Showing papers on "Klystron published in 2015"

Toward High-Power Klystrons With RF Power Conversion Efficiency on the Order of 90%

Abstract: The increase in efficiency of RF power generation for future large accelerators is considered a high priority issue. The vast majority of the existing commercial high-power RF klystrons operates in the electronic efficiency range between 40% and 55%. Only a few klystrons available on the market are capable of operating with 65% efficiency or above. In this paper, a new method to achieve 90% RF power conversion efficiency in a klystron amplifier is presented. The essential part of this method is a new bunching technique—bunching with bunch core oscillations. Computer simulations confirm that the RF production efficiency above 90% can be reached with this new bunching method. The results of a preliminary study of an $L$ -band, 20-MW peak RF power multibeam klystron for Compact Linear Collider with the efficiency above 85% are presented.

Stability Analysis of a Planar Multiple-Beam Circuit for $W$ -Band High-Power Extended-Interaction Klystron

Abstract: Circuit analysis of a multiple-beam version of a high-power extended-interaction klystron is performed. The circuit is based on the barbell cavity with five coplanar electron beams across the transverse section of the cavity. Although the basic circuit design is straightforward, stable operation is challenging due to the mode competition and the self-oscillation in an oversized multiple-gap cavity driven by multiple beam sources. The 3-D particle-in-cell (PIC) simulation technology and the space-charge wave theory were exploited to analyze the stability. The physical design of the interaction system was accomplished with the beam parameters of voltage 19 kV and of overall current 4 A (0.8 A $\times 5$ ). PIC results show that a power of 11.28 kW can be achieved at a frequency of 94.48 GHz with an instantaneous 3-dB bandwidth of 160 MHz. The corresponding gain and electric efficiency are 55.75 dB and 14.84%, respectively.

High power X-band RF test stand development and high power testing of the CLIC crab cavity

Abstract: This thesis describes the development and operation of multiple high power X-band RF test facilities for high gradient acceleration and deflecting structures at CERN, as re-quired for the e+ e- collider research programme CLIC (Compact Linear Collider). Signif-icant improvements to the control system and operation of the first test stand, Xbox-1 are implemented. The development of the second X-band test stand at CERN, Xbox-2 is followed from inception to completion. The LLRF (Low Level Radio Frequency) system, interlock system and control algorithms are designed and validated. The third test stand at CERN, Xbox-3 is introduced and designs for the LLRF and control systems are pre-sented. The first of the modulator/klystron units from Toshiba and Scandinova is tested. CLIC will require crab cavities to align the bunches in order to provide effective head-on collisions. An X-band travelling wave cavity using a quasi-TM11 mode for deflection has been designed, manufactured and tested at the Xbox-2 high power test stand. The cavity reached an input power level in excess of 50 MW, at pulse widths of 150 ns with a measured breakdown rate (BDR) of better than 10-5 breakdowns per pulse (BDs/pulse). At the nominal pulse width of 200 ns, the cavity reached an input power level of 43 MW with a BDR of 10-6 BDs/pulse. These parameters are well above the nominal design pa-rameters of an input power of 13.35 MW with a 200 ns pulse length. This work also de-scribes surface field quantities which are important in assessing the expected BDR when designing high gradient structures.

Experimental Realization of the High-Harmonic Gyrotron Oscillator With a Klystron-Like Sectioned Cavity

Abstract: High-harmonic terahertz-frequency-range gyrotrons require long-length operating cavities due to both weak electron-wave coupling and relatively low electron currents. Since diffraction $Q$ -factors of such cavities are very high, a great share of the radiated RF power is spent to ohmic losses. A sectioned klystron-like cavity was proposed as a way to combine a long electron-wave interaction region with a relatively low diffraction $Q$ -factor. In this brief, results of the first experiment under the high-harmonic gyrotron with the klystron-like cavity are reported. In this experiment, selective operation of the gyrotron at the second (0.55 THz) and the third (0.74 THz) cyclotron harmonics has been observed.

Experimental demonstration of enhanced self-amplified spontaneous emission by an optical klystron.

