks after intervention. Two weeks after intervention, changes in serum interleukin 1β (IL1β), interleukin 6 (IL6), tumor necrosis factor α (TNFα) and nerve growth factor (NGF) were analyzed, and the abundance of NF-κB and IκB-α proteins and levels of NF-κB and IκB-α mRNAs in the sciatic nerve were observed. The results showed that 10.6 μm laser moxibustion can relieve pain, improve microcirculation, and alleviate inflammation in DPN rats, possibly via the NF-κB inflammatory pathway.

A challenge in paediatrics: concurrent atopic dermatitis and vitiligo

Atopic dermatitis is one of the most common dermatoses globally. It has been established that it can often be associated with a variety of autoimmune diseases. Vitiligo is one of such comorbidities. This concurrent combination is most often found in paediatric practice, as an early onset is typical for both diseases. Early onset of vitiligo and involvement of a larger area of skin have been shown to be associated with higher odds of atopic dermatitis. The pathogenesis of vitiligo is characterized by altered immune responses, and genetic factors also counts. It has been shown that some of these mechanisms are shared with the pathogenesis of atopic dermatitis, but the issue warrants further study. Oxidative stress triggering melanocytes destruction is believed to be a key factor in the development of vitiligo. In this regard, patients with vitiligo are advised to use photoprotective agents. Today, the study of effects of visible light on the skin is a very topical issue, specifically, particular attention is paid to blue light (400-500 nm). Studies show that it is this wavelength that has a more pronounced negative effect on the skin. However, research findings are contradictory, as this spectrum radiation is used in the treatment of various dermatoses, including atopic dermatitis. Thus, the concurrent vitiligo and atopic dermatitis place certain restrictions on the choice of therapy, care products and photoprotective agents. A photoprotective agent for such difficult patients should protect the skin from exposure to as wide solar radiation spectrum as possible and at the same time not contain potentially allergenic components that can aggravate the course of atopic dermatitis.

Novel high-flux indoor solar simulator for high temperature thermal processes

A novel 32 kWe high flux solar simulator compound of eight xenon arc lamps coupled with a truncated paraboloid mirror and a secondary paraboloid mirror was designed, built, and tested. Collimated rays from a set of xenon arc lamps emulating outdoor solar radiation were reflected by a secondary set of paraboloid mirrors to a common system focus. Relative irradiance measurements were performed to obtain the xenon arc lamp radiation spectrum. Thermal power delivered by each lamp was evaluated by using a heat flux gauge mounted at the system focus. Concentrated thermal power was estimated by the heat superposition method, which allowed us to quantify both the total and the concentrated peak power along with the heat flux mapping. A 10.2% energy conversion efficiency was achieved. Experimental results determined a 3.0 kW total concentrated power on a 100 mm spot diameter resulting in a 1028 kWm−2 peak flux at the center; a lamp total thermal radiant power average of 615 W was achieved, and the lamp spectrum was compared with the 6200 K blackbody radiation spectrum.

Generation of rf radiation by low-intensity laser pulse trains in air.

In this paper, we analyze and numerically simulate mechanisms for generating directed rf radiation by a low-intensity laser pulse train (LPT) propagating in air. The LPT ionizes the air, forming a plasma filament. The ionization process relies on the background level of radioactivity which plays an important role in initiating a collisional ionization process. In our model a low-intensity LPT photoionizes background negative ions (produced by ambient ionizing radiation) and provides the seed electrons necessary to initiate collisional ionization. The intensity of the LPT is far below tunneling ionization levels. The ponderomotive forces associated with the LPT and self-fields drive plasma oscillations predominately in the radial direction. The driven radial electron currents in turn generate directed rf radiation. As the plasma density builds up on axis, the later portion of the LPT can defocus and limit the interaction length. The spectrum of the rf radiation consists of the fundamental frequency associated with the pulse separation time as well as harmonics. The rf generation mechanism is analyzed using fluid equations which incorporate, among other things, the effects of background radioactivity, photoionization, collisional ionization, ponderomotive and space-charge effects, and electron attachment-recombination processes. As an example, for a specific set of parameters, the rf spectrum and intensity are compared to experimental data.

Tunable frequency comb from echo-enabled harmonic generation free electron laser

We propose a novel scheme for the generation of a tunable soft x-ray frequency comb in a seeded free-electron laser (FEL) via the chirped pulse beating technology. Our research shows that harnessing the chirped pulse laser to imprint a submillimeter-scale energy modulation in the phase space of the relativistic electron beam together with the process of echo-enabled effect, multichromatic output soft x-ray radiation with a series of longitudinal modes can be amplified in an echo-enabled harmonic generation (EEHG) free electron laser, which finally forms a comb-liked shape in the frequency spectrum with the mode spacing frequency at terahertz (THz) band. Based on the theoretical and numerical analyses of the modulation process, the electron beam maintains a nanometer-scale microstructures due to the echo effect, while the beam obtains an energy modulation at submillimeter-scale from the chirped pulse beating laser. This leads to a series of longitudinal modes in the downstream radiator. Three-dimension time-dependent simulation results show that a frequency comb with a central wavelength of 8.9 nm can be generated directly with the help of chirped beating laser. The frequency spacing between the frequency lines on the radiation spectrum can be tuned easily by changing the parameters of chirped beating laser.

