Hybrid Gun Research Articles

High-brightness megahertz-rate beam from a direct-current and superconducting radio-frequency combined photocathode gun

High-brightness megahertz-rate electron beams are highly desired for cutting-edge applications in many areas of science. Photocathode electron guns capable of generating such beams with low dark current remain to be a challenging field. In this paper, we report breakthroughs with a hybrid gun combining a direct-current gap and a superconducting radio-frequency (SRF) cavity. The gun, employing K2CsSb photocathodes driven by a green laser, delivers a few MeV electron beam at 1 and 81.25 MHz rates with an average current up to 3 mA and a dark current several orders lower than current normal conducting continuous-wave guns. Emittance compensation and multipole field corrections have been applied to achieve a high-quality beam. The achievement will inspire the development of high-brightness SRF guns and promote megahertz-rate beam applications including coherent linac light sources and ultrafast electron diffraction/microscopy. Published by the American Physical Society 2024

Зносостійкі покриття на алюмінієвих сплавах

Aluminum alloys are widely used in industry. Recently, they are used as a replacement for steel for the manufacture of pulleys, gears, columns of hydraulic rotary transmissions of grabs, etc. This reduces the weight of the parts and reduces carbon emissions into the atmosphere. However, aluminum alloys have low abrasive wear resistance, so their use is possible with coatings on the surface. High-speed gas flame spraying (HVOF) was carried out on the equipment (Diamond Jet Hybrid gun). Arc coatings with a thickness of 500 µm were applied using FMI metallizer and FMI-2 powder wire (Cr6Al6B3Fe-base). PEO (oxido ceramic) coatings were synthesized on D16T aluminum alloy in an electrolyte of 3 g/l KOH + 2 g/l liquid glass (sodium silicate) with a pulsed current at a frequency of 50 Hz, with the ratio of the densities of the cathode and anode currents Jc/Ja+15/15 A /dm2. The duration of the PEO process is 60 min. The open porosity of the coatings was determined by the method of hydrostatic weighing. The phase composition of the surface layers was studied using a DRON-3.0 diffractometer. HVOF (VC) and PEO coatings have been found to have 3 to 4 times higher wear resistance than high carbon hardened steel 100Cr6 and 2 times higher than galvanic chromium coatings, but have high energy consumption. Two methods have the lowest energy consumption: electric arc spraying of coatings and hard anodizing. At the same time, the wear resistance of such coatings is significantly lower than that of coatings obtained by the PEO and HVOF (VC) methods. For the restoration of worn parts, the most appropriate methods are HVOF (VC) and electric arc spraying, as they allow applying thick coatings up to 5 mm. Conclusions: It was established that the studied HVOF (VC), PEO, EDP and hard anodized coatings significantly increase the abrasive wear resistance of aluminum alloy parts. HVOF (VC) and electric arc spraying methods can be used to protect new and worn parts from wear. PEO and hard anodizing methods can be used to protect against wear on new parts only. The use of these methods increases the wear resistance of parts made of aluminum alloys to the level of steel and allows replacing steel and cast iron with aluminum alloys with coatings, reducing the weight of parts and carbon emissions into the atmosphere.

6 MeV novel hybrid (standing wave - traveling wave) photo-cathode electron gun for a THz superradiant FEL

A novel 6 MeV hybrid photo-injector has been designed and constructed, based on a smaller-scale prototype previously built in UCLA’s Particle Beam Physics Laboratory. It has been commissioned at Ariel University in Israel as an on-going collaboration between the two universities. This unique, new generation design provides a radically simpler approach to RF feeding of a gun/buncher system, leading to a much shorter beam via velocity bunching owed to an attached traveling wave section of the photo-injector. This design offers better performance in beam parameters, providing a high quality electron beam, with energy of 6 MeV. The hybrid photo-injector was designed to provide emittance of approximately 3 μm, and pulse duration of 150 fs at up to 1 nC per pulse. The hybrid gun is driven by a SLAC XK5 klystron as the high power RF source, and third harmonic of a ∼35 fs IR Laser amplifier (266 nm) to extract electrons from the photo-cathode. The unique electron gun will produce a bunched electron pulse to drive a THz FEL, which will operate at the super-radiant regime, and therefore requires ambitious beam properties. This paper describes the gun and presents experimental results from the gun and its sub-systems, including energy and charge measurements, compared with the design simulations.