Abstract: We report the first experimental evidence of enhancement of self-amplified spontaneous emission, due to the use of an optical klystron. In this free-electron laser scheme, a relativistic electron beam passes through two undulators, separated by a dispersive section. The latter converts the electron-beam energy modulation produced in the first undulator in density modulation, thus enhancing the free-electron laser gain. The experiment has been carried out at the FERMI facility in Trieste. Powerful radiation has been produced in the extreme ultraviolet range, with an intensity a few orders of magnitude larger than in pure self-amplified spontaneous emission mode. Data have been benchmarked with an existing theoretical model.

Harmonic Content in the Beam Current in a Traveling-Wave Tube

Abstract: In a klystron, charge overtaking of electrons leads to an infinity of ac current on the electron beam. This paper extends the klystron theory of orbital bunching to a traveling-wave tube (TWT). We calculate the harmonic content of the beam current in a TWT that results from an input signal of a single frequency. We assume that the electron orbits are governed by Pierce’s classical three-wave, linear theory. The crowding of these linear orbits may lead to charge overtaking and, therefore, harmonic generation on the beam current, as in a klystron. We analytically calculate the buildup of harmonic content as a function of tube length from the input, and compare the results with the CHRISTINE code. Good agreement is found. Also found is the surprisingly high level of harmonic contents in the electron beam current, even when the TWT operates in the small signal regime. A dimensionless bunching parameter for a TWT, $X={(2P_{\rm{ in}}/(P_{b} C))}^{1/2}$ , is identified, which characterizes the harmonic content in the ac beam current, where $P_{{\textrm {in}}}$ is the input power of the signal, $P_{b}$ is the dc beam power, and $C$ is Pierce’s gain parameter.

The 3D split-ring cavity lattice: a new metastructure for engineering arrays of coupled microwave harmonic oscillators

Abstract: A new electromagnetic cavity structure, a lattice of 3D cavities consisting of an array of posts and gaps is presented. The individual cavity elements are based on the cylindrical re-entrant (or Klystron) cavity. We show that these cavities can also be thought of as 3D split-ring resonators, which is confirmed by applying symmetry transformations, each of which is an electromagnetic resonator with spatially separated magnetic and electric field. The characteristics of the cavity is used to mimic phonon behaviour of a one-dimensional (1D) chain of atoms. It is demonstrated how magnetic field coupling can lead to phonon-like dispersion curves with acoustical and optical branches. The system is able to reproduce a number of effects typical to 1D lattices exhibiting acoustic vibration, such as band gaps, phonon trapping, and effects of impurities. In addition, quasicrystal emulations predict the results expected from this class of ordered structures. The system is easily scalable to simulate two-dimensional and 3D lattices and shows a new way to engineer arrays of coupled microwave resonators with a variety of possible applications to hybrid quantum systems proposed.

Hybrid design optimization of high voltage pulse transformers for Klystron modulators

Abstract: This paper presents a generic hybrid optimization methodology based on space mapping techniques for the design of various high voltage pulse transformer structures used in klystron modulators. It is using two dimensioning models with different levels of complexity: a coarse model based on 2D FEA less accurate but cheaper to evaluate and a fine 3D FEA model more accurate but time consuming. A specific correction mechanism is applied to align the 2D FEA dimensioning model with the more accurate 3D FEA dimensioning model. With a suitable selection of the correction factors, the convergence of this hybrid optimal design methodology is obtained with a limited number of time consuming 3D FEA simulations. The method is applied to the optimal design of a monolithic high voltage pulse transformer for the CLIC klystron modulator. The influence of the klystron operating voltage on the size of the optimal pulse transformer is evaluated with the proposed design methodology.

Dataset to support article: 'Dynamic nuclear polarization enhanced NMR at 187 GHz/284 MHz using an extended interaction klystron amplifier'

