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Multiple-Collision Free-Electron Laser Compton Backscattering for a High-Yield Gamma-Ray Source
摘要： We observed multiple-collision free-electron laser (FEL)-Compton backscattering in which a multi-bunch electron beam makes head-on collisions with multi-pulse FELs in an optical cavity, using an infrared FEL system in the storage ring NIJI-IV. It was demonstrated that the measured spectrum of the multiple-collision FEL-Compton backscattering gamma rays was the summation of the spectra of the gamma rays generated at each collision point. Moreover, it was demonstrated that the spatial distribution of the multiple-collision FEL-Compton backscattering gamma rays was the summation of those of the gamma rays generated at each collision point. Our experimental results proved quantitatively that the multiple collisions in the FEL-Compton backscattering process are effective in increasing the yield of the gamma rays. By applying the multiple-collision FEL-Compton backscattering to high-repetition FEL devices such as energy recovery linac FELs, an unprecedented high-yield gamma-ray source with quasi-monochromaticity and wavelength tunability will be realized.
关键词： Compton backscattering,multiple collision,free-electron laser,gamma ray
更新于2025-09-16 10:30:52
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Exact distributions for bit error rate and channel capacity in free-space optical communication
摘要： Bit error rate (BER) and channel capacity are two important metrics to assess the performance of free-space optical communication (FSOC) systems. Due to the fading of the optical signal owing to the atmospheric effects, these two quantities behave as random variables. Most of the studies in this direction have focused on the calculation of only the average of these quantities. However, since the complete information about a random variable is encoded in its distribution, it is more informative to examine the latter itself. In this work, the authors derive exact probability density function (PDF) expressions for the BER and the channel capacity for an arbitrary irradiance model. In particular, they investigate these exact results for log-normal, gamma-gamma, and K distributions. For the BER analysis, they focus on the binary phase shift keying and quadrature phase shift keying modulation schemes. The authors' analytical reults are found to be in conformity with Monte Carlo simulations. The exact PDFs of the BER and the channel capacity reveal that there are several instances when the average is unable to capture the actual behaviour of these quantities, and therefore one must be careful in drawing conclusions based on the first moment only.
关键词： binary phase shift keying,bit error rate,quadrature phase shift keying,gamma-gamma distribution,channel capacity,log-normal distribution,K distribution,probability density function,free-space optical communication
更新于2025-09-12 10:27:22
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[IEEE 2019 IEEE 90th Vehicular Technology Conference (VTC2019-Fall) - Honolulu, HI, USA (2019.9.22-2019.9.25)] 2019 IEEE 90th Vehicular Technology Conference (VTC2019-Fall) - Performance of Free Space Optical Communication System under Jamming Attack and Its Mitigation over Non-Gaussian Noise Channel
摘要： In free space optical (FSO) communication, jamming can cause inaccuracy in the received information. In this paper, we investigate the impact of jamming over atmospheric turbulence (AT) fading channels. To describe the AT, negative exponential fading channel models are considered. The effect of jamming is studied over a single-input single-output (SISO) FSO link. We introduce a theoretical framework to acquire a closed-form expression of the average bit error rate (ABER) under jamming–leading to an additive non-Gaussian noise channel. It is observed by thorough analysis that a 2 × 1 FSO system performs better than SISO FSO system in presence of jamming signal. It is realized that under jamming the performance of FSO link is dependent on different AT conditions. Furthermore, increasing number of transmit apertures allows FSO system to significantly overcome the effect of jamming, in order to obtain an improved ABER.
