分类： 核科学技术 >> 辐射物理与技术 提交时间： 2025-02-19
摘要： Industrial linear accelerators often contain many bunches when their pulse widths are extended to microsec onds. As they typically operate at low electron energies and high currents, the interactions among bunches cannot be neglected. In this study, an algorithm is introduced for calculating the space charge force of a train with infinite bunches. By utilizing the ring charge model and the particle-in-cell (PIC) method and combin ing analytical and numerical methods, the proposed algorithm efficiently calculates the space charge force of infinite bunches, enabling the accurate design of accelerator parameters and a comprehensive understanding of the space charge force. This is a significant improvement on existing simulation software such as ASTRA and PARMELA that can only handle a single-bunch or a small number of bunches. The PIC algorithm is val idated in long-drift space transport by comparing it with existing models, such as the infinite-bunch, ASTRA single-bunch, and PARMELA several-bunch algorithms. The space charge force calculation results for the ex ternal acceleration field are also verified. The reliability of the proposed algorithm provides a foundation for the design and optimization of industrial accelerators.
分类： 物理学 >> 核物理学 提交时间： 2024-01-18
摘要： Very high-energy electrons (VHEE) are potential candidates for FLASH radiotherapy for deep-seated tumors. We proposed a compact VHEE facility based on an X-band high-gradient high-power technique. In this study, we investigated and realized the first X-band backward traveling wave (BTW) accelerating structure as the buncher for a VHEE facility. A method for calculating the parameters of single cells from the field distribution was introduced to simplify the design of the BTW structure. Time-domain circuit equations were applied to calculate the transient beam parameters of the buncher in the unsteady state. A prototype of the BTW structure with a thermionic-cathode diode electron gun was designed, fabricated, and tested at high power at the Tsinghua X-band High-power test stand. The structure successfully operated with 5-MW microwave pulses from the pulse compressor and outputted electron bunches with an energy of 8 MeV and a pulsed current of 108 mA.
分类： 物理学 >> 核物理学 提交时间： 2023-06-09 合作期刊: 《Nuclear Science and Techniques》
摘要： To implement the Tsinghua Thomson Scattering X-ray Source (TTX) upgrade plan and the Very Compact Inverse Compton Scattering Gamma-ray Source (VIGAS) program, a new 1.5-m traveling-wave accelerating structure was designed to replace the old 3-m SLAC-type structure with the aim of increasing the accelerating gradient from 15 to 30 MV/m. The new type of structure works in the 3π/4 mode with a comparatively low group velocity varying from 0.007c to 0.003c to increase the accelerating gradient at a given power. An elliptical iris was employed to reduce the surface field enhancement. The filling process of the low-group-velocity structure was analyzed using a circuit model. After fabrication, the structure was precisely tuned using the non-contact tuning method, followed by detailed low-power radiofrequency measurements. The structure was first installed and utilized at a beamline for the Terahertz experiment at Tsinghua University. After 120 h of conditioning, it is now operating at a gradient of 24.2 MV/m and a 20.7-MW input power, with the klystron operating at its full power. It is expected to generate an accelerating gradient of 30 MV/m when the klystron power is upgraded to 30 MW in the near future.
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