New Experimental Techniques for Neutrino Physics

中微子是宇宙中最丰富的粒子之一，它们是许多天体物理过程的关键，它们可能是解释宇宙中物质-反物质不对称的关键。已知它们在自然界中有三种类型，或“味道”。人们还观察到，中微子可以通过一种被称为中微子振荡的过程来改变味道。从这样的振荡实验中，我们发现中微子必须具有非零质量。这是已知的第一个迹象，表明在非常成功的粒子物理学标准模型之外存在着物理学。中微子质量仍然是物理学中最重要的开放问题之一，实验正在寻找确定它的方法，因为它们的丰度可能在我们宇宙的进化中发挥重要作用。在过去的80年里，由于电子能谱技术的日益强大，基于精确测量的直接实验室测定一直在扩大。2009年，PI提出了一种可以提取低能电子能谱的新技术。这项技术被称为回旋辐射发射光谱（CRES），它依赖于对磁场中电子回旋运动产生的相干辐射的探测和测量。中微子质量的知识对科学界有着广泛的影响，特别是在核物理、粒子物理和宇宙学领域。CRES技术作为低能电子光谱的一种通用技术，具有广泛的适用性。金属超导辐射热计用于后坐力探测也具有广泛的应用前景，在核反应堆监测和暗物质直接探测方面具有潜在的应用前景。麻省理工学院的本科生研究机会计划（UROP）促进了本科生的研究参与，该计划将学生和教师联系起来，并允许学生在整个学年从事基础研究。2009年，PI提出了一种可以提取低能电子能谱的新技术。CRES技术依赖于探测和测量磁场中电子回旋运动产生的相干辐射。这种基于频率的技术有能力克服使用氚直接进行中微子质量实验的传统光谱技术所施加的许多限制。由PI担任发言人的Project 8实验现已成功地演示了CRES技术如何有效地精确测量从放射性气体中释放的电子的动能。随着原理证明的牢固建立，该奖项将继续支持8号项目的研发计划的下一阶段，朝着从氚衰变中测量中微子质量的方向发展。特别是，下一阶段是对氚β光谱进行首次测量，以确定该技术的可扩展性。研究还将继续确定这项技术的最终能力：探测反向中微子的质量尺度。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Neutrinos are amongst the most abundant particles in the Universe, they are keys to many astrophysical processes, and they may hold the key to explaining the matter-antimatter asymmetry of the Universe. They are known to occur in nature in three types, or "flavors." It has also been observed that neutrinos could switch flavors through a process known as neutrino oscillation. From such oscillation experiments, it is found that neutrinos must have a non-zero mass. This is the first known indication that there is physics beyond the very successful Standard Model of Particle Physics. Neutrino mass remains one of the most important open questions in physics and experiments are searching for ways to determine it since with their abundance they could play an important role in the evolution of our Universe. Direct laboratory determinations based on the precise measurement of the beta spectrum have been expanding over the past 80 years due to increasingly powerful electron spectrometry techniques. In 2009, the PI proposed a new technique by which the energy spectrum of low energy electrons can be extracted. The technique, known as Cyclotron Radiation Emission Spectroscopy (CRES), relies on the detection and measurement of coherent radiation created from the cyclotron motion of electrons in a magnetic field. Knowledge of neutrino masses has broad implications for the scientific community, particularly in the fields of nuclear physics, particle physics, and cosmology. The CRES technique, being a general spectroscopic technique for low energy electrons, has broad applicability. The use of metallic superconducting bolometers for recoil detection also has broad reach, with potential applications in nuclear reactor monitoring and direct dark matter detection. Research engagement with undergraduate students is facilitated by MIT's Undergraduate Research Opportunity Program (UROP), which connects students and faculty and allows students to engage in basic research throughout the academic year.In 2009, the PI proposed a new technique by which the energy spectrum of low energy electrons can be extracted. The CRES technique relies on the detection and measurement of coherent radiation created from the cyclotron motion of electrons in a magnetic field. Such a frequency-based technique has the capability of overcoming many of the limitations imposed by traditional spectroscopic techniques used in direct neutrino mass experiments using tritium. The Project 8 experiment, of which the PI is the spokesperson, has now successfully demonstrated how the CRES technique is effective in precisely measuring the kinetic energy of electrons emitted from a radioactive gas. With the proof of principle firmly established, this award provides continued support of the next stage of Project 8's R&D program, moving toward a neutrino mass measurement from tritium beta decay. In particular, the next phase is to make a first measurement of a tritium beta spectrum in order to determine the scalability of the technique. Research will also continue to determine the technique's ultimate capability: to probe the inverted neutrino mass scale.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.