关键词： Additive non-Gaussian noise,exponential fading,signal-to-jamming ratio (SJR),bit error rate (BER),free space optical (FSO) communication,jamming,Gamma-Gamma fading
更新于2025-09-12 10:27:22
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Transmit laser selection for two hop decode and forward FSO communication with pointing errors
摘要： In this letter, two systems have been proposed for efficient unidirectional free space optical (FSO) cooperative communication-one with only transmit laser selection (TLS) and the other using optical spatial modulation (OSM) along with TLS. Performance analysis of such systems for Gamma-Gamma (G-G) fading channels both with and without Pointing errors have been carried out in terms of outage probability and average symbol error probability (ASEP). Our proposed TLS system over G-G channel (with pointing error) yields a signal to noise ratio (SNR) gain of at least 10 dBm over the conventional FSO system.
关键词： cooperative communication,Free space optical communication,transmit laser selection,pointing errors,Gamma-Gamma fading,optical spatial modulation
更新于2025-09-12 10:27:22
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A Temperature Compensation Method by Adjusting Gamma Voltages for High Luminance Uniformity of Active Matrix Organic Light-Emitting Diode Displays
摘要： In this paper, a temperature compensation method is proposed for active-matrix organic light-emitting diode (AMOLED) displays to achieve high luminance uniformity over a wide operating temperature range. The proposed temperature compensation method compensates for variation in OLED luminance according to temperature by adjusting the gamma voltages. To verify the proposed method, a built-in test circuit, which includes temperature sensors, current calculation block, current adjustment block, and gamma voltage generator, was fabricated using 90 nm complementary metal-oxide semiconductor process technology with 6 V high-voltage devices. The measurement results show that the proposed method achieves a high luminance uniformity with an OLED luminance variation of less than 1.54 cd/m2 over the temperature range of –45°C to 60°C. Therefore, the proposed temperature compensation method is suitable for AMOLED displays requiring high luminance uniformity.
关键词： gamma voltage,high luminance uniformity,temperature compensation,Organic light-emitting diode (OLED)
更新于2025-09-12 10:27:22
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Analysis of the Single-Crystalline Silicon Photovoltaic (PV) Module Performances Under Low γ - Radiation from Radioactive Source
摘要： The present paper is about an experimental evaluation of the terrestrial silicon single-crystalline solar PV module behavior under low gamma radiation. The simultanous proliferation of radioactive sources in Burkina Faso dominated by gamma type and the photovoltaic (PV) systems installations in both urban and rural areas justify this study. There is also high background radiation compared to normal in some region of the country. It has been shown that the photocurrent and the electric power increase while the photovoltage stays constant for an extremely low gamma radiation doses. This work proves that long time exposition to any low radiation can cause the reduction of the performance of the solar PV module. However for greater values of the dose, the photocurrent, the photovoltage and the electric power decrease. Hence, it is so important to protect PV equipments against gamma radiation by adjusting the PV installation height from the ground where high background radiation is notified or by putting reinforced concrete at their bottom faces. The two ways can be combinated adding the respect to radiation protection principle As Low As Reasonably Achievable (ALARA).
关键词： Low gamma (γ) - radiation,Single-Crystalline silicon,PV solar module,Dose,Dose rate
更新于2025-09-12 10:27:22
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Effective production of gammas, positrons, and photonuclear particles from optimized electron acceleration by short laser pulses in low-density targets
摘要： Electron acceleration has been optimized based on 3D particle-in-cell simulations of a short laser pulse interacting with low-density plasma targets to find the pulse propagation regime that maximizes the charge of high-energy electron bunches. This regime corresponds to laser pulse propagation in a self-trapping mode where the diffraction divergence is balanced by the relativistic nonlinearity such that relativistic self-focusing on the axis does not happen and the laser beam radius stays unchanged during pulse propagation in a plasma over many Rayleigh lengths. Such a regime occurs for a near-critical density if the pulse length considerably exceeds both the plasma wavelength and the pulse width. Electron acceleration occurs in a traveling cavity filled with a high-frequency laser field and a longitudinal electrostatic single-cycle field (“self-trapping regime”). Monte Carlo simulations demonstrated that a high electron yield allows an efficient production of gamma radiation, electron–positron pairs, neutrons, and even pions from a catcher-target.
