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

Active lower order mode damping for the four rod LHC crab cavity

The high luminosity upgrade planned for the LHC requires crab cavities to rotate bunches into alignment at the interaction points. They compensate for a crossing angle near to 500~$\mu$Rad. It is anticipated that four crab cavities in succession will be utilized to achieve this rotation either side of each IP in a local crossing scheme. A crab cavity operates in a dipole mode but always has an accelerating mode that may be above or below the frequency of the operating mode. Crab cavities are given couplers to ensure that unwanted acceleration modes are strongly damped however employing standard practice these unwanted modes will always have some level of excitation. Where this excitation has a random phase it might promote bunch growth and limit beam lifetime. This paper sets out a method for active control of the phase and amplitude of the unwanted lowest accelerating mode in the crab cavities. The paper investigates the level of suppression that can be achieved as a function cavity quality factor and proximity to resonance

Design and simulation studies of the novel beam arrival monitor pickup at Daresbury Laboratory

We present the novel beam arrival monitor pickup design currently under construction at Daresbury Laboratory, Warrington, UK. The pickup consists of four flat electrodes in a transverse gap. CST Particle Studio simulations have been undertaken for the new pickup design as well as a pickup design from DESY, which is used as a reference for comparison. Simulation results have highlighted two advantages of the new pickup design over the DESY design; the signal bandwidth is 25 GHZ, which is half that of the DESY design and the response slope is a factor of 1.6 greater. We discuss optimisation studies of the design parameters in order to maximise the response slope for bandwidths up to 50 GHz and present the final design of the pickup

W-band klystron upconverter driven by pseudospark-sourced electron beam

In this paper, a three-cavity klystron upconverter operating at W-band is presented. It is predicted to generate 40 W when driven by a 30 kV, 0.2 A electron beam. Pseudospark-sourced electron beam after post-acceleration was proposed to be used with the klystron upconverter because it has the advantage of low energy spread, high current density, and no need of any external guiding magnetic field

W-band klystron upconverter driven by pseudospark-sourced electron beam

In this paper, a three-cavity klystron upconverter operating at W-band is presented. It is predicted to generate 40 W when driven by a 30 kV, 0.2 A electron beam. Pseudospark-sourced electron beam after post-acceleration was proposed to be used with the klystron upconverter because it has the advantage of low energy spread, high current density, and no need of any external guiding magnetic field

High gradient testing of an X-band crab cavity at XBOX2

CERN’s Compact linear collider (CLIC) will require crab cavities to align the bunches to provide effective head-on collisions. An X-band quasi-TM11 deflecting cavity has been designed and manufactured for testing at CERN’s Xbox-2 high power standalone test stand. The cavity is currently under test and has reached an input power level in excess of 40MW, with a measured breakdown rate of better than 10-5 breakdowns per pulse. This paper also describes surface field quantities which are important in assessing the expected BDR when designing high gradient structures

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%