Articles written in Pramana – Journal of Physics

    • Planar electron beams in a wiggler magnet array

      Arti Hadap K C Mittal

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      Transport of high current (∼kA range with particle energy $\sim 1$ MeV) planar electron beams is a topic of increasing interest for applications in high-power (1–10 GW) and high-frequency (10–20 GHz) microwave devices such as backward wave oscillator (BWO), klystrons, gyro-BWOs, etc. In this paper, we give a simulated result for transport of electron beams with velocity $V_{b} = 5.23 \times 10^{8}$ cm s-1 , relativistic factor $\gamma = 1.16$, and beam voltage = ∼80 kV in notched wiggler magnet array. The calculation includes self-consistent effects of beam-generated fields. Our results show that the notched wiggler configuration with ∼6.97 kG magnetic field strength can provide vertical and horizontal confinements for a sheet electron beam with 0.3 cm thickness and 2 cm width. The feasibility calculation addresses to a system expected to drive for 13–20 GHz BWO with rippled waveguide parameters as width $w = 3.0$ cm, thickness $t = 1.0$ cm, corrugation depth $h = 0.225$ cm, and spatial periodicity $d = 1.67$ cm.

    • Investigation of non-uniform magnetic field on the beam particle energy exchange


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      This paper investigates the effect of a non-uniform magnetic field on beam particle energy exchange with three-dimensional particle-in-cell (3D-PIC) simulations. For this investigation, high current (kA range) planar sheet beam-driven rippled rectangular waveguide (RRWG) has been considered. For PIC simulations, beam current density was varied by changing the cathode cross-section (CS) in terms of thickness (beam thickness (BT)) with a common cathode width of 10 mm. There are four BTs (1 mm, 2 mm, 3 mm and 4 mm) and for each BT, seven types of magnetic field lines with the same magnitude of 0.6 T are used. These include one uniform magnetic field andsix non-uniform magnetic field patterns. In this paper, the complete structural design of RRWG to generate output power up to around 45 MegaWatt (MW) with a particular type of non-uniform magnetic field pattern/periodicity to guide the sheet electron beam-driven RRWG is discussed. The application of a non-uniform magnetic field pattern to a 2D sheet electron beam with spatial distribution or periodicity at minimum gaps (typically ≤ 1 mm) leads to the enhancement in output power at voltages operational in the backward region of the device.

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