Precision Measurements with the CHIP-TRAP Mass Spectrometer for Tests of Special Relativity

使用 CHIP-TRAP 质谱仪进行精密测量以测试狭义相对论

• 批准号: 1607429
• 负责人: Matthew Redshaw
• 金额: $ 20.01万
• 依托单位: Central Michigan University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2016
• 资助国家: 美国
• 起止时间: 2016-09-01 至 2020-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1607429&HistoricalAwards=false
• 关键词: Precision; Measurements; CHIP; TRAP; Mass

The goal of this project is to perform a very precise measurement of mass difference between two types of chlorine atoms: Chlorine-35 and Chlorine-36. These two isotopes have the same number of protons and electrons, so they have the same chemical properties, but chlorine-36 has one extra neutron, so they do not have the same mass. However, the mass difference is not simply the mass of the neutron. This is because, according to Einstein's famous equation, E = mc2, some of the mass of the extra neutron is given up as nuclear binding energy. Hence, by measuring the mass difference between chlorine-35 and chlorine-36, and accounting for the mass of the neutron, the chlorine-36 neutron binding energy can be determined. The mass difference measurement gives the right hand side of Einstein's equation and can be compared with other, independent measurements of the neutron binding energy that give the left hand side of Einstein's equation. These other measurements use precise spectroscopy techniques to measure the energy of gamma-rays (high energy electromagnetic radiation similar to x-rays) that are emitted just after a chlorine-35 nucleus captures a neutron to become chlorine-36 and releases the excess energy. The comparison of the mass difference and gamma ray energies then provides a direct test of E = mc2. This project will use high-precision Penning trap mass spectrometry to determine the mass difference between chlorine-35 and chlorine-36 by measuring the ratio of cyclotron frequencies of singly-charged ions containing these isotopes in the 12 Tesla magnetic field of the Central Michigan University High Precision Penning Trap (CHIP-TRAP). The cyclotron frequency will be determined using the image charge detection technique in which the image currents induced in the trap electrodes by the oscillating ion are detected and amplified with low noise cryogenic circuits. CHIP-TRAP will consist of a novel, double measurement trap structure that will enable the two ions whose mass ratio is to be determined to be simultaneously stored for long measurement times. Ultimately, the cyclotron frequency measurement for the two ions will be performed simultaneously, greatly reducing the effect of temporal magnetic field fluctuations. This technique should enable a precision in the mass ratio of 10 parts per trillion or less to be reached. Ions will be produced outside of the Penning trap using either a laser ablation ion source or a plasma ion source, and will be transported to a capture trap before being transferred to the precision measurement traps. This will reduce the amount of the long-lived (300,000 year half-life) chlorine isotope required for the experiment.

该项目的目的是对两种类型的氯原子之间的质量差进行非常精确的测量：氯-35和氯36。这两个同位素具有相同数量的质子和电子，因此它们具有相同的化学特性，但是氯-36具有一个额外的中子，因此它们的质量不相同。但是，质量差异不仅是中子的质量。这是因为，根据爱因斯坦著名的方程式E = MC2，某些额外中子的质量被赋予核结合能。因此，通过测量氯-35和氯-36之间的质量差异，并考虑了中子的质量，可以确定氯-36中子结合能。质量差测量给出了爱因斯坦方程的右侧，可以与其他独立的中子结合能的独立测量，这些中子结合能提供了爱因斯坦方程的左侧。这些其他测量值使用精确的光谱技术来测量γ射线的能量（高能电磁辐射类似于X射线），这些射线刚好在氯-35核后发出，捕获了中子变成氯-36并释放多余的能量。然后，质量差和γ射线能量的比较提供了E = MC2的直接测试。该项目将使用高精度的笔陷阱质谱法来确定氯35和氯36的质量差异，通过测量在密歇根大学中央密歇根大学高精度pen脚陷阱（chip-trap）中12个特斯拉磁场中包含这些同位素的单个同位素的转基因频率的比率。将使用图像电荷检测技术确定回旋频率，在该技术中，通过振荡离子在陷阱电极中诱导的图像电流被检测到并用低噪声低温性电路进行扩增。 Chip-Trap将由一种新型的双重测量陷阱结构组成，该结构将使两个离子能够同时存储在长时间的测量时间中。最终，将同时执行两个离子的回旋频率测量，从而大大降低了时间磁场波动的效果。该技术应以每万亿美元或更少的质量比率达到精度。离子将使用激光消融离子源或等离子离子源在笔陷阱外产生，并将转移到捕获陷阱中，然后再转移到精度测量陷阱。这将减少实验所需的长寿命（300,000年半衰期）氯同位素的数量。