分类： 核科学技术 >> 辐射物理与技术 提交时间： 2024-04-04
摘要： The High Energy Fragment Separator (HFRS), which is currently under construction, is a leading international radioactive beam device. Multiple sets of position-sensitive Twin Time Projection Chamber (TPC)detectors are distributed on HFRS for particle identification and beam monitoring. The twin TPCs’ readoutelectronics system operates in a trigger-less mode due to its high counting rate, leading to a challenge of handling large amounts of data. To address this problem, we introduced an event-building algorithm. This algorithmemploys a hierarchical processing strategy to compress data during transmission and aggregation. In addition,it reconstructs twin TPCs’ events online and stores only the reconstructed particle information, which significantly reduces the burden on data transmission and storage resources. Simulation studies demonstrated that thealgorithm accurately matches twin TPCs’ events and reduces more than 98% of the data volume at a countingrate of 500 kHz/channel.
分类： 物理学 >> 核物理学 提交时间： 2024-01-04
摘要： Charge strippers play an essential role in heavy-ion accelerators by stripping the projectile ions to higher charge states to enhance the acceleration efficiency downstream of the stripper. In the high-energy mode of the booster ring (BRing) of the high-intensity heavy-ion accelerator facility, the pre-accelerated ions from the iLinac will be stripped by a carbon foil to higher charge states and then injected into the BRing. The key parameters of the stripper and stripped ions were calculated, and the influence of stripping on the beam quality was discussed. To get high stripping efficiencies, the foil thicknesses and resultant charge state distributions for the typical ions were determined by the code ETACHA. The equilibrium thickness was obtained for the U beam, while the stripper thicknesses for the Xe and Kr beams were determined based on a compromise between the stripped charge states and the stripping efficiency. The energy loss, energy straggling, and emittance growth due to stripping have a non-negligible impact on the transport of the stripped beams and the injection of the ring. Therefore, these parameters were simulated by GEANT4. In addition, the foils temperature evolution, which greatly affects the foil lifetime, was simulated by ANSYS. The maximum temperature of the foil bombarded by the U and Xe beams with the nominal parameters will exceed the safe value in terms of the impact of evaporation on the foils lifetime. Given the foil temperature constraint, the highest tolerable beam intensity and the injected ion number into the ring were derived for different beam sizes. The results of this paper will present important reference data for the optimization design and commissioning of the beamline and injection to the BRing for the stripped ions.
分类： 核科学技术 >> 核科学与技术 提交时间： 2023-11-06
Yang, Mingyu
Qian, Yi
Pu, Tianlei
Lu, Weijian
Sun, Zhikun
Zhao, Hongyun
Zhang, Jiarui
Liu, Zhengqiang
摘要： HFRS (HIAF FRagment separator (HFRS) will be the radioactive secondary beam separation line on High-Intensity heavy-ion Accelerator Facility (HIAF) in China. Several TPC detectors, with high count rates, are planned for particle identification and beam monitoring at HFRS. This paper presents an event-driven internal memory and synchronous readout (EDIMS) prototype ASIC chip. The aim is to provide HFRS-TPC with high-precision time and charge measurements with high count rates and a large dynamic range. The first prototype EDIMS chip integrated 16 channels and is fabricated using a 0.18-um CMOS process. Each channel consists of a charge-sensitive amplifier, fast shaper, slow shaper, peak detect-and-hold circuit, discriminator with time-walk compensation, analog memory, and FIFO. The token ring is used for clock-synchronous readout. The chip is taped and tested.
分类： 核科学技术 >> 粒子加速器 提交时间： 2023-06-06
摘要： In this study, a phenomenological model of the radio frequency (RF) behavior of a superconducting cavity fundamental power coupler is proposed by analyzing the simulation results of a transient beam loading process in an extremely over-coupled superconducting cavity. Using this phenomenological model, the calculation of the transient reflected power from a superconducting cavity under beam loading can be mathematically simplified to algebraic operations without solving the differential equation governing the transient beam loading process, while maintaining the calculation accuracy. Moreover, this phenomenological model can facilitate an intuitive understanding of the significant surge in the time evolution of reflected power from a superconducting cavity in certain beam-loading processes. The validity of this phenomenological model was carefully examined in various beam loading processes and cavity conditions, and the method based on this phenomenological model was utilized in the transient RF analysis of the superconducting cavity system of the CAFe Linac, achieving satisfactory results.
分类： 物理学 >> 核物理学 提交时间： 2023-06-06
摘要： β衰变半衰期和β延迟中子发射（βn）在核物理和核能等基础科学和工业应用的发展中具有重要意义，其中β−衰变起着重要作用。许多理论模型已经被提出来描述β-衰变的半衰期，而对βn的系统研究仍然很少。本文旨在通过解析公式研究了β−-衰减半衰期和βn概率，并与实验数据进行了比较。通过考虑衰减能量、凹凸度和壳效应等主要因素，提出了β−-衰减性质的解析公式。采用自助法同时评价计算的总不确定性，由统计量和系统不确定性组成。评估了中子富区的β−-衰变半衰期、βn概率和相应的不确定性。实验中的半衰期被很好地再现了。更多的预测也提出了理论的不确定性，这有助于更好地理解实验结果和理论结果之间的差异
分类： 物理学 >> 核物理学 提交时间： 2023-05-31
摘要： A simulation code, GOAT, is developed to simulate single-bunch intensity-dependent effects and their interplay in the proton ring (pRing) of the Electron-Ion Collider in China (EicC) project. GOAT is a scalable and portable macroparticle tracking code written in Python and coded by object-oriented programming technology. It allows for transverse and longitudinal tracking, including impedance, space charge effect, electron cloud effect, and beam-beam interaction. In this paper, physical models and numerical approaches for the four types of high-intensity effects, together with the benchmark results obtained through other simulation codes or theories, are presented and discussed. In addition, a numerical application of the cross-talk simulation between the beam-beam interaction and transverse impedance is shown, and a dipole instability is observed below the respective instability threshold. Different mitigation measures implemented in the code are used to suppress the instability. The flexibility, completeness, and advancement demonstrate that GOAT is a powerful tool for beam dynamics studies in the EicC project or other high-intensity accelerators.
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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