下一代短寿命核素质量测量技术——双飞行时间探测器等时性质谱仪的原理研究

Mass measurements for exotic nuclei far from the valley of β-stability, which play an important role in various research such as nuclear structure and nuclear astrophysics, is one of frontiers of nuclear physics. However, due to the intrinsic disadvantages of measurement technique, all the mass spectrometry presently in the world can hardly reach the level of relative mass precision at the magnitude of several keV, for nuclei with very short half-lives down to several tens of microseconds..In order to meet the requirements of higher mass precision, we proposed an improved isochronous mass spectrometry with double time-of-flight detectors (IMS-DTOF) based on the HIRLF-CSR complex. In this project, we plan to test the validity of the basic principle of IMS-DTOF using experimental data, which have been obtained in previous online experiments. We will also find solutions for all the problems in the data analysis of IMS-DTOF and experimentally realize IMS-DTOF with expected mass resoling power..The territory on the nuclear chart that IMS-DTOF can be applied, not only cover the region for previous IMS, but also include most of N=Z nuclides and low-lying isomers. IMS-DTOF can be used to provide the required high-precision mass data to probe the associated physics. Besides, this project is a technique preparation of mass measurements for the future High Intensity Heavy-ion Accelerator Facility (HIAF). If IMS-DTOF become reality, China will reach the top level in the world for mass measurements of exotic nuclei with very short half-lives.

滴线附近短寿命奇异核的质量测量是当前原子核物理的前沿领域，对远离稳定线的奇异核结构和核天体物理的研究具有重要意义。由于测量机制的固有缺点，国际上现有的质谱仪在测量具有微秒级寿命的核素质量时质量精度通常难以达到1keV量级。为了填补这一技术空白，本项目拟探索储存环上等时性质谱仪的升级方案——双TOF等时性质谱仪（IMS-DTOF）的基本原理，并运用该原理处理在线实验数据，解决实际中IMS-DTOF可能遇到的问题，使双TOF等时性质谱仪的质量分辨到达预期的几个keV的量级。IMS-DTOF的测量对象不仅覆盖以前的范围，还将包括绝大部分短寿命N=Z核素和低激发能的同核异能态，在更高的精度水平上为相关物理的研究提供质量数据。此外，本项目还为强流重离子加速器HIAF在质量测量方面的工作探索新技术。IMS-DTOF的实现将使中国在短寿命核素质量测量领域达到世界领先水平。

储存环上的等时性质谱仪是高精度测量短寿命核素质量的重要实验方法之一。双TOF等时性质谱仪是近些年提出的进一步提升储存环质量测量精度的可行升级方案。本项目的目标是利用112Sn实验的数据建立双TOF等时性质谱仪的数据处理方法，并验证双TOF原理的可行性，讨论各种因素对质量分辨的影响。本项目提升了质量测量实验中的时间信号的定时精度，并初步完成了双TOF的数据处理程序，基本实现了申请书中提出的目标。但双TOF技术虽然可以提升等时性区间外的离子的循环周期分辨，但对等时性区间内的离子影响并不明显，故还需要进一步的研究其他影响因素。本项目的其他物理和技术的成果还包括In同位链的isomer激发能的演化趋势，isomer产额与角动量的关系，狭缝对等时性质量测量分辨的影响等。