Multi-beam Klystron Research Articles

Experimental study on an X-band coaxial multi-beam relativistic klystron amplifier

The advantages of the tri-axial relativistic klystron amplifier and the multi-beam klystron amplifier are analyzed, and then an X-band coaxial multi-beam relativistic klystron amplifier is designed in order to increase the output microwave power and frequency. Based on the results from partial-in-cell simulation, the experiment is performed on the Sinus accelerator. In experiment, the transmission and bunching of electron beam are analyzed, and then the amplifier is driven by a beam of 5.3 kA at 670 kV, and the maximum output power is 420 MW when input power is 30 kW, and frequency is 9.375 GHz. The experiment proves that a ten kW-level input power can drive the X-band coaxial multi-beam relativistic klystron amplifier to generate more than one hundred MW-level output power.

Analysis and design of X-band coaxial multi-beam relativistic klystron amplifier

The space charge limiting current in cylinder drifting tube and coaxial drifting tube and the energy that could be obtained and also the restrict magnetic field are analyzed, and the results show that it is propitious to change the energy of electron beam into microwave power in the coaxial conduit. The advantages of the tri-axial relativistic klystron amplifier and the multi-beam klystron amplifier are analyzed, then an x-band coaxial multi-beam relativistic klystron amplifier is designed by using a three-dimensional particle simulation software, and the transmition and the bunching of electron beam are analyzed. A 1.23 GW averaged microwave power over the oscillator period is generated by simulation with 600 kV electron beam voltage, 5 kA current and 0.8 T leading magnetic field density, the frequency is 9.37 GHz and the efficiency is 41%.

High-order photonic bandgap reflex klystron using carbon nanotube multi-beam cathode

The oscillation of a high-order mode TM330 is observed in a photonic bandgap multi-beam reflex klystron using nine electron beams generated from a carbon nanotube cathode. One side of a conventional metal cavity was replaced with a dielectric photonic crystal lattice to form a hybrid photonic-bandgap resonator, which uses lattice bandgap effects, resulting in a more uniform field of a higher-order mode, as well as the exclusion of some conventional-cavity-type modes, thereby reducing mode competition. The high-order and multi-beam concepts would be applicable to a terahertz radiation source when the device is micromachined.

Research Progress on X-Band Multibeam Klystron

The Institute of Electronics, Chinese Academy of Sciences, started developing X-band multibeam klystrons (MBKs) in 2000. Three types of X-band MBKs are currently under research and development; two types operate in the fundamental mode (TM010), and the other type operates in a high-order mode (coaxial TM310). These MBKs operate over the frequency range from 8 to 10 GHz and have peak powers of 50-100 kW, average powers of 2.5-5 kW, and bandwidths of 5%. The design considerations and testing results are presented in this paper. The technological problems, including nonhomogeneity of the RF electric field and low beam transmission, are also described. Further research work on the improvement of these MBKs is discussed.

Research Progress on C-band Broadband Multibeam Klystron

Several types of C-band broadband multibeam klystrons (MBKs) are under development at the Institute of Electronics, Chinese Academy of Sciences. These MBKs operate at various C-band frequencies and have peak powers of 30-200 kW, average powers of 2-10 kW, and bandwidths of 4%-7%. The design considerations for obtaining high power and wide instantaneous bandwidths and test results for these MBKs are presented in this paper. The main technical problems, including a power sag in the band, high voltage breakdown, and non-operating mode oscillation, are also discussed. Further research work for improving the performance of these MBKs is described

Exact Expressions of the Orbit-Curvature and Curvature-Radius of the Toroidal/Helical Orbits

Quite recently, a number of multi-beam klystrons (MBK) have been developed experimentally, and at least three different MBK models are already commercially available. Multi-beam klystrons operate at reduced electron-gun voltage, and higher total beam-current than the single-beam designs, thus preventing occasional destructive gun- diode discharges, and increasing the power-efficiency up to ~ 75%. The power-efficiency (measured as the ratio of output microwave power to input DC power) is however still limited, even in MBK, as it is obviously impossible to extract all the microwave energy from a sharply-bunched electron-beam, without having the high space-charge-density of the slowing beam force it into uncontrollable defocusing.