Abstract: A Dynamic Nuclear Polarisation (DNP) enhanced solid-state Magic Angle Spinning (MAS) NMR spectrometer which uses a 187 GHz (corresponding to (1)H NMR frequency of 284 MHz) Extended Interaction Klystron (EIK) amplifier as the microwave source is briefly described. Its performance is demonstrated for a biomolecule (bacteriorhodopsin), a pharmaceutical, and surface functionalised silica. The EIK is very compact and easily incorporated into an existing spectrometer. The bandwidth of the amplifier is sufficient that it obviates the need for a sweepable magnetic field, once set, for all commonly used radicals. The variable power (CW or pulsed) output from the EIK is transmitted to the DNP-NMR probe using a quasi-optic system with a high power isolator and a corrugated waveguide which feeds the microwaves into the DNP-NMR probe. Curved mirrors inside the probe project the microwaves down the axis of the MAS rotor, giving a very efficient system such that maximum DNP enhancement is achieved with less than 3 W output from the microwave source. The DNP-NMR probe operates with a sample temperature down to 90K whilst spinning at 8 kHz. Significant enhancements, in excess of 100 for bacteriorhodopsin in purple membrane (bR in PM), are shown along with spectra which are enhanced by ≈25 with respect to room temperature, for both the pharmaceutical furosemide and surface functionalised silica. These enhancements allow hitherto prohibitively time consuming experiments to be undertaken. The power at which the DNP enhancement in bR in PM saturates does not change significantly between 90K and 170 K even though the enhancement drops by a factor of ≈11. As the DNP build up time decreases by a factor 3 over this temperature range, the reduction in T1n is presumably a significant contribution to the drop in enhancement.

An X-band high-impedance relativistic klystron amplifier with an annular explosive cathode

Abstract: The feasibility of employing an annular beam instead of a solid one in the X-band high-impedance relativistic klystron amplifier (RKA) is investigated in theory and simulation. Small-signal theory analysis indicates that the optimum bunching distance, fundamental current modulation depth, beam-coupling coefficient, and beam-loaded quality factor of annular beams are all larger than the corresponding parameters of solid beams at the same beam voltage and current. An annular beam RKA and a solid beam RKA with almost the same geometric parameters are compared in particle-in-cell simulation. Output microwave power of 100 MW, gain of 50 dB, and power conversion efficiency of 42% are obtained in an annular beam RKA. The annular beam needs a 15% lower uniform guiding magnetic field than the solid beam. Our investigations demonstrate that we are able to use a simple annular explosive cathode immersed in a lower uniform magnetic field instead of a solid thermionic cathode in a complicated partially shielding magnetic field for designing high-impedance RKA, which avoids high temperature requirement, complicated electron-optical system, large area convergence, high current density, and emission uniformity for the solid beam. An equivalent method for the annular beam and the solid beam on bunching features is proposed and agrees with the simulation. The annular beam has the primary advantages over the solid beam that it can employ the immersing uniform magnetic field avoiding the complicated shielding magnetic field system and needs a lower optimum guiding field due to the smaller space charge effect.

Analysis and Simulation of a Multigap Sheet Beam Extended Interaction Relativistic Klystron Amplifier

Abstract: To improve the output power and electron efficiency and broaden the operating bandwidth, the three-gap extended output cavity was used in the relativistic klystron to replace the single-gap output cavity. The high-frequency characteristics of the three-gap extended cavity were studied. The electron load conductance was derived and corrected based on the theory of relativity, by which a more accurate relation of electron load conductance versus transmit angle can be obtained. The characteristic impedance is three times bigger than that of the single-gap cavity under the case of the 2 pi mode, which can improve the M-2(R/Q) and the beam-wave interaction efficiency. The model of sheet beam klystron (SBK) is comprised of three-gap input cavity, two-gap first idler, three-gap second idler cavity, and three-gap output cavity. The 3-D particle-in-cell simulation results show that for a 500 kV, 1 kA, 40.134 GHz, and 20 W input power, the SBK is capable of generating an output power higher than 142 MW with the gain of 68.5 dB, maximum interaction efficiency of 28.4%, and 3-dB bandwidth of 240 MHz.

Investigation of an X-band gigawatt long pulse multi-beam relativistic klystron amplifier

Abstract: To achieve a gigawatt-level long pulse radiation power in X-band, a multi-beam relativistic klystron amplifier is proposed and studied experimentally. By introducing 18 electron drift tubes and extended interaction cavities, the power capacity of the device is increased. A radiation power of 1.23 GW with efficiency of 41% and amplifier gain of 46 dB is obtained in the particle-in-cell simulation. Under conditions of a 10 Hz repeat frequency and an input RF power of 30 kW, a radiation power of 0.9 GW, frequency of 9.405 GHz, pulse duration of 105 ns, and efficiency of 30% is generated in the experiment, and the amplifier gain is about 45 dB. Both the simulation and the experiment prove that the multi-beam relativistic klystron amplifier can generate a long pulse GW-level radiation power in X-band.