关键词： electron acceleration,photonuclear particles,laser pulse,gamma radiation,positrons,low-density plasma
更新于2025-09-12 10:27:22
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Design of Energy Recovery Linac for a Source of High-Flux Gamma-ray by Laser Compton Scattering
摘要： We investigate the generations of a high-?ux γ-ray beams by laser Compton scattering. We performed the design of an energy recovery linac that produces a γ-ray beam with the ?ux of ～ 1013 photons/s. It is important to examine the e?ects on beam performances of the ERL in detail. Thus, we examined the e?ects of emittance growths on higher order modes in the superconducting linac and coherent synchrotron radiation in the designed lattice of the energy recovey linac. They were checked by performing the start-to-end simulation of multi-beam particle trackings in the designed 355 MeV ERL. It was shown that the energy recovery linacs by laser Compton scattering may provide monochromatic high-?ux gamma-ray beams. It is shown through our design studies that goals of γ-ray beam parameters in the ERL facility are achievable. Such an energy-tunable γ-ray beams that are generated by laser Compton scattering may be applied to nuclear resonance ?uorescence(NRF) measurements for the non-destructive detection of radioactive nuclear materials. The investigations show that our design studies provide a good optimized ERL parameters in terms of beam dynamics.
关键词： Supercavity,High-?ux gamma rays,Laser Compton scattering,Nuclear resonance ?uorescence,Energy recovery linac
更新于2025-09-12 10:27:22
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Investigation of optical and structural properties of aqueous CdS quantum dots under gamma irradiation
摘要： The optical properties of aqueous CdS quantum Dots (QDs) under gamma irradiation were systemically studied with dose of 0–20 kGy. The QDs synthesized by microwave assisted method with di?erent size and concentration. By transmission electron spectroscopy (TEM) the size of particle was indicated about 3–4 nm. The results show that degrading of photoluminescence of QDs is strongly depended on concentration, so that the fastest degradation is corresponded to low concentration. In other side, redshift of PL peck and bandgap edge was strongly depend on the initial size of QDs, thus the smaller size had the largest redshift. The X-ray di?raction analysis did not show changes in crystalline structure after gamma irradiation. The FTIR results did not show changes after gamma irradiation, as well. It has been found that the main mechanism of the behavior of QDs under gamma irradiation is growth of CdS QDs. These results showed that CdS QDs have a high potential to use as gamma dosimeter.
关键词： CdS,Gamma,Dosimeter,PL,Optical properties,Quantum dots
更新于2025-09-12 10:27:22
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Influence of Gamma-Irradiation on Structural, Optical and Photocatalytic Performance of TiO2 Nanoparticles Under Controlled Atmospheres
摘要： The effect of gamma-rays on structural, optical and photocatalytic properties of TiO2 nanoparticles under controlled atmospheres are studied to further improve photocatalytic performance. The sol–gel TiO2 powders were deposited with spin-coating technique, annealed at 500°C then finally irradiated by gamma-rays. The structural and optical characteristics of samples were investigated by Fourier transform infrared spectroscopy, x-ray diffraction and UV-visible spectroscopy (UV). The time-dependent density functional theory (TD-DFT) calculation are used to determine ground geometries and electronic structures of TiO2 nanostructures. DFT calculations present an excellent conformity with experimental results, and a high anisotropy in stretched thermal and electrical conductivity TiO2 nanostructures was found. Structural and optical results show that gamma radiation did not change the crystallinity of TiO2 nanostructures and leads to an optical band gap reduction to 3.039 eV. The gamma radiation effect on photocatalytic performance was investigated by methylene blue degradation as a typical pollutant. Gamma radiation has been discovered to improve considerably the degradation of pollutants compared with unirradiated TiO2.
关键词： optical properties,DFT,TiO2,Gamma ray radiation,photo catalysis
更新于2025-09-12 10:27:22