ARI-MA: Cavity Resonance Kinetic Inductance Detectors (CaRKIDs)

[39309betz]本课题的目标是研制高效、高分辨率的探测器。目前，用于核光谱学的最好的高纯度锗探测器（HPGe）在100 keV区域提供的分数能量分辨率仅为0.5%，这对核光谱学至关重要。在许多情况下，这一决议不足以区分具有威胁性的核材料和作为自然背景一部分的较为普通的物质。例如，在美国边境口岸，最常见的误报来源是混淆了186.211 keV的自然排放的226Ra（一种常见于粘土材料和土壤中的元素）和185.715 keV的易裂变235U。核材料分析中的另一个光谱挑战是将240Pu的104.2 keV强谱线与附近的103.7 keV x射线线分开。这些和其他谱线在100-200 keV区域的重叠为混合锕系样品的无损分析设定了误差预算。确定反应堆燃料样品中的同位素混合既提供了特征指纹，也提供了有关燃料（武器生产或发电）预期用途、反应堆类型和化学处理历史（如果有的话）的具体信息。此外，具有高效率和高分辨率的探测器可以为探测裂变物质提供新的能力。当在背景或重叠线存在的情况下测量微量放射性物质的微弱发射线时，分辨率较好的探测器产生较好的信噪比。这里提出的新型超导探测器有望提供比HPGe高30倍的能量分辨率，以及比低温微热量计高1000倍的截面灵敏度。这项拟议活动的智力价值在于，它有可能使伽马射线探测器的能量分辨率提高一个数量级以上，而且这一进步不仅对核安全，而且对天体物理学和核医学都将产生科学影响。提出的探测器依赖于一种叫做动态电感的效应，在这种效应中，超导体表面的宏观电感可以受到电离辐射吸收产生的不成对电子（准粒子）的影响。电感的变化由高q微波电路拾取，信号事件与任何其他光子计数器一样计数，但不同的是，脉冲高度可以在伽马吸收中以30 eV的能量分辨率测量。这一努力将在几个领域产生更广泛的影响。首先在科学方面，高能动能电感探测器的发展将影响伽马射线天文学的方向，甚至可能影响对暗物质的研究。在技术方面，这种影响将在非接触核分析方法的发展中感受到前所未有的灵敏度。最后，在教育方面，作为论文和博士后研究的一部分，参与研究的研究生和博士后可以自由探索广阔的开放领域。最后，资深人员将有一些令人兴奋的事情要做，并在科学博览会和外展活动中向K-12学生传达一些新的东西。

1039309BetzThe objective of this proposal is to develop detectors with high efficiency and high resolution. Currently, the best high-purity germanium detectors (HPGe) used in nuclear spectroscopy provide a fractional energy resolution of only 0.5% in the 100 keV region important in nuclear spectroscopy. In many cases this resolution is inadequate to discriminate between threatening nuclear materials and more mundane substances which are part of the natural background. For example, the most common source of false alarms at US border crossings is the confusion between the naturally occurring emission of 226Ra (an element commonly found in clay-bearing materials and soils) at 186.211 keV and the185.715 keV emission of fissile 235U. Another spectroscopic challenge in nuclear materials analysis is separating the intense 104.2 keV line of 240Pu from the nearby 103.7 keV X-ray of Pu X. These and other line overlaps in the 100-200 keV region set the error budget for nondestructive analysis of mixed actinide samples. Determining the isotopic mix in a reactor fuel sample provides both a characteristic fingerprint and specific information about the intended purpose of the fuel (weapons production or electricity generation), the type of reactor, and the history of chemical processing, if any. Further, detectors with high efficiency and high resolution can provide new capabilities for detecting fissile material. Detectors with better resolution produce a better signal-to-noise ratio when measuring faint emission lines from trace quantities of radioactive material in the presence of background or overlapping lines. The new superconducting detectors proposed here offer the promise of 30 times better energy resolution than HPGe, and perhaps 1000 times greater cross-sectional sensitivity compared to cryogenic microcalorimeters.The intellectual merit of the proposed activity derives from its potential to produce more than an order of magnitude improvement in the energy resolution of gamma ray detectors, and the scientific fallout this advance would have, not only for nuclear security, but also in astrophysics and nuclear medicine. The detectors proposed rely on an effect called kinetic inductance, in which the macroscopic inductance of the surface of a superconductor can be influenced by the creation of unpaired electrons (quasiparticles) through the absorption of ionizing radiation. The change in inductance is picked up by a high-Q microwave circuit, and the signal event is counted as with any another photon counter, but with the difference that the pulse heights can be measured with 30 eV energy resolution in the gamma absorption.The broader impact of this effort will be felt in several areas. First in science the development of high-energy kinetic inductance detectors will influence the direction of gamma ray astronomy and perhaps even the search for dark matter. In technology, the impact will be felt in the development of non-contact nuclear assay methods of unprecedented sensitivity. Finally, in education, the participants in the research, the graduate student and postdoc, will be free to explore a wide open area as part of thesis and postdoctoral research. Finally the senior personnel will have something exciting to do, and something new to convey to the K-12 students in the science fair and outreach activities.