Abstract
Dielectric assist accelerating (DAA) structures are being studied as an alternative to conventional disk-loaded copper structures. This article investigates numerically an efficient X-band DAA structure operating in a higher order mode of TM <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">02</sub> - π. This accelerating structure consists of dielectric disks with irises arranged periodically in a metallic enclosure. Through optimizations, the radio frequency (RF) power loss on the metallic wall can be significantly reduced, resulting in an extremely high quality factor Q <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> =134 525 and a very high shunt impedance r'=781 MΩ/m. The RF-to-beam power efficiency reaches 51% which is significantly higher than previously-reported Compact Linear Collider (CLIC)-G structures with an efficiency of only 33.5%. The optimum geometry of the regular and the end cells is described in detail. Due to the wide bandwidth from the dispersion relation of the accelerating mode, the DAA structure is allowed to have a maximum number of 72 regular cells with a frequency separation of 1.0 MHz, which is superior to that of conventional disk-loaded copper structures. In addition, the DAA structure is found to have a short-range transverse wakefield lower than that of the CLIC-G structure.
Highlights
O VER the past few decades, conventional disk-loaded copper radio frequency (RF) structures have been widely studied and used to accelerate particles in a variety of applications for scientific research [1], [2], medical cancer therapy [3], [4], and industrial processing [5], [6]
We explore numerically an efficient X-band Dielectric assist accelerating (DAA) structure operating in a TM02-π mode
The accelerating fields are distributed in the regular cell, which dominates the RF parameters such as the unloaded quality factor and the shunt impedance for a DAA structure
Summary
O VER the past few decades, conventional disk-loaded copper radio frequency (RF) structures have been widely studied and used to accelerate particles in a variety of applications for scientific research [1], [2], medical cancer therapy [3], [4], and industrial processing [5], [6]. A high accelerating gradient of up to 100 MV/m has been demonstrated at room temperature for an X-band copper structure, which has been studied as the baseline accelerating structure design for the Compact Linear Collider (CLIC) main linac [7]–[14] Such a structure is named “CLIC-G,” operating at 11.994 GHz in 2π/3 mode with an unloaded quality factor Q0 ≈ 5600, a shunt impedance r ≈ 92 M/m, and a power efficiency ηrf−beam ≈ 28.5%.
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