共查询到19条相似文献,搜索用时 125 毫秒
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加速器质谱(AMS)技术是上世纪70年代末发展起来的一种分析微量核素和探测稀有粒子的新方法。因其具有排除分子离子干扰以及鉴别同量异位素等多方面优势,故比常规分析技术和普通质谱计具有更高的灵敏度(丰度灵敏度可达到10-15)。自发展起来以来,这种技术己广泛应用于不同的研究领域。本文对AMS的基本原理、装置、技术发展以及其在核物理及核天体物理、地质年代学、生物医学示踪、环境监测等领域中的教学科研应用进行了详细阐述。 相似文献
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文章介绍了与散裂中子源相关的高功率(几十千瓦到几兆瓦)质子加速器的发展状况,比较了不同类型的加速器组合的优缺点和它们的应用范围,并着重介绍该类型加速器所研究的主要加速器物理和加速器技术问题,其中很多都是当今国际粒子加速器领域的前沿问题.文中还简单地介绍了中国散裂中子源(CSNS)计划的加速器概念设计方案. 相似文献
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为研究引张线技术在加速器准直测量中的应用和发展,首先简介了引张线技术原理,然后回顾了引张线准直法在加速器工程中的发展历史,接着介绍了引张线在加速器准直测量中的最新发展动态。最后讨论了各种引张线准直法的优缺点及其适宜环境,比较了国内外引张线准直法的发展与区别。指出引张线准直法的发展方向,给出了加速器准直测量的努力方向。 相似文献
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在物理应用技术发展上,加速器、远距离输电、火器等技术的发展经过一波三折,开始某一方向发展较快,后来受到相关条件、技术的制约,朝着另一方向发展,在发展中又遇到难以解决的新问题,而原技术的瓶颈随着相关技术的突破,得到解决,从而原来被冷落的技术又受到青睐,重新成为此类技术的主流. 相似文献
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非加速器实验,顾名思义,包括所有不使用加速器手段进行的粒子物理实验。如果从1912年发现宇宙线算起,它的历史已相当长久,加速器出现以前,宇宙线实验有过一段辉煌时期,在30年代发现了正电子和μ子,在40年代发现了π介子和K介子,对粒子物理学的建立与发展作出了重大贡献。50年代出现加速器以后,使用高流强人工束流的加速器实验成为粒子物理实验研究的主流,有力地推动着粒子物理的迅速发展,而“靠天吃饭”、流强极低的宇宙线实验仅在加速器当时达不到的“超高”能区起补充作用。但应指出,70年代初著名的大型37Cl太阳中微子地下实验不仅获得重要物理发现,而且在实验方向与技术上作出了有意义的探索,堪称后来新一代非加速器实验的先驱。 相似文献
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Deep learning models and graphics processing units have completely transformed the field of machine learning. Recurrent neural networks and long short-term memories have been successfully used to model and predict complex systems. However, these classic models do not perform sequential reasoning, a process that guides a task based on perception and memory. In recent years, attention mechanisms have emerged as a promising solution to these problems. In this review, we describe the key aspects of attention mechanisms and some relevant attention techniques and point out why they are a remarkable advance in machine learning. Then, we illustrate some important applications of these techniques in the modeling of complex systems. 相似文献
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Linear accelerators delivering high brightness electron beams are essential for a number of current and proposed accelerator applications, such as free electron lasers (FELs). In this kind of facilities the charge density is high enough to drive collective effects (wakefields) that, notwithstanding the high beam rigidity at energies up to the GeV range, may increase the beam emittance relative to the injection level, eventually degrading the nominal beam brightness. New theoretical developments and experimental capabilities, driven by the recent construction of vacuum-ultra-violet and X-ray linac-driven FELs, have advanced the present knowledge. This article describes the progress in the field of ultra-relativistic electron beam manipulation to maximize the final beam brightness, with a focus on the most recent techniques including optics design, pulse shaping and brightness optimization strategies. The theoretical models are supported by a review of the experimental results in now-running FEL facilities. 相似文献
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射频超导谐振腔可以工作在连续波或长宏脉冲模式. 射频超导技术已发展为加速各种带电粒子束的重要手段. 射频超导技术发展的前期受材料性能、腔的处理以及加工安装水平等的限制. 经过几十年的不断改进, 射频超导技术获得了重大突破. 射频超导腔应用到超导加速器上并成功运行, 积累了腔的质量控制工艺和工业化制备的大量经验. 近期国际上面对未来大科学装置项目, 在射频超导技术方面进行了大量的研发工作, 主要包括提高超导腔加速梯度的新腔型研究和采用新型材料(大晶粒铌材)超导腔的研究. 能量回收直线加速器(ERL)技术是近年来获得发展的重要加速器技术. ERL具有高效、节能、稳定性好、低辐射水平等优势, 被越来越多地应用到先进光源和自由电子激光装置中. 相似文献
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轨道校正是加速器束流调节最基本的步骤之一,也是目前各加速器实验室共同面对的问题之一。在传统方法中,线性代数工具被应用于各种类型的响应矩阵,以解决响应矩阵的奇异性等问题。提出一种基于机器学习的加速器轨道校正方法,可以避免处理响应矩阵的问题通过直接读取BPM数据和校正磁铁强度值实时构建机器学习模型快速地对轨道进行修正。对机器学习的轨道校正方法进行了介绍,并从数学公式、算法模型、在模拟和真实数据上的测试等方面对该方法进行了讨论。结果表明,在误差范围内该方法能有效的对加速器束流轨道进行校正。 相似文献
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B. Kanngießer W. Malzer I. Mantouvalou D. Sokaras A. G. Karydas 《Applied Physics A: Materials Science & Processing》2012,106(2):325-338
Quantitative X-ray fluorescence (XRF) and particle induced X-ray emission (PIXE) techniques have been developed mostly for
the elemental analysis of homogeneous bulk or very simple layered materials. Further on, the microprobe version of both techniques
is applied for 2D elemental mapping of surface heterogeneities. At typical XRF/PIXE fixed geometries and exciting energies
(15–25 keV and 2–3 MeV, respectively), the analytical signal (characteristic X-ray radiation) emanates from a variable but
rather extended depth within the analyzed material, according to the exciting probe energy, set-up geometry, specimen matrix
composition and analyte. Consequently, the in-depth resolution offered by XRF and PIXE techniques is rather limited for the
characterization of materials with micrometer-scale stratigraphy or 3D heterogeneous structures. This difficulty has been
over-passed to some extent in the case of an X-ray or charged particle microprobe by creating the so-called confocal geometry.
