Status of the Super-Kamiokande gadolinium project
Status of the Super-Kamiokande gadolinium project
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DOI：
10.1016/j.nima.2013.06.074
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发表时间：
2013-12
影响因子：
1.4
通讯作者：
T. Mori
中科院分区：
文献类型：
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作者：
T. Mori
宇宙中过去所有超新星爆炸释放的中微子的扩散通量被称为超新星遗迹中微子（SRN）。Super-Kamiokande（SK）通过探测器中的逆β衰变相互作用对这些SRN事件进行了搜索，在此过程中建立了世界上对这种尚未观测到的通量的最佳限制。这些限制在理论预测通量的大约两倍之内。但是这些搜索是背景有限的，如果没有一些重大的改进，进一步的进展将是困难的。提出了在SK探测器中加入钆（Gd）化合物来降低背景的方法。Gd在所有稳定核中具有最大的热中子俘获截面，俘获后产生8 MeV的γ级联。通过用Gd中子俘获产生的γ射线对正电子进行符合标记，我们可以识别SK中的主要SRN信号：逆β衰变。这种Gd负载技术应该允许SK进行世界上第一次对SRN信号的观测。我们将使用一个名为EGADS的专用测试设备演示掺钆水切伦科夫探测器的原理（掺钆水的透明度，掺钆水循环方法，中子捕获效率等）。EGADS由200吨水切伦科夫探测器、Gd溶解预处理装置、含Gd水循环系统和定制水透明度测量装置组成。自2012年以来，我们已经使用主要的EGADS水系统评估了Gd掺杂水循环。对EGADS总体性能的评估将在PMT安装后于2013年开始。
The diffuse flux of neutrinos released from all past supernova explosions in the universe is known as the supernova relic neutrinos (SRN). Super-Kamiokande (SK) has conducted searches for these SRN events via their inverse beta decay interactions in the detector, in the process establishing the world's best limits on this still unobserved flux. These limits are within about a factor of two of the theoretically predicted fluxes. But these searches are background limited, and without some major improvement further progress will be difficult. The addition of gadolinium (Gd) compound into the SK detector was proposed to reduce background. Gd has the largest thermal neutron capture cross-section among all stable nuclei and emits an 8 MeV γ cascade following the capture. By coincidental tagging of positrons with the γ rays from Gd neutron capture, we can identify the dominant SRN signal in SK: inverse beta decay. This Gd-loading technique should allow SK to make the world's first observation of a SRN signal. We will demonstrate the principle of a Gd-doped water Cherenkov detector (transparency of the Gd-doped water, Gd-doped water circulation method, neutron capture efficiency, etc) with a dedicated test facility named EGADS. EGADS consists of a 200 ton water Cherenkov detector, a Gd dissolving pre-treatment device, a Gd-capable water circulation system, and a custom-built water transparency measurement device. We have evaluated Gd-doped water circulation using the main EGADS water system since 2012. The evaluation of the overall performance of EGADS will start in 2013 after PMT installation.