1,721,236 research outputs found
Analytical Expressions for the Coupling Impedance of a Long Narrow Slot in a Coaxial Beam Pipe
No full textThe longitudinal impedance and loss factor for a long narrow slot in a coaxial pipe are calculated by means of the modified Bethe’s diffraction theory. The effects of the interference between the fields scattered by dipoles along the slot are taken into account, obtaining a final expression valid even for slots longer than the wavelength
Investigations on the multiple-sector hard-copper X-band accelerating structures
No full textThe development of advanced, high gradient accelerating structures is one of the leading activity of the particle accelerator community. In the technological research of new construction methods for these devices, high-power testing is a critical step for the verification of their viability. Recent experiments showed that accelerating cavities made out of hard copper, fabricated without high-temperature processes, can achieve better performance as compared with soft copper ones. Recently, we have built cavities using Tungsten Inert Gas welding and the high-power experiments confirmed that this joining process is a robust and low-cost alternative to brazing or diffusion bonding. This is a good solution for high-gradient operation, with a gradient of about 150 MV/m in X-band, at a breakdown rate of 10−3/pulse/meter using a shaped RF pulse with a 150 ns flat part. We continue the design, construction and high power tests of three-cells standing-wave X-band accelerating cavities fabricated with a split-open geometry, made of hard copper and vacuum-sealed by welding. Our aim is the fabrication of accelerating structures made out of hard copper alloys by using innovative cost-effective technologies. Moreover, our method of multiple-sector structures opens the way to new technological approaches and design methods, for example providing the possibility of placing dampers of the parasitic higher-order modes. Such structures with dampers allow for acceleration of multi-bunch beams, both in standing and in travelling-wave accelerating modality. This paper describes the design of two cavities made of multiple sectors that were fabricated at the Italian Institute for Nuclear Physics in Frascati, Italy (INFN-LNF), assembled by means of clamping and then joined with the Tungsten Inert Gas welding in order to preserve the hardness of the metal. These are three-cell standing-wave X-band accelerating cavities, to be operated in the π-mode. We report the low-power RF tests of the first one, made of two halves, and the RF design of the second one, made of four quadrants. Both structures were built for high-gradient tests at SLAC National Accelerator Laboratory
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
A syncitium model for the interpretation of the phenomenon of anomalous light flashes occurring in the human eye during space missions
No full textA low-perveance electron gun for a high-efficiency Ka-band klystron
No full textSelf-consistent analytic and numeric design for a set of electron guns with a high beams quality to be used in high-power Ka-band klystrons is presented in this paper. The set of electron guns can be used in the high-power Ka-band klystrons in order to
feed linear accelerating structures at 36 GHz with an estimated 20 MW input power by achieving an effective accelerating electric
field in the (100–150) MV/m range. In the framework of the Compact Light XLS project, a short Ka-band linearizer by working at
36 GHz able to provide an integrated voltage of at least 15 MV is proposed for bunch-phase linearization. In order to optimize the Ka-band klystrons efficiency for achieving 20 MW RF output power, different electron guns, beam focusing channel designs and the RF beam dynamics are examined and discussed in this paper
A SW Ka-Band linearizer structure with minimum surface electric field for the compact light XLS project
No full textThere is a strong demand for accelerating structures able to achieve higher gradients and more compact dimensions for the next generation of linear accelerators for research, industrial and medical applications. In the framework of the Compact Light XLS project, an ultra-high gradient higher harmonic RF accelerating structure is needed for the linearization of the longitudinal phase space. In order to determine the maximum sustainable gradients in normal conducting RF powered particle beam accelerators with extremely low probability of RF breakdown, investigations are in progress for using short accelerating structures in the Ka-band regime. We here report an electromagnetic design of a compact linearizer standing wave (SW) accelerating structure. The cavity has a length of about 8 cm and operates on the π-mode at 35.982 GHz, which is the third harmonic with respect to the Linac frequency (11.994 GHz). The accelerating gradient is 100 MV/m and the cavity geometry is optimized in order to minimize the surface peak electric field
A novel exact analytical expression for the magnetic field of a solenoid
No full textIn this paper we present the analytical calculations to derive the magnetic field of a solenoid by solving exactly a fractional integral with the use of a novel method. Starting from the Biot-Savart law, we consider a coil of negligible thickness with a stationary electric current. We derive the expressions of the on- and off-axes magnetic field components. The results have been compared to some simplified and known analytical formulae as well as to a commercial numerical code showing a good agreement
A syncytium model for the interpretation of the phenomenon of anomalous light flashes occuring in the human eye during space mission
No full textThe use of a syncitium model of the cristalline lens of the eye as a new tool to study the light flashes phenomenon seen by astronauts
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