Demonstration of efficient beam-wave interaction for a MW-level 48 GHz gyroklystron amplifier

Abstract

The development of high-frequency RF linear accelerators (linacs) requires consideration of several technological challenges, such as electron bunch linearization. Presented in this paper is the design of the interaction circuit for a 48 GHz MW-level three-cavity gyroklystron amplifier, appropriate for application as a millimeter wave power source in a 4 th harmonic linearizing system for an X-band linac. The output cavity is operated at the cylindrical TE0,2,1 mode, while the input and buncher cavities are operated at the TE0,1,1 mode. The interaction circuit has been designed using a combination of analytical calculations and particle-in-cell (PIC) simulations. The optimized gyroklystron is shown, through simulation, to deliver an output power of up to 2.3 MW with gain of 36 dB and efficiency of 44% at 48 GHz, when driven by a 140 kV, 37 A electron beam.

Design of a 48 GHz Gyroklystron Amplifier

“…In this article, the design of a 48 GHz gyroklystron amplifier has been presented. The preceding results presented in [13] and [14] have been summarized and expanded upon with additional discussion on the phase stability, which has been shown to meet the linearizer requirement if an appropriate modulator is used. The vacuum windows and input coupler have been designed.…”

“…4) The design was verified and reoptimized using particlein-cell (PIC) simulation in MAGIC [24], and the performance was tested over various input parameter sets. The main results described in [13] and [14] show that the gyroklystron's ideal-beam output power is 2.3 MW with a 37 A, 150 kV beam. With the optimized MIG's α-spread of 8.9%, the predicted output power of the gyroklystron is reduced to 2.0 MW.…”

“…By this structure, a rectangular TE 0,1 waveguide mode is converted to a TE 4,1,1 coaxial cavity mode and then to a TE 0,1,1 cylindrical cavity mode. The standard WR22 waveguide (5.69 mm × 2.84 mm) was selected for convenience of manufacture and the cavity dimensions are determined by the optimized interaction circuit [13]. The inner radius of the coaxial section (4 mm) is just larger than the cavity radius accounting for wall thickness.…”

“…Respectively, Nix et al [13] and Zhang et al [14] describe the work performed on the interaction circuit and magnetron injection gun (MIG) for this project. This article presents the detailed design of the other components in the gyroklystron, including the input coupler, vacuum windows, and the thermal analysis of the collector region.…”

Magnetron Injection Gun for High-Power Gyroklystron

“…The gyroklystrons have been used in applications such as radar and particle accelerators. A gyroklystron operating at 48 GHz with 2 MW output power was designed as a potential high-power microwave source to drive a linearizer for H2020 project CompactLight X-ray free-electron laser [11,12]. The beam-wave interaction circuit employed a three-cavity configuration.…”