Design and optimization of a W-band extended interaction klystron amplifier

Abstract: A three dimension high frequency circuit of an W band extended interaction klystron amplifier (EIA) is designed. With an electron beam of 17 kV and 0.34 A, and an input microwave power of 30 mW at 94.77 GHz, an average power of 580 W with power conversion efficiency of 10.03%, gain of 42.6 dB, 3dB Instantaneous bandwidth of more than 150 MHz is obtained. However, a peak output power of 50 mW is obtained by experiment. Based on the experiment result, optical system and RF circuit are optimized. Via optimization, a beam transmission of 100% is achieved, and with an electron beam of 18 kV and 0.28 A, and an input microwave power of 30 mW at 94.95 GHz, an average power of 374 W is obtained.

Two-frequency heating technique at the 18 GHz electron cyclotron resonance ion source of the National Institute of Radiological Sciences

Abstract: The two-frequency heating technique was studied to increase the beam intensities of highly charged ions provided by the high-voltage extraction configuration (HEC) ion source at the National Institute of Radiological Sciences (NIRS). The observed dependences on microwave power and frequency suggested that this technique improved plasma stability but it required precise frequency tuning and more microwave power than was available before 2013. Recently, a new, high-power (1200 W) wide bandwidth (17.1-18.5 GHz) travelling-wave-tube amplifier (TWTA) was installed. After some single tests with klystron and TWT amplifiers the simultaneous injection of the two microwaves has been successfully realized. The dependence of highly charged ions (HCI) currents on the superposed microwave power was studied by changing only the output power of one of the two amplifiers, alternatively. While operating the klystron on its fixed 18.0 GHz, the frequency of the TWTA was swept within its full limits (17.1-18.5 GHz), and the effect of this frequency on the HCI-production rate was examined under several operation conditions. As an overall result, new beam records of highly charged argon, krypton, and xenon beams were obtained at the NIRS-HEC ion source by this high-power two-frequency operation mode.

RF Breakdown of 805 MHz Cavities in Strong Magnetic Fields

Abstract: Ionization cooling of intense muon beams requires the operation of high-gradient, normal-conducting RF structures in the presence of strong magnetic fields. We have measured the breakdown rate in several RF cavities operating at several frequencies. Cavities operating within solenoidal magnetic fields B > 0.25 T show an increased RF breakdown rate at lower gradients compared with similar operation when B = 0 T. Ultimately, this breakdown behavior limits the maximum safe operating gradient of the cavity. Beyond ionization cooling, this issue affects the design of photoinjectors and klystrons, among other applications. We have built an 805 MHz pillbox-type RF cavity to serve as an experimental testbed for this phenomenon. This cavity is designed to study the problem of RF breakdown in strong magnetic fields using various cavity materials and surface treatments, and with precise control over sources of systematic error. We present results from tests in which the cavity was run with all copper surfaces in a variety of magnetic fields.

Ultra-precise short-pulse modulator for a 50MW RF output klystron for free-electron lasers

Abstract: Power modulators are used in a wide area of applications as for example collision experiments, generation of powerful light pulses, medical applications, water treatment or military applications. Typically, PFN or PFL modulators are used at high pulsed powers. However, the used switches have a low lifetime and the modulator needs to be tuned during commissioning. Furthermore, the pulse length is fixed. Because of these reasons, PFN/PFL modulators are more and more replaced by solid state modulators. Some types of semiconductor switches are turn-off capable which allows a variable pulse length. In the case of a load arc, the modulator can be turned off immediately to minimize the short circuit energy. This work describes the design and test results of an ultra precise 120 MW short-pulse modulator. The modulator generates a pulse of 370 kV with a rise time of less than 1μs and a nominal flat-top length of 3μs. The repetition rate is 100 Hz. It drives the klystrons feeding the LINAC of a free-electron laser at PSI (SwissFEL). The key requirement of the modulator is the flat-top stability. To achieve the required beam quality, a rms flat-top stability of 10 ppm is required. It is influenced by factors with random characteristics such as switching signal jitter or measurement noise. Especially the energy storage needs to be charged precise since it directly influences the flat-top. Component tolerances or temperature drifts do not need to be considered because they can be compensated. The first chapter gives a short overview on the application. Furthermore, existing modulator concepts are introduced. Two different types of modulators, namely the Marx-generator and pulse transformer based systems, are investigated more detailed. Based on these results, a pulse transformer based solution is selected. The modulator consists of twelve pulse generators connected to a split core transformer with six cores. The pulse generators include an active core reset circuit, eliminating the need of an additional winding. Since the IGBTs are operated at a pulsed current of 4 kA, a gate unit with fast over-current detection is developed and tested. The pulse transformer is designed based on the mechanical constraints given by the pulse generators. The pulse transformer is the key component of the system which defines the pulse shape. The leakage inductance and the distributed capacitance are determined by a 2D-FEM simulation. Moreover, the balancing of the IGBT collector currents is