High-power RF Conditioning of a Hybrid e-Gun at Ariel University

A novel hybrid photo injector is being commissioned at the Schlesinger center for compact accelerators in Ariel University. The hybrid gun is composed of a standing wave section (3.5 cells) and a traveling wave section (9 cells) in a single structure, and therefore has a much larger inner surface than a typical 1.5 cell electron gun. This gun will be driving a THz Free Electron Laser (FEL), operating at the super-radiance regime, and therefore requires extraordinary beam properties. First operation of the RF gun was in January 2018. High-power RF field entering a metallic cavity can severely damage the RF structure or the RF window. For this reason, in order to achieve the desired high-field gradients in the RF gun, a careful and extensive conditioning work on the gun is required. This is done by applying slowly increasing power levels into the structure, while monitoring the response constantly. To increase the efficiency and safety aspects of the conditioning work, we developed in-house routines and interlocks, controlled by a dedicated software. Methods and information of diagnostics elements in the RF system are presented, and the necessary requirements to simplify the conditioning work are outlined.

Structure and Wear Resistance of VC–FeCr and VC–FeCrСо Coatings Obtained by Supersonic Flame Spraying

We study the wear resistance of the coatings sprayed by the supersonic flame (HVOF) and plasma methods in dynamic vacuum from VC–FeCr and VC–FeCrCo powders obtained by mechanical alloying. The coatings were sprayed by using a Diamond-Jet hybrid gun (propane–oxygen) and JP5000 gun (kerosene–oxygen) installations. It was established that the wear resistance of these coatings is 75–100 times higher than the wear resistance of the D16 base. Moreover, it is 3–5 times higher than for Sh15 steel (HRC 60), 1.3 times higher than for the layer sprayed 80Kh20R3Т flux-cored wire, and 2.5 times higher than for the electric-arc coating from Kh6Yu6R3 powder wire in the case of friction against rigidly fixed abrasive.

Corrosion Behavior of WC-Co Coatings with VC Additions Applied by Thermal Sprayed HVOF

The addition of nanostructured VC particles in coatings WC-Co improves the mechanical properties of cermet processed by the thermal spray technique HVOF. These coatings are used to protect components from wear, high temperature and corrosion. In the other hand these coatings are an alternative to replace chrome plating in aerospace industry. The objective was study the corrosion resistance of bimodal coatings WC-Co-VC applied by thermal spray HVOF with different concentration of VC on AISI 304. Bimodal mixtures were obtained from commercial micro and nanostructured powders. Then it was deposited on AISI 304 using a HVOF hybrid gun and robotized arm. The electrochemical characterization was performed by polarization resistance and potentiodynamic polarization curves. It was determined that the anodic polarization curves the coatings present a tendency to passivation; however, they were more pronounced in sodium hydroxide. Addition of nanostructured VC particles to the cermet WC-12Co didn’t affect its corrosion resistance.

Wear resistance of HVOF sprayed coatings from mechanically activated thermally synthesized Cr3C2–Ni spray powder

In the current study a Cr3C2-Ni spray powder was produced by mechanically activated thermal synthesis. The following aspects were studied: (a) production and characteristics of spray powders, (b) spraying and characteristics of coatings by HVOF, and (c) abrasive wear resistance. A HVOF spray system Diamond Jet Hybrid 2700 (propane hybrid gun from Sulzer Metco) was used for deposition. Coating thickness was approximately 350-400 μm. The structure and composition of the coatings were determined by SEM and the phase composition by XRD methods. Coating surface hardness and microhardness in the cross- section were measured. Abrasive rubber-wheel wear (ARWW) and abrasive erosive wear (AEW) were tested. The wear resistance of the coatings produced from an experimental powder was comparable to that of a similar commercial one.

Progress on the Hybrid Gun Project at UCLA

UCLA/INFN-LNF/Univ. Rome has been developing the hybrid gun which has an RF gun and a short linac for velocity bunching in one structure. After the cavity was manufactured at INFN-LNF in 2012, tests of the gun was carried out at UCLA. The field in the standing wave part was 20% smaller than the simulation but the phase advance was fine. The cavity was commissioned successfully up to 13 MW. The beam test was performed at 11.5 MW and demonstrated the bunch compression.

