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Dovbnya, A.N.

Paper Title Page

 Accelerating complex "SALO" 

  • A.N.Dovbnya, I.S.Guk, S.G.Kononenko, F.A.Peev, A.S.Tarasenko (
    National Science Centre "Kharkov Institute of Physics and Technology", Kharkov, Ukraine
  • M. van der Wiel, J.I.M. Botman
    Technische Universiteit Eindhoven, Eindhoven, The Netherlands

During last three years NSC KIPT and Technische Universiteit Eindhoven develop the recirculator project with superconducting accelerating structure TESLA on energy up to 730 MeV. The accelerator will be disposed in existing buildings on linac LU2000 exit. The source of polarized electrons will allow to receive quasicontinuous beams with energy from 250 up to 730 MeV and a current up to 100 microA. RF photogun will accelerate continuous and impulse electron beams with a charge up to 1 nC in one bunch and an average current up to 1 . Base tasks which to be solved with the help of new accelerator: 1. Problems of fundamental nuclear physics 2. Framing accelerator driven sub-critical assembly facility, neutron source and its applications in different fields of science 3. Free electron laser 4. Radiation physics, nuclear physics applications, isotope manufacturing



 A Pulsed Modulator To Energize The Secondary-Emission Electron Source Of The Technological Accelerator 

  • A.N.Dovbnya, V.V.Zakutin, N.G.Reshetnyak, V.P.Romasko, I.A.Chertishchev
    Kharkov Institute of Physics and Technology, Kharkov, Ukraine

Experiments were made to investigate a pulsed modulator intended to energize the electron accelerator based on the secondary-emission electron source. The accelerator with a great pulse length (8 - 40 mks) and a pulse repetition rate up to 10 Hz is designed for material-surface treatment. To form long pulses in the modulator (with reservoir capacitor discharge through a step-up transformer), the nonlinear properties of the pulse-transformer core material are used, while the top of the pulse is formed through summation of a short spike and a flat-topped long-duration pulse. At a load resistance of 4300 Ohm; a voltage pulse with a spike amplitude of ~ 150 kV and a flat-topped pulse with an amplitude of ~ 130 kV of ~ 16 mks duration and a repetition frequency of 3 Hz were obtained. During formation of the beam with a current of ~ 100A the amplitude of the flat part of cathode voltage made ~ 100 kV.




 The Electron Accelerator Based on the Secondaryemission Electron Source for Material-Surface Treatment 

  • N.I.Ayzatskiy, A.N.Dovbnya, V.V.Zakutin, V.N.Boriskin, N.G.Reshetnyak, V.P.Romasko, N.A.Dovbnya
    Kharkov Institute of Physics and Technology, Kharkov, Ukraine

The paper reports the results of experimental studies on formation of electron beams in three types of secondary-emission sources. Experiments were carried out with a magnetron gun having a cylindrical anode (70 mm in diameter): 1) with a smooth cathode (40 mm in diameter) and a modified cathode: 2) with 4 longitudinal seams and 3) composed of 8 copper rods (5 mm in diameter). Parameters of beams were studied and beam indentations were obtained. In the first case the beam formation occurs with a current of ~40 A (at a cathode voltage of 40 kV) and an azimuthal uniformity of 5 %. In the second case, at a field nonuniformity of ~30%, the azimuthal nonuniformity is ~15 A. In the third case, at a field nonuniformity of ~60% there occurs formation of 8 separate beams having the form close to the half-ring and with a total current of ~10A (at a cathode voltage of 30 kV). The beam current amplitude stability in all the cases was 2 ... 5 %.



 Electron Beam Forming In The Magnetron Gun With Secondary-Emission Cathodes Of Different Materials 

  • A.N.Dovbnya, V.V.Zakutin, N.G.Reshetnyak, V.P.Romasko
    Kharkov Institute of Physics and Technology, Kharkov, Ukraine

A magnetron gun with a cold secondary-emission cathode in crossed fields is used as an electron source in the high-energy RF-devices. Experiments were carried out using the secondary-emission cathodes made of different metals: copper, aluminum, titanium, stainless-steel (cathode diameter of 40 mm, gun length of 140 mm). In experiments the electron beam production was observed. It has been established that the beam current dependence on the voltage obeys to the 3/2 law. Experiments demonstrated that despite the fact that the coefficient of secondary emission in the case of aluminum and titanium is less than unity, the processes of secondary-emission multiplication take place, apparently, on the cathode surface oxide layers formed in technical vacuum below 10-5 - 10-6 Torr and with the presence of organic materials inside the chamber.




