分类： 天文学 >> 天体物理学 提交时间： 2023-07-29
摘要： The pulsar radio emission mechanism remains an enigma since its discovery in 1967. The critical issue of origin of coherent emission is usually investigated separately from the micro-structure of individual pulses and characteristic emission frequency of pulsars... In this letter, these issues are interpreted in an unified scenario. The pulsar spin piles up magnetic field at the apex of last closed field line triggering magnetic reconnection. The resultant Alfven wave interacts with open field lines giving rise to coherent maser curvature and cyclotron emission. Such a scenario of coherent emission not only imposes new limit to emission site, nanoburst, and characteristic frequency, but also affects polarization and pair production required in maintaining a marginal stable circuit in radio emission of pulsars.
分类： 核科学技术 >> 粒子加速器 提交时间： 2023-07-08
摘要： Radio-frequency (RF) breakdown analysis and location are critical for successful development of high-gradient traveling-wave (TW) accelerators, especially those expected to generate high-intensity, high-power beams. Compared with commonly used schemes involving dedicated devices or complicated techniques, a convenient approach for breakdown locating based on transmission line (TL) theory offers advantages in the typical constant-gradient TW-accelerating structure. To deliver such an approach, an equivalent TL model has been constructed to equate the TW-accelerating structure based on the fundamental theory of the TL transient response in the time domain. An equivalence relationship between the TW-accelerating structure and the TL model has been established via analytical derivations associated with grid charts and verified by TL circuit simulations. Furthermore, to validate the proposed fault-locating method in practical applications, an elaborate analysis via such a method has been conducted for the recoverable RF-breakdown phenomena observed at an existing prototype of a TW-accelerating-structure-based beam injector constructed at the Huazhong University of Science and Technology. In addition, further considerations and discussion for extending the applications of the proposed method have been given. This breakdown-locating approach involving the transient response in the framework of TL theory can be a conceivable supplement to existing methods, facilitating solution to construction problems at an affordable cost.
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