论文标题
SNO+中微子检测器中的热驱动闪烁体流
Thermally-driven scintillator flow in the SNO+ neutrino detector
论文作者
论文摘要
SNO+中微子检测器是一个半径的丙烯酸球，填充了液体闪烁体，沉浸在充满水的地下洞穴中，垂直颈部薄（半径0.75 m），从球体从球体延伸到7 m向上延伸至纯化的氮气覆盖气体。为了解释闪烁体意外运动的时期，使用OpenFOAM进行了时间依赖性流动模拟。看来，从随后的24个H平均$^{222} \ Mathrm {rn} $污染物中引入的闪烁体污染引入的瞬时24 h平均模式推断出的运动，可以解释为由于通过探测器壁引起的浮力流在细壁边界层中的浮力。这种机制可能会导致污染物的运输，如果将其引入，则在几个小时的时间范围内将颈部从脖子上延伸到球体。如果闪烁体恰好是热分层的，则相同的强迫会在Brunt-Väisälä频率下在球形流动域中产生内部重力波。然而，振荡运动本质上是非扩散的，模拟证实，在颈部深度上施加强烈的热分层会由于短暂的热通量而减轻混合。
The SNO+ neutrino detector is an acrylic sphere of radius 6 m filled with liquid scintillator, immersed in a water-filled underground cavern, with a thin vertical neck (radius 0.75 m) extending upwards about 7 m from the sphere to a purified nitrogen cover gas. To explain a period of unexpected motion of the scintillator, time-dependent flow simulations have been performed using OpenFoam. It appears that the motion, inferred from subsequent 24 h-averaged patterns of transient $^{222}\mathrm{Rn}$ contamination introduced during earlier recirculation of scintillator, can be explained as owing to heat transfer through the detector wall that induced buoyant flow in a thin wall boundary layer. This mechanism can result in transport of contaminant, should it be introduced, down the neck to the sphere on a time scale of several hours. If the scintillator happens to be thermally stratified, the same forcing produces internal gravity waves in the spherical flow domain, at the Brunt-Väisälä frequency. Nevertheless, oscillatory motion being by its nature non-diffusive, simulations confirm that imposing strong thermal stratification over the depth of the neck can mitigate mixing due to transient heat fluxes.
