Trapped electron for neutrino mass measurement.

该提案的重点是在Geonium芯片中开发一种捕获电子，作为基础物理应用的微波辐射超灵敏探测器。具体来说，在两年的项目期间，我们的主要目标是提供一个基本的实验验证概念的能力，我们的捕获电子（或“地偶素原子”）用于计划中的未来中微子绝对质量标度m_beta的测量，从氚β衰变的居里谱的能量端点E_0 = 18.6 keV.目前正在进行的KArslruhe氚中微子实验（KATRIN）最近报道了m_beta<1.1 eV/c^2的上限，其最终精度为0.2 eV/c^2。中微子味振荡与宇宙学观测一起将最终边界分别设定为m_beta>50 meV/c^2，或在中微子质量等级“颠倒”或“正常”排序的情况下，m_beta>9 meV/c^2。这两个值定义了测量中微子质量所需的精度。两者都超出了KATRIN的范围。为了改善后者，提出了一种测量m_β的新型回旋共振发射光谱（克雷斯）技术。克雷斯允许检测（和计数）从放射源（例如氚）发射的β粒子，并测量它们的动能。位于美国的Project-8合作项目通过探测单个β粒子（从气态Kripton衰变而来）发出的微波辐射并测量其动能，在实验上证明了克雷斯的基本原理。利用这种方法，Project-8的目标是在未来将中微子质量测量的精度提高到40 meV/c^2。与此同时，2021年初，由伦敦（UCL）牵头的中微子质量测量量子技术（QTNM）联盟已经启动。QTNM正在开发一个克雷斯演示装置（CRESDA），最初使用氘源运行。最终的目标是在氚设施中测量m_beta（最终在国际合作范围内），可能在卡勒姆聚变能中心，虽然克雷斯的基本工作原理已经过测试，但在测量β粒子动能时达到的分辨率为15 eV/c^2。这比m_beta的“保证”测量所需的灵敏度低大约三个数量级。该方案的目的是提供一种微波量子传感器，捕获的电子，能够测量m_β与克雷斯技术，即使在最具挑战性的情况下，“正常”有序。在项目的两年时间里，我们的目标是用我们的地偶素微波传感器证明5 meV/c^2或更好的能量分辨率。这些实验将在苏塞克斯郡的一个现有的Geonium芯片设施上进行。我们与QTNM财团的合作将提供对Geonium传感器测量m_beta的适用性的外部评估。它还将允许规划其最终的后续整合到未来的氚就绪克雷斯设施。

This proposal is focused on developing a trapped electron in the geonium chip as an ultra-sensitive detector of microwave radiation for fundamental physics applications. Specifically, in the two years duration of the project, our main goal is to provide a basic experimental proof-of concept of the capacity of our trapped electron (or 'geonium atom') for the planned future measurement of the neutrino's absolute mass scale, m_beta, from the energy endpoint E_0 = 18.6 keV of the Kurie spectrum of the beta-decay of tritium.The currently ongoing KArslruhe TRItium Neutrino experiment (KATRIN) has recently reported an upper bound of m_beta<1.1 eV/c^2, and it aims at a final accuracy of 0.2 eV/c^2. Neutrino flavour oscillations together with cosmology observations set the ultimate boundary to m_beta>50 meV/c^2, or m_beta>9 meV/c^2 in the case of "inverted" or "normal" ordering of the neutrino mass hierarchy, respectively. These two values define the required accuracy for measuring the neutrino mass. Both are beyond the reach of KATRIN. In order to improve the latter, the novel Cyclotron Resonance Emission Spectroscopy (CRES) technique has been proposed for measuring m_beta. CRES allows for detecting (and counting) beta particles emitted from a radioactive source, such as tritium, and for measuring their kinetic energy. The US-based Project-8 collaboration has demonstrated experimentally the basic principle of CRES, by detecting the microwave radiation emitted by one single beta particle (decayed from gaseous Kripton) and measuring its kinetic energy. With this method, Project-8 aims at a future accuracy in the neutrino mass measurement of 40 meV/c^2. Meanwhile, in early 2021, the Quantum Technologies for Neutrino Mass Measurement (QTNM) consortium, lead by University College London (UCL), has been launched. QTNM is developing a CRES demonstrator apparatus (CRESDA), initially operated with a deuterium source. The ultimate goal is to measure m_beta (eventually within an international collaboration) in a tritium facility, possibly at Culham Centre for Fusion Energy.While the basic working principle of CRES has been tested, the resolution achieved in the measurement of the kinetic energy of the beta particles amounts to 15 eV/c^2. This is around three orders of magnitude below the required sensitivity for a "guaranteed" measurement of m_beta. This proposal aims at delivering a microwave quantum sensor, the trapped electron, capable of measuring m_beta with the CRES technique, even in the most challenging scenario of "normal" ordering. Within the two years duration of the project we aim at demonstrating an energy resolution of 5 meV/c^2 or better with our geonium microwave sensor. The experiments will be performed at Sussex with an existing geonium chip facility. Our cooperation with the QTNM consortium will provide an external assessment of the suitability of the geonium sensor for measuring m_beta. It will also allow for planning its eventual subsequent integration into the future tritium-ready CRES facility.