SNM Radiation Signature Classification Using Different Semi-Supervised Machine Learning Models

The timely detection of special nuclear material (SNM) transfers between nuclear facilities is an important monitoring objective in nuclear nonproliferation. Persistent monitoring enabled by successful detection and characterization of radiological material movements could greatly enhance the nuclear nonproliferation mission in a range of applications. Supervised machine learning can be used to signal detections when material is present if a model is trained on sufficient volumes of labeled measurements. However, the nuclear monitoring data needed to train robust machine learning models can be costly to label since radiation spectra may require strict scrutiny for characterization. Therefore, this work investigates the application of semi-supervised learning to utilize both labeled and unlabeled data. As a demonstration experiment, radiation measurements from sodium iodide (NaI) detectors are provided by the Multi-Informatics for Nuclear Operating Scenarios (MINOS) venture at Oak Ridge National Laboratory (ORNL) as sample data. Anomalous measurements are identified using a method of statistical hypothesis testing. After background estimation, an energy-dependent spectroscopic analysis is used to characterize an anomaly based on its radiation signatures. In the absence of ground-truth information, a labeling heuristic provides data necessary for training and testing machine learning models. Supervised logistic regression serves as a baseline to compare three semi-supervised machine learning models: co-training, label propagation, and a convolutional neural network (CNN). In each case, the semi-supervised models outperform logistic regression, suggesting that unlabeled data can be valuable when training and demonstrating value in semi-supervised nonproliferation implementations.

Связанные с осадками события возрастания электромагнитной компоненты вторичных космических лучей: спектральные измерения и анализ

We report the measurement results of differential spectra of electromagnetic radiation in the range 0.1–4 MeV, which occurs in the atmosphere as a component of secondary cosmic rays. Spectral monitoring was performed using a spectrometer based on the Nai (TL) crystal in 2022–2023. The main purpose of the measurements was to determine spectral characteristics of the electromagnetic radiation during increase events, when the electromagnetic radiation flux from the atmosphere rises by tens of percent with respect to the background level. From a thorough analysis of the spectra of many dozens of events, we have drawn a conclusion that although the lines of natural radionuclides are present on the spectra and contribute their share, their total contribution to the increase events is ~0.1 of the total energy supplied during an increase. We unambiguously conclude that the effect of increasing electromagnetic radiation during precipitation is not due to the presence of radionuclides in precipitation.

Precipitation-related increase events of the electromagnetic component of secondary cosmic rays: Spectral analysis

We report the measurement results of differential spectra of electromagnetic radiation in the range 0.1–4 MeV, which occurs in the atmosphere as a component of secondary cosmic rays. Spectral monitoring was performed using a spectrometer based on the Nai (TL) crystal in 2022–2023. The main purpose of the measurements was to determine spectral characteristics of the electromagnetic radiation during increase events, when the electromagnetic radiation flux from the atmosphere rises by tens of percent with respect to the background level. From a thorough analysis of the spectra of many dozens of events, we have drawn a conclusion that although the lines of natural radionuclides are present on the spectra and contribute their share, their total contribution to the increase events is ~0.1 of the total energy supplied during an increase. We unambiguously conclude that the effect of increasing electromagnetic radiation during precipitation is not due to the presence of radionuclides in precipitation.

Study on infrared radiation spectrum characteristics of new smokeless moxibustion and traditional moxibustion

ObjectiveThis study compares the infrared radiation spectral characteristics of new smokeless moxibustion and traditional moxibustion, thereby giving a scientific basis for the new smokeless moxa sticks as new materials for moxibustion. MethodsA highly sensitive infrared spectral detection system was employed for the detection of infrared spectra of new smokeless moxibustion and traditional moxibustion in an attempt to compare the differences between characteristic wavelength, infrared radiation peak, and infrared radiation intensity between two kinds of moxibustion. ResultFor both new smokeless and traditional moxibustion, the main peak of characteristic infrared spectra lies at 3.75 µm. There is no significant difference in the main peak of infrared radiation intensity between the two groups (P = 0.604). There is no significant difference in the two groups in terms of the total radiation intensity of the first characteristic peak (wavelength from 2.75 to 5.25 µm, P = 0.240) or the radiation intensity of the second characteristic peak (wavelength from 8 to 11.75 µm, P = 0.573). The total infrared radiation intensity of traditional moxibustion (wavelength from 1.5 to 18 µm, P = 0.029) is stronger in comparison to that of the new smokeless moxibustion. ConclusionIn terms of infrared spectral characteristics, the new smokeless moxibustion is virtually similar to traditional moxibustion. The highest radiation peak (wavelength 3.75 µm) is identical among the two groups. Thus, the new smokeless moxibustion has the potential as an alternative to traditional moxibustion in the future.

