Hardware improvements for nEXO research and development

中微子是宇宙中最丰富的粒子之一，但它们的临界性质，如绝对质量，尚不清楚。最近来自SNO、SuperKamiokande和Kamland等实验的结果表明，中微子有质量，但只能测量质量差。无中微子双β衰变为研究质量幅度和类型提供了独特的可能性。这一过程意味着单个原子核内两个核子同时发生β衰变，中微子以不离开原子核的方式相互作用。这只有在中微子具有质量和特殊性质的情况下才有可能。无中微子双β衰变的发现将意味着中微子是它们自己的反粒子。这种衰变，如果存在的话，将是极其罕见的，而SNO开发的非常低的背景技术将是使这次搜索成功的关键。本提案所要求的硬件将用于改进EXO-200探测器的背景缓解，该探测器用于搜索氙核的无中微子双贝塔衰变，并校准探测器对伽马射线的反应，伽玛射线是主要的本底来源。它还将为EXO计划的下一阶段Nexo提供设计校准系统、氡捕集器和氡筛选所需的工具

Neutrinos are one of the most abundant particles in the universe, yet their critical properties, like their absolute mass, are unknown. Recent results from experiments like SNO, SuperKamiokande and Kamland have demonstrated that neutrinos have mass, but only the mass differences could be measured. Neutrinoless double beta decay offers a unique possibility to investigate for the mass amplitude and type. This process implies the simultaneous beta decays of two nucleons within a single atomic nucleus, with neutrinos interacting in a way that they do not leave the nucleus. This is only possible if neutrinos possess mass and special properties. The discovery of neutrinoless double beta decay would imply that neutrinos are their own anti-particles. This decay, if it exists, will be extremely rare and the very low background techniques developed by SNO will be essential to bring this search to success. The hardware requested in this proposal will be utilized to improve background mitigation in the EXO-200 detector which searches for neutrino-less double beta decay of xenon-136 nuclei and to calibrate the detector response to gamma rays, the principal source of background. It will also provide the tools necessary to design the calibration system, radon trap and radon screening for nEXO, the next phase of the EXO program