High-accuracy Approximation to the Integrated Length of Toroidal/Helical Orbits

The new innovative concept of High Power Microwave (HPM) Amplifier recently introduced, combines Multi-Beam Klystron (MBK) and Electron Storage-Ring (ESR) technologies, by using closed, multi-turn Toroidal/Helical electron-orbits. The selected toroidal/helical orbit-configuration was defined as a parametric space-curve in three dimensional space R. We get the parametric equations of that orbit. A high-accuracy approximation has now been obtained for the total length of the Toroidal/Helical orbit, that attains much faster numerical computation. Higher accuracy could be attained by using a higher-order expansion of the orbit-length rate-of-increase.

High current density M-type cathodes for vacuum electron devices

We investigated high current density emission capabilities of M-type cathodes used for vacuum electron devices (VEDs). The experimental results of emission and lifetime evaluating in both close-spaced diode structure and electron gun testing vehicles are given. Emission current densities measured in the diode structure at 1020 °C Br in the CW mode were above 10 A/cm 2; while in electron gun testing vehicles, emission current densities were above 8 A/cm 2 in CW mode and above 32 A/cm 2 in pulsed mode, respectively. The current density above 94 A/cm 2 has been acquired in no. 0306 electron gun vehicle while the practical temperature is 1060 °C Br. For a comparison some of the data from I-scandate cathodes are presented. Finally, several application examples in practical travelling wave tubes (TWTs) and multi beam klystrons (MBKs) are also reported.

S-Band Multibeam Klystron With Bandwidth of 10%

A new type of S-band multibeam klystron has been developed at the Institute of Electronics, Chinese Academy of Sciences, China. The main methods for obtaining wide bandwidth include a multibeam electron gun with 18 beams, a periodic permanent magnet focusing system, a wide-band bunching system and filter-load double-gap coupling-cavity output circuit. The design methods and experimental results are given in this paper. The test results show that this device has a peak power of 120-160 kW, a bandwidth of 10%, a gain of 41 dB, a beam voltage of 16 kV, a weight of 45 kg and a length of 700 mm.

A variable high-power multi-beam klystron design

We describe here a 1.497 GHz multi-beam klystron with up to 13 kW of continuous output power, greater than 60% efficiency, and stable linear operation at ∼10% below saturation, whose design is based on direct extrapolation from klystrons operating in our electron accelerators. The beam perveance is individually adjusted with a zero-current control-electrode gun to match the parameters of a specific application, such as superconducting accelerating structures. The 18 beams are guided through six toroidal cavities, five operating at the fundamental and one at the 2nd harmonic, by a reverse periodic permanent magnet focusing system.

Recent progress in Multi-Beam Klystron in IECAS

Recent research progresses in Multi-Beam Klystron (MBK) in IECAS are briefly introduced in the letter. The S-band MBKs of IECAS have peak power of 120–250 kW, average power of 4–9 kW, efficiency of 35–45%, gain of 41–46 dB, beam voltage of 15–19 kV, and weight of 40–45 kg. Some key technical problems of MBK are also described and discussed. Among them, improving the design of MBK to obtain the required bandwidth, raising beam transmission to increase average power, eliminating oscillation and spray spectrum, overcoming window breakdown caused by magic mode, reducing breakdown times of electron.gun, are most important things for the practical MBK. Besides, further research work in MBK in IECAS is commented.

25 MW SMES-based power modulator

Based on a superconducting magnetic energy storage (SMES) a long-pulse klystron modulator has been designed for use in the TESLA Test facility (TTF) at DESY, Hamburg. A prototype with an output power of 25 MW is under development at Forschungszentrum Karlsruhe in cooperation with the office of engineering IbK at Karlsruhe. The system will deliver pulses of up to 130 kV and 1.7 ms pulse length with a flat top of /spl plusmn/0.5% at a repetition rate up to 10 Hz. Some of this new system's main features are the highly dynamic SMES (100 T/s), a switched-mode high voltage power supply (rated 14 kV/45 A), a fast thyristor power switch and an IGCT power switch rated 2.6 kA/14 kV. This demonstration system is to serve alternatively two klystrons of 5 MW RF output or one multibeam klystron of 10 MW RF output. A first set of the system components had been arranged to form a model of the modulator and 1 MW pulses were generated. The SMES and its cryostat have undergone initial testing at DC operation. The data acquisition and control system DOOCS under development at DESY has been adapted to the authors' computer and experimental environment.

Technology and emission properties of dispenser cathode with controlled porosity

We report on a controlled porosity dispenser cathode using a new design and new manufacturing technology. Emission properties of this cathode in the temperature range of 800–1050°C are significantly greater than L, M and MM cathodes. Novel application of such kind of cathodes may be electron sources for multi-beam klystrons, TWTs, linear accelerators etc.