Measurement of QEC by Penning-Trap Mass Spectrometry

在ECHo项目第二阶段（ECHo-100k）的框架内，PI团队的目标是为ECHo实验提供一个独立和直接测量的163Ho电子捕获（EC）的q值，其不确定度为几个eV。用于实现这一目标的工具是位于MPIK的高精度Penning-trap质谱仪PENTATRAP，目前正处于调试阶段。最终目标的实现取决于两个主要子项目的成功实现：第一个子项目包括开发稳定可靠的高电荷163Ho离子来源。由于样品只含有几纳克的163Ho，并且需要每秒产生几十个离子，因此将用稳定的165Ho优化源。为此，专门的测试设置正在开发中。它由电子束离子阱（EBIT）、90°磁选机和诊断站组成。在息税前利润中，各种离子生产技术将被广泛研究，以找到最适合我们需求的技术。在EBIT之后放置一个90°磁分离器，其质量电荷分辨能力约为400，以选择离子的某种电荷状态，然后将其发送到由带有荧光粉屏幕的微通道板（MCP）组成的诊断站。通过测试装置获得的结果将使我们能够建立一个离子源，该离子源将为Penning-trap质谱计PENTATRAP提供足够数量的163Ho高电荷离子。第二个子项目包括Penning-trap质谱计PENTATRAP的调试。质谱计被设计用来测量高电荷离子的质量比，相对不确定度为10E-11。它采用5个位于7T磁铁冷孔内的Penning陷阱和一个用于图像电荷检测的专用检测系统。调试意味着，首先，各种离子从离子源成功地传输到质谱仪，并在五个陷阱中的任何一个中连续捕获处于选定电荷状态的离子至少几个小时。其次，捕获的离子必须通过电阻离子冷却来冷却它们的捕获运动来准备测量。第三，捕集器必须使用参考离子进行优化，例如氩的高电荷离子。第四，必须用不同的相位分辨检测技术来证明确定参考离子的回旋加速器频率的能力，所需的相对不确定度最多为10E-11。最后，两个已知物质的质量比，如187Re和187Os，必须以大约10E-11的相对不确定度正确确定。这些子项目的成功实现将使我们能够实现我们的最终目标-以几个eV的不确定性确定163Ho的EC的q值。

Within the framework of the second phase of the ECHo project (ECHo-100k) the team of the PI has the goal to provide the ECHo experiment with an independently and directly measured Q-value of the electron capture (EC) in 163Ho with an uncertainty of a few eV. The tool to be used to reach this goal is the high-precision Penning-trap mass spectrometer PENTATRAP, which is located at the MPIK and is presently in the commissioning phase. An accomplishment of the ultimate goal depends on the successful realization of two main subprojects: The first subproject encompasses a development of a stable and reliable source of highly charged 163Ho ions. Since the sample contains just a few nanograms of 163Ho and a production rate of a few ten ions per second is needed, the source will be optimised with stable 165Ho. For this, a dedicated test setup is being under development. It is composed of an electron beam ion trap (EBIT), a 90° magnetic separator and a diagnostic station. In the EBIT various ion production techniques will be extensively investigated in order to find the one which would suit our demands best. A 90° magnetic separator with a mass-to-charge resolving power of about 400 will be placed after the EBIT to select a certain charge state of the ions which will then be sent to a diagnostic station consisting of a microchannel plate (MCP) with a phosphor screen. The results obtained with the test setup will allow us to build an ion source which will provide the Penning-trap mass spectrometer PENTATRAP with a sufficiently large number of highly charged ions of 163Ho. The second subproject consists of the commissioning of the Penning-trap mass spectrometer PENTATRAP. The mass spectrometer has been designed to measure mass ratios of highly charged ions with a relative uncertainty of 10E-11. It employs five Penning traps situated inside the cold bore of a 7T magnet and a dedicated detection system for image charge detection. The commissioning implies, first, a successful transport of various ions from an ion source to the mass spectrometer with successive trapping of the ions in a chosen charge state in any of the five traps for at least several hours. Second, the trapped ions must be prepared for measurements by cooling their trap motions by means of resistive ion cooling. Third, the traps must be optimized with reference ions, e.g., highly charged ions of argon. Fourth, the ability to determine the cyclotron frequency of the reference ions with a needed relative uncertainty of at most 10E-11 must be demonstrated with different phase resolving detection techniques. Finally, the mass ratio of two species with well-known masses, e.g. 187Re and 187Os, must be determined correctly with a relative uncertainty of about 10E-11. A successful realization of these subprojects will enable us to address our ultimate goal – the determination of the Q-value of the EC in 163Ho with an uncertainty of a few eV.