It is known that 12C beam transmission through the accelerator decreases at high beam currents. This effect depends on machine design and varies across different types of AMS instruments. For beam currents of about 100 μA, the effect is small on the 500 kV tandem CAMS unit, whereas beam saturation is observed for similar high beam currents on the 250 kV SSAMS unit. While this effect is very evident for high 12C beam currents, we have also observed that even the 13C beam is found to suffer modest transmission loss with beam current. As a result, the 13C/12C ratio does not remain constant with beam current. By correcting for the effects of 12C beam saturation and decreased 13C transmission, we have obtained online δ13C values that are more accurate and precise at moderately high beam currents for SSAMS.

中文翻译：

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稳定同位素光束传输对 SSAMS 在线 δ13C 的影响

众所周知12通过加速器的 C 束传输在高束流下减少。这种影响取决于机器设计，并因不同类型的 AMS 仪器而异。对于约 100 μA 的束流，对 500 kV 串联 CAMS 单元的影响很小，而在 250 kV SSAMS 单元上观察到类似高束流的束流饱和。虽然这种效果对于高12C 束电流，我们还观察到，即使13发现 C 束在束流下会遭受适度的传输损耗。结果，13C/12C 比率不随射束电流保持恒定。通过修正影响12C 束饱和度和降低13C传输，我们得到了在线δ13在 SSAMS 的中等高束电流下，C 值更加准确和精确。