An 20 kV, 210 mA electron gun for a sheet beam traveling wave tube have been designed. BFE and anode dimensions are optimized using CST code to converge the beam coming from planar cathode of rectangular size 1.2 mm×1 mm. The beam waist is formed at 11.2 mm from the cathode with the beam size of 1.1 mm× 0.22 mm. Novel PPM focusing system is designed for stable transport of the beam. In this case no side magnets are used and pole-pieces are extended after beam edge. Absence of side magnets will reduce the cost of magnetic material, weight of the tube and make easier to insert couplers. The horizontal position of extended pole-piece is after 5 mm from the side wall of the drift tube tunnel in order to make mechanically possible to extend the pole-pieces. NdFeB magnates with Br value 1.4 T are considered. The shielding pole piece is extended towards cathode region to get Brillouin flow. Beam transmission is achieved more than 95% up to 40 mm and 90% up to 70 mm in a tunnel suitable for W-band sheet beam TWT.

Closed short periodic cusped magnets consisting of miniature permanent magnets of material NdFeB 35H have been designed for transporting the sheet electron beam suitable for vacuum subterahertz devices. The aspect ratio of the magnetic tunnel is selected as 2 to provide proper focusing force in both horizontal and vertical directions. Numerical analysis performed by CST Particle Studio shows that both the peak value of the magnetic field and the nature of variation of the transverse components of the magnetic field along their respective transverse directions depend on the transverse thickness of the magnets. The peak value of the magnetic field increases by increasing the transverse thickness of the magnets. When the magnetic period, axial thickness, and transverse thickness of the magnets are 3.4, 1.3, and 8 mm, respectively, the simulated peak value of the magnetic field is 0.131 T. Under the tunnel of the aforementioned structure, the sheet electron beam of size 3 mm (width) x 0.15 mm (height), current density 100 A/cm(2), and kinetic energy 20 keV transports up to a 60-mm distance without any significant instability through the drift tube of tunnel size 5 mm (width) x 0.3 mm (height). When the magnetic period, axial thickness, and transverse thickness of the magnets are 2.8, 1, and 8 mm, respectively, the simulated peak value of the magnetic field is 0.181 T. Under the tunnel of this structure, the sheet electron beam of size 2 mm (width) x 0.1 mm (height), current density 120 A/cm(2), and kinetic energy 20 keV transports up to a 60-mm distance without any significant instability through the drift tube of tunnel size 3 mm (width) x 0.2 mm (height).

This paper presents the design of an eight beam electron gun using OPERA 3D code for pulsed amplifier. The electron gun has to deliver total current 560 (70×8) mA at voltage 6 kV. Each beam has a perveance of 0.15 μP making a total gun perveance of 1.2 μP corresponding to a total beam power of more than 3 kW. The cathode radius is 13.5 mm and individual emitter radius is 1.55 mm having current density 0.92 A/cm2. Focusing has been accomplished through solenoid. The beam pulsing can be accomplished through beam forming electrode relatively at lower negative potential at BFE with respect to cathode. This design has an added feature of cathode protection from ion bombardment with the application of additional ion barrier anode.

Sheet beam transport through closed periodic cusped magnet has been analysed. On the basis of analysis, closed PCM is designed to transport elliptical sheet beam of size 30 mm (width)×1.2 mm (thickness), beam voltage 120 kV, current density 600 A/cm2. This beam is selected for 30 GHz high power sheet beam klystron which has potential application for high gradient LINAC. Selection of aspect ratio of magnetic tunnel and magnetic period is the critical aspect. When aspect ratio of magnetic period is 4:1 and magnetic period is 10 mm, horizontal magnetic force profile matches nearly with horizontal space charge field profile. However, to get desired peak value of magnetic field is very critical. When magnetic period is 10 mm, cross-sectional size of magnetic tunnel is 42.4 mm (width) ×10.6 mm (height), axial thickness of each magnets is 4.2 mm, transverse thickness is 20 mm, the simulated value of magnetic field is 720 G. Above sheet beam with current density 100 A/cm2 transports up to 120 mm distance through this magnetic tunnel without any instability.

A four beam electron gun has been designed for multi-beam klystron using commercially available software OPERA 3D and the optimized beam focusing has been again examined through CST particle studio. This paper represents the effect of radial position of aperture in a pole piece in focusing of multi-beam electron gun. The operating voltage of electron gun is 4 kV with total beam current of 256 (64×4) mA and beam perveance of 1.01 μP which is equally divided among all the beamlets.

This paper represents the design of multi-beam (sixty-beam) electron gun and focusing system for high power, compact klystron. The beam voltage is 4 kV with a total beam current of 513 (8.55 × 60) mA which is equally divided among sixty-beam. Each beam has a perveance of 0.033 μP making a total gun perveance of 2.02 μP corresponding to a total beam power of more than 2 kW. The cathode radius is7 mm and individual emitter radius is 0.2 mm having current density 6.7 A/cm2. The design has been accomplished using OPERA 3D code. All beamlets have individual anode as well as BFE and a common focusing system. Potential difference between cathode and anode is 4 kV. A magnetic field of 1200 Gauss is applied along the beam axis. A major challenge for the development of multi-beam klystron is design and technology for the focusing of off-axis beamlets because off-axis beams are at various azimuths.

The Orotron is a device which is capable of producing moderate (few watts) to high power levels (few kilowatts) of millimeter and sub-millimeter wavelength radiation in the frequency range from GHz to Terahertz. It consists of an open resonator containing rectangular metal grating periodic RF structure and a sheet electron beam. In this paper, 100 GHz RF interaction structure for Orotron has been designed using CST-MWS which is a 3-D e.m. field simulator. The dispersion characteristics of the RF structure are being analyzed which give the information about axial propagation constant (beta) which in turn yield the phase velocity at a particular frequency.