VELA Machine Development and Beam Characterisation

Abstract: Recent developments on the VELA (Versatile Electron Linear Accelerator) RF photo-injector at Daresbury Laboratory are presented. These are three-fold; commissioning/installation, characterising and providing beam to users. Measurements for characterising the dark current (DC), 4-D transverse emittance, lattice functions and photoinjector stability are presented. User beam set ups to provide beam for electron diffraction and Cavity Beam Position Monitor development are summarised. INTRODUCTION VELA is a facility designed to provide a high quality electron beam for accelerator systems development, industrial and scientific applications. It comprises of a 2.5 cell S-band photocathode gun with copper photocathode providing beam to experiments in the accelerator hall and 2 dedicated user areas. More information on the layout, design and early commissioning can be found in [1,2]. INSTALLATION & COMMISSIONING As well as first commissioning of a second user area, Beam Area 2, in preparation for users in May 2015 a number of new devices were installed, including, a copper cathode, gun klystron, and transverse deflecting cavity (TDC).

X wave band over-mode relativistic klystron amplifier

Abstract: The invention discloses an X wave band over-mode relativistic klystron amplifier, which comprises an annular cathode, a resonant reflector, an input cavity, a first section of drift tube, a wave absorbing material, a buncher cavity, a second section of drift tube, an output cavity and a magnetic field coil, wherein the annular cathode is arranged at the most significant end of the structure and emits annular relativistic electron beams outwards under the action of high voltage pulse, the resonant reflector, the input cavity, the first section of drift tube, the wave absorbing material, the buncher cavity, the second section of drift tube and the output cavity are sequentially arranged at rear of the annular cathode, the magnetic field coil is installed at the periphery of the whole structure, the working mode of the resonant reflector, the input cavity, the buncher cavity and the output cavity is a TM02 mode, and the first section of drift tube and the second section of drift tube can transmit a TM01 mode The X wave band over-mode relativistic klystron amplifier can produce high power X wave band microwave

High-Power RF Testing of 1-MW, 352.2-MHz Continuous Wave Klystron Amplifier

Abstract: A 1-MW, 352.2-MHz continuous wave (CW) radio frequency (RF) test stand based on TH 2089 klystron amplifier is developed and tested up to its rated power. Klystron amplifier demands stringent performances from its beam bias power supply for its proper operation. A novel crowbar less solid-state modular topology is adopted for −100-kV, 25-A dc beam bias power supply and its achieved performance parameters are presented in this paper. Wire burn test, which is crucial for CW klystron amplifier, was conducted on this power supply to ensure that its stored energy during klystron arcing is less than 20-J. The criterion for the selection of test wire is also presented. A real-time control system is developed for proper sequence of operation of various power supplies as well as for control and monitoring of crucial parameters of this test stand. The testing of this high-power klystron amplifier is quite involved in nature and various tests have been carried out under several operating conditions before it is employed in the high-power RF test stand. This paper studies and analyzes the effect of variations of various parameters on the performance of this high-power klystron amplifier. Variation of output power and RF gain against RF input power as well as variation of RF phase over beam voltage is presented. Variations of RF output power against frequency, beam voltage, beam current, and mod-anode voltage are also presented. Heat run test was conducted on this klystron amplifier for 24 h to ensure its reliability.

