MAGIC-2D simulations of high efficiency hollow beam klystrons

Results from MAGIC-2D simulations of hollow beam, 800 MHz klystrons, with efficiencies on the order of 85% are presented. Such tubes employ the core oscillation method of electron bunching, which allows for most electrons in the beam to be contained within the bunch at the output cavity. By moving towards hollow beam geometries, the bunch at the output cavity presents a favourable phase and spatial profile for energy extraction, and thus, the overall tube efficiency can be maximised

Numerical design of high efficiency klystrons using core oscillation bunching

1-D and 2-D numerical simulations of 800 MHz klystrons with efficiencies approaching 90% are presented. While traditional klystrons employ monotonic electron bunching along their lengths, the core oscillation method allows for an improved bunch shape at the output cavity, facilitating maximum energy extraction. The core oscillation bunching scheme proves an attractive method for attaining high efficiency operation in klystrons, which can be used to reduce the power consumption of future particle accelerators

Analytical and Numerical Simulation of Multipactor within a Helical Resonant Filter

Multipactor analysis of a helical resonant filter has been performed using CST Particle Studio and analytically using a 1-D particle tracking code, based on the Runge-Kutta-Nystrom method. A comparison of results is presented

Particle-in-cell simulation of second and third harmonic cavity klystron

This paper outlines the results obtained from Magic software for the CSM_23 (Core Stabilization Method) klystron. This klystron implements the use of a second and third harmonic klystron to increase the efficiency. From the PIC simulation an efficiency of 78.1% was achieved

MAGIC2-D simulations of high efficiency klystrons using the core oscillation method

Klystrons employing traditional monotonic electron bunching are capable of efficiencies up to ~70%. The use of the core oscillation method (COM) of electron bunching has predicted a significant improvement in efficiency towards 90%. Here, we document refinements on previously presented geometries, with PIC simulations predicting efficiencies up to 85%

Transnational marriages in Yiwu, China: tensions over money

In this article, I explore the role of transnational marriages in the activities and strategies of trading networks, through the lens of money and uncertainty in marriage. I argue that uncertainty in spousal relations challenges the durability of such unions and hence the effectiveness of their role in trading activities. These uncertainties are shaped by intertwined factors, including especially the embedded relationship between commercial and social networks (for example, business partners, kinship, friendship) and spousal relations, the differing cultural values and practices of the partners to such unions, stereotypes, varying forms and degrees of trust and mistrust, and the dynamics of global markets and state policy. Uncertainties driven by these factors exacerbate mistrust in both marriages and trading relations; they also shape shifting orientations toward future life. Therefore, I argue that the role of marriage in trading activities should be neither simplified nor romanticized

A Millimeter-Wave Klystron Upconverter With a Higher Order Mode Output Cavity

Manufacturing of klystrons in the millimeter-wave frequency range is challenging due to the small size of the cavities and the ratio of the maximum gap voltage to the beam energy. The small dimensions also make difficult to produce devices with the output power required by a number of applications at millimeter wave, such as communications and spectroscopy. Operating with a higher order mode can be a potential solution, as a larger transverse size structure can be used. Unfortunately, high-order mode cavities have a lower impedance than in fundamental mode. In this paper is proposed a novel solution to overcome the reduced impedance by utilizing an upconverter, where all cavities except the output cavity are designed to work in high-order mode. To demonstrate the effectiveness of the approach, two klystron upconverters were designed. One has six cavities aiming to achieve a maximum output power of $~$90 W at 105 GHz. The second klystron upconverter was a simpler three-cavity structure designed for quick prototype. Millimeter-wave measurements of the three-cavity klystron upconverter are presented

Multipactor in 4 rod crab cavities:46th European Microwave Conference, EuMC 2016

Multipactor is a limiting factor in many SRF cavities due to the additional heat load and power absorption. In this paper we study multipactor in 4 rod crab cavities, which have deflecting rather than accelerating fields. The particles are tracked in CST Particle Studio for three different secondary emission yields (SEY) to differentiate between hard and soft multipacting barriers. It is shown that multipacting barriers exist at a transverse voltage of 2 MV for high SEY materials but that these trajectories do not appear with lower SEY materials suggesting that they will process away. © 2016 EuMA

Numerical simulation of high efficiency cylindrical beam klystrons

The High Efficiency International Klystron Activity (HEIKA) collaboration seeks to improve the efficiency of CW klystrons, with an eye to their use as RF sources for future particle accelerators.  Through investigating novel bunching techniques, such as the core oscillation method (COM), and bunching-alignment-collection (BAC) method, klystrons with predicted efficiencies approaching 90% have been demonstrated across numerical codes including AJDISK, MAGIC2-D, KlypWin, TESLA and Klys2D.  Recent numerical results of such devices featuring solid, cylindrical electron beams, will be presented