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Measurement of bunch length evolution in electron beam macropulse of S-band linac using coherent edge radiation
摘要： Intense coherent edge radiation (CER) with a power of 0.10 mW was observed in a straight line with an undulator of Kyoto University Free Electron Laser (KU-FEL). To investigate the evolution of a bunch length in a macropulse of an electron beam, a technique was developed using the CER beam. The measured air-extracted CER beam pro?le has a hollow structure resembling the ?rst-order Laguerre–Gaussian mode with asymmetric intensity in horizontal direction. It roughly agrees with the pro?le calculated considering the effective area of a de?ection mirror employed to extract the beam from the FEL optical cavity into air. The root-mean-squared (RMS) bunch length determined from a measured spectrum of the CER beam is 60 μm for an electron-beam macropulse. Changes in the CER intensity in the electron-beam macropulse were measured by diode detectors with short time constants at two frequencies. The evolution of the RMS bunch length was determined using the ratio of the CER intensity at the two frequencies. It could be concluded that the evolution correlated with the macropulse structure of the FEL power. Therefore, measuring the evolution of the CER intensity at multiple frequencies proved useful to control FEL macropulses.
关键词： Bunch length,Terahertz,Coherent edge radiation,Free-electron laser,Linac
更新于2025-09-23 15:23:52
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Quantum regime for dielectric Cherenkov radiation and graphene surface plasmons
摘要： In this article, we propose a quantum regime for Cherenkov free-electron laser (CFEL) and surface plasmon polaritons (SPPs) excited in dielectric and multilayer graphene waveguides, respectively. This quantum regime is realized when the momentum spread induced in the interaction is smaller than the photon recoil. The discrete momentum exchange characterizing this interaction yields a significantly narrow single emission line. To determine the condition of the quantum regime, we derive an expression for the gain in the Cherenkov effect using a quantum mechanical treatment. It is assumed that the effective spread in momentum is due to the finite interaction length L (or the propagation length in the case of SPPs). For both cases, CFEL and SPPs, the effects of electron beam and waveguide parameters on the possibility of the quantum regime are studied. We conclude that the quantum regime can be basically verified at low electron beam energy (<40 keV) and at emission wavelengths in the near infrared range (<5 μm) when L is in the order of millimeters. In the case of SPPs, we also show that the feasibility to realize quantum SPPs is enhanced by increasing the chemical potential and number of graphene layers.
关键词： Quantum light,Surface plasmon polaritons,Graphene,Cherenkov radiation
更新于2025-09-23 15:23:52
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Formation of a Track Template during PETP Irradiation with High-Energy Helium Ions for the Template Synthesis of Regular Microstructures
摘要： The features of obtaining track membranes (TMs) with the help of a classical cyclotron situated at Tomsk Polytechnic University are discussed. It is demonstrated that TMs can be employed as templates. The results of research into columnar nanostructures formed with the help of a TM template are presented. The creation of regular microstructures is investigated using deep X-ray lithography with synchrotron radiation and templates made of track membranes.
关键词： track membrane,argon ions,synchrotron radiation,helium ions,polyethylene terephthalate
更新于2025-09-23 15:23:52
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Current Status of Patient Radiation Exposure of Cardiac Positron Emission Tomography and Single-Photon Emission Computed Tomographic Myocardial Perfusion Imaging
摘要： BACKGROUND: Radiation exposure during nuclear cardiology procedures has received much attention and has prompted citations for radiation reduction. In 2010, the American Society of Nuclear Cardiology recommended reducing the average patient study radiation exposure to <9 mSv in 50% of studies by 2014. Cardiac positron emission tomography (PET) for myocardial perfusion imaging (MPI) has emerged within recent years, but current radiation exposure in cardiac nuclear PET laboratories is unknown. This study evaluated current reported patient radiation exposure from nuclear laboratories in the United States applying for Intersocietal Accreditation Commission accreditation for MPI using single photon emission computed tomography (SPECT) or PET. METHODS AND RESULTS: This was an analysis of nuclear cardiology studies submitted to the Intersocietal Accreditation Commission for either or both cardiac PET and SPECT accreditation. Cardiac SPECT data represented year 2015 while PET data combined years 2013 to 2015. Data was analyzed with χ2 and Mann-Whitney U tests (reported as median, 25th percentile, and 75th percentile). Reported PET MPI radiation exposure for 111 laboratories (532 patient cases) was 3.7 (3.2–4.1) mSv per study with no geographic variation. Reported SPECT MPI radiation exposure for 665 laboratories (3067 patient studies) was 12.8 (12.2–14.3) mSv. Highest radiation exposure was found in the South region. Technetium-only studies resulted in a median of 12.2 mSv per study. CONCLUSIONS: Radiation exposure from cardiac PET MPI in US laboratories applying for Intersocietal Accreditation Commission accreditation is low (111 laboratories, 3.7 mSv) and substantially lower than cardiac SPECT (665 laboratories, 12.8 mSv).