Analysis and Suppression of High-Order Mode Oscillation in an S-Band Klystron

Abstract: High-order mode oscillation occurred in an S-band experimental klystron with 300 MHz instantaneous bandwidth. The cause of the oscillation was analyzed and simulated. A method was proposed to suppress the oscillation through adjusting the structure and size of a resonant cavity in the tube, in which the high-order mode frequency can obviously be changed and the variation of the fundamental mode frequency is very small. Improved designs for the resonant cavity with Ansoft HFSS code and corresponding experiment have been performed, which shows that the simulation results are in good agreement with the experimental measurements. The testing result of an experimental klystron with this improved resonant cavity indicates that the high-order mode oscillation can effectively be suppressed.

MPC based supervisory control design for a Free Electron Laser

Abstract: This paper develops a Model Predictive Control based approach for controlling multiple Radio Frequency (RF) stations in a Free Electron Laser (FEL). Each RF station includes a klystron which delivers high RF power, of the order of 50 megawatts, to feed the cavities in which the electron beam is accelerated. A local PID controller at each RF station controls the RF voltage measured at the local cavities. The proposed MPC scheme acts as a supervisory control to keep the beam energy constant by adjusting the set points of the local PID loops. The concept has been successfully tested at the SwissFEL injector test facility with three full-scale RF stations.

Investigation of using shrinking method in construction of Institute for Research in Fundamental Sciences Electron Linear Accelerator TW-tube (IPM TW-Linac tube)

Abstract: Due to Iran's growing need for accelerators in various applications, IPM's electron Linac project has been defined. This accelerator is a 15 MeV energy S-band traveling-wave accelerator which is being designed and constructed based on the klystron that has been built in Iran. Based on the design, operating mode is π /2 and the accelerating chamber consists of two 60cm long tubes with constant impedance and a 30cm long buncher. Amongst all construction methods, shrinking method is selected for construction of IPM's electron Linac tube because it has a simple procedure and there is no need for large vacuum or hydrogen furnaces. In this paper, different aspects of this method are investigated. According to the calculations, linear ratio of frequency alteration to radius change is 787.8 MHz/cm, and the maximum deformation at the tube wall where disks and the tube make contact is 2.7μ m. Applying shrinking method for construction of 8- and 24-cavity tubes results in satisfactory frequency and quality factor. Average deviations of cavities frequency of 8- and 24-cavity tubes to the design values are 0.68 MHz and 1.8 MHz respectively before tune and 0.2 MHz and 0.4 MHz after tune. Accelerating tubes, buncher, and high power couplers of IPM's electron linac are constructed using shrinking method.

High-power extended-interaction klystron with ladder-type structure

Abstract: The characteristics of the planar ladder-type multi-gap resonant cavity are investigated,including the mode distribution,characteristic impedance( R / Q),coupling coefficient and the operating stability. The high-frequency interaction system for a W-band high-power extended interaction klystron was designed. The nonlinear performances such as the saturated power,gain,efficiency,as well as bandwidth are predicted by using the three-dimension Particle-in-Cell technology. The modulation and bunching of the beam and the physics of the interaction between the beam and the multigap resonant cavity were explored. PIC simulation results showthat the output power is up to 1. 8 k W at the frequency of94. 52 GHz with the voltage of 16 k V and beam current of 0. 6 A. This power corresponds to a gain of 47. 7 d B and an efficiency of 19. 4% respectively. The sweep-frequency simulations with the same drive power showthat the 3-d B bandwidth of 210 M Hz can be achieved.

A new compact self-coherent high power microwave source based on dual beams

Abstract: In this paper, a compact self-coherent high power microwave source based on dual beams is presented. It consists of a two-cavity triaxial klystron amplifier (TKA) (noted as the outer sub-source below) and a multiwave Cerenkov generators (noted as the inner sub-source) inserted in the TKA's inner conductor. These two sub-sources share a common cathode and the magnetic field. The injected signals to the outer sub-source are leakage microwaves from the inner sub-source through the anode-cathode gap (A-K gap). Particle-in-cell simulation shows that when the diode voltage is 687 kV and the axial magnetic field is 0.8 T, two microwaves with power of 1.02 GW and 2.65 GW and the same frequency of 9.72 GHz are generated in the inner and the outer sub-source, respectively; the corresponding power efficiencies are 24% and 31%. Two sub-sources reach the phase locking at 23 ns with a phase difference fluctuation within ±3°. The fast and stable phase locking in the voltage ranging from 665 kV to 709 kV further suggests that the proposed source is promising for coherent power combination and to export a higher power of combined microwaves.

