分类： 物理学 >> 核物理学 提交时间： 2025-07-03
Zhang, Mr. Ze-Kun
han, Miss rui
Chen, Prof. Zhi-Qiang 陈志强
Tian, Dr. Guoyu
Liu, Dr. Bing-Yan
Zhang, Dr. Xin
Sun, Dr. Hui
Li, Mr. Qin
Zhang, Dr. Peiyan Zhang Peiyan
Shi, Mr. Fudong
Guo, Mr. Rui
摘要： The neutron yields induced by 500 MeV/u 4He ions bombarding a thick uranium target have been measured by the time-of-flight method at Heavy Ion Research Facility in Lanzhou. Simulations employing three Monte Carlo codes, GEANT4, FLUKA, and PHITS, were performed to calculate neutron yields under conditions identical to the experiment. The results indicate that all three codes reproduce key features of the experimental energy spectrum distribution to varying degrees, though each exhibits distinct advantages and limitations across specific energy intervals and spatial angles. This study provides critical data for optimizing the spallation target and subcritical reactor designs in accelerator-driven subcritical systems.
分类： 核科学技术 >> 辐射物理与技术 提交时间： 2023-05-31
摘要： Carbon-ion radiotherapy (CIRT) offers unique physical and biological advantages over photon radiotherapy. However, somematerials and devices in the CIRT treatment room become radioactive under bombardment by therapeutic carbon-ion beamsdue to nuclear reactions, thereby leading to possible radiation hazards to medical staff and additional and unwanted dosesto patients. This study assessed the level of induced radioactivity in the treatment room of the Heavy-Ion Medical Machine(HIMM) in Wuwei. Monte Carlo simulations using PHITS were performed for a conservative case under the conditions ofmaximum beam energy and intensity provided by the HIMM facility. The geometry and configuration of Treatment Room2 of the HIMM facility in Wuwei were adopted. We evaluated the activation of air, the phantom, and the components ofthe beamline, such as the primary collimator (PC), ridge filter (RF), and multileaf collimator (MLC). For air activation,we calculated the medical staff immersion external exposure and inhalation internal exposure caused by the correspondingradionuclides. For phantom activation, we estimated the additional dose to the patients family members owing to secondaryphotons after treatment. In addition, the exemption or non-exemption of the component material activation was assessed.The results showed that external radiation caused by air activation was the main source of the annual effective dose atapproximately 0.5mSv/y. The induced radioactivity exposure to family members of a patient after CIRT was approximately40Sv, sufficiently lower than the public dose limit of 1mSv/a. The induced radioactivity of the PC, RF, and MLC was allabove the exempt levels after the devices were retired, whereas the induced radioactivity of the RS and compensator couldreach the exempt levels after one patient session. Our study indicated that medical staff engaged in CIRT should stay awayfrom the high-dose-rate area of induced radioactivity along the beam direction, shorten the residence time in the treatmentroom as much as possible, and store the activated components in isolation after the equipment is out of use. Thus, this studyprovides guidance for accurately assessing the level of induced radioactivity in the treatment room for CIRT.
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