关键词： technetium,accreditation,myocardial perfusion imaging,positron emission tomography,radiation exposure
更新于2025-09-23 15:23:52
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GENERATION OF COMPLEX SOURCE POINT EXPANSIONS FROM RADIATION INTEGRALS (Invited Paper)
摘要： This paper discusses methods for expanding fields radiated by arbitrary sources enclosed by a certain minimum sphere in terms of Complex Source Point (CSP) beams. Two different approaches are reviewed; the first one is based on a spectral radiation integral, where the Fourier-spectrum is obtained by far field matching. The second approach consists of two steps: first, the equivalence principle is applied to a sphere enclosing the real sources, and a continuous equivalent electric current distribution is obtained in terms of spherical waves; then, the continuous current is extended to complex space and its SW components are properly filtered and sampled to generate the discrete set of CSPs. In both cases, the final result is a compact finite series representation with a number of terms that matches the degrees of freedom of arbitrary radiated fields; it is particularly efficient when the fields are highly directional and the observation domain is limited to a given angular sector. The fact that the CSPs rigorously respect Maxwell's equations ensures the validity of the expansion from near to far zone and allows one to incorporate the CSP representation in a generalized admittance matrix formalism for the analysis of complex problems.
关键词： CSP beams,field expansion,degrees of freedom,generalized admittance matrix,spectral matching,radiation integrals,Complex Source Point,spherical waves
更新于2025-09-23 15:23:52
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Evaluation of Radiation Characteristics of Xenon Short Arc Lamp by Numerical Simulation; 数値解析を用いたキセノンショートアークランプの放射特性評価;
摘要： In this study, an arc numerical simulation model of xenon short arc lamp was developed by modifying numerical simulation model of free burning arc. The influence of the difference in the filling gas pressure on the energy consumed by the lamp voltage, current and gas radiation was investigated. It became clear that the radiation power of the xenon arc lamp strongly depends on the filling gas pressure. Furthermore, when the lamp is turned on with constant power, the radiation efficiency is determined by the balance between the radiation power density and the high temperature arc volume, and as a result, it is clear that the maximum value exists of the radiation power fraction.
关键词： Numerical Simulation,Xenon Arc Lamp,Radiation,Xenon,Energy Balance
更新于2025-09-23 15:23:52
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UV optical measurements of the Nozomi spacecraft interpreted with a two-component LIC-flow model <i>(Corrigendum)</i>
摘要： We found a typographical error regarding the uncertainty of the helium flow direction in our published paper Nakagawa et al. (2008). The helium flow direction should be (258.7 ± 8.0°, 3.4 ± 8.0°) instead of (258.7 ± 3.4°). As a consequence, the description for the helium flow direction in page 39 has to be replaced by “Residuals of simulated intensities with respect to observations attained minimum values for a downwind direction of (78.78 ± 8.0°, ?3.48 ± 8.0°), corresponding to an upwind direction of (258.78 ± 8.0°, 3.48 ± 8.0°).” All conclusions of the original paper remain unaffected. H. Nakagawa is grateful to Priscilla Frisch for pointing out this error.