Temperature Compensation and Improved Ballistic Performance in a Solid-Propellant Electrothermal-Chemical (SPETC) 40-mm Gun

A solid-propellant electrothermal-chemical (SPETC) 40-mm gun has been designed, constructed, and tested in the indoor firing facilities of the Soreq Propulsion Division Laboratory. An external injector device converts the electric energy stored in the capacitors of the pulse forming network (PFN) into a high-temperature plasma jet that penetrates the gun cartridge and boosts the whole ballistic process. However, unlike large-caliber SPETC systems, in which electric energy is limited to ignition purposes, the 40-mm SPETC gun is a genuine hybrid gun with almost equal electric and chemical contributions. There is experimental evidence that this unique feature induces a very peculiar initial propellant temperature compensation mechanism. It seems that when a significant part of the propelling energy comes from the plasma, i.e., electric energy is not only predominant at the ignition stage of the firing but also later on, then the temperature sensitivity of the propellant tends to vanish. A simple theoretical model supports the experimental findings. The large amount of electric energy is also responsible for a recorded ballistic improvement of 15% in the projectile muzzle kinetic energy. Calibrated simulations show that an optimal tailoring of the power pulse shape and suitable propellant grain geometry should further increase by 10% the muzzle kinetic energy. These modifications are in progress and results should be soon available

Multi-scale modeling and analysis of an industrial HVOF thermal spray process

A hybrid (deterministic/stochastic) fundamental model is proposed for the major physico-chemical processes involved in an industrial HVOF thermal spray process (Diamond Jet hybrid gun, Sulzer Metco, Westbury, NY, USA). The model includes continuum type differential equations that describe the evolution of gas and particle temperature and velocity, and a rule-based stochastic simulator that predicts the evolution of the coating microstructure. Regarding gas/particle dynamics, the Reynolds- and Favre-averaged Navier–Stokes equations and the energy balance equations are solved with the renormalization group (RNG) k– ε turbulence model, and the particle trajectories, temperature histories and melting degrees are determined using the fourth-order Runge–Kutta method. On the microscopic particle deposition process, the formation of coating microstructure is captured by the Madejski deformation model and several rules that govern splat formation, solidification and coating growth. Based on the proposed model, a detailed comprehensive parametric analysis is carried out to study the relationship between the key process parameters and the particle in-flight behavior as well as the resulting coating properties.

MULTISCALE MODELING OF HVOF THERMAL SPRAY PROCESS

The major physicochemical processes involved in an industrial HVOF thermal spray process (Diamond Jet hybrid gun, Sulzer Metco, Westbury NY) are studied by a comprehensive multiscale model. The model includes continuum type differential equations that describe the dynamics of gas phase and particles of different sizes, and a rule-based stochastic simulator that predicts the evolution of coating microstructure. On the macroscopic gas/particle dynamics side, the Favre-averaged Navier-Stokes equations and energy balance equations are solved with the renormalization group (RNG) k-ɛ turbulence model, and the particle trajectories, temperature histories and melting degrees are determined using the 4th order Runge-Kutta method. On the microscopic particle deposition side, the formation of coating microstructure is captured by certain rules that encapsulate the main physical features of particle deposition, deformation, solidification and coating growth. Parametric analysis based on the developed multiscale model is carried out to study the relationship between the macroscopic operating conditions and the particle in-flight behavior as well as the resulting coating microstructure.

Diamond Jet Hybrid HVOF Thermal Spray: Gas-Phase and Particle Behavior Modeling and Feedback Control Design

This paper focuses on the modeling and control of an industrial high-velocity oxygen-fuel (HVOF) thermal spray process (Diamond Jet hybrid gun, Sulzer Metco, Westbury, NY). We initially develop a fundamental model for the process that describes the evolution of the gas thermal and velocity fields and the motion and temperature of particles of different sizes and explicitly accounts for the effect of the powder size distribution. Using the proposed model, a comprehensive parametric analysis is performed to systematically characterize the influence of controllable process variables such as the combustion pressure and oxygen/fuel ratio, as well as the effect of the powder size distribution, on the values of the particle velocity, temperature, and degree of melting at the point of impact on the substrate. (These are the variables that directly influence coating microstructure and porosity, which, in turn, determine coating strength and hardness; see the second article of this series for details.) A feedback control system that aims to control the volume-based average particle velocity and melting ratio by directly manipulating the flow rates of fuel, oxygen, and air at the entrance of the HVOF gun is developed and applied to a detailed mathematical model of the process. Closed-loop simulations show that the feedback controller is effective in driving the controlled outputs to the desired set-point values and is also robust with respect to various kinds of disturbances in the operating environment.

