Development of the QWR Power Coupler for the NICA Injector
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GED PARTICLE ACCELERATORS FOR NUCLEAR TECHNOLOGIES
Development of the QWR Power Coupler for the NICA Injector1 T. A. Lozeevaa, S. V. Matsievskiya,*, M. V. Lalayana, and M. A. Gusarovaa aNational
Research Nuclear University MEPhI (Moscow Engineering Physics Institute), Moscow, 115409 Russia *e-mail: [email protected] Received June 7, 2018; revised June 7, 2018; accepted July 7, 2018
Abstract—A new accelerator complex, Nuclotron based Ion Collider fAcility (NICA), is being created on the basis of the Joint Institute for Nuclear Research (JINR, Dubna, Russia) to study the properties of dense baryonic matter. It is planned to use superconducting sections as part of the accelerator injector NICA. The first of these sections will consist of quarter-wave coaxial resonators, working at a frequency of 162 MHz with β = 0.12 [1, 2]. For effective operation of such resonators, it is necessary to develop a reliable RF power input device. This article describes the power input design, based on a coaxial waveguide. Issues of thermal reliability of the device are considered, and electrodynamic characteristics are presented. Keywords: accelerators of charged particles, superconducting resonators, high-frequency power DOI: 10.1134/S1063778818110133
INTRODUCTION According to the plans for the modernization of the NICA collider injection system [1], the possibility of replacing the LU-20 injector warm accelerator structure with a superconducting cavity system is under consideration. In order to reduce the production cost, the accelerating system is devised to be modular. Each section will consist of several cells with the same phase velocity. The first section in the system will consist of superconducting quarter-wave resonators (QWR) with a reduced phase velocity of 0.12 at a frequency of 162 MHz [2]. For the accelerating superconducting cavity operation, an RF power input (coupler) is required. It is preferable to develop a universal coupler suitable for each group of quarter-wave resonators. Thus, the power input must allow quality factor tuning in the range of (1.5−3) × 105 at 30 kW CW. Additionally, the thermal load on the cryogenic system, introduced by the coupler, should be minimal. In this paper, the design of the power input device based on a coaxial waveguide (Fig. 1) is presented, issues of vacuum and thermal reliability are discussed, and the electrodynamic characteristics presented.
QWR vacuum insulation and protect the resonator from contamination in the case of seal failures of the internal connections. Coupling is carried out by means of an antenna. The power input is connected to the cavity perpendicular to the beam channel. This makes it possible to minimize the distortions introduced by the coupler in respect to the parallel layout. Field asymmetry compensation is achieved by placing the probe on the opposite wall of the resonator. Power input coupling tuning is done by adjusting the antenna depth of immersion in the range of 15– 30 mm. The antenna tip is rounded for the reduction of the field overvoltage
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