The field of view of the X-ray spectrometer is spatially restricted by a polycapillary X-ray lens within a sensitive microvolume
formed by the two inter-sectioned focal regions. The precise scanning of the analyzed specimen through the confocal microvolume
results in depth-sensitive measurements, whereas the additional 2D scanning microprobe possibilities render to element-specific
3D spatial resolution (3D micro-XRF and 3D micro-PIXE). These developments have contributed since 2003 to a variety of fields
of applications in environmental, material and life sciences. In contrast to other elemental imaging methods, no size restriction
of the objects investigated and the non-destructive character of analysis have been found indispensable for cultural heritage
(CH) related applications. The review presents a summary of the experimental set-up developments at synchrotron radiation
beamlines, particle accelerators and desktop spectrometers that have driven methodological developments and applications of
confocal X-ray microscopy including depth profiling speciation studies by means of confocal X-ray absorption near edge structure
(XANES) spectroscopy. The solid mathematical formulation developed for the quantitative in-depth elemental analysis of stratified
materials is exemplified and depth profile reconstruction techniques are discussed. Selected CH applications related to the
characterization of painted layers from paintings and decorated artifacts (enamels, glasses and ceramics), but also from the
study of corrosion and patina layers in glass and metals, respectively, are presented. The analytical capabilities, limitations
and future perspectives of the two variants of the confocal micro X-ray spectroscopy, 3D micro-XRF and 3D micro-PIXE, with
respect to CH applications are critically assessed and discussed. 相似文献
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Richard Klíma 《Czechoslovak Journal of Physics》1958,8(4):404-410
A theory of phase motion in a synchronous circular accelerator is derived for the case that, in addition to the accelerating component of a high-frequency field, a component acts on a particle which deforms the path of the particle. For an accelerator with constant period of revolution and fixed magnetic field the result is asymptotic focusing of the particles to a certain phase s.In conclusion the author thanks Dr. M. Seidl for suggesting this paper and for many remarks during its elaboration. He also thanks members of the seminary of the sector of accelerators for criticisn and, last but not least, L. Krlín for friendly cooperation. 相似文献
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Maria Nicolai Alexander Sävert Maria Reuter Michael Schnell Jens Polz Oliver Jäckel Leonhard Karsch Michael Schürer Melanie Oppelt Jörg Pawelke Malte C. Kaluza 《Applied physics. B, Lasers and optics》2014,116(3):643-651
Laser-accelerated electron pulses have been used to irradiate human tumors grown on mice’s ears during radiobiological experiments. These experiments have been carried out with the JETI laser system at the Institute of Optics and Quantum Electronics in Jena, Germany. To treat a total of more than 50 mice, a stable and reliable operation of the laser-electron accelerator with a dose rate exceeding 1 Gy/min was necessary. To achieve this, a sufficient number of electrons at energies in excess of 5 MeV had to be generated. The irradiation time for a single mouse was a few minutes. Furthermore, the particle pulses’ parameters needed to remain achievable for a time period of several weeks. Due to the online detection of the radiation dose, the unavoidable shot-to-shot fluctuations, currently still typical for laser-based particle accelerators, could be compensated. The results demonstrate that particle pulses generated with laser-based accelerators have the potential to be a future alternative for conventional particle accelerators used for the irradiation of tumors. 相似文献
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Dr. S. Puri 《Zeitschrift für Physik A Hadrons and Nuclei》1970,233(4):358-367
The existing results on the theory of stochastic cyclic accelerators are extended using the methods of difference equations and random-walk theory. The theoretical guidelines provided by this paper should be sufficient to allow an evaluation of the feasibility of making a practical machine using the principle of stochastic acceleration. It is found that the average time required for the acceleration of a particle to its final energy is approximately one-third of that in the existing results. It is shown that the diffusion constant in energy space can be very simply expressed in terms of the meansquare voltage applied at the accelerator gap and the bandwidth of the applied-field spectrum for the practical case of interest. The required power input and the resistive input impedance for the accelerator are calculated taking particle losses into account. 相似文献