The $\nu$-Angra experiment has developed an antineutrino detector intended to operate at sea level, a few dozen meters from the core of a nuclear reactor. The operating principle of the detector is based on the water Cherenkov light detection to be in compliance with the safety rules of the power plant operator. The detector is exposed to a high rate of background events, mainly due to cosmic rays, making its veto system a key element for efficient background rejection. The $\nu$-Angra Collaboration has designed a veto detector composed of three layers filled with water for both passive shielding and active detection of crossing particles. The veto surrounds a volume of 1.50$\times$1.05$\times$1.39m³, in which a target detector is placed, where the search for anti-neutrino events occurs. Any external particle hitting the detector must cross at least 25cm of water before reaching this internal volume, which is protected by the veto structure, thus providing an important barrier against neutrons and low energy particles. In addition, the veto system has been instrumented with eight 8-inch photomultiplier tubes to detect external particles that may eventually reach the target detector. By making use of a trigger system based on scintillating paddles, energy distribution and detection efficiency of the veto system were assessed for different detector positions. This paper, therefore, presents the achieved results related to the characterization of such system concerning the detection of cosmic-ray muon particles passing through it.

这 $\nu$-安格拉（Angra）实验已经开发出一种反中微子探测器，该探测器旨在在距核反应堆核心几十米的海平面上运行。探测器的工作原理基于Cherenkov水光探测器，符合发电厂操作员的安全规定。探测器主要由于宇宙射线而暴露于高背景事件中，因此其否决系统成为有效背景抑制的关键因素。这 $\nu$-Angra Collaboration设计了一种由三层充满水的否决检测器组成的否决检测器，用于被动屏蔽和交叉粒子的主动检测。否决权环绕1.50$\times$1.05$\times$1.39m ³，其中放置了目标检测器，在其中进行了反中微子事件的搜索。任何撞击到检测器的外部粒子在到达该内部容积之前必须经过至少25cm的水，该内部容积受到否决权结构的保护，从而为抵抗中子和低能粒子提供了重要的屏障。此外，否决系统还配备了八个8英寸光电倍增管，以检测可能最终到达目标检测器的外部颗粒。通过使用基于闪烁桨的触发系统，针对不同的检测器位置评估了否决系统的能量分布和检测效率。因此，本文介绍了与表征这种系统有关的特性有关的结果，该系统涉及对穿过它的宇宙射线μ子粒子的检测。