Some external neutron and gamma source experiments were carried out to study the origin of the background.

还应用外置伽玛源和中子源进行了实验，以判断本底的来源。

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Sealed neutron source and gamma source used in nuclear logging have strong radioactivity which is harmful to operators.

核测井使用的密封中子源和伽马源具有较强的放射性，对操作人员有一定的辐射损伤。

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Interestingly, an April 18 paper in the journal Nature reported that upper limits for neutrinos measured from IceCube are low enough that gamma-ray bursts are unlikely to be the sole source of ultra-high energy cosmic rays.

CNN: Why gamma-ray burst shocked scientists