 Injector of Electron Linac for NESTOR Storage Ring 

  • M.I.Ayzatskiy, A.N.Dovbnya, V.A.Kushnir, V.V.Mytrochenko, A.N.Opanasenko, S.A.Perezhogin, V.F.Zhiglo
    National Science Center "Kharkov Institute of Physic and Technology", Kharkov, Ukraine

Design of the compact S-band injector and results of simulation of particle dynamics are presented in the report. The injector consists of the low-voltage diode electron gun and a bunching system based on the resonant system with the evanescent oscillations. RF field increases in amplitude along the axis in such bunching system. RF power is supplied to the injector through a coaxial coupler. The injector can be supplied with two types of the guns: 25 kV, 250 mA and 25 kV, 1.5 A. The first gun will provide the linac with the electron beam in a long pulse regime (1500 ns) while the second one will be used in a short pulse regime (40 ns). The resonance system of the injector has been optimized to obtain the electron bunches with energy about 1 MeV, phase length less than 20 and energy spread less than 5% (for 70 % particles) at the linac entrance. The coaxial coupler allows applying the solenoid magnetic field along the bunching system. Influence of magnetic field configuration on beam parameters is described.



 Investigation Of Electron Beam Parameters In Magnetron Guns At Reduced Voltages  

  • A.N.Dovbnya, V.V.Zakutin, N.G.Reshetnyak
    Kharkov Institute of Physics and Technology, Kharkov, Ukraine

The paper presents the results from investigations into the generation of electron beams and their parameters in magnetron guns with secondary-emission cathodes. The beam parameters were investigated for two cases. In the first case the magnetron gun cathode diameter was 40 mm, and the anode diameter was 70 mm. In the second case the magnetron gun cathode diameter was 2 mm, and the anode diameter was 7 mm. The experiments have shown that in the first case, with the anode diameter of 70 mm and the cathode voltage of 10 kV, the beam current was 7.5 A. The magnetic field value was 600 Oe. At a cathode voltage of 6 kV the beam current was 3A, however, then the amplitude and the triggering pulse decay rate should be increased to 100 kV/mks. In the second case at a pulse decay of ~1200 kV/mks and a cathode voltage of 7 kV the beam current was 2 A at a magnetic field value of ~3000 Oe. The beam current as a function of the amplitude and the magnetic field distribution was studied.




 The Electron Accelerator Based On The Secondary-Emission Electron 

  • N.G.Reshetnyak, A.N.Dovbnya, M.I.Ayzatskiy, V.N.Boriskin, V.V.Zakutin, V.P.Romasko, I.A.Chertishchev, N.A.Dovbnya
    Kharkov Institute of Physics and Technology, Kharkov, Ukraine

The electron accelerator for radiation technology purposes is being created at the NSC KIPT. The accelerator is designed to have a particle energy up to 200 keV and a beam power up to 5 MWt/cm2 at a voltage pulse duration between 8 and 40 mks and a pulse repetition rate up to 10 Hz. A magnetron gun with a cold secondary-emission cathode in cross fields is used as an electron source. Results are reported from the experiments on electron beam production in the magnetron gun (the diameters of the cathode and anode being 40 mm and 78 mm, respectively). The longitudinal magnetic field was measured to range from 1500 to 2300 Oe. In one of the modes of operation, an accelerated electron energy of ~ 100 keV was obtained (beam current 110 A, duration ~ 16 mks), the power density on the target was ~ 4 MW/cm2. Targets made from different materials (stainless steel, aluminum, etc.) were exposed to radiation.



 RF Electron Guns With Plasma-Assisted Emission Cathodes 

  • M.I.Ayzatskiy, A.N.Dovbnya, I.V.Khodak, V.A.Kushnir, V.V.Mytrochenko
    The National Science Center "Kharkov Institute of Physic and Technology" (KIPT), Kharkov, Ukraine

Electron beams with charge up to 100 nC in a nanosecond current pulse can be generated by photoemission RF guns. Thermal heating of a cathode caused by high power flow density of laser pulse limits the increasing of the pulse charge. The alternative way the high charge can be achieved in RF guns is the application of cathodes with plasma-assisted electron emission. The feature of the cathodes is high emission current density (>102 /cm2). It was proposed earlier to apply in RF guns plasma cathodes based on ferroelectrics. Results of beam dynamics simulation and results of the experimental research of one-cell S-band RF gun operation with driven plasma cathode are considered in the paper. Results of operation of experimental samples of the cathode are provided and analysed.