Determining the focal spot limit of 1 MeV X-ray targets: Monte Carlo simulation of the point spread function

作者：Wang, Jiayue; Shi, Jiaru; Huang, Wenhui; Tang, Chuanxiang^*

来源：Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment , 2017, 846: 43-49.

DOI：10.1016/j.nima.2016.10.054

• 1 MeV X-ray
• Focal spot limit
• Point spread PSF)
• Monte Carlo simulation

Among all microfocus X-ray tubes, 1 MeV has remained a "gray zone" despite its universal application in radiation therapy and non-destructive testing. One challenge existing in fabricating 1 MeV microfocus X-ray tubes is beam broadening inside metal anodes, which limits the minimum focal spot size a system can obtain. In particular, a complete understanding of the intrinsic broadening process, i.e., the point-spread PSF) of X-ray targets is needed. In this paper, relationships between PSF and beam energy, target thickness and electron incidence angle were investigated via Monte Carlo simulation. Focal spot limits for both transmission and reflection-type tungsten targets at 0.5, 1 and 1.5 MeV were calculated, with target thicknesses ranging from 1 mu m to 2 cm. Transmission-type targets with thickness less than 5 pm could achieve micrometer-scale spots while reflection-type targets exhibited superiority for spots larger than 100 pm. In addition, by demonstrating the spot variation at off-normal incidence, the role of unidirectional beam was explored in microfocus X-ray systems. We expect that these results can enable alternative designs to improve the focal spot limit of X-ray tubes and benefit accurate photon source modeling.

• 出版日期2017-2-21
• 单位清华大学