Thin-disk laser for muonic atoms spectroscopy

用于μ子原子光谱的薄盘激光器

• 批准号: 209386059
• 负责人: Professor Dr. Thomas Graf
• 金额: --
• 依托单位: Institut für Strahlwerkzeuge (IFSW)
• 依托单位国家: 德国
• 项目类别: Research Grants
• 财政年份: 2012
• 资助国家: 德国
• 起止时间: 2011-12-31 至 2014-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/209386059?language=en
• 关键词: Thin; disk; laser; muonic; atoms

At the Paul Scherrer Institute, Switzerland, we have recently measured the 2S-2P energy difference in muonic hydrogen (an atom formed by a negative muon and a proton) by means of laser spectroscopy, allowing us to determine the rms charge radius of the proton. The new proton radius value of 0.84184(67) fm is 10 times more precise than previously obtained. However, it disagrees by 4 standard deviations from the value extracted from hydrogen spectroscopy and also by 5 standard deviations from electron-proton scattering data. The origin of the discrepancies is not yet known. It may come either from hydrogen-like atoms theory, or from a problem in the determination of the most accurately know fundamental constant (the Rydberg constant), or from an unexpected proton shape, or it occurs from uncalculated or new effects.The variance of the various proton radius values has led to a very alive discussion in various field of physics: particle and nuclear physics (proton structure, new physics, scattering analysis), in atomic physics (hydrogen energy level theory, fundamental constants) and fundamental theories (bound-state problems, QED, effective field theories). Several new experiments and proposals have also been triggered worldwide.In order to shed some light onto this proton radius conundrum we plan to measure several transition frequencies between the 2S and the 2P states in muonic He3 and He4 ions. Beside helping to solve the proton radius puzzle these measurements will result in the best determination of the alpha-particle and helion rms charge radii to a relative accuracy of at least 0.03% corresponding to an absolute precision of 0.0005 fm. These radii represent interesting and precise parameters to check few-nucleon ab-initio calculations, effective field nuclear theories and potentials.Furthermore when combined with the 1S-2S transition in He+ these measurements will give rise to the most accurate test of the crucial QED terms in hydrogen-like atoms.The main goal of this project described in this application is the development of a thin-disk laser suited for the measurements of several 2S-2P transitions in muonic helium. The challenge for this work is the realization of a thin-disk laser with at least 150 mJ pulse energy (with 20 ns pulse width), a delay between trigger and emission of the pulse smaller than 400 ns, random triggerable to repetition rates up to 1kHz.Beside being necessary for precision spectroscopy of muonic helium this laser system may find an interesting application in the field of muon spin resonance and holds the potential for the development of new thin-disk laser technologies.A thin-disk laser system has been already developed in a collaboration between A. Antognini, ETHZ (former Max Planck Institut für Quantenoptik) and the IFSW for the muonic hydrogen Lamb shift experiment. This development has enabled the measurement in beam time 2009 at PSI of the proton radius. Together with the low-energy beam line it was the most challenging development necessary for this measurement.With this project our collaboration would like to improve the pulse energy, stability and reliability of this thin-disk laser system, particularly in view of the muonic helium Lamb shift experiment (this experiment has been approved by the international research committee for particle physics at the PSI). With this project we would like to develop a thin-disk laser oscillator delivering pulses up to 60 mJ energy (ca 20 ns long) with delays of about 250 ns. This is a factor of 6 increase in energy compared with the present set-up. Moreover we will advance the performance of our multi-pass amplifier to output pulse energies of 150 mJ (a factor of 3 increase). These developments could find application in high power (kW power) cw and fs regimes and contribute to thin-disk technology advances.Such a laser with high pulse energy and short delay is also suited for future muon spin resonance applications in line with new proposals at PSI.For this project, which is in the framework of a DACH collaboration between ETHZ and IFSW, we ask the support for 2 PhD students: one for each involved institute. The students will work not only at the development of the thin-disk laser and related technologies but also at spectroscopy of muonic helium.

在瑞士的Paul Scherrer研究所，我们最近通过激光光谱测量了μ子氢（由负μ子和质子形成的原子）的2S-2 P能量差，使我们能够确定质子的均方根电荷半径。新的质子半径值为0.84184（67）fm，比以前获得的精确10倍。然而，它不同意从氢光谱提取的值的4个标准偏差，也从电子-质子散射数据的5个标准偏差。差异的起因尚不清楚。它可能来自类氢原子理论，也可能来自确定最准确的基本常数的问题（里德伯常数），或者来自一个意想不到的质子形状，或者它发生在未计算的或新的效应。各种质子半径值的变化导致了物理学各个领域的一个非常活跃的讨论：粒子和核物理（质子结构，新物理，散射分析），原子物理（氢能级理论，基本常数）和基础理论（束缚态问题，QED，有效场论）。为了解决质子半径难题，我们计划测量μ子He 3和He 4离子2S和2 P态之间的跃迁频率。除了有助于解决质子半径难题，这些测量将导致最好的确定α粒子和氦离子均方根电荷半径的相对精度至少为0.03%，对应于0.0005 fm的绝对精度。这些半径代表了检验少核子从头计算的有趣和精确的参数，有效场核理论和势的研究。此外，当与He+中的1 S-2S跃迁相结合时，这些测量将引起对类氢原子中关键QED项的最精确测试。本申请中描述的该项目的主要目标是开发薄的-适用于测量μ子氦中几个2S-2 P跃迁的圆盘激光器。这项工作的挑战是实现至少150 mJ脉冲能量的薄盘激光器（脉冲宽度为20 ns），脉冲的触发和发射之间的延迟小于400 ns，该激光系统除了用于μ子氦的精密光谱学之外，还可能在μ子自旋共振领域找到有趣的应用，开发新的薄片激光技术的潜力。Antognini，ETHZ（前马克斯普朗克量子光学研究所）和IFSW的μ子氢兰姆位移实验。这一发展使测量束时间2009年在PSI的质子半径。与低能光束线一起，这是该测量所需的最具挑战性的发展。通过该项目，我们的合作希望提高该薄盘激光系统的脉冲能量，稳定性和可靠性，特别是考虑到μ子氦兰姆位移实验（该实验已获得PSI粒子物理国际研究委员会的批准）。在这个项目中，我们希望开发一种薄盘激光振荡器，提供高达60 mJ的能量（约20 ns长）的脉冲，延迟约250 ns。与目前的设置相比，这是能量增加的6倍。此外，我们将提高我们的多通放大器的性能，输出脉冲能量为150 mJ（增加3倍）。这些发展可以在大功率领域得到应用。（千瓦功率）连续波和飞秒激光，并有助于薄磁盘技术的进步。这种具有高脉冲能量和短延迟的激光器也适用于未来的μ子自旋共振应用，符合PSI的新建议。对于这个项目，这是ETHZ和IFSW之间的DACH合作框架，我们要求支持2名博士生：每个参与机构一个。学生们不仅将致力于薄盘激光器和相关技术的发展，而且还将致力于μ子氦的光谱学。