Frequency-domain interferometry for the determination of time delay between two extreme-ultraviolet wave packets generated by a tandem undulator

Synchrotron radiation, emitted by relativistic electrons traveling in a magnetic field, has poor temporal coherence. However, recent research has proved that time-domain interferometry experiments, which were thought to be enabled by only lasers of excellent temporal coherence, can be implemented with synchrotron radiation using a tandem undulator. The radiation generated by the tandem undulator comprises pairs of light wave packets, and the longitudinal coherence within a light wave packet pair is used to achieve time-domain interferometry. The time delay between two light wave packets, formed by a chicane for the electron trajectory, can be adjusted in the femtosecond range by a standard synchrotron technology. In this study, we show that frequency-domain spectra of the tandem undulator radiation exhibit fringe structures from which the time delay between a light wave packet pair can be determined with accuracy on the order of attoseconds. The feasibility and limitations of the frequency-domain interferometric determination of the time delay are examined.

Impact of trans-Planckian excitations on black-hole radiation in dipolar condensates

We consider a quasi-one-dimensional dipolar condensate in a steplike analog black hole setup. It is shown that the existence of roton excitations leaves significant imprints onto the Hawking radiation spectrum. The emitted radiation depends on the depth of the roton minimum, and is in general more intense. In addition, we find a novel spontaneous particle creation mechanism with no counterpart in nondipolar condensates. Our results establish that dipolar condensates offer a richer and more versatile environment for the simulation of particle production from the quantum vacuum in the presence of horizon interfaces than contact-interaction condensates.

Effect of the primary oxidizer stream jet velocities on the ignition and combustion characteristics of pulverized coal under MILD oxy-coal combustion conditions

MILD oxy-coal combustion technology is a prospective technology with the potential for CO2 capture and storage, and it is characterized by the intense flue gas recirculation to preheat the fuel and to dilute the oxidizer due to the oxidizer or fuel jet with high velocity. The effect of the primary oxidizer stream jet velocities ranging from 1.7 m/s to 11.2 m/s on the coal ignition and combustion characteristics were experimentally investigated on a flat flame pulverized coal burner at various oxygen concentrations of 5%-21% and gas temperatures of 1473–1873 K under O2/CO2 and O2/N2 atmospheres. The coal flame images were recorded by the digital camera, and the flame structure evolution and ignition delay times of coal particles were analyzed at different primary oxidizer stream jet velocities and hot coflow conditions. The coal combustion radiation spectrum was monitored by an optical fiber spectrometer and the coal particle temperatures were derived with the two-color pyrometry. The results showed that the bright yellow soot flame gradually disappeared with the decrease of O2 concentration when CO2 replaced N2. The difference of ignition delay times between O2/CO2 atmosphere and O2/N2 atmosphere decreased from 2.8 ms to 0.2 ms when the primary air jet velocity increased from 1.7 m/s to 11.2 m/s at 1473 K and 5% O2. This meant the elevated jet velocity was beneficial to offset the delayed effect of the physicochemical properties of CO2 on coal ignition. The peak coal particle temperature increased by 68 K at 1873 K and 5% O2 under O2/CO2 atmosphere with the highest jet velocity owing to the accelerated diffusion of O2 into coal particle stream. Moreover, a dimensionless coal particle temperature parameter η was proposed to characterize the variation of the peak coal particle temperature caused by the improved heat transfer and mass transport between the coflow and coal particles under high jet velocity. The maximum value of η was 1.053 at 1873 K and 21% O2 under O2/CO2 atmosphere with the jet velocity of 11.2 m/s, indicating the increased jet velocity had the predominant effect on the increase of peak particle temperature at high gas temperature and O2 concentration.

Smith–Purcell radiation controlled by the transmission characteristics and quality factor of a layer

Photonic crystal structures have attracted significant attention because of their ability to confine light, especially outgoing waves in a bandgap. In this study, we investigate a layer that can control the Smith–Purcell radiation. The results show that transmission characteristics and quality factor of a 1D photonic crystal can narrow the radiation spectrum and enhance the radiation intensity. From another perspective, the entire structure can be treated as a composite grating, the radiation spectra of which are obtained by theoretical calculations and agree with that from the analysis based on the role of the 1D photonic crystal. Therefore, it can be concluded that the radiation from a composited structure can be simplified by the radiation controlled by the 1D metal photonic crystal, and it provides a fast way to reshape the radiation spectra by designing the transmission characteristic and quality factor of the photonic crystal. Furthermore, a layer with special transmission characteristics and quality factor above a reflection grating can be used to achieve coherent and tunable Smith–Purcell radiation, which is significant for the development of band-controllable light or terahertz radiation sources.