分类： 物理学 >> 核物理学 提交时间： 2024-02-19
摘要： Big Bang nucleosynthesis (BBN) theory predicts the primordial abundances of the light elements 2H (referred to as deuterium, or D for short), 3He, 4He, and 7Li produced in the early universe. Among these, deuterium, the first nuclide produced by BBN, is a key primordial material for subsequent reactions. To date, the uncertainty in predicted deuterium abundance (D/H) remains larger than the observational precision. In this study, the Monte Carlo simulation code PRIMAT was used to investigate the sensitivity of 11 important BBN reactions to deuterium abundance. We found that the reaction rate uncertainties of the four reactions d(d, n)3He, d(d, p)t, d(p, )3He, and p(n, )d had the largest influence on the calculated D/H uncertainty. Currently, the calculated D/H uncertainty cannot reach observational precision even with the recent LUNA precise d(p, )3He rate. From the nuclear physics aspect, there is still room to largely reduce the reaction-rate uncertainties; hence, further measurements of the important reactions involved in BBN are still necessary. A photodisintegration experiment will be conducted at the Shanghai Laser Electron Gamma Source (SLEGS) Facility to precisely study the deuterium production reaction of p(n, )d.
分类： 核科学技术 >> 辐射物理与技术 提交时间： 2023-11-06
摘要： HVE-400 ion implanter is special ion implantation equipment for semiconductor materials boron and phosphorus doping. The ion source and extraction deflection system are at high voltage platform, while the corresponding control system is at ground voltage position. The control signals and measurement signals of various parameters at the high-voltage end need to be transmitted between ground voltage and high voltage through optical fibers to isolate high voltage. Upgrading is carried out due to the aging of the optical fiber transmission control and monitoring system, which cannot work stably. The transformation replaces the original distributed single-point control method with an advanced distributed centralized control method, and integrates all control and monitoring functions into an industrial control computer for digital operation and display. In the computer software, two kinds of automatic calculation of ion mass number are designed.After upgrading, the implanter high-voltage platform control and monitoring system features digitalization, centralized control, high reliability, strong anti-interference, fast communication speed, and easy operation.
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