关键词： ISM: atoms,ultraviolet: ISM,Sun: UV radiation,addenda,errata
更新于2025-09-23 15:23:52
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Thermal structure of a hot non-flaring corona from Hinode/EIS
摘要： Aims. In previous studies, a very hot plasma component has been diagnosed in solar active regions through the images in three different narrow-band channels of Atmospheric Imaging Assembly (AIA) on board the Solar Dynamics Observatory (SDO). This diagnostic from extreme ultraviolet (EUV) imaging data has also been supported by the matching morphology of emission in the hot Ca XVII line, as observed with Extreme-Ultraviolet Imaging Spectrometer (EIS) on board Hinode. This evidence is debated because of the unknown distribution of the emission measure along the line of sight. Here we investigate in detail the thermal distribution of one such region using EUV spectroscopic data. Methods. In an active region observed with SDO/AIA, Hinode/EIS, and X-ray telescope (XRT), we select a sub-region with a very hot plasma component and another cooler sub-region for comparison. The average spectrum is extracted for both, and 14 intense lines are selected for analysis that probe the 5.5 < log T < 7 temperature range uniformly. From these lines, the emission measure distributions are reconstructed with the Markov-chain Monte Carlo method. Results are cross-checked in comparison with the two sub-regions, with a different inversion method, with the morphology of the images, and with the addition of fluxes measured with narrow, and broadband imagers. Results. We find that, whereas the cool region has a flat and featureless distribution that drops at temperature log T ≥ 6.3, the distribution of the hot region shows a well-defined peak at log T = 6.6 and gradually decreasing trends on both sides, thus supporting the very hot nature of the hot component diagnosed with imagers. The other cross-checks are consistent with this result. Conclusions. This study provides a completion of the analysis of active region components, and the resulting scenario supports the presence of a minor very hot plasma component in the core, with temperatures log T > 6.6.
关键词： techniques: imaging spectroscopy,Sun: UV radiation,Sun: corona,techniques: spectroscopic,Sun: X-rays, gamma rays
更新于2025-09-23 15:23:52
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AIP Conference Proceedings [Author(s) PROCEEDINGS OF THE 12TH INTERNATIONAL CONFERENCE ON SYNCHROTRON RADIATION INSTRUMENTATION – SRI2015 - New York, NY USA (6–10 July 2015)] - Physical optics simulations with Phase for SwissFEL beamlines
摘要： PHASE is a software tool for physical optics simulation based on the stationary phase approximation method. The code is under continuous development since about 20 years and has been used for instance for fundamental studies and ray tracing of various beamlines at the Swiss Light Source. Along with the planning for SwissFEL a new hard X-ray free electron laser under construction, new features have been added to permit practical performance predictions including diffraction effects which emerge with the fully coherent source. We present the application of the package on the example of the ARAMIS 1 beamline at SwissFEL. The X-ray pulse calculated with GENESIS and given as an electrical field distribution has been propagated through the beamline to the sample position. We demonstrate the new features of PHASE like the treatment of measured figure errors, apertures and coatings of the mirrors and the application of Fourier optics propagators for free space propagation.
关键词： beamline optics,X-rays,XFEL,synchrotron radiation
更新于2025-09-23 15:23:52
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[IEEE 2018 IEEE Conference on Antenna Measurements & Applications (CAMA) - Va?ster?s (2018.9.3-2018.9.6)] 2018 IEEE Conference on Antenna Measurements & Applications (CAMA) - Guidelines for Millimeter-Wave Antenna Measurements
摘要： The characterization of physically small antennas in the millimeter-wave range has proven to be a challenge. Several research groups have developed new antenna measurement systems to be able to characterize millimeter-wave antennas. These measurement systems mainly focus on the establishment of a well-defined connection between test equipment and the antenna-under-test (AUT) for radiation pattern measurements. However, uncertainties affecting the measurement results are not always well understood. We have investigated the effect of misalignment, the effectiveness of an anechoic environment for frequencies up to 90 GHz and the impact of spurious radiation of the probe.
关键词： anechoic environment,probe radiation,60 GHz,probe connection,uncertainty analysis,alignment,Millimeter wave,antenna measurement
更新于2025-09-23 15:23:52