Diamond Jet Hybrid HVOF Thermal Spray: Rule-Based Modeling of Coating Microstructure

This paper focuses on the computational modeling and simulation of the microstructure of coatings produced by an industrial high-velocity oxygen-fuel (HVOF) thermal spray process (Diamond Jet hybrid gun, Sulzer Metco, Westbury, NY). On the basis of an understanding of the coating structure and mechanisms of pore formation inside of the coating obtained from experimental studies, a stochastic simulation procedure is used to explore the evolution of the microstructure of the coatings. In the coating growth model, the velocity, temperature, and degree of melting of the particles hitting the substrate are determined by a previously developed mathematical model (first article of this series) describing gas and particle behavior, and the complex characteristics of the thermally sprayed coatings are captured by applying certain basic rules that encapsulate the main physical features of the deposition process. In addition to providing useful insight into pore formation and coating growth, the model is used to mak...

Gun Propulsion Concepts. Part I: Fundamentals

AbstractModern gun propulsion techniques are driven by the desire to increase muzzle kinetic energy as a means to enhance weapon lethality, reduce costs, increase reliability, and improve vulnerability. In recent years, a significant part of research and developmental activities has been focused not only on conventional solid‐propellant and novel liquid‐propellant gun propulsion techniques but also on advanced concepts, particularly those offering substantial performance increase. High performance can be achieved by pure electric systems(coil or rail gun) as well as by combining chemical propulsion either with gasdynamic principles (light gas gun or ram accelerator) or with electrothermal techniques (hybrid gun). Part I of this paper deals with the fundamentals of projectile acceleration techniques. The objective is to provide the basis for understanding gun technology and to lay the basis for assessing present and future developments.

Rotating machines-power supplies for the next generation of EM accelerators

The next generation of electromagnetic launchers (EMLs) will require compact, lightweight power supplies which can generate high-magnitude, repetitive current pulses of a very specific shape. Additionally, a simple, reliable system in which logistic concerns are minimized is required. Rotating machines, in particular compulsators, can meet these needs. The compulsator is a specialized alternator which has been designed to produce a series of high-power pulses. A number of advantages are inherent in the use of these devices for EML applications. In addition to high energy and power density, and the lack of additional power conditioning components, the machines are well-suited for the requirements of an electromagnetic (EM) gun circuit. The compulsator produces an alternating voltage which drives the current pulse through a current zero, achieving the desired pulsewidth. Conceptual designs of compulsator-driven pulsed power systems for use in 18 missions of interest were analyzed. These missions, which are summarized, include a wide variety of projectile masses and launch energies. Power supplies were designed to accommodate five types of launchers for each mission: railguns, coilguns, thermal-electric guns, hybrid guns, and the advanced electric gun. The hybrid gun represents a railgun with a thermal-electric injector and the advanced gun is a hypothetical far-term coilgun. The results of this analysis, including a general description of the compulsator, design assumptions, the methods used to achieve the desired pulse shape,s a discussion of magnetic energy recovery, gyroscopic effects, and scaling information are included. >

A compact CMA spectrometer with axially integrated hybrid electron-ion gun for ISS, AES and sputter depth profile analysis

Abstract Until now, the combined application of electrons and ions in surface analysis required two separate sources for electrons and ions with different incidence angles. The newly developed hybrid electron-ion gun, however, allows bombardment of the same sample area both with noble gas ions and with electrons coming from the same direction. By integrating such a hybrid gun axially in a cylindrical mirror energy analyser (CMA) a sensitive compact single flange spectrometer obtains for ion scattering spectroscopy (ISS), Auger electron spectroscopy (AES), and sputtering all within normal beam incidence. This concept makes accurate beam centring very easy. Additionally, the bombardment from the same direction both for sputtering and for surface analysis brings advantages in depth profiling. The scattering angle for ISS has a constant value of about 138°. The hybrid gun delivers typically an electron beam current of −20 μA at 3 keV for AES, and an ion beam current of +40 nA and +1.2 μA at 2 keV for ISS and sputtering respectively. The switching time between ISS, AES, and sputtering mode is about 0.1 s. So this system is best suited for automatically controlled depth profile analysis. The design and operation of this new system will be described and some applications will be discussed.

The structural design and the electron optics of a hybrid electron-ion gun

Describes a new kind of a particle gun called the hybrid gun. It is able to deliver a finely focused electron or ion beam simply by reversing the polarity of the acceleration voltage. The detailed design features of the gun are given and the electron-ion optical properties are discussed. For typical operation in surface analytical instrumentation the hybrid gun delivers in the electron mode at 3 keV acceleration voltage a beam current of 30 mu A in a spot of 200 mu m FWHM and in the ion beam mode at 2 kV, with an ionisation voltage from 200 to 400 V, a beam current of 0.5 mu A to 3 mu A in a spot of 100 mu m FWHM. The applications of the new gun in surface analytical instrumentation are briefly discussed.