Electron beam gun with kinematic coupling for high power RF vacuum devices

Abstract: An electron beam gun for a high power RF vacuum device has components joined by a fixed kinematic coupling [8a] to provide both precise alignment and high voltage electrical insulation of the components. The kinematic coupling [8a] has high strength ceramic elements directly bonded to one or more non-ductile rigid metal components using a high temperature active metal brazing alloy. The ceramic elements have a convex surface that mates with concave grooves [9] in another one of the components. The kinematic coupling, for example, may join a cathode assembly and/or a beam shaping focus electrode [6, 7] to a gun stem [10], which is preferably composed of ceramic. The electron beam gun may be part of a high power RF vacuum device such as, for example, a gyrotron, klystron, or magnetron.

Influence of High-Frequency Characteristic of a Cavity on the Phase Shift in the Relativistic Klystron Amplifier

Abstract: The influences of the eigenfrequency and the intrinsic quality factor of a cavity on the phase shift in the relativistic klystron amplifier (RKA) are investigated. An analytical expression is derived to describe the phase of the gap voltage in a cavity. The theoretical and simulation results indicate that the eigenfrequency of the buncher cavity can significantly affect the phase shift of the output microwave in the RKA. In contrast, the influences of the eigenfrequency and the intrinsic quality factor of the output cavity on the phase shift of the RKA are small. The analytical expression can effectively estimate the phase difference among different RKAs resulting from the machining and assemblage inconformity in the experiment. It is suggested that the differences among the eigenfrequencies of the buncher cavities should be managed in 0.1% of the operation frequency to achieve phase locking among different RKAs.

Microwave induced plasma discharge in multi-cell superconducting radio-frequency cavity

Abstract: A R&D effort for in situ cleaning of 1.5 GHz Superconducting Radio Frequency (SRF) cavities at room temperature using the plasma processing technique has been initiated at Jefferson Lab. This is a step toward the cleaning of cryomodules installed in the Continuous Electron Beam Accelerator Facility (CEBAF). For this purpose, we have developed an understanding of plasma discharge in a 5-cell CEBAF-type SRF cavity having configurations similar to those in the main accelerator. The focus of this study involves the detailed investigations of developing a plasma discharge inside the cavity volume and avoids the breakdown condition in the vicinity of the ceramic RF window. A plasma discharge of the gas mixture Ar–O2 (90%:10%) can be established inside the cavity volume by the excitation of a resonant 4π/5 TM010-mode driven by a klystron. The absence of any external magnetic field for generating the plasma is suitable for cleaning cavities installed in a complex cryomodule assembly. The procedures developed in these experimental investigations can be applied to any complex cavity structure. Details of these experimental measurements and the observations are discussed in the paper.

Design of Magnetron power source from three phase supply

Abstract: Electromagnetic radiations are phenomena that takes the form of self propagating waves in a vacuum or in matter. Microwaves are a part of the electro-magnetic (EM)radiation spectrum, with a frequency range of 300Mhz to 300Ghz.Microwave heating is applied in ceramics, Metallic powder, Food products, Wood, Polymers, Rubber, Textile & Paper. Various sources of microwaves include the Magnetron, Klystron, Travelling-wave tube (TWT) and gyrotron. These devices work in the density modulated mode rather than the current modulated mode. This means that they work on the basis of clumps of electrons flying through them, rather than using a continuous stream. The scope of this project work requires us to focus on such a device namely Magnetron.

Power supply design for Magnetron power source from single phase supply

Abstract: Electromagnetic radiations are phenomena that take the form of self propagating waves in a vacuum or in matter. Microwaves are a part of the electro-magnetic (EM) radiation spectrum, with a frequency range of 300Mhz to 300Ghz.Microwave heating is applied in ceramics, Metallic powder, Food products, Wood, Polymers, Rubber, Textile & Paper. Various sources of microwaves include the Magnetron, Klystron, Travelling-wave tube (TWT) and gyrotron. These devices work in the density modulated mode rather than the current modulated mode. This means that they work on the basis of clumps of electrons flying through them, rather than using a continuous stream. The scope of this project work requires us to focus on such a device namely Magnetron.